I am brand new to Arduino hardware. I have developed a prototype for the city museum for a display. It will require 10-12 Uno cards that need to be reset at the same time. Can I parallel the switches to one master switch? Required: pullup resistors, diodes? Anybody done this? Diagrams? BTW, this is fully volunteer work - not for profit.
Yes. The reset-input has a 10K pull-up resistor and the reset switch is grounded so it "overpowers" the resistor.
If you wire 10 in parallel you'll have 1K of pull-up resistance and any one of the built-in reset switches, or an external switch, will reset them all.
IMPORTANT: All boards must be connected to the same Ground .
I would connect a diode (eg 1n4148) in series with each reset line. Anode to the reset lines. Cathode to a 10k pullup, switch to ground.
Reasoning: The diode will stop one board reset from resetting all the others. It may not be needed it the perfect case but will be very helpful if there are issues and you have to troubleshoot which board is going awry .
You can simply power them down then when wanted turn on the power. You could do this with an arduino, I would use something in the 12V range and power the Vin on each with a SEPIC or Buck converter putting out about 8 volts. If they are on the same circuit maybe you can just cycle the breaker. Just trying to keep it simple.
Thanks, it's for a museum display and I volunteered to help out. I think I have a great starting point with the suggestions on the diodes and the 10K resistor. I have used similar arrangements with 4055 logic circuits (I am that old ). I will post wiring diagrams of a proven working circuit, unless I get smoke
There is no need nor use for a pulldown resistor. Reset is an active LOW input.
If the boards are reset by an Arduino output then a transistor and current limiting resistor may be required for draining all the capacitors on the Reset inputs. No such extra components are required if a mechanical switch is used.