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two relays

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  two relays John Larkin <jjlarkin@highlandtechnology.com> - 2017-03-23 16:10 -0700
    Re: two relays Lasse Langwadt Christensen <langwadt@fonz.dk> - 2017-03-23 16:27 -0700
      Re: two relays John Larkin <jjlarkin@highlandtechnology.com> - 2017-03-23 16:46 -0700
        Re: two relays Lasse Langwadt Christensen <langwadt@fonz.dk> - 2017-03-23 17:00 -0700
        Re: two relays Spehro Pefhany <speffSNIP@interlogDOTyou.knowwhat> - 2017-03-24 02:49 -0400
          Re: two relays John Larkin <jjlarkin@highlandtechnology.com> - 2017-03-24 08:14 -0700
            Re: two relays tabbypurr@gmail.com - 2017-03-24 08:55 -0700
              Re: two relays Spehro Pefhany <speffSNIP@interlogDOTyou.knowwhat> - 2017-03-24 19:26 -0400
                Re: two relays John Larkin <jjlarkinxyxy@highlandtechnology.com> - 2017-03-24 17:37 -0700
    Re: two relays whit3rd <whit3rd@gmail.com> - 2017-03-23 17:08 -0700
      Re: two relays Steve Wilson <no@spam.com> - 2017-03-24 00:28 +0000
        Re: two relays John Larkin <jjlarkin@highlandtechnology.com> - 2017-03-23 19:27 -0700
          Re: two relays Steve Wilson <no@spam.com> - 2017-03-24 04:55 +0000
            Re: two relays John Larkin <jjlarkin@highlandtechnology.com> - 2017-03-24 08:18 -0700
              Re: two relays Bob Engelhardt <BobEngelhardt@comcast.net> - 2017-03-24 13:29 -0400
          Re: two relays bitrex <bitrex@de.lete.earthlink.net> - 2017-03-24 11:17 -0400
            Re: two relays John Larkin <jjlarkin@highlandtechnology.com> - 2017-03-24 09:07 -0700
              Re: two relays bitrex <bitrex@de.lete.earthlink.net> - 2017-03-24 16:21 -0400
                Re: two relays tabbypurr@gmail.com - 2017-03-24 14:28 -0700
                  Re: two relays bitrex <bitrex@de.lete.earthlink.net> - 2017-03-24 18:26 -0400
                    Re: two relays tabbypurr@gmail.com - 2017-03-25 01:00 -0700
                      Re: two relays bitrex <bitrex@de.lete.earthlink.net> - 2017-03-25 12:55 -0400
                        Re: two relays krw@notreal.com - 2017-03-25 13:34 -0400
    Re: two relays George Herold <gherold@teachspin.com> - 2017-03-23 17:18 -0700
    Re: two relays bloggs.fredbloggs.fred@gmail.com - 2017-03-24 06:27 -0700
      Re: two relays John Larkin <jjlarkin@highlandtechnology.com> - 2017-03-24 08:19 -0700

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#453271 — two relays

https://dl.dropboxusercontent.com/u/53724080/Circuits/Power/Two_Relays.JPG


-- 

John Larkin         Highland Technology, Inc

lunatic fringe electronics 

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#453282

Den fredag den 24. marts 2017 kl. 00.10.56 UTC+1 skrev John Larkin:
> https://dl.dropboxusercontent.com/u/53724080/Circuits/Power/Two_Relays.JPG
> 

A) uses cheap resistors and lowside control 

so I'd say it has the other beat on everything but current and if that 
such is a big issue get some 12V relays

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#453286

On Thu, 23 Mar 2017 16:27:18 -0700 (PDT), Lasse Langwadt Christensen
<langwadt@fonz.dk> wrote:

>Den fredag den 24. marts 2017 kl. 00.10.56 UTC+1 skrev John Larkin:
>> https://dl.dropboxusercontent.com/u/53724080/Circuits/Power/Two_Relays.JPG
>> 
>
>A) uses cheap resistors and lowside control 

But it uses twice as much supply current as is necesary. The switches
are isolated DIPswitch sections. Ckt B is out because it needs SPDT
switches.

