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Surrendering to the 555 Timer Option

Started by Ricky C May 11, 2020
On 5/12/2020 12:19 AM, bitrex wrote:
> On 5/11/2020 10:31 PM, Ricky C wrote: >> On Monday, May 11, 2020 at 10:11:56 PM UTC-4, bitrex wrote: >>> On 5/11/2020 9:13 PM, Ricky C wrote: >>>> On Monday, May 11, 2020 at 8:06:14 PM UTC-4, Jon Elson wrote: >>>>> edward.ming.lee@gmail.com wrote: >>>>> >>>>>> On Monday, May 11, 2020 at 9:50:01 AM UTC-7, Jon Elson wrote: >>>>>>> Ricky C wrote: >>>>>>> >>>>>>> >>>>>>>> I need to turn on a sounder for 1 second out of 4. >>>>>>> >>>>>>> Why not use an ATTINY13A microcontroller chip?  It is truly >>>>>>> micropower, >>>>>>> can >>>>>>> be programmed in C, and has 5 general-purpose I/O pins.  Your >>>>>>> program >>>>>>> should >>>>>>> only be a couple lines of code.  This chip casts about $0.50 in low >>>>>>> quantity, a programmer can be had on eBay for about $10 and the >>>>>>> development software is all free. >>>>>> >>>>>> 555 timers goes for around 10 cents. >>>>> Plus at least 3 additional components, including a pretty large, >>>>> low-leakage >>>>> capacitor.  the ATTINY13A only requires a decoupling cap, and maybe >>>>> will run >>>>> without.  Also, getting large asymmetry of the on/off time can be >>>>> an issue >>>>> with the 555.  With the micro, you can get any time you want.  I am >>>>> not one >>>>> of those "put a micro in everything" guys, but this particular case >>>>> does >>>>> seem to warrant it.  In general, I don't like seeing RC timers with >>>>> delays >>>>> over a second. >>>> >>>> Normally I *am* one of the "digital is great" guys.  But in this >>>> case the design is for a ventilator which is mostly made of off the >>>> shelf electronics.  I am shooting for no use of anything that might >>>> not be so available down the road and the circuits should be easy to >>>> make in low tech processes.  So while programming MCUs are not >>>> exactly state of the art, I prefer to not use it if I can avoid it. >>>> There's also the issue of power supply.  When the thing is first >>>> powering up there is no voltage on the supercap.  I suppose I could >>>> use a couple of diodes to multiple source the MCU power.  I did look >>>> at the idea a while back since it is an obvious route.  I need at >>>> least two comparators which is not hard to find in MCUs either. >>>> >>>> The remaining part of the circuit is a constant current source to >>>> charge up the supercap.  I suppose that could be done by the MCU and >>>> a pass transistor.  If a PNP were used would that provide reverse >>>> current flow protection?  I suppose if the base were held at the >>>> collector voltage it would reverse bias the BE junction and prevent >>>> flow.  Otherwise the CB junction would be forward biased and the PNP >>>> would act as a very poor transistor still, no? >>>> >>>> I think the hard spec would be for the MCU to continue to work down >>>> to 2.0 volts or below.  I suppose a watch CPU would work at very low >>>> voltages, but then we are back to hard to source components.  How >>>> many MCUs are built to work over 2.0 to 5.25 volts with two >>>> comparators and/or an ADC? >>>> >>> >>> I reviewed the ventilator schematic that one company made public, you'll >>> be happy to know it uses a 555 timer! >>> >>> Other than that the business-end of the main board is not too >>> complicated; H-bridges to drive the blower motors and a bit of glue >>> logic. >>> >>> The rest of the commercial ventilator design is power supplies, a >>> relatively antiquated microprocessor board, display and display >>> driver/lighting circuitry, and boards with the chips for all the >>> external sensors that integrate mass airflow, velocity, O2 level, >>> respiration rate, and such into the microprocessor. >> >> Sounds a lot like what these guys are doing.  I don't know what they >> are using for the important sensors.  They have some kit type >> temperature sensor boards like they sell at the hobby shops.  Same for >> the H bridge, L298N.  Funny you can get modules from aliexpress >> cheaper than the chip at Digikey!  They seem to be using an Arduino >> Uno for the device controller.  Not sure what they are using for the >> display or controls yet. >> > > The commercial vent design looked both over-engineered and antiquated > simultaneously like a lot of medical/aerospace stuff. A lot of swish $2 > op-amps and comparators (maybe because it was designed to run off > battery-power for a while but for low frequency/DC tasks like they were > in not really necessary) doing pedestrian things plus an obscure > processor using external RAM and ROM like an embedded device from the > early 90s.
Maybe they're only allowed to use "medical grade" op amps or something. IDK much about the standards for life-critical designs, not an area I would much like to get into. is there a "medical grade" 555?
