Re: Master Clock contact spark quenching


John Hubert
 

If this is done in the musical world - then I think the assumption that any effect on the timing (i.e. lengthening of coil current duration) is insignificant.  

In a clock circuit, if you do get the polarity wrong, the diode (assume 1N400X type) can cope with the forward current (about 300 mA and it is OK to an Amp) and the dial concerned dial simply doesn’t advance - so easily spotted and corrected.  I have never in 10 years with maybe 50 dials running knowingly had a diode fail.

John

On 7 Jan 2021, at 10:33, Ian Richardson via groups.io <irichar361@...> wrote:

In the pipe organ world, the use of diodes in direct electric actions is standard practice.  I have just fitted up a direct action unit extension organ with about 200 electromagnetic valves, each runs on 15 vdc. and carries a current of about 250mA.  Each coil is shunted with 1N400X diodes or equivalent. There is no sparking - imagine if there was, the organ woiuld break down every day as the coils are activated hundreds of times with each performance!  The diodes cost about €1 per 100.

The point about polarity is, of course, valid but simply solved by using a high current silicon diode in series with the power supply.  If connected the correct way round, all works well; if the wrong way round, it doesn't work at all, so it "fails safe".

Ian R
Auvergne,
France




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