Peter L. Peres wrote:
>
> On Tue, 5 Nov 2002, Roman Black wrote:
>
> *>No, the cap goes between the base and EMITTER,
> *>NOT the collector! Putting the cap between base
> *>and collector is stupid as it couples the back emf
> *>to turn the transistor back on, exactly the reason
> *>you are getting vibration now.
>
> He isn't getting vibration, he said it does not work at all,


Wrong. I quote: "No, I don4t trying in lab.
I4m testing outdoors and the relay vibrating when
it has to turn off"

> it does not
> couple back emf anywhere

Wrong again, it's an NPN transistor driving a
relay with it's collector, therefore when the
relay turns off the collector goes high (to
about 1v higher to turn on the catch diode) and
WHEN the collector goes high your suggestion of
a cap to the base WILL turn the transistor back
on, giving exactly the vibration he complained of.
You may have forgot that the transistor is driven
from a slowly changing analogue voltage, and when
turning off the base will be JUST below 0.6v.
Any + going voltage at the base will cause the
vibration he complained of.

> (it's not stupid, it's a Miller integrator

I know *you're* not stupid and I respect your
opinion and experience, BUT that suggestion
sure was. ;o)

> Please
> check your facts before contra-posting.

Since you posted a stupid suggestion and then
were wrong TWICE in your rebuttal to me I suggest
you check your facts. :o)

No need to apologise, just put it down to
experience. A cap C-B in that circuit is stupid,
a cap B-E will fix his problem.
-Roman

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