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
-- 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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