Suppress transients on old burglar alarm

Started by Terry Pinnell June 4, 2018
My 20 year old burglar alarm control has developed a fault that I've
spent the last couple of days trying to fix. Before I ditch it and go
through the hassle of installing a new one I'm seeking help here please.

Q1:  An extreme longshot as I researched in 2012 but the company had
long folded, but... Anyone have or know a source of the circuit diagram
for the Autona 2250 Control Unit?

FWIW, screenshot inside the control unit's case
https://www.dropbox.com/s/4xd19m9cvdqfpr9/Autona2250-1.jpg?dl=0

Q2: A useful second best would be *any* circuit of a bog-standard,
commercial, wired unit designed for a series of normally closed
microswitches.

I made this one myself about 35 years ago and *suspect* that it will be
broadly similar, but I'd like to eliminate guesswork:
https://www.dropbox.com/s/cxl6zarvmqsnkem/Burglar%20Alarm-ex%20Leigh.gif?dl=0

It's being triggered spuriously. Two successive nights, 01:05 and 12:35.
During late stages of trouble-shooting (i.e. after checking all
switches) I found that I could trigger it by switching on light of the
cupboard in which unit is mounted, powered from same 240V source.

I suspect a failed capacitor. But I don't relish dismantling it to get
at the two PCBs and even if I did I doubt I'd find it.

Q3: Using the access I have to the power supplies (240 V AC, 15 V AC,
13V DC) and the pairs of wires from the string of N/C microswitches,
what transient suppression should I try adding at one or more of these
external points please, and in what priority?


Terry, East Grinstead, UK
On 06/04/2018 05:55 AM, Terry Pinnell wrote:
> My 20 year old burglar alarm control has developed a fault that I've > spent the last couple of days trying to fix. Before I ditch it and go > through the hassle of installing a new one I'm seeking help here please. > > Q1: An extreme longshot as I researched in 2012 but the company had > long folded, but... Anyone have or know a source of the circuit diagram > for the Autona 2250 Control Unit? > > FWIW, screenshot inside the control unit's case > https://www.dropbox.com/s/4xd19m9cvdqfpr9/Autona2250-1.jpg?dl=0 > > Q2: A useful second best would be *any* circuit of a bog-standard, > commercial, wired unit designed for a series of normally closed > microswitches. > > I made this one myself about 35 years ago and *suspect* that it will be > broadly similar, but I'd like to eliminate guesswork: > https://www.dropbox.com/s/cxl6zarvmqsnkem/Burglar%20Alarm-ex%20Leigh.gif?dl=0 > > It's being triggered spuriously. Two successive nights, 01:05 and 12:35. > During late stages of trouble-shooting (i.e. after checking all > switches) I found that I could trigger it by switching on light of the > cupboard in which unit is mounted, powered from same 240V source. > > I suspect a failed capacitor. But I don't relish dismantling it to get > at the two PCBs and even if I did I doubt I'd find it. > > Q3: Using the access I have to the power supplies (240 V AC, 15 V AC, > 13V DC) and the pairs of wires from the string of N/C microswitches, > what transient suppression should I try adding at one or more of these > external points please, and in what priority? > > > Terry, East Grinstead, UK >
I think you'd be much better off re-capping it, but you could try a Tripp-lite Isobar. They're my standard power strip, and the 8-outlet ones have four filter stages, so that each pair of outlets is isolated from the others as well as from the line. If the problem is high-frequency crud on the line, that will probably help, but for low frequency stuff you'd need a ferroresonant transformer. On the other hand, it might easily be getting in on the sensing loop, in which case a 10 nF cap right at the terminals might be the ticket. Make sure to keep the leads super short, like zero millimetres short. Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics Briarcliff Manor NY 10510 http://electrooptical.net https://hobbs-eo.com
Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:

>On 06/04/2018 05:55 AM, Terry Pinnell wrote: >> My 20 year old burglar alarm control has developed a fault that I've >> spent the last couple of days trying to fix. Before I ditch it and go >> through the hassle of installing a new one I'm seeking help here please. >> >> Q1: An extreme longshot as I researched in 2012 but the company had >> long folded, but... Anyone have or know a source of the circuit diagram >> for the Autona 2250 Control Unit? >> >> FWIW, screenshot inside the control unit's case >> https://www.dropbox.com/s/4xd19m9cvdqfpr9/Autona2250-1.jpg?dl=0 >> >> Q2: A useful second best would be *any* circuit of a bog-standard, >> commercial, wired unit designed for a series of normally closed >> microswitches. >> >> I made this one myself about 35 years ago and *suspect* that it will be >> broadly similar, but I'd like to eliminate guesswork: >> https://www.dropbox.com/s/cxl6zarvmqsnkem/Burglar%20Alarm-ex%20Leigh.gif?dl=0 >> >> It's being triggered spuriously. Two successive nights, 01:05 and 12:35. >> During late stages of trouble-shooting (i.e. after checking all >> switches) I found that I could trigger it by switching on light of the >> cupboard in which unit is mounted, powered from same 240V source. >> >> I suspect a failed capacitor. But I don't relish dismantling it to get >> at the two PCBs and even if I did I doubt I'd find it. >> >> Q3: Using the access I have to the power supplies (240 V AC, 15 V AC, >> 13V DC) and the pairs of wires from the string of N/C microswitches, >> what transient suppression should I try adding at one or more of these >> external points please, and in what priority? >> >> >> Terry, East Grinstead, UK >> > >I think you'd be much better off re-capping it, but you could try a >Tripp-lite Isobar. They're my standard power strip, and the 8-outlet >ones have four filter stages, so that each pair of outlets is isolated >from the others as well as from the line. > >If the problem is high-frequency crud on the line, that will probably >help, but for low frequency stuff you'd need a ferroresonant transformer. > >On the other hand, it might easily be getting in on the sensing loop, in >which case a 10 nF cap right at the terminals might be the ticket. Make >sure to keep the leads super short, like zero millimetres short. > >Cheers > >Phil Hobbs
