Servo Tester ccts for motor control - RC Groups
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Apr 26, 2001, 04:59 AM
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Servo Tester ccts for motor control

This discussion started on the "Motor cutoff" thread. Basically we were saying that motor control can be achieved by mounting a "Servo tester" on the model to drive the ESC with the potentiometer / variable resistor in the circuit mounted on the handle and connected via a pair of insulated control lines.

As jrb has pointed out there are several published servo testers e.g. at

Ccts 1, 2, 3 and 5 of these can easily be converted by simply making the pot remote on the handle. In the circuit diagrams the component I'm talking about is :

Cct 1 - P1 1K
Cct 2 - P2 100K
Cct 3 - P1 2K7 (2.7K)
Cct 5 - P1 4k7 (4.7K)

When two of the connections are shown connected together this can be done at the handle so you still only need to run 2 wires to the plane.

Cct 4 uses all 3 connections on the pot so it would need adjusting a little but the others give you plenty of choice.

Cct 5 is probably the best of them from our point of view because the component values are reasonable and it's very simple. You can run the circuit from the 5V supply from the BEC in the Speed Control or direct from the motor battery depending on how many cells you're using. I usually use a slightly different IC (i.e. TS555 or ICM7555, the CMOS versions) for better stability but any old cheapo 555 timer will do.

It would probably also be possible to buy a commercial tester and pull it apart but the circuits aren't very difficult to build so I don't think it's worth it.

Good Luck - Steve
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Apr 26, 2001, 08:40 AM
jrb's Avatar
Thanks for looking at the details and posting your thoughts into a new thread.

Hope someone goes for it!