>
>so I'd say it has the other beat on everything but current and if that 
>such is a big issue get some 12V relays

I have the 5V relays in stock.

Circuit C looks most efficient. I'd prefer to not use a switcher.

The relays are DPDT, so it is possible to use the extra contacts to do
the more-pullin-than-holding-current trick. Apply 12 volts until the
relay pulls in, then switch to a low holding current. That's circuit
A, with the extra NC contact shorting the resistor.



 


-- 

John Larkin         Highland Technology, Inc

lunatic fringe electronics 

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#453288

Den fredag den 24. marts 2017 kl. 00.46.42 UTC+1 skrev John Larkin:
> On Thu, 23 Mar 2017 16:27:18 -0700 (PDT), Lasse Langwadt Christensen
> <langwadt@fonz.dk> wrote:
> 
> >Den fredag den 24. marts 2017 kl. 00.10.56 UTC+1 skrev John Larkin:
> >> https://dl.dropboxusercontent.com/u/53724080/Circuits/Power/Two_Relays.JPG
> >> 
> >
> >A) uses cheap resistors and lowside control 
> 
> But it uses twice as much supply current as is necesary. The switches
> are isolated DIPswitch sections. Ckt B is out because it needs SPDT
> switches.
> 
> >
> >so I'd say it has the other beat on everything but current and if that 
> >such is a big issue get some 12V relays
> 
> I have the 5V relays in stock.
> 
> Circuit C looks most efficient. I'd prefer to not use a switcher.
> 
> The relays are DPDT, so it is possible to use the extra contacts to do
> the more-pullin-than-holding-current trick. Apply 12 volts until the
> relay pulls in, then switch to a low holding current. That's circuit
> A, with the extra NC contact shorting the resistor.

yeh, if holding voltage is less than 2.5V that could get A on par with C
so it is down to 4 resistors vs. 2 zeners
 

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#453348

On Thu, 23 Mar 2017 16:46:37 -0700, the renowned John Larkin
<jjlarkin@highlandtechnology.com> wrote:

>On Thu, 23 Mar 2017 16:27:18 -0700 (PDT), Lasse Langwadt Christensen
><langwadt@fonz.dk> wrote:
>
>>Den fredag den 24. marts 2017 kl. 00.10.56 UTC+1 skrev John Larkin:
>>> https://dl.dropboxusercontent.com/u/53724080/Circuits/Power/Two_Relays.JPG
>>> 
>>
>>A) uses cheap resistors and lowside control 
>
>But it uses twice as much supply current as is necesary. The switches
>are isolated DIPswitch sections. Ckt B is out because it needs SPDT
>switches.
>
>>
>>so I'd say it has the other beat on everything but current and if that 
>>such is a big issue get some 12V relays
>
>I have the 5V relays in stock.
>
>Circuit C looks most efficient. I'd prefer to not use a switcher.

Noise an issue? Then I don't suppose you could just PWM the drives? 

Then you get a WDT for free. ;-) 


>The relays are DPDT, so it is possible to use the extra contacts to do
>the more-pullin-than-holding-current trick. Apply 12 volts until the
>relay pulls in, then switch to a low holding current. That's circuit
>A, with the extra NC contact shorting the resistor.
>
 

-- 
Best regards, 
Spehro Pefhany

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#453390

On Fri, 24 Mar 2017 02:49:55 -0400, Spehro Pefhany
<speffSNIP@interlogDOTyou.knowwhat> wrote:

>On Thu, 23 Mar 2017 16:46:37 -0700, the renowned John Larkin
><jjlarkin@highlandtechnology.com> wrote:
>
>>On Thu, 23 Mar 2017 16:27:18 -0700 (PDT), Lasse Langwadt Christensen
>><langwadt@fonz.dk> wrote:
>>
>>>Den fredag den 24. marts 2017 kl. 00.10.56 UTC+1 skrev John Larkin:
>>>> https://dl.dropboxusercontent.com/u/53724080/Circuits/Power/Two_Relays.JPG
>>>> 
>>>
>>>A) uses cheap resistors and lowside control 
>>
>>But it uses twice as much supply current as is necesary. The switches
>>are isolated DIPswitch sections. Ckt B is out because it needs SPDT
>>switches.
>>
>>>
>>>so I'd say it has the other beat on everything but current and if that 
>>>such is a big issue get some 12V relays
>>
>>I have the 5V relays in stock.
>>
>>Circuit C looks most efficient. I'd prefer to not use a switcher.
>
>Noise an issue? Then I don't suppose you could just PWM the drives? 