Thanks Phil. The Tripp-lite Isobar would be impractical in my case. Not only is the mains supply to the alarm unit wired directly from the wall light switch but the under stairs cupboard is jam-packed with stuff. I'll try the small caps idea. As I've said I don't intend dismantling, it will have to be connected at the external connections. Without the circuit diagram I'm handicapped. but my loop of N/C switches are wired to #13 and #14 in my diagram. So are you suggesting a single cap to those? Obviously the lead will then be at least 5 mm in that case. Would a simple filter on one or more of the three power supplies I described also be helpful? Terry, East Grinstead, UK
On 06/04/2018 12:05 PM, Terry Pinnell wrote:
> Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote: > >> On 06/04/2018 05:55 AM, Terry Pinnell wrote: >>> My 20 year old burglar alarm control has developed a fault that I've >>> spent the last couple of days trying to fix. Before I ditch it and go >>> through the hassle of installing a new one I'm seeking help here please. >>> >>> Q1: An extreme longshot as I researched in 2012 but the company had >>> long folded, but... Anyone have or know a source of the circuit diagram >>> for the Autona 2250 Control Unit? >>> >>> FWIW, screenshot inside the control unit's case >>> https://www.dropbox.com/s/4xd19m9cvdqfpr9/Autona2250-1.jpg?dl=0 >>> >>> Q2: A useful second best would be *any* circuit of a bog-standard, >>> commercial, wired unit designed for a series of normally closed >>> microswitches. >>> >>> I made this one myself about 35 years ago and *suspect* that it will be >>> broadly similar, but I'd like to eliminate guesswork: >>> https://www.dropbox.com/s/cxl6zarvmqsnkem/Burglar%20Alarm-ex%20Leigh.gif?dl=0 >>> >>> It's being triggered spuriously. Two successive nights, 01:05 and 12:35. >>> During late stages of trouble-shooting (i.e. after checking all >>> switches) I found that I could trigger it by switching on light of the >>> cupboard in which unit is mounted, powered from same 240V source. >>> >>> I suspect a failed capacitor. But I don't relish dismantling it to get >>> at the two PCBs and even if I did I doubt I'd find it. >>> >>> Q3: Using the access I have to the power supplies (240 V AC, 15 V AC, >>> 13V DC) and the pairs of wires from the string of N/C microswitches, >>> what transient suppression should I try adding at one or more of these >>> external points please, and in what priority? >>> >>> >>> Terry, East Grinstead, UK >>> >> >> I think you'd be much better off re-capping it, but you could try a >> Tripp-lite Isobar. They're my standard power strip, and the 8-outlet >> ones have four filter stages, so that each pair of outlets is isolated >>from the others as well as from the line. >> >> If the problem is high-frequency crud on the line, that will probably >> help, but for low frequency stuff you'd need a ferroresonant transformer. >> >> On the other hand, it might easily be getting in on the sensing loop, in >> which case a 10 nF cap right at the terminals might be the ticket. Make >> sure to keep the leads super short, like zero millimetres short. >> >> Cheers >> >> Phil Hobbs > > Thanks Phil. The Tripp-lite Isobar would be impractical in my case. Not > only is the mains supply to the alarm unit wired directly from the wall > light switch but the under stairs cupboard is jam-packed with stuff. > > I'll try the small caps idea. As I've said I don't intend dismantling, > it will have to be connected at the external connections. Without the > circuit diagram I'm handicapped. but my loop of N/C switches are wired > to #13 and #14 in my diagram. So are you suggesting a single cap to > those? Obviously the lead will then be at least 5 mm in that case. > > Would a simple filter on one or more of the three power supplies I > described also be helpful? > > Terry, East Grinstead, UK >
Using megohm pulldowns in an alarm circuit is mental. You can't wet the switch contacts, and any water that gets in is liable to make the whole thing useless by shorting out one or more of the switches. If the input structure is unprotected 12V CMOS with megohm pulldowns, the 10-nf cap should help, and 100-nf might be better. You've got at least 4V of noise immunity in that circuit, so it's unlikely to be RF, in which case 5 mm leads won't make a difference. With a biggish cap across the loop terminals, any capacitive or inductive transient will pretty well go away. Another possibility is that the line transient is making the +12V rail sag by a lot if it hits at the wrong time, and when it comes back up the supply pin responds a bit faster than the loop, leading to a transient LOW input. The cap would actually make that worse, but it's a long shot--metal gate CMOS is pretty slow, and the transient LOW would only last for 100 ns or so. So the cap ought to fix it, I think. Don't use too big a capacitance, because you don't want to damage the switch contacts. You might even want to put 1k or so in series with the loop, with the cap right at the terminals. That'll let the cap wet the contacts without burning them, so the cap can be as big as you like. Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 hobbs at electrooptical dot net http://electrooptical.net
Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:

>On 06/04/2018 12:05 PM, Terry Pinnell wrote: >> Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote: >> >>> On 06/04/2018 05:55 AM, Terry Pinnell wrote: >>>> My 20 year old burglar alarm control has developed a fault that I've >>>> spent the last couple of days trying to fix. Before I ditch it and go >>>> through the hassle of installing a new one I'm seeking help here please. >>>> >>>> Q1: An extreme longshot as I researched in 2012 but the company had >>>> long folded, but... Anyone have or know a source of the circuit diagram >>>> for the Autona 2250 Control Unit? >>>> >>>> FWIW, screenshot inside the control unit's case >>>> https://www.dropbox.com/s/4xd19m9cvdqfpr9/Autona2250-1.jpg?dl=0 >>>> >>>> Q2: A useful second best would be *any* circuit of a bog-standard, >>>> commercial, wired unit designed for a series of normally closed >>>> microswitches. >>>> >>>> I made this one myself about 35 years ago and *suspect* that it will be >>>> broadly similar, but I'd like to eliminate guesswork: >>>> https://www.dropbox.com/s/cxl6zarvmqsnkem/Burglar%20Alarm-ex%20Leigh.gif?dl=0 >>>> >>>> It's being triggered