Let's Make Robots!

Servo problem: only 1 direction.

Another noobquestion here :)

 We have a servo modified for continuous rotation and when we get the 5V power from the PICAXE 28X1 it works just fine, but when we attach the red and black wire directly to a 9V battery it turns only one direction (Clockwise). It seems it's not making a difference between clockwise and counterclockwise :(

 This is the code:

main:
servo 0,75
servo 7,75             =for the servo bug :(
pause 1000
low 0
pause 1000
servo 0,225
pause 1000
low 0
pause 1000
goto main

 The servo stops exactly when it has to but it turns only one direction :( Somebody knows what could be the problem? It works fine on the 5V but not on 9V...

We want to use the separate 9V because we don't want to burn something (we're poor students :D). We are going to use 3 servos total; 2 modified for moving the robot, and 1 with a Sharp IR mounted on it. Is it safe to use them together without risking to burn something? Cause then we have no problem :P The servo's are S3003's BTW

Thanks in advance,

Stef

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Because you are running it on the wrong voltage, pulses from your MCU are no longer high enough to be recognised. The controller IC is probably cmos and as a rule, the pulse needs to be at least 2/3 of the supply to be recognised. As mentioned above do not run your servos at such a high voltage as you will wreck them. Use a 6V regulator or run them off of your 5V supply or use a sepperate battery pack (4.8V-6V).
Thanks! This is the usefull answer I was looking for :) But when I power 3 servo's from the pins of the microcontroller, the current gets higher, so I guess I better use a seperate 6V battery pack to avoid wrecking the mC?
That would be the easiest. Just connect the ground of the 6V pack to the ground of your 9V so your control signals have a return path. another option is to use a low dropout voltage regulator to run your MCU from the 6V pack. eg. a LM2940CT-05 will give you a 5V supply from an input of 5.5V or higher with 1A of current.

What you need is called an H-bridge.  http://en.wikipedia.org/wiki/H-bridge

Use 2 outputs on your chip for each motor and you can change the direction. 

Not for modified servos. They are built into the servos already.

If you don't want to burn anything, why are you feeding 9V to your servos? Servos are normally rated for 6V or some for 7.2V. Also, a standard 9V battery doesn't have much power. Use a separate 6V source.