On Monday, May 11, 2020 at 7:21:16 AM UTC-4, piglet wrote:
> On 11/05/2020 9:22 am, Jasen Betts wrote: > > > > CD4060 does an execellent low power oscillator, 3:1 can be > > got with a pair of diodes, but 2V is a bit low. > > > > Correct. The CD4060 is not spec'd below 3V but the 74HC4060 is most > definitely spec'd from 2V to 6V. Assuming a osc frequency can be found > where the HC4060 runs at low enough Idd to satisfy the OP then something > like this might suffice .... > > <www.dropbox.com/s/l6aahkcdghpcxps/4060beeper1in4.jpg?raw=1> > > I drew a 2n7002 for the gate but that part will have too high Vgson for > 2V use and a better choice substituted. > > piglet
I don't have an NPN or NFET in the BOM, just a PNP and a PFET. I could use the PNP as pair of diodes for a wire OR, but that's going to put a minimum Vgs of about 0.7 volts which might be too much and turn it on with only a 3 mA load. There is nothing in the data sheet of the HC4060 to make me think it can source the 3 mA directly without more voltage loss than I'd prefer. I was going to say I could drive the load directly from the 555 timer, but the CMOS version has more voltage drop than I'd like. As I think about this, I'm starting to like the HC4060. I can use the spare section of JK FF to turn the 0, 1, 2, 3 count into a single pulse of each four. Using different taps will allow patterns which might be better than a single beep every four seconds. I am having trouble finding a 74HC4060 spice file. Nexperia has something called hc_tnomi.cir, but it doesn't seem to be a functional model, just timing or drive capability. When I tried to bring it into LTspice it generated a 5 pin model with the pins named 0, 1, 2, 3, 5. I see CD4060 models mentioned people have created, but the files seem to be hosted on dead sites. I found files in the LTspice group, but I can't seem to make them work. One of them is CD4060Bg-model.txt which contains ".SUBCKT CD4060Bg". Should this be renames as a .lib or some other file? The .asy file and a test schematic are provided. It can't seem to find the guts complaining about an unknown subcircuit. I do find LTspice to be one of the most confusing to use tools I've ever encountered. It's one of those things that you have to stay fresh with or the details just kill you. I'm really liking this approach though, so I'm willing to put up with a bit of effort to simulate this circuit. -- Rick C. -- Get 1,000 miles of free Supercharging -- Tesla referral code - https://ts.la/richard11209
On Monday, May 11, 2020 at 10:13:31 PM UTC-4, bitrex wrote:
> On 5/11/2020 10:11 PM, bitrex wrote: > > On 5/11/2020 9:13 PM, Ricky C wrote: > >> On Monday, May 11, 2020 at 8:06:14 PM UTC-4, Jon Elson wrote: > >>> edward.ming.lee@gmail.com wrote: > >>> > >>>> On Monday, May 11, 2020 at 9:50:01 AM UTC-7, Jon Elson wrote: > >>>>> Ricky C wrote: > >>>>> > >>>>> > >>>>>> I need to turn on a sounder for 1 second out of 4. > >>>>> > >>>>> Why not use an ATTINY13A microcontroller chip?&nbsp; It is truly > >>>>> micropower, > >>>>> can > >>>>> be programmed in C, and has 5 general-purpose I/O pins.&nbsp; Your program > >>>>> should > >>>>> only be a couple lines of code.&nbsp; This chip casts about $0.50 in low > >>>>> quantity, a programmer can be had on eBay for about $10 and the > >>>>> development software is all free. > >>>> > >>>> 555 timers goes for around 10 cents. > >>> Plus at least 3 additional components, including a pretty large, > >>> low-leakage > >>> capacitor.&nbsp; the ATTINY13A only requires a decoupling cap, and maybe > >>> will run > >>> without.&nbsp; Also, getting large asymmetry of the on/off time can be an > >>> issue > >>> with the 555.&nbsp; With the micro, you can get any time you want.&nbsp; I am > >>> not one > >>> of those "put a micro in everything" guys, but this particular case does > >>> seem to warrant it.&nbsp; In general, I don't like seeing RC timers with > >>> delays > >>> over a second. > >> > >> Normally I *am* one of the "digital is great" guys.&nbsp; But in this case > >> the design is for a ventilator which is mostly made of off the shelf > >> electronics.&nbsp; I am shooting for no use of anything that might not be > >> so available down the road and the circuits should be easy to make in > >> low tech processes.&nbsp; So while programming MCUs are not exactly state > >> of the art, I prefer to not use it if I can avoid it.&nbsp; There's also > >> the issue of power supply.&nbsp; When the thing is first powering up there > >> is no voltage on the supercap.&nbsp; I suppose I could use a couple of > >> diodes to multiple source the MCU power.&nbsp; I did look at the idea a > >> while back since it is an obvious route.&nbsp; I need at least two > >> comparators which is not hard to find in MCUs either. > >> > >> The remaining part of the circuit is a constant current source to > >> charge up the supercap.&nbsp; I suppose that could be done by the MCU and a > >> pass transistor.&nbsp; If a PNP were used would that provide reverse > >> current flow protection?&nbsp; I suppose if the base were held at the > >> collector voltage it would reverse bias the BE junction and prevent > >> flow.&nbsp; Otherwise the CB junction would be forward biased and the PNP > >> would act as a very poor transistor still, no? > >> > >> I think the hard spec would be for the MCU to continue to work down to > >> 2.0 volts or below.&nbsp; I suppose a watch CPU would work at very low > >> voltages, but then we are back to hard to source components.&nbsp; How many > >> MCUs are built to work over 2.0 to 5.25 volts with two comparators > >> and/or an ADC? > >> > > > > I reviewed the ventilator schematic that one company made public, you'll > > be happy to know it uses a 555 timer! > > In a fairly pedestrian way tho, generating a clock for the motor-driver > H-bridges I believe.