spuriously. Two successive nights, 01:05 and 12:35. >>>> During late stages of trouble-shooting (i.e. after checking all >>>> switches) I found that I could trigger it by switching on light of the >>>> cupboard in which unit is mounted, powered from same 240V source. >>>> >>>> I suspect a failed capacitor. But I don't relish dismantling it to get >>>> at the two PCBs and even if I did I doubt I'd find it. >>>> >>>> Q3: Using the access I have to the power supplies (240 V AC, 15 V AC, >>>> 13V DC) and the pairs of wires from the string of N/C microswitches, >>>> what transient suppression should I try adding at one or more of these >>>> external points please, and in what priority? >>>> >>>> >>>> Terry, East Grinstead, UK >>>> >>> >>> I think you'd be much better off re-capping it, but you could try a >>> Tripp-lite Isobar. They're my standard power strip, and the 8-outlet >>> ones have four filter stages, so that each pair of outlets is isolated >>>from the others as well as from the line. >>> >>> If the problem is high-frequency crud on the line, that will probably >>> help, but for low frequency stuff you'd need a ferroresonant transformer. >>> >>> On the other hand, it might easily be getting in on the sensing loop, in >>> which case a 10 nF cap right at the terminals might be the ticket. Make >>> sure to keep the leads super short, like zero millimetres short. >>> >>> Cheers >>> >>> Phil Hobbs >> >> Thanks Phil. The Tripp-lite Isobar would be impractical in my case. Not >> only is the mains supply to the alarm unit wired directly from the wall >> light switch but the under stairs cupboard is jam-packed with stuff. >> >> I'll try the small caps idea. As I've said I don't intend dismantling, >> it will have to be connected at the external connections. Without the >> circuit diagram I'm handicapped. but my loop of N/C switches are wired >> to #13 and #14 in my diagram. So are you suggesting a single cap to >> those? Obviously the lead will then be at least 5 mm in that case. >> >> Would a simple filter on one or more of the three power supplies I >> described also be helpful? >> >> Terry, East Grinstead, UK >>
Thanks, much appreciate your sticking with me. However I'm finding much of your reply rather hard going. I'm just a shed hobbyist, and a lapsed one at that. (I finished my last project about 20 years ago. I'm into video-making now) That's mainly why I posted here rather than in S.E.D, my usual group in the past! Which circuit are you referring to there and in the following please?
>Using megohm pulldowns in an alarm circuit is mental. You can't wet the >switch contacts, and any water that gets in is liable to make the whole >thing useless by shorting out one or more of the switches.
What are your assumptions about the (to me) largely unknown Autona circuit? As mentioned, I'm guessing that it's similar to my own home made alarm. But you sound as if you're confident of that?
>If the input structure is unprotected 12V CMOS with megohm pulldowns, >the 10-nf cap should help, and 100-nf might be better. You've got at >least 4V of noise immunity in that circuit, so it's unlikely to be RF, >in which case 5 mm leads won't make a difference.
>With a biggish cap across the loop terminals, any capacitive or >inductive transient will pretty well go away. Another possibility is >that the line transient is making the +12V rail sag by a lot if it hits >at the wrong time, and when it comes back up the supply pin responds a >bit faster than the loop, leading to a transient LOW input. The cap >would actually make that worse, but it's a long shot--metal gate CMOS is >pretty slow, and the transient LOW would only last for 100 ns or so. > >So the cap ought to fix it, I think. Don't use too big a capacitance, >because you don't want to damage the switch contacts. You might even >want to put 1k or so in series with the loop, with the cap right at the >terminals. That'll let the cap wet the contacts without burning them, >so the cap can be as big as you like.
Anyway, unfortunately I've had to suspend work on fixing the noise problem. Annoyingly, although it checked out OK two days ago, I'm now *not* getting close to zero resistance with my DMM on #13 and #14. So there's a break somewhere in my 9-switch N/C loop. I wired this up two decades ago and regrettably my documentation on wiring was hasty and not done with maintenance in mind! So fixing that issue is now priority. Any tips from anyone on how to accelerate that please? Terry, East Grinstead, UK
On 06/05/2018 01:52 AM, Terry Pinnell wrote:
> Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote: > >> On 06/04/2018 12:05 PM, Terry Pinnell wrote: >>> Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote: >>> >>>> On 06/04/2018 05:55 AM, Terry Pinnell wrote: >>>>> My 20 year old burglar alarm control has developed a fault that I've >>>>> spent the last couple of days trying to fix. Before I ditch it and go >>>>> through the hassle of installing a new one I'm seeking help here please. >>>>> >>>>> Q1: An extreme longshot as I researched in 2012 but the company had >>>>> long folded, but... Anyone have or know a source of the circuit diagram >>>>> for the Autona 2250 Control Unit? >>>>> >>>>> FWIW, screenshot inside the control unit's case >>>>> https://www.dropbox.com/s/4xd19m9cvdqfpr9/Autona2250-1.jpg?dl=0 >>>>> >>>>> Q2: A useful second best would be *any* circuit of a bog-standard, >>>>> commercial, wired unit designed for a series of normally closed >>>>> microswitches. >>>>> >>>>> I made this one myself about 35 years ago and *suspect* that it will be >>>>> broadly similar, but I'd like to eliminate guesswork: >>>>> https://www.dropbox.com/s/cxl6zarvmqsnkem/Burglar%20Alarm-ex%20Leigh.gif?dl=0 >>>>> >>>>> It's being triggered spuriously. Two successive nights, 01:05 and 12:35. >>>>> During late stages of trouble-shooting (i.e. after checking all >>>>> switches) I found that I could trigger it by switching on light of the >>>>> cupboard in which unit is mounted, powered from same 240V source. >>>>> >>>>> I suspect a failed capacitor. But I don't relish dismantling it to get >>>>> at the two PCBs and even if I did I doubt I'd find it. >>>>> >>>>> Q3: Using the access I have to the power supplies (240 V AC, 15 V AC, >>>>> 13V DC) and the pairs of wires from the string of N/C microswitches, >>>>> what transient suppression should I try adding at one or more