Rather not. This is a picoseconds-jitter thing, and switchers are
jitter generators.

>
>Then you get a WDT for free. ;-) 

That's great! What's a WDT?


-- 

John Larkin         Highland Technology, Inc

lunatic fringe electronics 

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#453406

On Friday, 24 March 2017 15:14:54 UTC, John Larkin  wrote:
> On Fri, 24 Mar 2017 02:49:55 -0400, Spehro Pefhany
> <speffSNIP@interlogDOTyou.knowwhat> wrote:
> >On Thu, 23 Mar 2017 16:46:37 -0700, the renowned John Larkin
> ><jjlarkin@highlandtechnology.com> wrote:
> >
> >>On Thu, 23 Mar 2017 16:27:18 -0700 (PDT), Lasse Langwadt Christensen
> >><langwadt@fonz.dk> wrote:
> >>
> >>>Den fredag den 24. marts 2017 kl. 00.10.56 UTC+1 skrev John Larkin:
> >>>> https://dl.dropboxusercontent.com/u/53724080/Circuits/Power/Two_Relays.JPG
> >>>> 
> >>>
> >>>A) uses cheap resistors and lowside control 
> >>
> >>But it uses twice as much supply current as is necesary. The switches
> >>are isolated DIPswitch sections. Ckt B is out because it needs SPDT
> >>switches.
> >>
> >>>
> >>>so I'd say it has the other beat on everything but current and if that 
> >>>such is a big issue get some 12V relays
> >>
> >>I have the 5V relays in stock.
> >>
> >>Circuit C looks most efficient. I'd prefer to not use a switcher.
> >
> >Noise an issue? Then I don't suppose you could just PWM the drives? 
> 
> 
> Rather not. This is a picoseconds-jitter thing, and switchers are
> jitter generators.
> 
> >
> >Then you get a WDT for free. ;-) 
> 
> That's great! What's a WDT?

Watchdog timer I guessed.


NT

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#453469

On Fri, 24 Mar 2017 08:55:26 -0700 (PDT), the renowned
tabbypurr@gmail.com wrote:

>On Friday, 24 March 2017 15:14:54 UTC, John Larkin  wrote:
>> On Fri, 24 Mar 2017 02:49:55 -0400, Spehro Pefhany
>> <speffSNIP@interlogDOTyou.knowwhat> wrote:
>> >On Thu, 23 Mar 2017 16:46:37 -0700, the renowned John Larkin
>> ><jjlarkin@highlandtechnology.com> wrote:
>> >
>> >>On Thu, 23 Mar 2017 16:27:18 -0700 (PDT), Lasse Langwadt Christensen
>> >><langwadt@fonz.dk> wrote:
>> >>
>> >>>Den fredag den 24. marts 2017 kl. 00.10.56 UTC+1 skrev John Larkin:
>> >>>> https://dl.dropboxusercontent.com/u/53724080/Circuits/Power/Two_Relays.JPG
>> >>>> 
>> >>>
>> >>>A) uses cheap resistors and lowside control 
>> >>
>> >>But it uses twice as much supply current as is necesary. The switches
>> >>are isolated DIPswitch sections. Ckt B is out because it needs SPDT
>> >>switches.
>> >>
>> >>>
>> >>>so I'd say it has the other beat on everything but current and if that 
>> >>>such is a big issue get some 12V relays
>> >>
>> >>I have the 5V relays in stock.
>> >>
>> >>Circuit C looks most efficient. I'd prefer to not use a switcher.
>> >
>> >Noise an issue? Then I don't suppose you could just PWM the drives? 
>> 
>> 
>> Rather not. This is a picoseconds-jitter thing, and switchers are
>> jitter generators.
>> 
>> >
>> >Then you get a WDT for free. ;-) 
>> 
>> That's great! What's a WDT?
>
>Watchdog timer I guessed.
>
>
>NT

Yes-- if the output sticks 'on' the coil fries (maybe- with almost 6x
normal dissipation) and the relay drops out. 

