Does not control digital servos

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Does not control digital servos

Postby erk1313 » Sun Apr 26, 2009 6:19 am

Just wanted to confirm others are having the same problem with DIGITAL servos:

I tested the MicroSerialServo controller with two digital servos, Futaba and Traxxas brands. The servos would barely move, sometimes trigger the yellow LED, and prevent other servos from moving. The test involved starting the servos at position 1500, and sweeping up and down from there. I know the setup works fine, because I can immediately hook up analog servos and control them through an entire range of motion.

Thoughts?
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Re: Does not control digital servos

Postby nexisnet » Sun Apr 26, 2009 12:39 pm

I don't think the problem's you're seeing have anything to do with whether the servos are analog or digital, as that distinction only has to do with how the servos control themselves internally, the servo signal protocol is exactly the same.

That being said, digital servos do tend to control their positions more tightly than comparable analog servos, with the unfortunate side effects of generating more ambient electrical noise, and drawing more power, either of which could be what is interfering with your servo controler. Of course, you would see exactly the same effect with a high-torque analog servo under load.

If the yellow light is coming back on, it sounds like your servo controller is being reset, which would mean that your digital servos are drawing too much current from your power source, and the voltage is dropping to the point where the servo controller resets (I'm assuming you're powering the servos and the controller from the same source here). There are a couple of things you can try to address this problem, particularly making sure your servo power supply can source enough current for all of your servos, and separating the servo power and controller power sources. If you're servos are drawing a lot of power, it's also a good idea to power them directly through wires rather than through the servo controller circuit board bus.

If you're still having trouble, can you describe your power and wiring setup in detail?

Good luck!

-Adam
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Re: Does not control digital servos

Postby erk1313 » Wed Apr 29, 2009 10:54 am

Thanks for the quick reply! Sorry I must have missed the reply email.

I will try using a bigger power supply. Any idea on how much power a typical RC servo uses?

-Eric
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Re: Does not control digital servos

Postby nexisnet » Wed Apr 29, 2009 10:57 am

Servo current draw depends on the servo (particularly how powerful its motor is), and how hard it's working. A very ballpark rule of thumb I use is try to have at least 1 amp available per 100 Oz*in of torque.

-Adam
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