Can I check 400Hz PWM on a servo tester?

[hogster]

Hi all

I've just ordered one of these servo testers:

http://www.cmldistribution.co.uk/cml_pr ... 0000006047

to try and debug my non-flying X8, and but after reading it hit me – will I actually be able to use it for setting the end points of 400Hz ESCs, or even to monitor the PWM output coming from the AQ. I hope so

Many thanks

David

[SuperSharpShooter]

If you have an arducopter board you can use that to check the pwm that is being output by your receiver or the AQ board by connecting the output you want to measure into one of the radio inputs on the APM and then looking on the status screen.

I understand it can also be done with a multiwii board but I don't have experience with it myself.

[hogster]

Hi SSS, thanks for your reply. Does this mean I should not attempt to use the servo tester to measure the output of my AQ?

Thanks David

[SuperSharpShooter]

[kinderkram]

[hogster]

Hi Norbert, sorry I should have mentioned that it can also give a readout of PWM: "7. PW (Pulse Width) Shows the Pulse Width of the Transmitter Channel."

So really my concern is whether something designed to look for 50Hz PWM (I assume?) will be damaged by seeing PWM at 8 times that frequency. I don't imagine so, but the comment in the wiki about 400Hz PWM being able to damage / kill an analogue servo got me worried ...

Many thanks David

[aBUGSworstnightmare]

Hi David,

the UniTest2 is what you're looking for (http://www.sm-modellbau.de/pdf/UniTest2_Translation.pdf); but it looks like it's no longer available (or currently out of stock; don't know): odellbau.de/shop/

Maybe you know somebody with a digital scope; it's the best for such a measuring task. A logic tester is also an option, since it's also able to measure the frequency of the input signal (i.e Saleae Logic https://www.saleae.com/logic).

Analog Servos usually 'get nuts' when you drive them with high input frequencies; that's why some of them might get damaged.

Joerg

[hogster]

That Salea Logic device looks very neat. For a similar price, maybe a portable scope like this might be something I should consider for debugging in general ...

http://www.ebay.co.uk/itm/Portable-Mini ... 2c799a6bc4

Cheers David

[JussiH]

Those small pocket DSOs are usually no good for any serious work and are rarely recommended, but it works for very basic stuff...but if I was you, I would skip it and save up for something like a Rigol DS1052E, which is well worth the extra money.

I can tell you that AQ puts out a very clean and jitterfree 400 hz PWM signal....

If the question is to set up the ESC´s, its usually the case with SimonK´s and similar that even though they support signals up to 450 hz they dont require them and will work down to the "normal" RX radio update rate of aroudn 50 hz and lower. ESC32 supports from 40 up to 450 hz input PWM signal, so does SimonK and BLheli.

So if you get a servo tester that shows the PWM width of the signal, It can be used to calibrate ESCs that require a stick calibration routine. You dont need a special one to run "fast update" ESCs

[Max]

I don't know about Spektrum or most other brand Rxs, but some systems allow you to connect the Rx to a computer via serial link, to update firwmare, set failsafes, and so on. Usually includes a way to monitor the actual channel outputs as well.

-Max