Re: Master Clock contact spark quenching


John Haine
 

That's because it's opto isolated, it needs a current of ~3 mA into the input pin to light up the internal LED, so you drive it through a suitable resistor to get that current from whatever voltage is across the contacts.  In this case with 12 V that would be 12/3 = 4 K ohms, or 3.9 K NPV. 

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