--sp 


-- 
Best regards, 
Spehro Pefhany

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#453477

On Fri, 24 Mar 2017 19:26:01 -0400, Spehro Pefhany
<speffSNIP@interlogDOTyou.knowwhat> wrote:

>On Fri, 24 Mar 2017 08:55:26 -0700 (PDT), the renowned
>tabbypurr@gmail.com wrote:
>
>>On Friday, 24 March 2017 15:14:54 UTC, John Larkin  wrote:
>>> On Fri, 24 Mar 2017 02:49:55 -0400, Spehro Pefhany
>>> <speffSNIP@interlogDOTyou.knowwhat> wrote:
>>> >On Thu, 23 Mar 2017 16:46:37 -0700, the renowned John Larkin
>>> ><jjlarkin@highlandtechnology.com> wrote:
>>> >
>>> >>On Thu, 23 Mar 2017 16:27:18 -0700 (PDT), Lasse Langwadt Christensen
>>> >><langwadt@fonz.dk> wrote:
>>> >>
>>> >>>Den fredag den 24. marts 2017 kl. 00.10.56 UTC+1 skrev John Larkin:
>>> >>>> https://dl.dropboxusercontent.com/u/53724080/Circuits/Power/Two_Relays.JPG
>>> >>>> 
>>> >>>
>>> >>>A) uses cheap resistors and lowside control 
>>> >>
>>> >>But it uses twice as much supply current as is necesary. The switches
>>> >>are isolated DIPswitch sections. Ckt B is out because it needs SPDT
>>> >>switches.
>>> >>
>>> >>>
>>> >>>so I'd say it has the other beat on everything but current and if that 
>>> >>>such is a big issue get some 12V relays
>>> >>
>>> >>I have the 5V relays in stock.
>>> >>
>>> >>Circuit C looks most efficient. I'd prefer to not use a switcher.
>>> >
>>> >Noise an issue? Then I don't suppose you could just PWM the drives? 
>>> 
>>> 
>>> Rather not. This is a picoseconds-jitter thing, and switchers are
>>> jitter generators.
>>> 
>>> >
>>> >Then you get a WDT for free. ;-) 
>>> 
>>> That's great! What's a WDT?
>>
>>Watchdog timer I guessed.
>>
>>
>>NT
>
>Yes-- if the output sticks 'on' the coil fries (maybe- with almost 6x
>normal dissipation) and the relay drops out. 
>
>--sp 

Damned sticky relay deserves to die. Makes an example for other
relays.




-- 

John Larkin         Highland Technology, Inc
picosecond timing   precision measurement 

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com

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#453290

On Thursday, March 23, 2017 at 4:10:56 PM UTC-7, John Larkin wrote:
> https://dl.dropboxusercontent.com/u/53724080/Circuits/Power/Two_Relays.JPG
> 

Resistors are a waste of power, Zeners are relatively expensive, and choosing
to use 5V relays when one only has 12V power is... not the best design decision.
Besides, Zeners sometimes fail short.

One could also use an LM317 as current source, putting the two relay coils
in series, with the switches shunting each coil...
GAAA now you've got ME doing this silly stuff!

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#453295

whit3rd <whit3rd@gmail.com> wrote:

> On Thursday, March 23, 2017 at 4:10:56 PM UTC-7, John Larkin wrote:
>> https://dl.dropboxusercontent.com/u/53724080/Circuits/Power/Two_Relays
>> .JPG 
>> 
> 
> Resistors are a waste of power, Zeners are relatively expensive, and
> choosing to use 5V relays when one only has 12V power is... not the
> best design decision. Besides, Zeners sometimes fail short.
> 
> One could also use an LM317 as current source, putting the two relay
> coils in series, with the switches shunting each coil...
> GAAA now you've got ME doing this silly stuff!

Agreed. A silly problem that wastes everyone's time.

