From: jch on
Nicholas O. Lindan wrote:

> The "standard" way to connect this circuit to an enlarging timer would be to
> leave the switch closed and plug the 120V leads into the timer. This may not
> work very well.
>
> If the timer controls the 120V then the capacitor doesn't get fully charged
> and the shutter solenoid doesn't get a high voltage kick to slam it closed.
> Without the higher voltage the solenoid may not work or work sluggishly and
> erratically.
>
> You need to wire a relay where the switch is located - the coil of the relay
> goes to the timer and the relay contacts are wired across the switch. You
> need a SPST relay with a 120VAC 60Hz coil. You can get one at Radio Shack.
_____
Indeed, you need that initial higher voltage to "kick" the solenoid,
then hold it with a lower voltage. The above solution using an
interposed relay is the correct way to do the job. Not complex, just a
bit more wiring. I also concur about the need for a fuse, and the
higher voltage rating of the capacitor. I would use a full wave
rectifier. For this service, they are about 3/8 inch in diameter, and
1/4 inch high, having four leads; live, neutral, plus and minus. It
would be good to know the DC resistance of the solenoid coil. With that
information we can check the sizing of the resistor in terms of Ohms and
wattage rating.
--
Regards / JCH
From: Nicholas O. Lindan on
Quick question: what is the provenance of the circuit?
Is it the one that was in the long-roll camera that supplied
the shutter?

--
Nicholas O. Lindan, Cleveland, Ohio
Darkroom Automation: F-Stop Timers, Enlarging Meters
http://www.darkroomautomation.com/index2.htm
n o lindan at ix dot netcom dot com


From: John on
Nicholas O. Lindan wrote:
> Quick question: what is the provenance of the circuit?
> Is it the one that was in the long-roll camera that supplied
> the shutter?

Yes. The circuit minus the parts for 'Instant' shutter with flash.