On Wed, 30 Aug 2017 14:00:13 -0400
rickman  wrote:

>Folderol wrote on 8/29/2017 1:33 PM:
>> On Mon, 28 Aug 2017 18:56:01 +0000
>> Jim H  wrote:
>>
>>> On Wed, 23 Aug 2017 22:29:55 +0100, in
>>> , Folderol 
>>> wrote:
>>>
>>>>
>>>> First off, charge voltage is inversely proportional to temperature, and
one of
>>>> the companies I contacted was kind enough to send me a schematic of a
simple
>>>> compensated voltage regulator, with a thermister which had to be *in*
*Thermal*
>>>> *contact* with the battery under charge.
>>>
>>>
>>> Would you care to share that schematic? Please?
>>>
>> I'd be more than happy to, only that was a long time ago, and that along
with
>> many other documents of the time have long since disappeared.
>>
>> From memory there wasn't much to it. An op-amp driving a power transistor as
an
>> emitter-follower, then a diode to protects against the battery feeding back
>> when the power was off. Control was from a high resistance feedback path
from
>> the battery terminals (so negligable drain on the battery) and somewhere in
that
>> lot was the thermistor and a preset pot.
>>
>> Current limiting was crude - just a resistor in series with the transistor
>> collector.
>>
>> Not a lot of help I'm afraid :(
>>
>> Hmmm, thinking a bit more. The thermistor and preset weren't directly in the
>> feedback but in the potential divider producing the reference voltage.
>>
>> Actually it's remarkable what you remember once you actually start thinking
>> about things. One resister from the battery + to the inverting pin of the
>> op-amp. Something like 470k I think, and the same from there to the common
>> ground.
>> A resistor from a zenner reference to the non-inverting pin of the op-amp,
then
>> resistor - preset - thermistor from there to ground. No idea what the values
>> were, nor what specific thermistor it was
>
>I believe I saw a modern copy of that circuit.  Instead of the opamp, pot
>and many other components it has an MCU.  Otherwise identical...
>

Fascinating.

Had they also swapped out the current limiting resistor for a light bulb,
like I did? A simple 'device' that not only provides protection but gives you
an immediate idea of what sort of current is passing, lighting up really
brightly if there's a short cicuit.

If not, presumably you could just cut a hole in the right place and attach one.

--
W J G

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