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Sensors, Actuators, and Robotics » Strange Problem with Servo

February 01, 2010
by ecornwell
ecornwell's Avatar

Hello,

I had some old Tower Hobbies STD TS-53 servos sitting around so I thought I'd try and use them. So far, I'm not having good luck. I tried the servosquirter code and ran into a problem. I have the servo hooked up to PB2 as instructed and when I apply power, I get a reading on the screen. As soon as I try to enter '[' or ']' for a new position it seems as if the whole thing resets.

Here is the result from my UART output:

ba2740
baba2790
bababa

After the first "ba" I hit '[' after the the "baba" I hit ']'.

The servo moves just a little bit and looks like it's twitching back and forth more than anything.

Any ideas?

Thanks!

February 01, 2010
by Phrank916
Phrank916's Avatar

My guess would be a power issue. What are you powering everything with? The 9V battery? I was running the NerdKit with LCD and also the LCD back-light along with a PS2 joystick and a servo the other night and the same thing was happening, and I'm powering the breadboard rails with a 5V 1A wall=wart. I determined everything was just drawing too much power after I disconnected the LCD back-light power and it worked fine.

February 01, 2010
by mongo
mongo's Avatar

Yup! Sounds like the servo has a little bit of an inrush issue. (pulls a little too much current to get going). Try adding a capacitor to the point where you tie in the power leads. I had to do the same with my little Futaba servos. I added a little 100uF 16V capacitor and it solved the problem here. The pic is a little over-exposed but you can see the cap right behind the servo plugs. This is the dual servo setup from another thread here in the forums.

alt image text

February 01, 2010
by ecornwell
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Thanks, I was wondering if it would be something like this. Time to stock up on some other parts! :)

February 01, 2010
by ecornwell
ecornwell's Avatar

Sorry, I forgot to reply completely. I've got a wall wart hooked up that came with the LED Array kit.

February 01, 2010
by Phrank916
Phrank916's Avatar

mongo- Thanks for the capacitor idea! I actually just salvaged a few caps off a broken audio pre-amp board. I'm gonna make use of one!

February 01, 2010
by mongo
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...and thanks to you Phrank for figuring out the multi servo thing...

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