ctclibby
Well-Known Member
Data signal: does not the servo controller ( Mardec ... right ) send a specific pulse width to turn the servo one direction, another pulse width to turn the servo the other direction? PWM.Thanks for your quick reply. I will try to answer or comment some of the items:
- data signal: I mean the pulse of 1000 to 2000 microsecs at approx 50Hz repetition, issued by the Arduino of the Mardec. Not really a PWM, but I have seen that an AnalogWrite is used in the code of the MardeC
- Twisted? No, not even in parallel, one wire running completely alone (it is a real "antenna")
- Current probe? No probe for low currents available. Should I just use a low value series resistor?
I have a 4 channel Tek, so I could monitor data, power and ground.
Problem is we have to reproduce the original setup to see the problems, but I will remember the suggestion.
- The glitches can be seen with an approximative guess of width, but could not yet be captured, as there are a number of glitches, and not all fire the servo.
- Servo controller: what do you mean ? The Arduino of the Mardec? The electronics inside the servo?
- We use the standard Arduino code of Arcomora (Mardec is the decoder unit in the Arcomora family). I am not ready to code that type of control software. I have written a small "DCC sniffer" or servo controllers, but Mardec has a lot of functions...
And we are highly confident that is not the cause, but who knows? I keep this possibility open.
- Do you mean inputting a pulse on a free Arduino pin to check the reaction?
- I agree: the "DCC controlled engines" are big spikes emitters, some more than others, and this is reproductible ( e.g. one engine gives the prob once on 10 runs , another one once on 2 runs)
Will continue in order to get a stable solution, thanks again
Phil.
Not saying a single line ( antenna ) is or is not the problem although I would at least wrap a ground around it only connected at one location ... probably the servo.
low values resistor is just going to add to the impedance of your probe. The resistance part of the impedance is probably not the problem, that 10pF cap might be. If needed you can sorta create a current probe by using a choke from old pcb - torriod with a few wraps of wire. For testing run the single signal line through the center; maybe wrap it once or twice if needed. It would not be calibrated and could be pretty noisy but could serve purpose.
Output a pulse on a Arduino port pin during the initialization of the servo port to trigger scope. If the controller is resetting intermittently you would see this during idle times of the servo. Since you are not writing the code, maybe something to look at when all else fails. You are probably right though, controller is probably working okiedokie.
Last and not least maybe an EMI coating on the inside of the engine shell - probably overkill and one of the last things you can try.
