servo jittering

Denzel

Senior Member
a few weeks ago I mentioned the robotic arm I was planning to build and how to go about it. I purchased 3 servos for the shoulder and elbow and used a servo I already had for the rotating base. the construction went like a dream and although I broke my only picaxe 28x before getting the PCB prepared I managed to run the four servos from an 08m on breadboard. The arm is very powerful and can pick anything up from a 9v battery to a tennis ball without a strain so overall im very pleased with the results so far...

However. When I first turn the device on. the servo in the base jitters and swerves randomly for about 10 seconds before the programme starts but it works fine after this. The servo in the base is about 2 years old and was used in the fuselage of a model plane (petrol) I am stumped as to what is causing this..

this is the first bit of my code:
Output 0 's1
Output 1 's2
Output 4 's3,s4
Main:
low 0
low 1
low 4
goto goservo

goservo:
'shoulder
servo 4,70 'top
'elbow
servo 1,225 'end when coming up.
pause 2500
'base
servo 0,220 'far left
pause 2500

Any Ideas?
thanks
 

Technical

Technical Support
Staff member
The base is being controlled by output 0. On the 08M this is also the download communication pin, so during a download (and any sertxd, debug commands) the servo will be receiving random serial data pulses. This may well cause it to go a bit wobbly! A jumper link may help!

If this is happening at start up make sure the serin pin is also tied low correctly (via the 10k/22k download circuiit). If not the chip may think a new download is taking place and transmit data.
 
Top