servo jitter during power-on

[qtommer]

im currently building a RC car and controlling the left/right steering mechanism using a servo.

Each time i switch on my power supply to power the circuit, the servo tends to jitter abit causing the servo to unwantedly turn
I believe this is caused by the power supply spiking during the transition from off to on when i turn on the circuit using a switch.

In the course of troubleshooting, when I removed the PWM input wire to the motor, the spike was still there when "SWITCHED ON" . however, when i removed the power supply input to the servo, there was no jitter whatsoever when "SWITCHED ON"

This confirms that the culprit is the power supply rail. I tried to add filter caps between the power rail and ground but the jitter did not go away.

Coming back from the lab (like 5 mins ago), I googled to see how I can fix the problem and flyback diodes came-up ..However, fly-back diodes seem to be used to counter the spikes during power-off. My servo does not jitter during power-off but only during power-on.


Is there any way which I can remove this jittering caused by the power rail spike during power-on? thanks=)

ps.s my servos are calibrated to idle at 1.5ms. and at the point of discussion , there are no PWM signals entering the servo. just the power supply and the ground connection.

 

[MikeMl]

AFIK the problem is internal to the servos. They will do it whenever the power lead is reconnected, regardless if the 1.5ms pulse train is present or not.

 

[KeepItSimpleStupid]

Try, for what it's worth, bring up the power supply slowly manually with and without a pulse train, but I doubt there will be any differences.

 

[Mr RB]

Why do you need to turn the steering servo power off on a RC car?

Under no-load the servo probably consumes less than 20mA, many are under 10mA.

 

[Pommie]

You don't mention what is controlling the servo so this is only a guess, try tying the signal wire to ground with a 10k resistor.

Mike.

 

[sillypig]

Why do you need to turn the steering servo power off on a RC car?

Under no-load the servo probably consumes less than 20mA, many are under 10mA.

i have had this problem i used a ferrite ring on the signal input turned 4 times around and it solved the problem