On 06/07/2018 07:03 AM, Terry Pinnell wrote:
> Terry Pinnell <me@somewhere.invalid> wrote:
>
>> Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:
>>
>>> On 06/06/2018 12:38 PM, Terry Pinnell wrote:
>>>> 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
>>>
>>>
>>> LoopA 0-----RRRR-----*---------> Terminal block 13 or 15 or 17
>>> 510 |
>>> CCC
>>> CCC 100 nF
>>> |
>>> LoopB 0--------------*---------> Terminal block 14 or 16 or 18
>>>
>>> The 510-ohm resistor will let the cap supply 24 mA briefly, which is
>>> probably enough to wet the contacts but certainly not enough to burn
>>> them. The peak power dissipation will be about 1-1/4 watts, but it's
>>> only for 50 microseconds, so a half-watt resistor should be fine.
>>>
>>> Cheers
>>>
>>> Phil Hobbs
>>
>> Many thanks, hope to try that later today.
>>
>> Terry, East Grinstead, UK
>
> Before trying your filter I re-assembled in the slight hope that my
> removal/replacement (and touching up a couple of joint that looked
> mildly suspicious) might have fixed the spurious triggering. I tried a
> few dozen times, switching the cupboard lamp on/off as described
> earlier, and so far so good!
>
> Left the temporary sounder in place to try over a few successive nights
> and will report back on final outcome.
>
> Thanks for your patient help, which is much appreciated.
>
> Terry, East Grinstead, UK
>
No worries. Now move somewhere where there are fewer burglars. ;)
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