of these >>>>> external points please, and in what priority? >>>>> >>>>> >>>>> Terry, East Grinstead, UK >>>>> >>>> >>>> I think you'd be much better off re-capping it, but you could try a >>>> Tripp-lite Isobar. They're my standard power strip, and the 8-outlet >>>> ones have four filter stages, so that each pair of outlets is isolated >>> >from the others as well as from the line. >>>> >>>> If the problem is high-frequency crud on the line, that will probably >>>> help, but for low frequency stuff you'd need a ferroresonant transformer. >>>> >>>> On the other hand, it might easily be getting in on the sensing loop, in >>>> which case a 10 nF cap right at the terminals might be the ticket. Make >>>> sure to keep the leads super short, like zero millimetres short. >>>> >>>> Cheers >>>> >>>> Phil Hobbs >>> >>> Thanks Phil. The Tripp-lite Isobar would be impractical in my case. Not >>> only is the mains supply to the alarm unit wired directly from the wall >>> light switch but the under stairs cupboard is jam-packed with stuff. >>> >>> I'll try the small caps idea. As I've said I don't intend dismantling, >>> it will have to be connected at the external connections. Without the >>> circuit diagram I'm handicapped. but my loop of N/C switches are wired >>> to #13 and #14 in my diagram. So are you suggesting a single cap to >>> those? Obviously the lead will then be at least 5 mm in that case. >>> >>> Would a simple filter on one or more of the three power supplies I >>> described also be helpful? >>> >>> Terry, East Grinstead, UK >>> > > Thanks, much appreciate your sticking with me. However I'm finding much > of your reply rather hard going. I'm just a shed hobbyist, and a lapsed > one at that. (I finished my last project about 20 years ago. I'm into > video-making now) That's mainly why I posted here rather than in S.E.D, > my usual group in the past! > > Which circuit are you referring to there and in the following please? > >> Using megohm pulldowns in an alarm circuit is mental. You can't wet the >> switch contacts, and any water that gets in is liable to make the whole >> thing useless by shorting out one or more of the switches. >
I was looking at the schematic you linked. It has the loop running from +12 to a CMOS logic input, with gigantic pulldown resistors, 12M in parallel with 4.7M = 3.7M in one case. The logic threshold can be anywhere from about 1/3 to 2/3 of the supply rail, so if there's a microamp of leakage in the loop with a switch open, the alarm may not go off, and if there's 2 microamps, it definitely won't go off. That's pretty poor design, given that the alarm maker has no idea how it's going to be wired up or how the cable is going to be routed. Basements get wet, for instance.
> What are your assumptions about the (to me) largely unknown Autona > circuit? As mentioned, I'm guessing that it's similar to my own home > made alarm. But you sound as if you're confident of that? >
I hope not!
>> If the input structure is unprotected 12V CMOS with megohm pulldowns, >> the 10-nf cap should help, and 100-nf might be better. You've got at >> least 4V of noise immunity in that circuit, so it's unlikely to be RF, >> in which case 5 mm leads won't make a difference. > >> With a biggish cap across the loop terminals, any capacitive or >> inductive transient will pretty well go away. Another possibility is >> that the line transient is making the +12V rail sag by a lot if it hits >> at the wrong time, and when it comes back up the supply pin responds a >> bit faster than the loop, leading to a transient LOW input. The cap >> would actually make that worse, but it's a long shot--metal gate CMOS is >> pretty slow, and the transient LOW would only last for 100 ns or so. >> >> So the cap ought to fix it, I think. Don't use too big a capacitance, >> because you don't want to damage the switch contacts. You might even >> want to put 1k or so in series with the loop, with the cap right at the >> terminals. That'll let the cap wet the contacts without burning them, >> so the cap can be as big as you like. > > Anyway, unfortunately I've had to suspend work on fixing the noise > problem. Annoyingly, although it checked out OK two days ago, I'm now > *not* getting close to zero resistance with my DMM on #13 and #14. So > there's a break somewhere in my 9-switch N/C loop. I wired this up two > decades ago and regrettably my documentation on wiring was hasty and not > done with maintenance in mind! So fixing that issue is now priority. > > Any tips from anyone on how to accelerate that please?
Try working all the switches several times. What resistance are you getting? Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 hobbs at electrooptical dot net http://electrooptical.net
Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:

>On 06/05/2018 01:52 AM, Terry Pinnell wrote: >> Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote: >> >>> On 06/04/2018 12:05 PM, Terry Pinnell wrote: >>>> Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote: >>>> >>>>> On 06/04/2018 05:55 AM, Terry Pinnell wrote: >>>>>> My 20 year old burglar alarm control has developed a fault that I've >>>>>> spent the last couple of days trying to fix. Before I ditch it and go >>>>>> through the hassle of installing a new one I'm seeking help here please. >>>>>> >>>>>> Q1: An extreme longshot as I researched in 2012 but the company had >>>>>> long folded, but... Anyone have or know a source of the circuit diagram >>>>>> for the Autona 2250 Control Unit? >>>>>> >>>>>> FWIW, screenshot inside the control unit's case >>>>>> https://www.dropbox.com/s/4xd19m9cvdqfpr9/Autona2250-1.jpg?dl=0 >>>>>> >>>>>> Q2: A useful second best would be *any* circuit of a bog-standard, >>>>>> commercial, wired unit designed for a series of normally closed >>>>>> microswitches. >>>>>> >>>>>> I made this one myself about 35 years ago and *suspect* that it will be >>>>>> broadly similar, but I'd like to eliminate guesswork: >>>>>>
https://www.dropbox.com/s/cxl6zarvmqsnkem/Burglar%20Alarm-ex%20Leigh.gif?dl=0