I think they are doing all that in the software or at least in the Arduino. I've only been to a couple of meetings and the software isn't talked about in much detail. -- Rick C. +- Get 1,000 miles of free Supercharging +- Tesla referral code - https://ts.la/richard11209
On Tuesday, May 12, 2020 at 12:23:40 AM UTC-4, bitrex wrote:
> On 5/12/2020 12:19 AM, bitrex wrote: > > On 5/11/2020 10:31 PM, Ricky C wrote: > >> On Monday, May 11, 2020 at 10:11:56 PM UTC-4, bitrex wrote: > >>> On 5/11/2020 9:13 PM, Ricky C wrote: > >>>> On Monday, May 11, 2020 at 8:06:14 PM UTC-4, Jon Elson wrote: > >>>>> edward.ming.lee@gmail.com wrote: > >>>>> > >>>>>> On Monday, May 11, 2020 at 9:50:01 AM UTC-7, Jon Elson wrote: > >>>>>>> Ricky C wrote: > >>>>>>> > >>>>>>> > >>>>>>>> I need to turn on a sounder for 1 second out of 4. > >>>>>>> > >>>>>>> Why not use an ATTINY13A microcontroller chip?&nbsp; It is truly > >>>>>>> micropower, > >>>>>>> can > >>>>>>> be programmed in C, and has 5 general-purpose I/O pins.&nbsp; Your > >>>>>>> program > >>>>>>> should > >>>>>>> only be a couple lines of code.&nbsp; This chip casts about $0.50 in low > >>>>>>> quantity, a programmer can be had on eBay for about $10 and the > >>>>>>> development software is all free. > >>>>>> > >>>>>> 555 timers goes for around 10 cents. > >>>>> Plus at least 3 additional components, including a pretty large, > >>>>> low-leakage > >>>>> capacitor.&nbsp; the ATTINY13A only requires a decoupling cap, and maybe > >>>>> will run > >>>>> without.&nbsp; Also, getting large asymmetry of the on/off time can be > >>>>> an issue > >>>>> with the 555.&nbsp; With the micro, you can get any time you want.&nbsp; I am > >>>>> not one > >>>>> of those "put a micro in everything" guys, but this particular case > >>>>> does > >>>>> seem to warrant it.&nbsp; In general, I don't like seeing RC timers with > >>>>> delays > >>>>> over a second. > >>>> > >>>> Normally I *am* one of the "digital is great" guys.&nbsp; But in this > >>>> case the design is for a ventilator which is mostly made of off the > >>>> shelf electronics.&nbsp; I am shooting for no use of anything that might > >>>> not be so available down the road and the circuits should be easy to > >>>> make in low tech processes.&nbsp; So while programming MCUs are not > >>>> exactly state of the art, I prefer to not use it if I can avoid it. > >>>> There's also the issue of power supply.&nbsp; When the thing is first > >>>> powering up there is no voltage on the supercap.&nbsp; I suppose I could > >>>> use a couple of diodes to multiple source the MCU power.&nbsp; I did look > >>>> at the idea a while back since it is an obvious route.&nbsp; I need at > >>>> least two comparators which is not hard to find in MCUs either. > >>>> > >>>> The remaining part of the circuit is a constant current source to > >>>> charge up the supercap.&nbsp; I suppose that could be done by the MCU and > >>>> a pass transistor.&nbsp; If a PNP were used would that provide reverse > >>>> current flow protection?&nbsp; I suppose if the base were held at the > >>>> collector voltage it would reverse bias the BE junction and prevent > >>>> flow.&nbsp; Otherwise the CB junction would be forward biased and the PNP > >>>> would act as a very poor transistor still, no? > >>>> > >>>> I think the hard spec would be for the MCU to continue to work down > >>>> to 2.0 volts or below.&nbsp; I suppose a watch CPU would work at very low > >>>> voltages, but then we are back to hard to source components.&nbsp; How > >>>> many MCUs are built to work over 2.0 to 5.25 volts with two > >>>> comparators and/or an ADC? > >>>> > >>> > >>> I reviewed the ventilator schematic that one company made public, you'll > >>> be happy to know it uses a 555 timer! > >>> > >>> Other than that the business-end of the main board is not too > >>> complicated; H-bridges to drive the blower motors and a bit of glue > >>> logic. > >>> > >>> The rest of the commercial ventilator design is power supplies, a > >>> relatively antiquated microprocessor board, display and display > >>> driver/lighting circuitry, and boards with the chips for all the > >>> external sensors that integrate mass airflow, velocity, O2 level, > >>> respiration rate, and such into the microprocessor. > >> > >> Sounds a lot like what these guys are doing.&nbsp; I don't know what they > >> are using for the important sensors.&nbsp; They have some kit type > >> temperature sensor boards like they sell at the hobby shops.&nbsp; Same for > >> the H bridge, L298N.&nbsp; Funny you can get modules from aliexpress > >> cheaper than the chip at Digikey!&nbsp; They seem to be using an Arduino > >> Uno for the device controller.&nbsp; Not sure what they are using for the > >> display or controls yet. > >> > > > > The commercial vent design looked both over-engineered and antiquated > > simultaneously like a lot of medical/aerospace stuff. A lot of swish $2 > > op-amps and comparators (maybe because it was designed to run off > > battery-power for a while but for low frequency/DC tasks like they were > > in not really necessary) doing pedestrian things plus an obscure > > processor using external RAM and ROM like an embedded device from the > > early 90s. > > Maybe they're only allowed to use "medical grade" op amps or something. > IDK much about the standards for life-critical designs, not an area I > would much like to get into. is there a "medical grade" 555?
