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By TransientJay
#203654
Hi,

This is unrelated to my previous post. I am using a Tsunami and it's suffering from some erratic triggering. I'm using triggers 1 - 6 but am using LONG lengths of cable to them - probably 12 - 15 metres. I'm thinking this is causing it but thought I'd check. If so, I guess the best option is to get a localised Arduino to trigger the Tsunami but will the long distance from the trigger sensors also cause an issue here?
User avatar
By robertsonics
#203665
12 to 15 meters is very, very long for logic level signals. Even if you use an Arduino locally to detect the triggers, you're still going to have an issue trying to communicate over that distance using logic level async serial. The right way to do this is would be to have an Arduino to read the trigger inputs and use a transceiver on each end of the serial communications between the Arduino and Tsunami. You could try RS232 using one of these on each end (make sure you pay attention to RX/TX in the cable):

https://www.sparkfun.com/products/449

It will probably work, but 15 meters is long even for RS232. The best solution would be to use RS422, which easily can go hundreds of feet, but I don't see that SparkFun has a ready-to-go solution for that.
User avatar
By TS-Mark
#203666
Hi TransientJay,

The long cables are almost certainly the issue here. If you are seeing triggers get tripped erratically, that is most likely because you are not using shielded cables and RF interference is triggering false-positives on your inputs.

If you switch to shielded cables, make sure to ground one end of them to earth ground (not the shared ground between your triggers and the Tsunami).

Another option (while not really necessary here) would be to use ethernet cable with RJ45 connectors and breakouts for your trigger connections similar to the project shown in this video. This is probably a bit overkill here and shielded wire should resolve your issue.

I hope this helps explain the cause and offers a couple of good solutions for you without needing to add too much extra hardware.