>>>>>> >>>>>> It's being triggered spuriously. Two successive nights, 01:05 and 12:35. >>>>>> During late stages of trouble-shooting (i.e. after checking all >>>>>> switches) I found that I could trigger it by switching on light of the >>>>>> cupboard in which unit is mounted, powered from same 240V source. >>>>>> >>>>>> I suspect a failed capacitor. But I don't relish dismantling it to get >>>>>> at the two PCBs and even if I did I doubt I'd find it. >>>>>> >>>>>> Q3: Using the access I have to the power supplies (240 V AC, 15 V AC, >>>>>> 13V DC) and the pairs of wires from the string of N/C microswitches, >>>>>> what transient suppression should I try adding at one or more of these >>>>>> external points please, and in what priority? >>>>>> >>>>>> >>>>>> Terry, East Grinstead, UK >>>>>> >>>>> >>>>> I think you'd be much better off re-capping it, but you could try a >>>>> Tripp-lite Isobar. They're my standard power strip, and the 8-outlet >>>>> ones have four filter stages, so that each pair of outlets is isolated >>>> >from the others as well as from the line. >>>>> >>>>> If the problem is high-frequency crud on the line, that will probably >>>>> help, but for low frequency stuff you'd need a ferroresonant transformer. >>>>> >>>>> On the other hand, it might easily be getting in on the sensing loop, in >>>>> which case a 10 nF cap right at the terminals might be the ticket. Make >>>>> sure to keep the leads super short, like zero millimetres short. >>>>> >>>>> Cheers >>>>> >>>>> Phil Hobbs >>>> >>>> Thanks Phil. The Tripp-lite Isobar would be impractical in my case. Not >>>> only is the mains supply to the alarm unit wired directly from the wall >>>> light switch but the under stairs cupboard is jam-packed with stuff. >>>> >>>> I'll try the small caps idea. As I've said I don't intend dismantling, >>>> it will have to be connected at the external connections. Without the >>>> circuit diagram I'm handicapped. but my loop of N/C switches are wired >>>> to #13 and #14 in my diagram. So are you suggesting a single cap to >>>> those? Obviously the lead will then be at least 5 mm in that case. >>>> >>>> Would a simple filter on one or more of the three power supplies I >>>> described also be helpful? >>>> >>>> Terry, East Grinstead, UK >>>> >> >> Thanks, much appreciate your sticking with me. However I'm finding much >> of your reply rather hard going. I'm just a shed hobbyist, and a lapsed >> one at that. (I finished my last project about 20 years ago. I'm into >> video-making now) That's mainly why I posted here rather than in S.E.D, >> my usual group in the past! >> >> Which circuit are you referring to there and in the following please? >> >>> Using megohm pulldowns in an alarm circuit is mental. You can't wet the >>> switch contacts, and any water that gets in is liable to make the whole >>> thing useless by shorting out one or more of the switches. >> > >I was looking at the schematic you linked.
But that was not the Autona schematic! From my original post: "Anyone have or know a source of the circuit diagram for the Autona 2250 Control Unit?" "I made this one myself about 35 years ago and *suspect* that it will be broadly similar, but I'd like to eliminate guesswork: https://www.dropbox.com/s/cxl6zarvmqsnkem/Burglar%20Alarm-ex%20Leigh.gif?dl=0
>It has the loop running from >+12 to a CMOS logic input, with gigantic pulldown resistors, 12M in >parallel with 4.7M = 3.7M in one case. The logic threshold can be >anywhere from about 1/3 to 2/3 of the supply rail, so if there's a >microamp of leakage in the loop with a switch open, the alarm may not >go off, and if there's 2 microamps, it definitely won't go off. That's >pretty poor design, given that the alarm maker has no idea how it's >going to be wired up or how the cable is going to be routed. Basements >get wet, for instance.
You're undoubtedly right about the poor design (as I said, I'm a hobbyist) but I certainly knew how it was to be used!
>> What are your assumptions about the (to me) largely unknown Autona >> circuit? As mentioned, I'm guessing that it's similar to my own home >> made alarm. But you sound as if you're confident of that? >> > >I hope not!
> >>> If the input structure is unprotected 12V CMOS with megohm pulldowns, >>> the 10-nf cap should help, and 100-nf might be better. You've got at >>> least 4V of noise immunity in that circuit, so it's unlikely to be RF, >>> in which case 5 mm leads won't make a difference. >> >>> With a biggish cap across the loop terminals, any capacitive or >>> inductive transient will pretty well go away. Another possibility is >>> that the line transient is making the +12V rail sag by a lot if it hits >>> at the wrong time, and when it comes back up the supply pin responds a >>> bit faster than the loop, leading to a transient LOW input. The cap >>> would actually make that worse, but it's a long shot--metal gate CMOS is >>> pretty slow, and the transient LOW would only last for 100 ns or so. >>> >>> So the cap ought to fix it, I think. Don't use too big a capacitance, >>> because you don't want to damage the switch contacts. You might even >>> want to put 1k or so in series with the loop, with the cap right at the >>> terminals. That'll let the cap wet the contacts without burning them, >>> so the cap can be as big as you like. >> >> Anyway, unfortunately I've had to suspend work on fixing the noise >> problem. Annoyingly, although it checked out OK two days ago, I'm now >> *not* getting close to zero resistance with my DMM on #13 and #14. So >> there's a break somewhere in my 9-switch N/C loop. I wired this up two >> decades ago and regrettably my documentation on wiring was hasty and not >> done with maintenance in mind! So fixing that issue is now priority. >> >> Any tips from anyone on how to accelerate that please? > >Try working all the switches several times. What resistance are you >getting? >
The cause was down to my oversight. I'd forgotten that one of my nine switches was a PIR motion detector in the lounge. It needs a 12V supply and I was testing with all power removed. With power applied, the entire loop is now closed, so that side-issue is resolved. In the absence of any external filtering suggestions (for the AUTONA circuit!) I dismantled the unit to access the PCB. I removed all the caps and checked their capacitance. All were roughly OK so I replaced them. In the morning I'll reassemble and test, but with no optimism. In your initial reply you said "I think you'd be much better off re-capping it," and I'm now wondering if I've interpreted that correctly. Should I have literally replaced all of them regardless, despite the fact that all showed correct values? Terry, East Grinstead, UK
On 06/05/18 12:40, Terry Pinnell wrote:
> Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote: > >> On 06/05/2018 01:52 AM, Terry Pinnell wrote: >>> Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote: >>> >>>> On 06/04/2018 12:05 PM, Terry Pinnell wrote: >>>>> Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote: >>>>> >>>>>> On 06/04/2018 05:55 AM, Terry Pinnell wrote: >>>>>>> My 20 year old burglar alarm control has developed a fault that I've >>>>>>> spent the last couple of days trying to fix. Before I ditch it and go >>>>>>> through the hassle of installing a new one I'm seeking help here please. >>>>>>> >>>>>>> Q1: An extreme longshot as I researched in 2012 but the company had >>>>>>> long folded, but... Anyone have or know a source of the circuit diagram >>>>>>> for the Autona 2250 Control Unit? >>>>>>> >>>>>>> FWIW, screenshot inside the control unit's case >>>>>>> https://www.dropbox.com/s/4xd19m9cvdqfpr9/Autona2250-1.jpg?dl=0 >>>>>>> >>>>>>> Q2: A useful second best would be *any* circuit of a bog-standard, >>>>>>> commercial, wired unit designed for a series of normally closed >>>>>>> microswitches. >>>>>>> >>>>>>> I made this one myself about 35 years ago and *suspect* that it will be >>>>>>> broadly similar, but I'd like to eliminate guesswork: >>>>>>>
https://www.dropbox.com/s/cxl6zarvmqsnkem/Burglar%20Alarm-ex%20Leigh.gif?dl=0
>>>>>>> >>>>>>> It's being triggered spuriously. Two successive nights, 01:05 and 12:35. >>>>>>> During late stages of trouble-shooting (i.e. after checking all >>>>>>> switches) I found that I could trigger it by switching on light of the >>>>>>> cupboard in which unit is mounted, powered from same 240V source. >>>>>>> >>>>>>> I suspect a failed capacitor. But I don't relish dismantling it to get >>>>>>> at the two PCBs and even if I did I doubt I'd find it. >>>>>>> >>>>>>> Q3: Using the access I have to the power supplies (240 V AC, 15 V AC, >>>>>>> 13V DC) and the pairs of wires from the string of N/C microswitches, >>>>>>> what transient suppression should I try adding at one or more of these >>>>>>> external points please, and in what priority? >>>>>>> >>>>>>> >>>>>>> Terry, East Grinstead, UK >>>>>>> >>>>>> >>>>>> I think you'd be much better off re-capping it, but you could try a >>>>>> Tripp-lite Isobar. They're my standard power strip, and the 8-outlet >>>>>> ones have four filter stages, so that each pair of outlets is isolated >>>>> >from the others as well as from the line. >>>>>> >>>>>> If the problem is high-frequency crud on the line, that will probably >>>>>> help, but for low frequency stuff you'd need a ferroresonant transformer. >>>>>> >>>>>> On the other hand, it might easily be getting in on the sensing loop, in >>>>>> which case a 10 nF cap right at the terminals might be the ticket. Make >>>>>> sure to keep the leads super short, like zero millimetres short. >>>>>> >>>>>> Cheers >>>>>> >>>>>> Phil Hobbs >>>>> >>>>> Thanks Phil. The Tripp-lite Isobar would be impractical in my case. Not >>>>> only is the mains supply to the alarm unit wired directly from the wall >>>>> light switch but the under stairs cupboard is jam-packed with stuff. >>>>> >>>>> I'll try the small caps idea. As I've said I don't intend dismantling, >>>>> it will have to be connected at the external connections. Without the >>>>> circuit diagram I'm handicapped. but my loop of N/C switches are wired >>>>> to #13 and #14 in my diagram. So are you suggesting a single cap to >>>>> those? Obviously the lead will then be at least 5 mm in that case. >>>>> >>>>> Would a simple filter on one or more of the three power supplies I >>>>> described also be helpful? >>>>> >>>>> Terry, East Grinstead, UK >>>>> >>> >>> Thanks, much appreciate your sticking with me. However I'm finding much >>> of your reply rather hard going. I'm just a shed hobbyist, and a lapsed >>> one at that. (I finished my last project about 20 years ago. I'm into >>> video-making now) That's mainly why I posted here rather than in S.E.D, >>> my usual group in the past! >>> >>> Which circuit are you referring to there and in the following please? >>> >>>> Using megohm pulldowns in an alarm circuit is mental. You can't wet the >>>> switch contacts, and any water that gets in is liable to make the whole >>>> thing useless by shorting out one or more of the switches. >>> >> >> I was looking at the schematic you linked. > > But that was not the Autona schematic! > > From my original post: > > "Anyone have or know a source of the circuit diagram for the Autona 2250 > Control Unit?" > > "I made this one myself about 35 years ago and *suspect* that it will be > broadly similar, but I'd like to eliminate guesswork: > https://www.dropbox.com/s/cxl6zarvmqsnkem/Burglar%20Alarm-ex%20Leigh.gif?dl=0 > >> It has the loop running from >> +12 to a CMOS logic input, with gigantic pulldown resistors, 12M in >> parallel with 4.7M = 3.7M in one case. The logic threshold can be >> anywhere from about 1/3 to 2/3 of the supply rail, so if there's a >> microamp of leakage in the loop with a switch open, the alarm may not >> go off, and if there's 2 microamps, it definitely won't go off. That's >> pretty poor design, given that the alarm maker has no idea how it's >> going to be wired up or how the cable is going to be routed. Basements >> get wet, for instance. > > You're undoubtedly right about the poor design (as I said, I'm a > hobbyist) but I certainly knew how it was to be used! > >>> What are your assumptions about the (to me) largely unknown Autona >>> circuit? As mentioned, I'm guessing that it's similar to my own home >>> made alarm. But you sound as if you're confident of that? >>> >> >> I hope not! > >> >>>> If the input structure is unprotected 12V CMOS with megohm pulldowns, >>>> the 10-nf cap should help, and 100-nf might be better. You've got at >>>> least 4V of noise immunity in that circuit, so it's unlikely to be RF, >>>> in which case 5 mm leads won't make a difference. >>> >>>> With a biggish cap across the loop terminals, any capacitive or >>>> inductive transient will pretty well go away. Another possibility is >>>> that the line transient is making the +12V rail sag by a lot if it hits >>>> at the wrong time, and when it comes back up the supply pin responds a >>>> bit faster than the loop, leading to a transient LOW input. The cap >>>> would actually make that worse, but it's a long shot--metal gate CMOS is >>>> pretty slow, and