Electronics / Controllers: July 2008 Archives

The servo tester that I ordered last week arrived by mail today. Still no sign of the ESC from Hong Kong so I can't wire everything up, but it's a start.

I go the E-Sky EK2-0907 servo tester from Hobby Lobby. With shipping, it was $13.69 although you can get it for a few less dollars if you shop around. I just wanted a basic model and it fit the bill. Most of the units that I see on ebay are identical to this.

You really can't get much simpler. It has inputs for battery power (5-6V) and two server outputs. There were no instructions enclosed but except for wiring it up wrongly, I can't see what the instructions would've said.

On an RC model, you would hook the servo motors to the servo tester to make sure that they were operating correctly (i.e., moving through their full range) in order to diagnose whether your servos were sticking or your RC receiver wasn't sending the right signals.

I'll be using it as my throttle control. I'll be plugging the motor ESC (electronic speed control) into the servo teste. The ESC looks like a servo to the unit and so if you dial in 0, the motor should be at a low RPM or stop; and 10 would be full speed.

I took the servo tester apart and it looks like the main knob is a standard 5K potentiometer. That means that once my testing is finished, I can replace it with a Magura 5K pot throttle that is standard for many e-motorcycles. For now, I'll leave it be.

The main controller chip is most likely something like a 555 timer chip. Basically a servo tester sends out 10-20msec pulses every 60 msec and the servo throw depends on the length of the pulse (10 msec for minimal throw; 20 for max). This is an efficient design and one that's very resistant to RF noise and signal loss. Which means I can make the controller wire pretty long (and unshielded) without too many problems.

The other thing that arrived was a Venon Smart Temp. I was about to buy a cheap BBQ or auto indoor/outdoor thermometer so that I could monitor my engine temperature when I noticed the Venom was just a few dollars more. The neat thing about it is that it will also monitor my BEC/servo voltage too. And if the motor temp exceeds a pre-programmed limit, it can limit the throttle to a pre-programmed limit. So I can set it, for example, that if the motor gets over 60C, then the max throttle is reduced to 60% to protect the motor.

Hopefully my ESC will come tomorrow or Wednesday. My house is filling up with parts that I can't use! I should also be working on the motor mount as well as get some of the servo wiring and BEC placement done in preparation. I could also use some more Dean's connectors....

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This page is a archive of entries in the Electronics / Controllers category from July 2008.

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