Medical equipment has to be proven to not harm the patient. It is not required to otherwise be fail safe. Military gear often has to continue working in spite of any single failure. That's a different animal indeed. I don't know what the restrictions are on this project. It is entirely possible it will never produce anything other than a hobby project. There are any number of alternative ventilator designs that simply were never produced for who knows what reason. One question I have not asked is even if they design this device and get someone to produce it, how do they know anyone wants to use it? Have they asked any of the end users what they need? What they require it to do and how it will fit into a medical setting. Not my problem. I'm just designing an alarm board. They might ask me to lay out other parts. -- Rick C. ++ Get 1,000 miles of free Supercharging ++ Tesla referral code - https://ts.la/richard11209
On 5/12/2020 1:40 AM, Ricky C wrote:
> On Monday, May 11, 2020 at 10:13:31 PM UTC-4, bitrex wrote: >> On 5/11/2020 10:11 PM, bitrex wrote: >>> On 5/11/2020 9:13 PM, Ricky C wrote: >>>> On Monday, May 11, 2020 at 8:06:14 PM UTC-4, Jon Elson wrote: >>>>> edward.ming.lee@gmail.com wrote: >>>>> >>>>>> On Monday, May 11, 2020 at 9:50:01 AM UTC-7, Jon Elson wrote: >>>>>>> Ricky C wrote: >>>>>>> >>>>>>> >>>>>>>> I need to turn on a sounder for 1 second out of 4. >>>>>>> >>>>>>> Why not use an ATTINY13A microcontroller chip?&nbsp; It is truly >>>>>>> micropower, >>>>>>> can >>>>>>> be programmed in C, and has 5 general-purpose I/O pins.&nbsp; Your program >>>>>>> should >>>>>>> only be a couple lines of code.&nbsp; This chip casts about $0.50 in low >>>>>>> quantity, a programmer can be had on eBay for about $10 and the >>>>>>> development software is all free. >>>>>> >>>>>> 555 timers goes for around 10 cents. >>>>> Plus at least 3 additional components, including a pretty large, >>>>> low-leakage >>>>> capacitor.&nbsp; the ATTINY13A only requires a decoupling cap, and maybe >>>>> will run >>>>> without.&nbsp; Also, getting large asymmetry of the on/off time can be an >>>>> issue >>>>> with the 555.&nbsp; With the micro, you can get any time you want.&nbsp; I am >>>>> not one >>>>> of those "put a micro in everything" guys, but this particular case does >>>>> seem to warrant it.&nbsp; In general, I don't like seeing RC timers with >>>>> delays >>>>> over a second. >>>> >>>> Normally I *am* one of the "digital is great" guys.&nbsp; But in this case >>>> the design is for a ventilator which is mostly made of off the shelf >>>> electronics.&nbsp; I am shooting for no use of anything that might not be >>>> so available down the road and the circuits should be easy to make in >>>> low tech processes.&nbsp; So while programming MCUs are not exactly state >>>> of the art, I prefer to not use it if I can avoid it.&nbsp; There's also >>>> the issue of power supply.&nbsp; When the thing is first powering up there >>>> is no voltage on the supercap.&nbsp; I suppose I could use a couple of >>>> diodes to multiple source the MCU power.&nbsp; I did look at the idea a >>>> while back since it is an obvious route.&nbsp; I need at least two >>>> comparators which is not hard to find in MCUs either. >>>> >>>> The remaining part of the circuit is a constant current source to >>>> charge up the supercap.&nbsp; I suppose that could be done by the MCU and a >>>> pass transistor.&nbsp; If a PNP were used would that provide reverse >>>> current flow protection?&nbsp; I suppose if the base were held at the >>>> collector voltage it would reverse bias the BE junction and prevent >>>> flow.&nbsp; Otherwise the CB junction would be forward biased and the PNP >>>> would act as a very poor transistor still, no? >>>> >>>> I think the hard spec would be for the MCU to continue to work down to >>>> 2.0 volts or below.&nbsp; I suppose a watch CPU would work at very low >>>> voltages, but then we are back to hard to source components.&nbsp; How many >>>> MCUs are built to work over 2.0 to 5.25 volts with two comparators >>>> and/or an ADC? >>>> >>> >>> I reviewed the ventilator schematic that one company made public, you'll >>> be happy to know it uses a 555 timer! >> >> In a fairly pedestrian way tho, generating a clock for the motor-driver >> H-bridges I believe. > > I think they are doing all that in the software or at least in the Arduino. I've only been to a couple of meetings and the software isn't talked about in much detail. >
Can't recall what its function was exactly have to look again, it may have just been setting a PWM base frequency. The company prolly uses the same blower-board for a number of products; annoying to have to run a clock for that from the processor up to the board and re-program processor-derived clock for different motor characteristics on different products. Slap a 555 on there and change one resistor for a different machine.
