Re: Master Clock contact spark quenching


markotime
 

Another thing about contacts: Some level of current must be carried through mechanical contacts
to prevent buildup of oxide or other contaminants which will eventually inhibit conductivity.  If
memory serves me correctly, "sealing" current is the proper term.  For Hipp, there is probably
enough wiping action to prevent buildup if the "needle" is part of the circuit.  I'm inclined to use
optical devices rather than mechanical contacts.
Haven't yet worked my way thru Arduino logic for a Hipp solution.

On 1/8/2021 6:12 AM, Simon Taylor wrote:

The GPO used a 200 ohm resistor in series with a 1 micro farad capacitor across the contacts on later type 36 clocks with simple make contacts. The earlier types with make before break contacts had a 2000 ohm resistor. and worked with the earlier relay 90A which had 2 x 500 ohm coils in parallel.

All of the contacts are made of 10% iridium and 90% platinum. The hipp toggle contacts pass between 400-500mA for the pendulum drive coil. Although running a GPO slave cct direct it is quite possible, I would still recommend using either traditional relay (coil 2000-5000 ohms) or a solid state device or arduino system.
--
Simon GPO Clocks

http://www.lightstraw.uk/gpo/clocksystems/index.html


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