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opto esc and FC power source, grounding

techsgin

Junior Member
#1
Hi All

I have Flip32+ FC (flight controller) connected to 4 OPTO ESC (DYS SN20A).
I have one "3A UBEC Module Low Ripple Bluesky".
Powering the FC was an easy task, I have just plugged the "UBEC 5v out" to one of the free motor pins.

Now I need to connect 2 more elements:

1.12 WS2182b LEDS (12 x 18mA = 216mA)
2. MICRO MinimOSD (500mA i.e 0.5 A)


1. Can I just split the UBEC 5V out into 3 pairs and power both FC, LED and OSD from a single 3A UBEC as there is enough current capacity ? what about noise ?

2. In case the answer for question No. 1 is NO, and I will need to use a second UBEC for better FC noise isolation do I need to share the grounds ?

3. the VBAT sensor ground comes directly from the battery can this cause ground differential ? do i really need to connect the VBAT ground or the "Plus" wire should be sufficient ?

Thanks TechSgin
 

Craftydan

Hostage Taker of Quads
Staff member
Moderator
Mentor
#2
Hey TechSgin, Welcome to the forum!

1. That should work . . . sorta.

Those parts (Flip32, minim, RX, LEDs) should be way under 3A draw, and none are particularly strong noise sources, so you should be fine . . .

. . . but the LEDs in particular may give you a headache. the UBEC is probably set to 5v, and that's fine for all the devices limit wise -- they all like a 5v source -- but the WS2182 series LEDs (B's included) have an issue that the control logic "high" level needs to be fairly close to their power level. The issue is the Flip32 board down-regulates the input voltage to 3.3v for the processor, so a "high" signal coming out is 3-ish volts, not 5-ish volts. What you are likely to find is nothing smokes but the the LEDs don't work, and if you lower the voltage for the LEDs, they'll start responding. How low you need to go is up to manufacturing variation, but the tolerance isn't leaning in your favor.

To fix this properly, you'll need a separate regulator for the LEDs for which I'd recommend something like these. Connect the "In" to the battery, and using a multimeter set the pot until it outputs 3.5v (Blue starts to fade below this). Plug that into the LED's power rail and signal goes to port 4. If you have trouble with it still, you may need a simple RC filter (resistor in-line, Cap between data and ground) to clean any noise off the line -- the chip inside is particularly sensitive.

2. skip.

3. I always recommend single pin, single plug for VBat sensors, but that's just to prevent mixing polarity with raw battery voltage -- if you only have one pin, you can't plug it in backwards. So long as your regulator (UBEC) powering the Flip32 shares ground with the battery, the voltage measurements should be more than accurate enough.