On 5/12/2020 1:50 AM, Ricky C wrote:
> On Tuesday, May 12, 2020 at 12:23:40 AM UTC-4, bitrex wrote: >> On 5/12/2020 12:19 AM, bitrex wrote: >>> On 5/11/2020 10:31 PM, Ricky C wrote: >>>> On Monday, May 11, 2020 at 10:11:56 PM UTC-4, bitrex wrote: >>>>> On 5/11/2020 9:13 PM, Ricky C wrote: >>>>>> On Monday, May 11, 2020 at 8:06:14 PM UTC-4, Jon Elson wrote: >>>>>>> edward.ming.lee@gmail.com wrote: >>>>>>> >>>>>>>> On Monday, May 11, 2020 at 9:50:01 AM UTC-7, Jon Elson wrote: >>>>>>>>> Ricky C wrote: >>>>>>>>> >>>>>>>>> >>>>>>>>>> I need to turn on a sounder for 1 second out of 4. >>>>>>>>> >>>>>>>>> Why not use an ATTINY13A microcontroller chip?&nbsp; It is truly >>>>>>>>> micropower, >>>>>>>>> can >>>>>>>>> be programmed in C, and has 5 general-purpose I/O pins.&nbsp; Your >>>>>>>>> program >>>>>>>>> should >>>>>>>>> only be a couple lines of code.&nbsp; This chip casts about $0.50 in low >>>>>>>>> quantity, a programmer can be had on eBay for about $10 and the >>>>>>>>> development software is all free. >>>>>>>> >>>>>>>> 555 timers goes for around 10 cents. >>>>>>> Plus at least 3 additional components, including a pretty large, >>>>>>> low-leakage >>>>>>> capacitor.&nbsp; the ATTINY13A only requires a decoupling cap, and maybe >>>>>>> will run >>>>>>> without.&nbsp; Also, getting large asymmetry of the on/off time can be >>>>>>> an issue >>>>>>> with the 555.&nbsp; With the micro, you can get any time you want.&nbsp; I am >>>>>>> not one >>>>>>> of those "put a micro in everything" guys, but this particular case >>>>>>> does >>>>>>> seem to warrant it.&nbsp; In general, I don't like seeing RC timers with >>>>>>> delays >>>>>>> over a second. >>>>>> >>>>>> Normally I *am* one of the "digital is great" guys.&nbsp; But in this >>>>>> case the design is for a ventilator which is mostly made of off the >>>>>> shelf electronics.&nbsp; I am shooting for no use of anything that might >>>>>> not be so available down the road and the circuits should be easy to >>>>>> make in low tech processes.&nbsp; So while programming MCUs are not >>>>>> exactly state of the art, I prefer to not use it if I can avoid it. >>>>>> There's also the issue of power supply.&nbsp; When the thing is first >>>>>> powering up there is no voltage on the supercap.&nbsp; I suppose I could >>>>>> use a couple of diodes to multiple source the MCU power.&nbsp; I did look >>>>>> at the idea a while back since it is an obvious route.&nbsp; I need at >>>>>> least two comparators which is not hard to find in MCUs either. >>>>>> >>>>>> The remaining part of the circuit is a constant current source to >>>>>> charge up the supercap.&nbsp; I suppose that could be done by the MCU and >>>>>> a pass transistor.&nbsp; If a PNP were used would that provide reverse >>>>>> current flow protection?&nbsp; I suppose if the base were held at the >>>>>> collector voltage it would reverse bias the BE junction and prevent >>>>>> flow.&nbsp; Otherwise the CB junction would be forward biased and the PNP >>>>>> would act as a very poor transistor still, no? >>>>>> >>>>>> I think the hard spec would be for the MCU to continue to work down >>>>>> to 2.0 volts or below.&nbsp; I suppose a watch CPU would work at very low >>>>>> voltages, but then we are back to hard to source components.&nbsp; How >>>>>> many MCUs are built to work over 2.0 to 5.25 volts with two >>>>>> comparators and/or an ADC? >>>>>> >>>>> >>>>> I reviewed the ventilator schematic that one company made public, you'll >>>>> be happy to know it uses a 555 timer! >>>>> >>>>> Other than that the business-end of the main board is not too >>>>> complicated; H-bridges to drive the blower motors and a bit of glue >>>>> logic. >>>>> >>>>> The rest of the commercial ventilator design is power supplies, a >>>>> relatively antiquated microprocessor board, display and display >>>>> driver/lighting circuitry, and boards with the chips for all the >>>>> external sensors that integrate mass airflow, velocity, O2 level, >>>>> respiration rate, and such into the microprocessor. >>>> >>>> Sounds a lot like what these guys are doing.&nbsp; I don't know what they >>>> are using for the important sensors.&nbsp; They have some kit type >>>> temperature sensor boards like they sell at the hobby shops.