pittfsae

Hi,

I recently purchased a high voltage servo and I am trying to figure out what the standard signal voltage is and what the standard microsecond pulses are for 0-180 degrees and what 1 degree increments are.

I've searched online and called technical support for a couple companies with no solid answer. I'm assuming the signal is 5V, but I would like to confirm that.

If any of you know this information, or where I can find it I would greatly appreciate the help.

pittfsae

If it helps understand why I need to know this, I am using a ProTek R/C 170T "Chad Bradley Team Edition - High Torque" Digital Servo.

I am using a 12 car battery with a bec to power it and an arduino for the signal control. What I need to know is what voltage signal to send and what pulse length I need to control it.

It is for a race car I'm building in college. Thanks in advance!

bigedmustafa

My Feedback: (2)

Hi pittfsae,

I apologize for not being able to answer your questions directly, but I can point you to the folks who should be able to help: http://www.protekrc.com/customer-care/

Most "high voltage" servos are recent designs made to run directly from 7.4V two cell Lithium Polymer batteries, with output voltages as high as 8.4V. Hopefully the folks at ProTek RC can fill in the rest of the information you require. Good luck with your project, and feel free to post pictures or updates!

pittfsae

I'm pretty sure I talked to their tech support already, and the guy on the phone just said they use the industry standard voltage and pulse widths. However I don't know what those standards are and neither did he.

Thank you for the kind response though bigedmustafa!

Please keep the responses coming!

HarryC

My Feedback: (1)

There isn't an industry standard, but most model radio manufacturers have clustered around a common set of figures. Pulse voltage about 4V. Timing pulse is normally minimum 0.9 milliseconds to maximum 2.1 milliseconds with centre at 1.5 milliseconds, refreshed only 40 to 50 times per second with long pauses between each pulse, i.e. one pulse every 20 milliseconds, though digital servos can typically cope with refresh every 10 milliseconds. What angles this drives the servo to is dependent on each type of servo, there is no standard. Typically the pulse can drive it to around 90 - 100 degrees total travel, except for retract servos which can travel 180 degrees. it's rare for a "normal" servo to be able to travel 180 degrees, many have physical stops inside them which block the output shaft turning as far as 180 degrees, many have electronics which will not recognise a pulse short or long enough to drive them that far.

I note that the spec for the servo says max voltage 7.4V. That's not what most of us call "HV", HV should go up to 8.4V. An HV servo exists purely so we can use unregulated 2S lipos instead of 4 or 5 cell nickel batteries. A 2S lipo's nominal voltage is 7.4V but fully charged is 8.4V. If the voltage has dropped to 7.4V no load, the lipo is well discharged. So an HV servo spec should read max voltage 8.4V. But who knows what this brand has done with its electronics, is their spec of max 7.4V just ignorance on the part of whoever wrote the website and it really is 8.4V, or did they make an error in designing the servo electronics and it truly is limited to 7.4V? Unless you can get written confirmation from the manufacturer that their website is wrong and the servo is rated up to 8.4V, I would regulate its main power supply to 7.4V.

pittfsae

Thank you Harry! That confirmed my thoughts on how these servos operate. I have confirmed with tech support that it can handle 8.4V max and that it can make 180 degrees of travel.

Rafael23cc

My Feedback: (6)

Google is awesome.

https://www.google.com/webhp?sourcei...gnal%20voltage

Rafael

sidgates

My Feedback: (2)

Pitt,
I agree with Harry's comments. If I need a 180 degree servo I add end resistors to the end of the pot element. If the servo pot is 1.5K I add approx. 150 ohm resistor to each end. The exact value is determined by experiment.