Hi all,

I want to extend the servo leads to around 40m. I will be controlling the servo using the Turnigy Servo Tester. What method can I use to achieve this?
Thanks.

 

What method can I use to achieve this?

Um... Splicing?

 

Um... Splicing?

But will the PWM signal work fine with a 40m lead?

 

Depending upon system parameters the lead inductance may pose a problem -- That said; it won't cost you much to try it before 'moving on' to more sophisticated/expensive approaches

Best regards
HP

 

What is the PWM frequency?
What is the PWM amplitude?
What are the PWM minimum and maximum duty cycles or pulse widths?
What is the load impedance at the end of the long cable?
Is coax cable a viable option in your application and environment?
Is power available at the end of the long cable for a signal receiver circuit?

ak

 

What is the PWM frequency?
What is the PWM amplitude?
What are the PWM minimum and maximum duty cycles or pulse widths?
What is the load impedance at the end of the long cable?
Is coax cable a viable option in your application and environment?
Is power available at the end of the long cable for a signal receiver circuit?

ak

All crucial questions is a definitive quantitative solution required --- Tho' I be lazy So I'd just try it - if it appears to work verification of waveforms/transient response should establish reliability... My $.02

Best regards
HP

 

I would also measure the voltage at the servo for the 4.6v minimum.
The frequency is fairly low at usually 300-400Hz.
Max.

 

I would also measure the voltage at the servo for the 4.6v minimum.
The frequency is fairly low at usually 300-400Hz.
Max.

The Turnigy servo tester signal repetition rate is almost certainly 50 Hz (i.e., 20 mS). The pulse width can be between about 1 mS and 2 mS, depending on the commanded position. The exact change from a center of 1.5 mS pulse width can vary by servo and can even be adjusted by the user with some set-ups.

John

 

I haven't looked but I would assume that you can buy an extender the same place you bought the servo.

 

I read somewhere for analog servos the frequency is30-50 Hz, and for digital servos it is 300 to 400 Hz.

I haven't looked but I would assume that you can buy an extender the same place you bought the servo.

I have never seen one for 40m?
That is a 150ft drum of cable.
Max.

 

I read somewhere for analog servos the frequency is30-50 Hz, and for digital servos it is 300 to 400 Hz.



I have never seen one for 40m?
That is a 150ft drum of cable.
Max.

Of course it goes without saying (Re: digital systems) that transient time requirements determine the required bandwidth...

Best regards
HP

 

I have never seen one for 40m?
That is a 150ft drum of cable.
Max.

Oops. I was thinking more like 40mm.

 

Depending upon system parameters the lead inductance may pose a problem -- That said; it won't cost you much to try it before 'moving on' to more sophisticated/expensive approaches

Best regards
HP

Not just inductance - impedance could be an issue with that much cable, a mis match would probably cause ringing.

Just a guess - but I'm thinking twisted pair is probably the bare minimum to get at least some sort of predictability into the characteristic impedance.

 

Not just inductance - impedance could be an issue with that much cable, a mis match would probably cause ringing...

My reply assumed an analog selsyn/synchro arrangement wherein transmission line phenomena would be of negligible significance -- That said, I agree that a 'proper' transmission line presenting a predictable characteristic impedance is the only way to go where any bandwidth is required

Best regards
HP

 

If t is something like a 5 V PWM signal, RS422/485 can drive miles, but requires DC power at the receiving end.

ak

 

I wondered about the 40m requirement as well. The longest servo extender (for RC servos) was 900mm... That I could find

 

@Dritech

Oh my! Upon careful review of comments to this thread it appears my interpretation of the OP was over-general -- thus it seems you're referring to 'servos' as applied to robotics/RC models, etc...? Score another 'Litella moment' for HP (to wit: "Never mind"

Best regards
HP

 

-- thus it seems you're referring to 'servos' as applied to robotics/RC models, etc...?

HP

Working with motion control and servo's, That one used to catch me out at first.
Max.