&nbsp; Same for >>>> the H bridge, L298N.&nbsp; Funny you can get modules from aliexpress >>>> cheaper than the chip at Digikey!&nbsp; They seem to be using an Arduino >>>> Uno for the device controller.&nbsp; Not sure what they are using for the >>>> display or controls yet. >>>> >>> >>> The commercial vent design looked both over-engineered and antiquated >>> simultaneously like a lot of medical/aerospace stuff. A lot of swish $2 >>> op-amps and comparators (maybe because it was designed to run off >>> battery-power for a while but for low frequency/DC tasks like they were >>> in not really necessary) doing pedestrian things plus an obscure >>> processor using external RAM and ROM like an embedded device from the >>> early 90s. >> >> Maybe they're only allowed to use "medical grade" op amps or something. >> IDK much about the standards for life-critical designs, not an area I >> would much like to get into. is there a "medical grade" 555? > > Medical equipment has to be proven to not harm the patient. It is not required to otherwise be fail safe. Military gear often has to continue working in spite of any single failure. That's a different animal indeed. > > I don't know what the restrictions are on this project. It is entirely possible it will never produce anything other than a hobby project. There are any number of alternative ventilator designs that simply were never produced for who knows what reason. One question I have not asked is even if they design this device and get someone to produce it, how do they know anyone wants to use it? Have they asked any of the end users what they need? What they require it to do and how it will fit into a medical setting. > > Not my problem. I'm just designing an alarm board. They might ask me to lay out other parts. >
How do ya prove a product doesn't harm the patient, anyway? It could become sentient and hit them in the face with a hose out of spite! I mean sure it seems very unlikely but anything could happen, I guess. Some kind of logical positivism-thing
On Tuesday, May 12, 2020 at 1:36:03 AM UTC-4, Ricky C wrote:
> On Monday, May 11, 2020 at 7:21:16 AM UTC-4, piglet wrote: > > On 11/05/2020 9:22 am, Jasen Betts wrote: > > > > > > CD4060 does an execellent low power oscillator, 3:1 can be > > > got with a pair of diodes, but 2V is a bit low. > > > > > > > Correct. The CD4060 is not spec'd below 3V but the 74HC4060 is most > > definitely spec'd from 2V to 6V. Assuming a osc frequency can be found > > where the HC4060 runs at low enough Idd to satisfy the OP then something > > like this might suffice .... > > > > <www.dropbox.com/s/l6aahkcdghpcxps/4060beeper1in4.jpg?raw=1> > > > > I drew a 2n7002 for the gate but that part will have too high Vgson for > > 2V use and a better choice substituted. > > > > piglet > > I don't have an NPN or NFET in the BOM, just a PNP and a PFET. I could use the PNP as pair of diodes for a wire OR, but that's going to put a minimum Vgs of about 0.7 volts which might be too much and turn it on with only a 3 mA load. There is nothing in the data sheet of the HC4060 to make me think it can source the 3 mA directly without more voltage loss than I'd prefer. I was going to say I could drive the load directly from the 555 timer, but the CMOS version has more voltage drop than I'd like. > > As I think about this, I'm starting to like the HC4060. I can use the spare section of JK FF to turn the 0, 1, 2, 3 count into a single pulse of each four. Using different taps will allow patterns which might be better than a single beep every four seconds. I am having trouble finding a 74HC4060 spice file. Nexperia has something called hc_tnomi.cir, but it doesn't seem to be a functional model, just timing or drive capability. When I tried to bring it into LTspice it generated a 5 pin model with the pins named 0, 1, 2, 3, 5. > > I see CD4060 models mentioned people have created, but the files seem to be hosted on dead sites. > > I found files in the LTspice group, but I can't seem to make them work. One of them is CD4060Bg-model.txt which contains ".SUBCKT CD4060Bg". Should this be renames as a .lib or some other file? The .asy file and a test schematic are provided. It can't seem to find the guts complaining about an unknown subcircuit.