What drives the SPST and SPDT switches in (A) (B) and (C)? Are they 12V 
relays? If not, do they require additional resistors and zeners?

What happens to two zeners in series with an overvoltage on the 12V 
supply?

Why not simply use a 12V version of the 5V relays? 

Or use a 5V supply?

The problem is not scalable. What if you have to drive three relays?

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#453320

On Fri, 24 Mar 2017 00:28:14 GMT, Steve Wilson <no@spam.com> wrote:

>whit3rd <whit3rd@gmail.com> wrote:
>
>> On Thursday, March 23, 2017 at 4:10:56 PM UTC-7, John Larkin wrote:
>>> https://dl.dropboxusercontent.com/u/53724080/Circuits/Power/Two_Relays
>>> .JPG 
>>> 
>> 
>> Resistors are a waste of power, Zeners are relatively expensive, and
>> choosing to use 5V relays when one only has 12V power is... not the
>> best design decision. Besides, Zeners sometimes fail short.
>> 
>> One could also use an LM317 as current source, putting the two relay
>> coils in series, with the switches shunting each coil...
>> GAAA now you've got ME doing this silly stuff!
>
>Agreed. A silly problem that wastes everyone's time.
>
>What drives the SPST and SPDT switches in (A) (B) and (C)? Are they 12V 
>relays? If not, do they require additional resistors and zeners?
>
>What happens to two zeners in series with an overvoltage on the 12V 
>supply?
>
>Why not simply use a 12V version of the 5V relays? 
>
>Or use a 5V supply?
>
>The problem is not scalable. What if you have to drive three relays?

Actually, I do have to drive three relays.


-- 

John Larkin         Highland Technology, Inc

lunatic fringe electronics 

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#453335

John Larkin <jjlarkin@highlandtechnology.com> wrote:

> On Fri, 24 Mar 2017 00:28:14 GMT, Steve Wilson <no@spam.com> wrote:
> 
>>whit3rd <whit3rd@gmail.com> wrote:
>>
>>> On Thursday, March 23, 2017 at 4:10:56 PM UTC-7, John Larkin wrote:
>>>> 
https://dl.dropboxusercontent.com/u/53724080/Circuits/Power/Two_Relays
>>>> .JPG 
>>>> 
>>> 
>>> Resistors are a waste of power, Zeners are relatively expensive, and
>>> choosing to use 5V relays when one only has 12V power is... not the
>>> best design decision. Besides, Zeners sometimes fail short.
>>> 
>>> One could also use an LM317 as current source, putting the two relay
>>> coils in series, with the switches shunting each coil...
>>> GAAA now you've got ME doing this silly stuff!
>>
>>Agreed. A silly problem that wastes everyone's time.
>>
>>What drives the SPST and SPDT switches in (A) (B) and (C)? Are they 12V 
>>relays? If not, do they require additional resistors and zeners?
>>
>>What happens to two zeners in series with an overvoltage on the 12V 
>>supply? 
>>
>>Why not simply use a 12V version of the 5V relays? 
>>
>>Or use a 5V supply?
>>
>>The problem is not scalable. What if you have to drive three relays?
> 
> Actually, I do have to drive three relays.

Easy Peasy. Just use the SPST or SPDT contacts in your (A)(B) and (C) 
switches.

Problem solved. Next?
 

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#453393

On Fri, 24 Mar 2017 04:55:58 GMT, Steve Wilson <no@spam.com> wrote:

