John , back in December you gave me a circuit for a remote turn on for an amplifier. I am just getting to test this circuit and I have some oscillation on the relay when it drops out. I suspect that some positive feedback (hysteresis) is needed. What is the best way to implement this? ...Mike DeAngelis
PING: John Fields
Jan 19, 2006
3 Replies
Without being refreshed as to what the circuit looked like, I\'d have
to guess. Can you post the circuit?
Sure, here it is.
+5V>-+-----------+---+---------------+-----+---+ | | | |R1 | | | | COM | | 10K] | | | +------+ | | | | CR1 | | | |K | O | | +-[ | | | | [200] | | | +------+ | | | | | |Rd | | | NO | | | | [10K]-+---G NCH | | >-+--[2.2M]---+---|----|-/ LM393 S VIN>---[10K]-+--|-/ LM393 |+ | | U1B | | | | U1A [51µF]| | | [200] [1N4148]| C1| | | | | |A | | | | | GND>-+-------+---+---------------+---+-----+---------+Also, I've set the input threshold to switch at 0.1V, so that eliminates one pot. You need the other one (Rd) to adjust your amplifier turn-off delay time because of the tolerance and leakage current of C1. Also, I've decreased the value of C1 to 51µF in order to decrease its potential leakage current.
John Fields
Professional Circuit Designer
.
"John Fields" wrote in message
news:0ca0t15aajektac2j7rja4gnuau4np7tr4@4ax.com...
> On Wed, 18 Jan 2006 21:28:52 GMT, "Mike DeAngelis"
> wrote:
>
> >John , back in December you gave me a circuit for a remote turn on for an
> >amplifier. I am just getting to test this circuit and I have some
> >oscillation on the relay when it drops out. I suspect that some positive
> >feedback (hysteresis) is needed. What is the best way to implement this?
>
> ---
> Without being refreshed as to what the circuit looked like, I\'d have
> to guess. Can you post the circuit?
>
> --
> John Fields
> Professional Circuit Designer
OK.
I don\'t think it\'s coming from the first stage, since by the time
the relay opens, U1A- should be pretty close to ground, which is
about 100mV below the switching threshold for the first stage.
That leaves the second stage, and I\'d try this:
+V
+--------------+----------+ |
| | | | COM
| | | +------+ |
| | | |K | O
| | [4K7][DIODE] [COIL]- |
| | | | | O-> |
| +--|--[1M]----+ +------+ |
|Rd | | | | NO
[10K]--------+---G NCH
--|-------------|-/ LM393 S
| | U1B |
| | |
| | |
| | |
--+--------------+----------------+
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