BLDC motor BL_Heli ESC beacon triggering every PSU OCP I've tried; any solution?

[Fractal]

Hi!

I know this might be very specific to drones and automation but I will try to make it comprehensive

I've had this issue when powering certain drone ESCs through a linear bench PSU where the startup beacon seems to trigger OCP thus failing to start

For anyone that has worked with BL_Heli ESCs, it is the bootup tone you hear on startup that is produced by exciting the motors

My previous PSU (a fairly old motech/amrel LPS-305 triple output) had a pretty long transient response time of 200us, which I assumed to be part of the issue, so I upgraded to one with a much lower value of <50us (a 2007 Motech/BK Precision LPS-505N), but that didn't resolve it!

Even when setting both main outputs in parallel to double the current capacity to 6A, it just won't start, keeps triggering OCP and rebooting

So far I've also tried using fatter leads, adding a small capacitor, but still no beans.

Does that sound in any way like an issue you've experienced before?

The weird part is, it only does it with some of the smallest size 1S motors; 0802-1002 19-25000kv spinners. Even my larger 1S 18650 Wingman with 1202.5 11500kV spinners -and the same ESC manages to start fine.
And of course 3" 3S, 4S and even 5" 5s are no issue

How could it be?

Could using a larger cap/cap bank to further smooth out the transients help? how would I measure/calculate the capacitance required?

Thanks!

[thm_w]

What capacitor did you try?
Some of these ESC's have multiple capacitors on the input, 1000's of uF. Would resolve the issue if you added enough capacitance, and the continuous draw of the ESC is less than 6A.
You could use a scope to measure the voltage at the ESC and see how much it dips.


A single 18650 battery can put out 10 to 30A continuous current or more depending on the model. A 3A linear power supply is not even close to that.

[james_s]

I would try a much larger capacitor, perhaps 20k uF. You could also try and find a schematic for the power supply and add a capacitor to the OCP circuit to make it respond slightly slower.

[Fractal]

Good points; I've only tried a couple 500-600uF caps that came with some larger-size ESCs for power filtering.

I'll see if going much larger resolves this on a special power lead; Not sure about adding one internally as it would permanently reduce it's OCP reactivity

[james_s]

If that doesn't work, add a resistor between the PSU and capacitor to limit the max current.