the transient LOW would only last for 100 ns or so. >>>> >>>> So the cap ought to fix it, I think. Don't use too big a capacitance, >>>> because you don't want to damage the switch contacts. You might even >>>> want to put 1k or so in series with the loop, with the cap right at the >>>> terminals. That'll let the cap wet the contacts without burning them, >>>> so the cap can be as big as you like. >>> >>> Anyway, unfortunately I've had to suspend work on fixing the noise >>> problem. Annoyingly, although it checked out OK two days ago, I'm now >>> *not* getting close to zero resistance with my DMM on #13 and #14. So >>> there's a break somewhere in my 9-switch N/C loop. I wired this up two >>> decades ago and regrettably my documentation on wiring was hasty and not >>> done with maintenance in mind! So fixing that issue is now priority. >>> >>> Any tips from anyone on how to accelerate that please? >> >> Try working all the switches several times. What resistance are you >> getting? >> > > The cause was down to my oversight. I'd forgotten that one of my nine > switches was a PIR motion detector in the lounge. It needs a 12V supply > and I was testing with all power removed. With power applied, the entire > loop is now closed, so that side-issue is resolved. > > In the absence of any external filtering suggestions (for the AUTONA > circuit!) I dismantled the unit to access the PCB. I removed all the > caps and checked their capacitance. All were roughly OK so I replaced > them. In the morning I'll reassemble and test, but with no optimism. > > In your initial reply you said "I think you'd be much better off > re-capping it," and I'm now wondering if I've interpreted that > correctly. Should I have literally replaced all of them regardless, > despite the fact that all showed correct values? > > Terry, East Grinstead, UK >
In the modern era (say since 1975) it's really only wet electrolytics that have the problem. It's not the capacitance that's usually the issue, but the effective series resistance (ESR). As caps dry out, the ESR goes up, so an ESR tester is the thing. Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics Briarcliff Manor NY 10510 http://electrooptical.net http://hobbs-eo.com
Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:

>On 06/05/18 12:40, Terry Pinnell wrote: >> Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote: >> >>> On 06/05/2018 01:52 AM, Terry Pinnell wrote: >>>> Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote: >>>> >>>>> On 06/04/2018 12:05 PM, Terry Pinnell wrote: >>>>>> Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote: >>>>>> >>>>>>> On 06/04/2018 05:55 AM, Terry Pinnell wrote: >>>>>>>> My 20 year old burglar alarm control has developed a fault that I've >>>>>>>> spent the last couple of days trying to fix. Before I ditch it and go >>>>>>>> through the hassle of installing a new one I'm seeking help here please. >>>>>>>> >>>>>>>> Q1: An extreme longshot as I researched in 2012 but the company had >>>>>>>> long folded, but... Anyone have or know a source of the circuit diagram >>>>>>>> for the Autona 2250 Control Unit? >>>>>>>> >>>>>>>> FWIW, screenshot inside the control unit's case >>>>>>>> https://www.dropbox.com/s/4xd19m9cvdqfpr9/Autona2250-1.jpg?dl=0 >>>>>>>> >>>>>>>> Q2: A useful second best would be *any* circuit of a bog-standard, >>>>>>>> commercial, wired unit designed for a series of normally closed >>>>>>>> microswitches. >>>>>>>> >>>>>>>> I made this one myself about 35 years ago and *suspect* that it will be >>>>>>>> broadly similar, but I'd like to eliminate guesswork: >>>>>>>>
https://www.dropbox.com/s/cxl6zarvmqsnkem/Burglar%20Alarm-ex%20Leigh.gif?dl=0
>>>>>>>> >>>>>>>> It's being triggered spuriously. Two successive nights, 01:05 and 12:35. >>>>>>>> During late stages of trouble-shooting (i.e. after checking all >>>>>>>> switches) I found that I could trigger it by switching on light of the >>>>>>>> cupboard in which unit is mounted, powered from same 240V source. >>>>>>>> >>>>>>>> I suspect a failed capacitor. But I don't relish dismantling it to get >>>>>>>> at the two PCBs and even if I did I doubt I'd find it. >>>>>>>> >>>>>>>> Q3: Using the access I have to the power supplies (240 V AC, 15 V AC, >>>>>>>> 13V DC) and the pairs of wires from the string of N/C microswitches, >>>>>>>> what transient suppression should I try adding at one or more of these >>>>>>>> external points please, and in what priority? >>>>>>>> >>>>>>>> >>>>>>>> Terry, East Grinstead, UK >>>>>>>> >>>>>>> >>>>>>> I think you'd be much better off re-capping it, but you could try a >>>>>>> Tripp-lite Isobar. They're my standard power strip, and the 8-outlet >>>>>>> ones have four filter stages, so that each pair of outlets is isolated >>>>>> >from the others as well as from the line. >>>>>>> >>>>>>> If the problem is high-frequency crud on the line, that will probably >>>>>>> help, but for low frequency stuff you'd need a ferroresonant transformer. >>>>>>> >>>>>>> On the other hand, it might easily be getting in on the sensing loop, in >>>>>>> which case a 10 nF cap right at the terminals might be the ticket. Make >>>>>>> sure to keep the leads super short, like zero millimetres short. >>>>>>> >>>>>>> Cheers >>>>>>> >>>>>>> Phil Hobbs >>>>>> >>>>>> Thanks Phil. The Tripp-lite Isobar would be impractical in my case. Not >>>>>> only is the mains supply to the alarm unit wired directly from the wall >>>>>> light switch but the under stairs cupboard is jam-packed with stuff. >>>>>> >>>>>> I'll try the small caps idea. As I've said I don't intend dismantling, >>>>>> it will have to be connected at the external connections. Without the >>>>>> circuit diagram I'm handicapped. but my loop of N/C switches are wired >>>>>> to #13 and #14 in my diagram. So are you suggesting a single cap to >>>>>> those? Obviously the lead will then be at least 5 mm in that case. >>>>>> >>>>>> Would a simple filter on one or more of the three power supplies I >>>>>> described also be helpful? >>>>>> >>>>>> Terry, East Grinstead, UK >>>>>> >>>> >>>> Thanks, much appreciate your sticking with me. However I'm finding much >>>> of your reply rather hard going. I'm just a shed hobbyist, and a lapsed >>>> one at that. (I finished my last project about 20 years ago. I'm into >>>> video-making now) That's mainly why I posted here rather than in S.E.D, >>>> my usual group in the