Overloading a Servo Through the Trigger Pin? 3

[Helepolis]

Hello all,

Sorry in advance for the "stupid" question, but i just couldn't find the answer online and i want to be 100% sure that the component will not be damaged.

I'm using the SAVOX - SW0241MG, the servo is rated for 7.4VDC.
To control the servo I'm using an (Arduino based) PLC, the servo and PLC each has its own power supply.
The output pins on the PLC generate a pulse of 24VDC.

Might the servo be damaged if i connect its trigger pin wire to the 24VDC output of the PLC?

 

[MikeHalloran]

Absent a real specification or appnotes for the servo, I'd assume the higher voltage pulse will be a problem.

But do read up on voltage dividers.



Mike Halloran
Pembroke Pines, FL, USA

 

[Helepolis]

Thank you for the quick reply and for the tip on the voltage dividers.

Yeah the specs provided by the servo manufacturer are very basic.

 

[IRstuff]

I would think that it's a near certainty that the servo will get damaged with 24V

TTFN (ta ta for now)
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[itsmoked]

Yep Damage City.

You can use a Zener diode and a resistor to solve the problem.

Put the Zener from ground pointing to the servo pin and the 10kΩ resistor from the servo pin to the PLC. Use a 7.2V Zener.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[Helepolis]

Excellent, thabk you all for the help!

 

[itsmoked]

I left out the resistor value: 10kΩ

Keith Cress
kcress -

http://www.flaminsystems.com

 

[waross]

As Hawkeye Pierce said to the General;
"Take another star out of petty cash!" grin

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[mikekilroy]

Late to the party, but comment non the less... Zener means making the input non linear. Don't do it.

Instead, use a voltage divider to reduce 24v peak to 10v peak: so do the math. Short the math, use a 15k in series with a 10k resistor, and feed the servo from the junction of them

http://www.KilroyWasHere<dot>com

 

[Skogsgurra]

I thought those servos were pulse controlled? Then a non-linear input wouldn't cause any trouble. But the source impedance may.

Gunnar Englund

http://www.gke.org

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Half full - Half empty? I don't mind. It's what in it that counts.

 

[mikekilroy]

I should not have posted, sorry. I ASSUMED this was a typical +/-10v analog input command servo. Looking at their website, there are NO specs for input command; it seems to be a tiny model car controller! So all our comments about 24V PWM harming the command input are out the window with no specs given. Thank you for the correction Skogsgurra

http://www.KilroyWasHere<dot>com

 

[SceneryDriver]

24V will absolutely damage the servo. Those are RC servos, and expect a ~5V PWM control signal. Most are designed to run on 4.8 - 6V (NiCad battery voltages). A few can operate on up to 7.2V. REALLY large RC servos can have separate motor power (12V or 24VDC) but still expect to see a 5V PWM signal for control.

For reference:

https://en.wikipedia.org/wiki/Servo_(radio_control)

SceneryDriver

 

[Helepolis]

Thanks!