How to wirelessly control multiple relays with millisecond accuracy?

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A line of devices which are 500ft to a thousand feet apart in the woods need to be turned on and off simultaneously. This needs to be extremely low cost and simple to make. Considering real time clock controlled relays, or radio control. What would be the least expensive approach? And how to learn?

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LoRa radios would probably be the least expensive…or run physical chain/rope and yanking it might be cheaper

Look at other similar projects online for how to learn - the part that might be tricky is how simultaneous they need to be…

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Hi @Outside ,

I’d probably recommend a GNSS receiver with programmable time pulse output. Achieving 1ms accuracy should be straightforward. But it depends if this is a one-time event, or something that repeats (a few times per second or every few seconds). If you can tell us a bit more about your application, we can give you more suggestions.

Best wishes,
Paul

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Absolutely, want to be able to have these relays simultaneously open and close many times an hour over 5 days. It can easily be accomplished with a timer that’s GPS controlled or remotely by radio signal. Looking for the least expensive way. Right now we are using equipment that cost over $1,000 per unit. They are GPS controlled. There are also timer relays that unfortunately won’t work for more than 8 hours or so before they get out of sync.

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So is it timed or remote control?
For example, suppose you want to synch strobe flashes in a stadium, they flash for a few seconds when the home team hits a home run/kicks a goal. The signal or trigger to flash is toggled by the scorekeeper’s remote control, but the duration is handled by the controller on the individual lights. No GPS here.

Traffic control lights are largely on timers but can be controlled, in part, remotely for special events or ambulances or even a pedestrian Push For Walk button.

What are you using now for $1000 but can easily be accomplished cheaper? This benchmark is useful when comparing among techniques.

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You NEED millisecond accuracy? I don’t know how you’d do that directly without running wires, then you’d need to think about voltage drop, ringing, lightning induced current and so on.

If you have a GPS unit on each node with 1pps output, then you could transmit a command that basically says “At 12:53PM + 501mS, turn on output 3” The micro can time milliseconds reasonably accurately if it already knows “It’s 12:52 PM, I have a command in the queue at this time, so I need to watch the 1PPS input, and then count 501mS and execute the command”

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