>John Larkin <jjlarkin@highlandtechnology.com> wrote:
>
>> On Fri, 24 Mar 2017 00:28:14 GMT, Steve Wilson <no@spam.com> wrote:
>> 
>>>whit3rd <whit3rd@gmail.com> wrote:
>>>
>>>> On Thursday, March 23, 2017 at 4:10:56 PM UTC-7, John Larkin wrote:
>>>>> 
>https://dl.dropboxusercontent.com/u/53724080/Circuits/Power/Two_Relays
>>>>> .JPG 
>>>>> 
>>>> 
>>>> Resistors are a waste of power, Zeners are relatively expensive, and
>>>> choosing to use 5V relays when one only has 12V power is... not the
>>>> best design decision. Besides, Zeners sometimes fail short.
>>>> 
>>>> One could also use an LM317 as current source, putting the two relay
>>>> coils in series, with the switches shunting each coil...
>>>> GAAA now you've got ME doing this silly stuff!
>>>
>>>Agreed. A silly problem that wastes everyone's time.
>>>
>>>What drives the SPST and SPDT switches in (A) (B) and (C)? Are they 12V 
>>>relays? If not, do they require additional resistors and zeners?
>>>
>>>What happens to two zeners in series with an overvoltage on the 12V 
>>>supply? 
>>>
>>>Why not simply use a 12V version of the 5V relays? 
>>>
>>>Or use a 5V supply?
>>>
>>>The problem is not scalable. What if you have to drive three relays?
>> 
>> Actually, I do have to drive three relays.
>
>Easy Peasy. Just use the SPST or SPDT contacts in your (A)(B) and (C) 
>switches.
>
>Problem solved. Next?
> 

The best way to do three or more relays is probably to take advantage
of the pullin/hold current differential, using the second set of DPDT
contacts on each relay. That only needs one resistor per relay, and
saves the most power when they are on. Or off.

I guess that's the best way, period.


-- 

John Larkin         Highland Technology, Inc

lunatic fringe electronics 

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#453419

On 3/24/2017 11:18 AM, John Larkin wrote:
> The best way to do three or more relays is probably to take advantage
> of the pullin/hold current differential, using the second set of DPDT
> contacts on each relay. That only needs one resistor per relay, and
> saves the most power when they are on. Or off.
>
> I guess that's the best way, period.
>
>

But ... the contacts are most certainly break-before-make, so timing 
could be a problem.  Depending upon inertia of armature, flyback diode 
current, ...  No experience, just a thought.

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#453392

On 03/23/2017 10:27 PM, John Larkin wrote:

>> What drives the SPST and SPDT switches in (A) (B) and (C)? Are they 12V
>> relays? If not, do they require additional resistors and zeners?
>>
>> What happens to two zeners in series with an overvoltage on the 12V
>> supply?
>>
>> Why not simply use a 12V version of the 5V relays?
>>
>> Or use a 5V supply?
>>
>> The problem is not scalable. What if you have to drive three relays?
>
> Actually, I do have to drive three relays.
>
>

I thought engineering was sometimes described as "making what you need 
out of what you have."

Sometimes a 12V supply and 5V relays is what you have.

Anyone can make a "design decision" to spend more money

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#453409

On Fri, 24 Mar 2017 11:17:53 -0400, bitrex
<bitrex@de.lete.earthlink.net> wrote:

>On 03/23/2017 10:27 PM, John Larkin wrote:
>
>>> What drives the SPST and SPDT switches in (A) (B) and (C)? Are they 12V
>>> relays? If not, do they require additional resistors and zeners?
>>>
>>> What happens to two zeners in series with an overvoltage on the 12V
>>> supply?
>>>
>>> Why not simply use a 12V version of the 5V relays?
>>>
>>> Or use a 5V supply?
>>>
>>> The problem is not scalable. What if you have to drive three relays?
>>
>> Actually, I do have to drive three relays.
>>
>>
>
>I thought engineering was sometimes described as "making what you need 
>out of what you have."
>
>Sometimes a 12V supply and 5V relays is what you have.

We try to avoid adding new parts to stock. We have 6640 stock numbers
already.


-- 

John Larkin         Highland Technology, Inc

lunatic fringe electronics 

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#453439

On 03/24/2017 12:07 PM, John Larkin wrote:
> On Fri, 24 Mar 2017 11:17:53 -0400, bitrex
> <bitrex@de.lete.earthlink.net> wrote:
>
>> On 03/23/2017 10:27 PM, John Larkin wrote:
>>
>>>> What drives the SPST and SPDT switches in (A) (B) and (C)? Are they 12V
>>>> relays? If not, do they require additional resistors and zeners?
>>>>
>>>> What happens to two zeners in series with an overvoltage on the 12V
>>>> supply?
>>>>
>>>> Why not simply use a 12V version of the 5V relays?
>>>>
>>>> Or use a 5V supply?
>>>>
>>>> The problem is not scalable. What if you have to drive three relays?
>>>
>>> Actually, I do have to drive three relays.
>>>
>>>
>>
>> I thought engineering was sometimes described as "making what you need
>> out of what you have."
>>
>> Sometimes a 12V supply and 5V relays is what you have.
>
> We try to avoid adding new parts to stock. We have 6640 stock numbers
> already.
>
>

