Servo not working correctly when using the Servo demo for myRIO

[JamesMcK]

Hello,

I'm very sorry if this posted in the wrong area and apoligise for poor spelling and grammar but was wondering if I could get some help.

I am running the servo demo from the project guide and following the video at https://www.youtube.com/watch?v=QXHe0DFbUdc and I am not getting the expected results.

I have tried it with two different servo's. One being a BSP GS-9025MG 2.5kg Mini Throttle Steering RC Servo Metal Gears 1/16 (from amazon), which when plugged spins back and forth and never settles, I have to reduce the frequency to 16 hz for it to stay still but then it only slightly moves when I change the PWM.

The second is from the Mindset Servo and control board from Maplins http://www.maplin.co.uk/p/mindsets-servo-and-controller-board-solder-kit-n10jg, The only information on the servo is it is  a tower-pro SG-5010 DiGi hi-speed. When I connect this to the myRIO I can hear it buzzing away but it does not move. I tried to connect the Ground and voltage up to 4xAA batteries and have the angular postion command input connected up to pin  B/PWM0[27] but then I didn't get any buzzing sound.

I have tested both with a potentiometer connected to 4xAA batteries and they work fine.

I am not that great with circuits and can't figure out what to do. Is the small one getting too much power? Should i fit a resistor or capacitor parrallel with the power and ground ? If so how strong a resistor or capacitor should I use? Is the larger servo not getting enough power? How to I connect it to a different power source from the myRIO? Do I need to run it through some sort of relay?

Thank-you very much for any help you can give,

Kind Regards,

James

[JamesMcK]

Hello,

I managed to fix the problem by coonecting 4xAA batteries in parrellel with the power and ground coming from myRIO.

I'm still not really sure why this makes it work correctly so if any one could shed some light on it that would be great!

[Bob_Schor]

Is the only power to the myRIO and the servo motors coming from the 4 AA batteries?  Batteries have a voltage rating (governed by their internal chemistry) and current rating (governed by, among other things, their size, or how much "oomph" they have).  If you really connected them in parallel, then you were using a constant 1.5 voltage, but providing more current drive, which your circuit appears to require.

Bob Schor

[JamesMcK]

Thank-you Bob

I connected up a transistor and to my understanding this now gives enough current for the servo to work.