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WALL TRANSFORMER V BATTERY PACK FOR SERVOS Answered

Hi there.
While testing some code on three servos using my picaxe 18m2 project board I initially had them powered of the 4x1.5v battery pack. This was working smooth enough, but because I eventually plan to power seven servos (for a robot arm project) I thought I'd try using a 7.5v wall transformer but they didn't seem to like this as the smoothness of movement was gone as they slowed and sped up and were jittery.
 Is the 7.5 a bit much, a few resistors maybe? Or prehaps capacitors would smooth things out. I'm not overly electronically gifted, robot builders guide is all I've got to go on.

cheers. john. 

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jonnymelon
jonnymelon

7 years ago

Looking again at the wall transformer, its actully 6.5v, but it draws only 700Ma of current. I don't know what it was previously used for, I found it among a load of odds and ends. How much current would I need to supply several servos do you think? All the grounds are common, as I mentioned, it worked fine with the battery pack.

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mpilchfamily
mpilchfamily

Reply 7 years ago

Look at the specs on the servos and do the math.

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mpilchfamily
mpilchfamily

7 years ago

The wall wart isn't a good option because it can't supply the amount of current the servos need to draw. If you keep trying to run the servos on the wall wart you will burn out the wall wart.

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caitlinsdad
caitlinsdad

7 years ago

You might have to look into this but I think when you power from an outside or additional source you need to share a common ground with the microprocessor. The data line is tied into the controller of the servo so something happens where the servo acts erratically. Could also be that the wall wart is not supplying enough power to run the servo motors.