>
>
>>John Fields wrote:
>>
>>>>>>
>>>
>>>
>>>
>>>>I want to build a circuit which produces 12 V pulses once per minute, of
>>>>alternating polarity, in order to drive a large WWII German slave clock
>>>>which I want to hang on my wall.
>>>
>>>
>>>---
>>>Is this what you want? (View in Courier)
>>>
>>>+12V _ _
>>> | | || |
>>> | | | | |
>>>0V___| |____________ ____________| |_______ _ _ _
>>> | |
>>> | | |
>>>-12V ||_|
>>
>>Yes. 1/2 second long pulses into a 2785 ohm coil. I know there are
>>various ways of accomplishing this with a quartz oscillator, but I've
>>become interested in driving the system from the 50 Hz mains frequency,
>>so I want to do it that way now.
>
>
> ---
> OK.
>
> I'll post a schematic for you, here, sometime tomorrow.
Thanks John. Don't go to a lot of trouble, though. It's only a hobby project.
Having looked at optocouplers, I'm wondering if they are the way to go. I even found an optocoupler which includes a Schmitt trigger, and the data sheet suggests that it can be used for "A.C. to TTL conversion - square wave shaping":
formatting link
The only problem is that the maximum reverse voltage which the optocoupler's LED can withstand is 6 V. I need to connect it to 6 V AC RMS, or 8.5 V peak. Could I put a resistor in series with the LED to give the correct forward current, and a diode in inverse parallel to prevent the reverse voltage building up?
Many thanks,
Chris