I got the 4060 to simulate, but it is really, really slow. I've been simulating the entire design for around 150 seconds of simulation time and not even noticed the delay. This model is taking around 1 second for a millisecond of simulation time. Not workable with a clock running slower than 10 Hz. Maybe I'll just trust that the clock circuit works and rig up my own model. I really only need the bottom few bits. As I said before, that's the bother of using LTspice. It can be so hard to find workable models. I am liking the 4060 for this though. I think I can find good ways to deal with the decoding and output drive. -- Rick C. --- Get 1,000 miles of free Supercharging --- Tesla referral code - https://ts.la/richard11209
On 12/05/2020 02:57, Ricky C wrote:
> On Monday, May 11, 2020 at 9:29:28 PM UTC-4, whit3rd wrote: >> On Monday, May 11, 2020 at 9:50:01 AM UTC-7, Jon Elson wrote: >>> Ricky C wrote: >> >>>> I need to turn on a sounder for 1 second out of 4. >>> >>> Why not use an ATTINY13A microcontroller chip? It is truly micropower... >> >>> Very slow timers are problematic in analog circuitry. >> >> The main problem, is parts count. It takes something like >> three op amps to get a long risetime >> by feeding 15 mV into a 1 Mohm/ 0.1uF integrator and detect >> both the 1/4 time level-crossing, and do the reset at the >> 4/4 time point. Half a dozen resistors. There's just a lot of >> components to pick-and-place. Then there's the power problem: >> an LT6002 micropower quad amp isn't bad, but isn't cheap, either. > > Not sure what that circuit would be doing. One of the first circuits I tried was a comparator with about half a dozen passives. A positive feedback resistor moves the Vth up and down on a voltage divider threshold at the positive input. To get different duty cycles a diode and resistor are paralleled with a resistor for the negative feedback to the cap. This is essentially the same as the two inverter loop, but instead of two inverters to provide different polarities to the resistor and cap a single comparator with two inputs do the same job. Instead of reversing the polarity of the cap relative to the single input, the comparator uses positive feedback to move the threshold. > > I would probably be using a comparator oscillator but I can't get them to simulate properly in LTspice. The cap should be charging to the positive input, but at lower Vcc it trips much sooner and mucks up the duty cycle a lot. I can't figure this out at all. I've tried every single comparator in the LTspice library thinking a voltage reference was getting in the way or something. None of them work properly at the low end of the specified voltage range. >
Huh ! Did you look at the model I posted ? You don't need the diode for 3:1 mark space, it does work on 2V in LTSpice, uses an LTC1441 (dual), can drive 13mA, Iq about 5uA - what more do you want ? The LTC1441 is a bit pricy but you could use any low power RRIO CMOS comp (or op amp that's happy being a comp.). (Microchip do MCP6543 at $0.35 which has chip enable) - never had much joy with running microchip models in LTSpice - but that wouldn't bother me - and you are not having any joy simulating LT comps in LTSpice) MK
On Tuesday, May 12, 2020 at 5:40:26 AM UTC-4, Michael Kellett wrote:
> On 12/05/2020 02:57, Ricky C wrote: > > On Monday, May 11, 2020 at 9:29:28 PM UTC-4, whit3rd wrote: > >> On Monday, May 11, 2020 at 9:50:01 AM UTC-7, Jon Elson wrote: > >>> Ricky C wrote: > >> > >>>> I need to turn on a sounder for 1 second out of 4. > >>> > >>> Why not use an ATTINY13A microcontroller chip? It is truly micropower... > >> > >>> Very slow timers are problematic in analog circuitry. > >> > >> The main problem, is parts count. It takes something like > >> three op amps to get a long risetime > >> by feeding 15 mV into a 1 Mohm/ 0.1uF integrator and detect > >> both the 1/4 time level-crossing, and do the reset at the > >> 4/4 time point. Half a dozen resistors. There's just a lot of > >> components to pick-and-place. Then there's the power problem: > >> an LT6002 micropower quad amp isn't bad, but isn't cheap, either. > > > > Not sure what that circuit would be doing. One of the first circuits I tried was a comparator with about half a dozen passives. A positive feedback resistor moves the Vth up and down on a voltage divider threshold at the positive input. To get different duty cycles a diode and resistor are paralleled with a resistor for the negative feedback to the cap. This is essentially the same as the two inverter loop, but instead of two inverters to provide different polarities to the resistor and cap a single comparator with two inputs do the same job. Instead of reversing the polarity of the cap relative to the single input, the comparator uses positive feedback to move the threshold. > > > > I would probably be using a comparator oscillator but I can't get them to simulate properly in LTspice. The cap should be charging to the positive input, but at lower Vcc it trips much sooner and mucks up the duty cycle a lot. I can't figure this out at all. I've tried every single comparator in the LTspice library thinking a voltage reference was getting in the way or something. None of them work properly at the low end of the specified voltage range. > > > > Huh ! > > Did you look at the model I posted ? > > You don't need the diode for 3:1 mark space, it does work on 2V in > LTSpice, uses an LTC1441 (dual), can drive 13mA, Iq about 5uA - what > more do you want ? > > The LTC1441 is a bit pricy but you could use any low power RRIO CMOS > comp (or op amp that's happy being a comp.). > > (Microchip do MCP6543 at $0.35 which has chip enable) - never had much > joy with running microchip models in LTSpice - but that wouldn't bother > me - and you are not having any joy simulating LT comps in LTSpice)
