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Simple engineer with no background in electronics/electrical engineering here.

I have 2 instruments (emitter and detector) that are synchronized by a Trigger signal. This signal is sent via BNC cable.

I want to put the emitter in a quite far distance from the detector, and I want to know if there is a way to send/receive trigger signal through wireless (Bluetooth?) or through ethernet?

Trigger signal is a 20 kHz square signal from 0 to 3.3 V.

Is there a risk for a delay in triggering?

Thanks

Simple Engineer
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  • Sending a trigger signal through a network is fairly useless due to variable network delay, at least assuming you need it to be remotely accurate. Analog radio should work though. Could even use a voice system since its 20kHz. – user1850479 Aug 18 '21 at 02:13
  • So if I google analog radio emitter (?) I should find some electronic solution to solve my problem? – Simple Engineer Aug 18 '21 at 02:16
  • How closely do the two devices need to be synchronized? 50 microseconds? 1 microsecond? 50 nanoseconds? – Math Keeps Me Busy Aug 18 '21 at 03:39
  • @MathKeepsMeBusy : I tested with a 15m BNC cable, and I found a delay between 70 to 80 ns... and by our standard, this delay is acceptable – Simple Engineer Aug 18 '21 at 04:26
  • @simpleengineer: so, what is the maximum delay you can accept? We need a hard number in seconds. What is the maximum jittering of the delay you can accept (I.e. two triggers might both be within the allowable maximum delay, but not necessarily identical. What is the maximum difference of delay that you can accept?)? Hard numbers please, or else I'll recommend an Ethernet-controlled catapult that throws marbles against a trigger button at the receiver ;-) – mmmm Aug 18 '21 at 07:34
  • @mmmm: Really good question, I have no idea what i the maximum acceptable delay... we always used (short) BNC cables, so we never asked ourselves what would be the acceptable delay. I did a back of an envelop calculation, and an acceptable delay should be less than 10 micro seconds – Simple Engineer Aug 20 '21 at 06:34

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I have in the past built custom hardware with point to point Ethernet connections that could reliable get transmit delays on the order of 1us. But something like that can take a lot of effort to develop.

There is also such a thing as Time Sensitive Networking (TSN) that can be used with Ethernet. And there are off the shelf products for it.

Both of the above options are going to be way more expensive and complicated than just sending a simple trigger signal down a wire.

If you need to send something for a long distance then you just need the right driver and receiver.

For long distance the transmitter and receiver would typically be differential, and possibly isolated if large ground offsets can occur.

One cheap option is to just use a raw RS422/RS485 transceiver on both ends of a long coax or twisted pair wire. The transceiver chips are typically only a few dollars at the most. You can probably get a couple of transceiver development boards pretty cheap. It should be possible to make this work for several thousand feet with the right setup.

user4574
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  • Thank you for the extensive reply. So if my understanding is correct, if I use 2 RS422/RS485 and connect one to my trigger output from the emitter and the second one to the trigger input of the detector, I should be able to send trigger signal? – Simple Engineer Aug 18 '21 at 05:14
  • That is correct. The trigger output goes to the input one transceiver and the detector goes to the output of the other transceiver. Make sure you use transceivers that are rated for high speed (like > 1MBPS) and properly terminate the receiver to match the impedance of your cabling. Also its possible that you would need to use isolated transceivers (or a regular transceiver + digital isolator) if you have large ground offsets. – user4574 Aug 18 '21 at 20:40
  • Woah thanks you very much mate... I will try your solution... I will try to get help of electronic engineer in my lab to get these done! – Simple Engineer Aug 20 '21 at 06:15