Re: Master Clock contact spark quenching
If I only had to drive slaves from the Synchronome, an opto isolator would be the obvious choice. I already have one.
An Aduino with ready made shield is probably the easiest way to convert a 30 second pulse to a one minute bipolar drive for the flip clock. Easier than building from discrete components. If I do that, then using the Aduino as an electronic relay to drive the slave clocks would make sense.
I am thinking of using a cheap Chinese motor/power switch shield with an Aduino to generate the bipolar drive for the flip clock. Generating a bipolar signal requires and H driver circuit, as used to drive stepper motors or DC motors. If I get a Auduino wifi version, there is the potential to use an on-line NTP server as the master clock, complete with automatic daylight time corrections. The only problem is that shipping times from China are currently about 3 to 6 months.
The master still needs to drive its own solenoid coil and case fitted slave, so a snubber circuit would still serve a purpose.
On 5.01.21 10:54 pm, John Haine wrote:
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.