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Recharging A/C on '96 LH Car
Chrysler Dodge, Plymouth, Jeep, Eagle, etc info/talk (rec.autos.makers.chrysler)
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#11
 
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Re: Recharging A/C on '96 LH Car -
05-04-2007
, 11:54 PM
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Bob Shuman wrote: "maxpower" <damnnickname (AT) yahoo (DOT) com> wrote in message news:_8WdncLT2cFgFqbbnZ2dnUVZ_qiqnZ2d (AT) comcast (DOT) com... I believe what you are referring to is a small capacitor of some sort to absorb the voltage spikes generated from the compressor cycles off Glenn Yes, this could certainly be the case and would make sense, but if so, then it is not shown in the FSM's electrical schematic. I just looked at the FSM schematics. See my other post, but bottom line is that it contains two back-to-back zener diodes - so polarity doesn't matter. |
That's *if* they both clamp at the same voltage, though.
Take care.
Ken
#12
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Bill Putney wrote: Bob Shuman wrote: "maxpower" <damnnickname (AT) yahoo (DOT) com> wrote in message news:_8WdncLT2cFgFqbbnZ2dnUVZ_qiqnZ2d (AT) comcast (DOT) com... I believe what you are referring to is a small capacitor of some sort to absorb the voltage spikes generated from the compressor cycles off Glenn Yes, this could certainly be the case and would make sense, but if so, then it is not shown in the FSM's electrical schematic. I just looked at the FSM schematics. See my other post, but bottom line is that it contains two back-to-back zener diodes - so polarity doesn't matter. Hi Bill... That's *if* they both clamp at the same voltage, though. Take care. Ken |
There's no reason to think otherwise. As an electronics designer of
over 25 years, I can think of no other reason in that application other
than to make polarity an insignificant issue while still clamping the
spikes. If you can think of a reason to have a second opposite-polarity
zener - and of a different zener voltage, that would be good to know.
As it is, biasing the zener in the forward (non-zener) direction will
clamp at less than a volt (as a regular - non-zener - diode would).
Bill Putney
(To reply by e-mail, replace the last letter of the alphabet in my
address with the letter 'x')
#13
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Ken Weitzel wrote: Bill Putney wrote: Bob Shuman wrote: "maxpower" <damnnickname (AT) yahoo (DOT) com> wrote in message news:_8WdncLT2cFgFqbbnZ2dnUVZ_qiqnZ2d (AT) comcast (DOT) com... I believe what you are referring to is a small capacitor of some sort to absorb the voltage spikes generated from the compressor cycles off Glenn Yes, this could certainly be the case and would make sense, but if so, then it is not shown in the FSM's electrical schematic. I just looked at the FSM schematics. See my other post, but bottom line is that it contains two back-to-back zener diodes - so polarity doesn't matter. Hi Bill... That's *if* they both clamp at the same voltage, though. Take care. Ken Ken, There's no reason to think otherwise. As an electronics designer of over 25 years, I can think of no other reason in that application other than to make polarity an insignificant issue while still clamping the spikes. If you can think of a reason to have a second opposite-polarity zener - and of a different zener voltage, that would be good to know. |
zeners are generally used for inductive suppression of AC-powered loads,
not DC powered. I suspect the schematic drawer got it wrong.
You do not want reversed polarity on a DC system. In this kind of
setup, the clamp voltage on a back-to-back zener arraingement cannot
be lower than around 15 volts or the one zener would avalanche at
normal voltage in the system, and probably burn up. And applying
a reverse voltage of 15 volts to a DC system isn't a good idea, even if
the DC system is powered, particularly when it's being generated by
a collapsing electromagnetic field, which can dump quite a lot of
amperage for a short time.
It should be a normal diode, with polarity reversed.
Ted
#14
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"Bill Putney" <bptn (AT) kinez (DOT) net> wrote in message news:f1i2v2$vbp$1 (AT) news (DOT) isdn.net... Ken Weitzel wrote: Bill Putney wrote: Bob Shuman wrote: "maxpower" <damnnickname (AT) yahoo (DOT) com> wrote in message news:_8WdncLT2cFgFqbbnZ2dnUVZ_qiqnZ2d (AT) comcast (DOT) com... I believe what you are referring to is a small capacitor of some sort to absorb the voltage spikes generated from the compressor cycles off Glenn Yes, this could certainly be the case and would make sense, but if so, then it is not shown in the FSM's electrical schematic. I just looked at the FSM schematics. See my other post, but bottom line is that it contains two back-to-back zener diodes - so polarity doesn't matter. Hi Bill... That's *if* they both clamp at the same voltage, though. Take care. Ken Ken, There's no reason to think otherwise. As an electronics designer of over 25 years, I can think of no other reason in that application other than to make polarity an insignificant issue while still clamping the spikes. If you can think of a reason to have a second opposite-polarity zener - and of a different zener voltage, that would be good to know. Frankly, I question that it is a back-to-back Zener at all. back-to-back zeners are generally used for inductive suppression of AC-powered loads, not DC powered. I suspect the schematic drawer got it wrong. You do not want reversed polarity on a DC system. In this kind of setup, the clamp voltage on a back-to-back zener arraingement cannot be lower than around 15 volts or the one zener would avalanche at normal voltage in the system, and probably burn up. And applying a reverse voltage of 15 volts to a DC system isn't a good idea, even if the DC system is powered, particularly when it's being generated by a collapsing electromagnetic field, which can dump quite a lot of amperage for a short time. It should be a normal diode, with polarity reversed. Ted Its a bi-directional zener diode. It is used to control induced voltage from |
provides a path for the spike of about 200 volts. This protects the other
components in the system from voltage spikes.
Glenn
#15
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Frankly, I question that it is a back-to-back Zener at all. back-to-back zeners are generally used for inductive suppression of AC-powered loads, not DC powered. I suspect the schematic drawer got it wrong. You do not want reversed polarity on a DC system. In this kind of setup, the clamp voltage on a back-to-back zener arraingement cannot be lower than around 15 volts or the one zener would avalanche at normal voltage in the system, and probably burn up. And applying a reverse voltage of 15 volts to a DC system isn't a good idea, even if the DC system is powered, particularly when it's being generated by a collapsing electromagnetic field, which can dump quite a lot of amperage for a short time. It should be a normal diode, with polarity reversed. Ted |
Bill Putney
(To reply by e-mail, replace the last letter of the alphabet in my
address with the letter 'x')
#16
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ed Mittelstaedt wrote: Frankly, I question that it is a back-to-back Zener at all. back-to-back zeners are generally used for inductive suppression of AC-powered loads, not DC powered. I suspect the schematic drawer got it wrong. You do not want reversed polarity on a DC system. In this kind of setup, the clamp voltage on a back-to-back zener arraingement cannot be lower than around 15 volts or the one zener would avalanche at normal voltage in the system, and probably burn up. And applying a reverse voltage of 15 volts to a DC system isn't a good idea, even if the DC system is powered, particularly when it's being generated by a collapsing electromagnetic field, which can dump quite a lot of amperage for a short time. It should be a normal diode, with polarity reversed. Ted I don't disagree with anything you said. Just going by the schematic. Bill Putney (To reply by e-mail, replace the last letter of the alphabet in my address with the letter 'x') |
With the back-to-back zener, the reverse (negative) voltage is at least
limited to the zener voltage (probably in the -15 to -20 volt range).
It is easier to design internal power bus protection for other
electronics in the system for -20 volt spikes than for -200 volt spikes.
Bill Putney
(To reply by e-mail, replace the last letter of the alphabet in my
address with the letter 'x')
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