past! >>>> >>>> Which circuit are you referring to there and in the following please? >>>> >>>>> Using megohm pulldowns in an alarm circuit is mental. You can't wet the >>>>> switch contacts, and any water that gets in is liable to make the whole >>>>> thing useless by shorting out one or more of the switches. >>>> >>> >>> I was looking at the schematic you linked. >> >> But that was not the Autona schematic! >> >> From my original post: >> >> "Anyone have or know a source of the circuit diagram for the Autona 2250 >> Control Unit?" >> >> "I made this one myself about 35 years ago and *suspect* that it will be >> broadly similar, but I'd like to eliminate guesswork: >> https://www.dropbox.com/s/cxl6zarvmqsnkem/Burglar%20Alarm-ex%20Leigh.gif?dl=0 >> >>> It has the loop running from >>> +12 to a CMOS logic input, with gigantic pulldown resistors, 12M in >>> parallel with 4.7M = 3.7M in one case. The logic threshold can be >>> anywhere from about 1/3 to 2/3 of the supply rail, so if there's a >>> microamp of leakage in the loop with a switch open, the alarm may not >>> go off, and if there's 2 microamps, it definitely won't go off. That's >>> pretty poor design, given that the alarm maker has no idea how it's >>> going to be wired up or how the cable is going to be routed. Basements >>> get wet, for instance. >> >> You're undoubtedly right about the poor design (as I said, I'm a >> hobbyist) but I certainly knew how it was to be used! >> >>>> What are your assumptions about the (to me) largely unknown Autona >>>> circuit? As mentioned, I'm guessing that it's similar to my own home >>>> made alarm. But you sound as if you're confident of that? >>>> >>> >>> I hope not! >> >>> >>>>> If the input structure is unprotected 12V CMOS with megohm pulldowns, >>>>> the 10-nf cap should help, and 100-nf might be better. You've got at >>>>> least 4V of noise immunity in that circuit, so it's unlikely to be RF, >>>>> in which case 5 mm leads won't make a difference. >>>> >>>>> With a biggish cap across the loop terminals, any capacitive or >>>>> inductive transient will pretty well go away. Another possibility is >>>>> that the line transient is making the +12V rail sag by a lot if it hits >>>>> at the wrong time, and when it comes back up the supply pin responds a >>>>> bit faster than the loop, leading to a transient LOW input. The cap >>>>> would actually make that worse, but it's a long shot--metal gate CMOS is >>>>> pretty slow, and the transient LOW would only last for 100 ns or so. >>>>> >>>>> So the cap ought to fix it, I think. Don't use too big a capacitance, >>>>> because you don't want to damage the switch contacts. You might even >>>>> want to put 1k or so in series with the loop, with the cap right at the >>>>> terminals. That'll let the cap wet the contacts without burning them, >>>>> so the cap can be as big as you like. >>>> >>>> Anyway, unfortunately I've had to suspend work on fixing the noise >>>> problem. Annoyingly, although it checked out OK two days ago, I'm now >>>> *not* getting close to zero resistance with my DMM on #13 and #14. So >>>> there's a break somewhere in my 9-switch N/C loop. I wired this up two >>>> decades ago and regrettably my documentation on wiring was hasty and not >>>> done with maintenance in mind! So fixing that issue is now priority. >>>> >>>> Any tips from anyone on how to accelerate that please? >>> >>> Try working all the switches several times. What resistance are you >>> getting? >>> >> >> The cause was down to my oversight. I'd forgotten that one of my nine >> switches was a PIR motion detector in the lounge. It needs a 12V supply >> and I was testing with all power removed. With power applied, the entire >> loop is now closed, so that side-issue is resolved. >> >> In the absence of any external filtering suggestions (for the AUTONA >> circuit!) I dismantled the unit to access the PCB. I removed all the >> caps and checked their capacitance. All were roughly OK so I replaced >> them. In the morning I'll reassemble and test, but with no optimism. >> >> In your initial reply you said "I think you'd be much better off >> re-capping it," and I'm now wondering if I've interpreted that >> correctly. Should I have literally replaced all of them regardless, >> despite the fact that all showed correct values? >> >> Terry, East Grinstead, UK >> >In the modern era (say since 1975) it's really only wet electrolytics >that have the problem. It's not the capacitance that's usually the >issue, but the effective series resistance (ESR). As caps dry out, the >ESR goes up, so an ESR tester is the thing. > >Cheers > >Phil Hobbs
Thanks, understood. I reckon it was a waste of effort removing and replacing five caps yesterday. I'd missed Cursitor Doom's reply to stevwolf18 in the 'Capacitor Tester' thread: "If whatever meter you have won't measure ESR, you're wasting your time." And also not spotted that his tester is an Atlas ESR https://www.peakelec.co.uk/acatalog/jz_esr70.html not an Atlas LCR like mine. I'm reluctant to spend on an ESR tester. Seems unlikely I'd use it a lot. Is there any other way I can test whether one of the five caps (1uF, 3 x 47uF, 2200uF) is the cause of the spurious alarm activation? BTW, I see no 'bulging' in any of them. Returning to Q3 of my original three questions, from the little you know about the Autona unit can you suggest any practical advice like: "Try a filter like this...across the mains." "Try a filter like this ... across the transformer secondary." "Try an RC filter like this ... across the 12V DC supply, or like this in series with it..." "Try X ohms in series with input to connector #13 and Y uf to any 0V connector". (#13/#14 are the 'loop' connections, as shown in my original illustration.) IOW, anything practical I can try. Terry, East Grinstead, UK
On Wednesday, June 6, 2018 at 9:38:26 AM UTC-7, Terry Pinnell wrote:
> Is there any other way I can test whether one of the five caps (1uF, 3 x > 47uF, 2200uF) is the cause of the spurious alarm activation? BTW, I see > no 'bulging' in any of them.
Here in Silicon Valley, the total price for all of those would be less than US$2 for 50 WVDC at a retail hobbyist store (and even less for lower voltages). If you do not already have them in your junque box, and because this is a one-time event, I would just replace them all. Even at hobbyist rates, your time is probably worth more than that.