Yes, thanks for your design. It does use two comparators with a number of discretes (8 or 9?) even if both parts are in one package, and has the problem in simulation I mentioned where the negative input from the capacitor will trip before it reaches the positive input level. That happens with every LT comparator I tried which was every one in the library. My design has a dual comparator with internal reference already for level sensing of the Vin and the Vbb on the supercap. Not that that means much. I suppose two different comparators could be used on the same design as opposed to an entirely different chip or the same comparators with a voltage reference added. They make comparators in quads, right? The 4060 seems like the best bet of all I've seen so far. Too bad I can't find a decent model. The comparator is a good solution too, but it really bugs me that I can't simulate it properly. There is something wrong that I am missing. -- Rick C. --+ Get 1,000 miles of free Supercharging --+ Tesla referral code - https://ts.la/richard11209
On 12/05/2020 11:09, Ricky C wrote:
> On Tuesday, May 12, 2020 at 5:40:26 AM UTC-4, Michael Kellett wrote: >> On 12/05/2020 02:57, Ricky C wrote: >>> On Monday, May 11, 2020 at 9:29:28 PM UTC-4, whit3rd wrote: >>>> On Monday, May 11, 2020 at 9:50:01 AM UTC-7, Jon Elson wrote: >>>>> Ricky C wrote: >>>> >>>>>> I need to turn on a sounder for 1 second out of 4. >>>>> >>>>> Why not use an ATTINY13A microcontroller chip? It is truly micropower... >>>> >>>>> Very slow timers are problematic in analog circuitry. >>>> >>>> The main problem, is parts count. It takes something like >>>> three op amps to get a long risetime >>>> by feeding 15 mV into a 1 Mohm/ 0.1uF integrator and detect >>>> both the 1/4 time level-crossing, and do the reset at the >>>> 4/4 time point. Half a dozen resistors. There's just a lot of >>>> components to pick-and-place. Then there's the power problem: >>>> an LT6002 micropower quad amp isn't bad, but isn't cheap, either. >>> >>> Not sure what that circuit would be doing. One of the first circuits I tried was a comparator with about half a dozen passives. A positive feedback resistor moves the Vth up and down on a voltage divider threshold at the positive input. To get different duty cycles a diode and resistor are paralleled with a resistor for the negative feedback to the cap. This is essentially the same as the two inverter loop, but instead of two inverters to provide different polarities to the resistor and cap a single comparator with two inputs do the same job. Instead of reversing the polarity of the cap relative to the single input, the comparator uses positive feedback to move the threshold. >>> >>> I would probably be using a comparator oscillator but I can't get them to simulate properly in LTspice. The cap should be charging to the positive input, but at lower Vcc it trips much sooner and mucks up the duty cycle a lot. I can't figure this out at all. I've tried every single comparator in the LTspice library thinking a voltage reference was getting in the way or something. None of them work properly at the low end of the specified voltage range. >>> >> >> Huh ! >> >> Did you look at the model I posted ? >> >> You don't need the diode for 3:1 mark space, it does work on 2V in >> LTSpice, uses an LTC1441 (dual), can drive 13mA, Iq about 5uA - what >> more do you want ? >> >> The LTC1441 is a bit pricy but you could use any low power RRIO CMOS >> comp (or op amp that's happy being a comp.). >> >> (Microchip do MCP6543 at $0.35 which has chip enable) - never had much >> joy with running microchip models in LTSpice - but that wouldn't bother >> me - and you are not having any joy simulating LT comps in LTSpice) > > Yes, thanks for your design. It does use two comparators with a number of discretes (8 or 9?) even if both parts are in one package, and has the problem in simulation I mentioned where the negative input from the capacitor will trip before it reaches the positive input level. That happens with every LT comparator I tried which was every one in the library. > > My design has a dual comparator with internal reference already for level sensing of the Vin and the Vbb on the supercap. Not that that means much. I suppose two different comparators could be used on the same design as opposed to an entirely different chip or the same comparators with a voltage reference added. They make comparators in quads, right? > > The 4060 seems like the best bet of all I've seen so far. Too bad I can't find a decent model. The comparator is a good solution too, but it really bugs me that I can't simulate it properly. There is something wrong that I am missing. >
I don't see a problem in LTSpice with the LTC1441 - and I carefully checked the inputs at switching time - all looks OK. The Microchip model for the MCP6541 won't run in LTSpice. It runs in Microchip's simulator - current (average) running = 3uA. Max output current isn't great - you would need a MOSFET. If you use the MCP6543 with enable the BOM is: 1 chip, 4 resistors and 1 cap, plus the "power" device. Almost no change in F from 2V to 5V, no diodes. It should work with any RRIO comparator - but the Microchip one looks pretty keen value unless you go Chinese. MK