Really weird ESC arming problem, please help! NOW SOLVED!

[hogster]

Just to give this thread a happy ending, I've now found a way of reliably getting all 8 ESCs to arm when I plug in

On the main power leads going to the distribution board on the X8, I've soldered a male balance connector in parallel, and in series with the positive lead there's a 10R resistor. So now, I connect the balance plug of the 6S pack to the male balance connector first which powers the system up, and then I connect the main power plugs (with no sparking!).

This works every time, provided the system has sat unpowered for a good 30 seconds or so before plugging in the balance connector ... if you power everything down and immediately reconnect the balance plugs the ESCs don't arm for some reason. But in reality it will take a while to swap batteries anyway, so hopefully that will never be an issue in the field.

Onwards and upwards!

David

[kinderkram]

Good job!
No more magic smoke makes the builder happy and the pilot, too.

[hogster]

Absolutely

I've just spent some more time re-balancing my props, some of which I'm ashamed to say weren't balanced very well by me

Coupled with reducing the tilt rate D, I'm hoping for some more successful hops in the garden soon ...

David

[kinderkram]

Someone from the UK shouldn't talk about the weather.
It's raining cats&dogs here in Germany...

[hogster]

Eh? I didn't mention the weather!

[hogster]

Oh I just went out to do some test flying and my clever anti-spark device doesn't actually make the ESCs start up reliably It works maybe every 1 in 5 attempt ... I will try a larger resistor to reduce the spike still further, but I'm just guessing now really.

Any other thoughts would be much appreciated.

Many thanks, David

PS. At least it's flying now ... once I've got it to arm that is

[chschmid]

Measure your current with Motors not running.
Then calculate the resistor you need U=R*I.
e.g.
You use a 4s Lipo 16.8V when full and connecting.
With lets say 15V your system starts up well.
Your System draws 2A with Video downlink ect.
U=R*I, R=U/I, 1.8/2 = 0.9 so a 1Ohm resistor would match.
If you can live with 14V
2.8/2 = 1.4
If your System draws 0.5A and 15V
1.8/.05 = 3.6Ohm

You use a 10Ohm resistor. So your voltage Drops to low before connecting without resistor.

Does that help?

I use a 1.5Ohm Resistor, 2A draw at 4s. That works perfect.
Use two 1Watt resistors or 1 2Watt R.



Cheers
Christof

[hogster]

Hi Christof,

Thanks for your reply I'm using a 6S pack and I believe it draws about 0.5A when at idle, so V = I*R = 0.5*10 = 5V drop across the resistor. I don't think it's a low-voltage problem, although I do wonder whether the sudden inrush current to charge all 8 caps is causing a much larger voltage drop which is upsetting the ESCs in an altogether different manner.

As the AQ doesn't output PWM until armed, the ESCs should immediately start beeping at 1Hz after powering up to indicate they're waiting for good PWM - without the 10R resistor they will never boot up correctly. So maybe somewhere in the middle would be best ...

Many thanks for your help!

David

[chschmid]

Hi David

It is exactly this issue I have had many times. Your voltage drop is 5V. So fully charged you get 25.2V or 25V. The Systems sees only 20V. The ESC's might check for low voltage which is 3.33V per cell. If the ESC shuts down at 3.4 - voila.

The caps draw an incredible current at loading time but for a very very short time. It is many 100Amps. I cant remember how much it was when I calculated it but I was puzzled about the number.

Try a 25.2 - 22.2 = 3V / 3/.5 = 6Ohm Resistor or lets say below 6Ohm. It is worth a try.

Cheers
Christof

[kinderkram]

If you skip the anti-spark, e.g. by plugging the + first and then plugging the GND, do the ESC start up correctly?