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Q450 v3 - Power distribution board - short circuit after soldering ESC or not?

lpinho

Junior Member
#1
Hi all,

just bought a Q450 v3 quad frame.

I solder all ESCs to the Q450 v3 power board.

To check if everything is ok, I used my multimeter in transistor mode and:

- 1st, + with +
Result: Started with a value that reached 0 after a few seconds (common behavior when connectivity exists)
- 2nd, + with -
Expecting: No value
Result: Value on screen will rise until I get a stable 1550

At this time I though I had a short circuit

So, I turned the multimeter to the resistance mode and repeated the tests:

- 1st, + with +, R = 0
- 2nd, + with -, R will increase (didn't wait for the final value)

I had a few extra ESC around and tried to connect the multimeter to their battery terminals and I got similar values (if I connect the multimeter to the battery connector I get value in the transistor mode and in the resistance mode like in the board after soldering the ESCs).

Does this mean that this is the normal behavior? Or I have a short circuit?

BTW: I run the tests before soldering the ESC and the transistor test returned a negative conductivity

LINEcamera_share_2015-06-24-03-02-53.jpg

Thanks for all your help,

Luis Pinho
 

Craftydan

Hostage Taker of Quads
Staff member
Moderator
Mentor
#3
You've got the ESCs wired in, right?

The ESCs have a fairly large capacitor in each for filtering -- all in parallel so that makes a VERY large capacitor bank. The instant your multimeter applies a current across the voltage rails (which it does for either continuity or resistance measurements), that capacitor bank will look like a short as they sink as much current as your multimeter will source.

After a few seconds to charge up the caps, you're down to the internal input resistance of the ESCs themselves. That shouldn't be infinite but I'd expect it to be in the k-ohm region while the voltage/current is too low to boot.
 

jipp

Senior Member
#6
woohoo. congrats. itsa great feeling once it takes off for the first time.
well heck, i get that feeling every time it goes up in the air. im hooked.
chris.