My idea for a "fault tolerant" version:

<https://www.dropbox.com/s/hnkq65xj4nv5r6e/File%20Mar%2024%2C%204%2006%2016%20PM.jpeg?dl=0>

Haven't tested. Or Spiced. May not work...

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#453451

On Friday, 24 March 2017 20:21:13 UTC, bitrex  wrote:
> On 03/24/2017 12:07 PM, John Larkin wrote:
> > On Fri, 24 Mar 2017 11:17:53 -0400, bitrex
> > <bitrex@de.lete.earthlink.net> wrote:
> >
> >> On 03/23/2017 10:27 PM, John Larkin wrote:
> >>
> >>>> What drives the SPST and SPDT switches in (A) (B) and (C)? Are they 12V
> >>>> relays? If not, do they require additional resistors and zeners?
> >>>>
> >>>> What happens to two zeners in series with an overvoltage on the 12V
> >>>> supply?
> >>>>
> >>>> Why not simply use a 12V version of the 5V relays?
> >>>>
> >>>> Or use a 5V supply?
> >>>>
> >>>> The problem is not scalable. What if you have to drive three relays?
> >>>
> >>> Actually, I do have to drive three relays.
> >>>
> >>>
> >>
> >> I thought engineering was sometimes described as "making what you need
> >> out of what you have."
> >>
> >> Sometimes a 12V supply and 5V relays is what you have.
> >
> > We try to avoid adding new parts to stock. We have 6640 stock numbers
> > already.
> >
> >
> 
> My idea for a "fault tolerant" version:
> 
> <https://www.dropbox.com/s/hnkq65xj4nv5r6e/File%20Mar%2024%2C%204%2006%2016%20PM.jpeg?dl=0>
> 
> Haven't tested. Or Spiced. May not work...

Are you one of those unlimited budget people?


NT

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#453461

On 03/24/2017 05:28 PM, tabbypurr@gmail.com wrote:
> On Friday, 24 March 2017 20:21:13 UTC, bitrex  wrote:
>> On 03/24/2017 12:07 PM, John Larkin wrote:
>>> On Fri, 24 Mar 2017 11:17:53 -0400, bitrex
>>> <bitrex@de.lete.earthlink.net> wrote:
>>>
>>>> On 03/23/2017 10:27 PM, John Larkin wrote:
>>>>
>>>>>> What drives the SPST and SPDT switches in (A) (B) and (C)? Are they 12V
>>>>>> relays? If not, do they require additional resistors and zeners?
>>>>>>
>>>>>> What happens to two zeners in series with an overvoltage on the 12V
>>>>>> supply?
>>>>>>
>>>>>> Why not simply use a 12V version of the 5V relays?
>>>>>>
>>>>>> Or use a 5V supply?
>>>>>>
>>>>>> The problem is not scalable. What if you have to drive three relays?
>>>>>
>>>>> Actually, I do have to drive three relays.
>>>>>
>>>>>
>>>>
>>>> I thought engineering was sometimes described as "making what you need
>>>> out of what you have."
>>>>
>>>> Sometimes a 12V supply and 5V relays is what you have.
>>>
>>> We try to avoid adding new parts to stock. We have 6640 stock numbers
>>> already.
>>>
>>>
>>
>> My idea for a "fault tolerant" version:
>>
>> <https://www.dropbox.com/s/hnkq65xj4nv5r6e/File%20Mar%2024%2C%204%2006%2016%20PM.jpeg?dl=0>
>>
>> Haven't tested. Or Spiced. May not work...
>
> Are you one of those unlimited budget people?
>
>
> NT
>

SOT-23 TL431s are like 4 cents...

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