Since I’m not an electrical engineer and they teach nothing about oscilloscopes in traffic engineering classes, I’ve been viewing lots of videos about using scopes on YouTube. After seeing W2AEW’s video, I thought I’d get an Arduino and make a “poor man’s TDR” (as he calls it) by having the Arduino output pulses.
This is really quite simple. Too simple.
So simple it didn’t work.
Initially, it looked pretty good. I don’t know about the accuracy of the Arduino, but I imagine that it is good enough. The problem, I’m guessing, is the current. An Arduino is pretty limited (40 mA), so pushing it through a cable and expecting it to be able to act like the video might be pushing it.
Anyway, for the sake of showing, here’s what I did…
The Arduino Sketch
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The Circuit
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It’s pretty simple. Plug the scope probe into pin #7 and ground the scope probe ground to the Arduino.
The Results
Without any coax or with a ~6 foot piece of RG-58 open at the other end, I can see the step from the pulse. But when I connect a 50-ohm dummy load, the voltage drops.
Without a load:
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With a load:
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Note the difference in voltage between the two. I had the scope set to DC for these to keep the baseline the same, and the voltage per division was 1V.
Back to the drawing board.
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