How to convert brushed flight controller to brushless


#1

Wondering if anyone from MMC tried this already? I have an old scisky board that I want to try it with.


#2

Do it!
I’ll get round to it over winter with an old scisky too.


#3

I don’t know the value of the diode he used lol.


#4

He says 1K resistors across the motor pads.


#5

yes but the diode he used to drop the 2s voltage. would you know?


#6

This video is the hard way…
Power FC off of balance connector from 2s…no diode.

Hijack PWM signal from FET pad as pictured:

Use any ESC’s you please


#7

I believe a 1N400 diode would drop voltage to between 4.1V and 4.3V so should be fine. But as @Jtwalkz says there are ways to do it without a diode too, H8 silverware brushless builds do it differently too.


#8

I followed this diagram and it was very easy, using racerstar 6a esc’s and their 1103 8000kv motors, on betaflight configuration tab I used oneshot configuration for the esc’s, and did not do anything else to the esc. I originally had set it to pwm and it gave me a lot of wobbles.


#9

Hi mate. Germanium Diodes principally have a PN Junction barrier charge that requires a 0.2V Voltage drop.

For Silicon Diode PN Junctions, this value is increased to around 0.6V for the voltage across the PN Junction to be sufficient, that the energy provided will cause a flow of electrons across that junction.

This occurs for all Germanium and Silicon PN junctions respectively.

Therefore, a transistor comprising a PN or one comprising an NP junction of Germanium, will have a break down barrier voltage required of 0.2 volts before electrons will flow across the junction, and therefore a transistor made of Silicon shall require a breakdown voltage of around 0.6V to achieve the same result.

Whilst this is an ideal voltage of 0.2V or 0.6V most of these components use Silicon now anyway, it does not mean the figures are concise. Some components might be rated at 0.5 or 0.4V or otherwise. Germanium Diodes are used principally in RF applications, for example, to provide half wave rectification in an AM Receiver.

In fact, one germanium diode, is really all you need (save for an antenna) to create a crystal radio.

Germanium, diodes replaced the Cats Whisker which used a small amount of Galena, to form a Junction.

I have a Cats Whisker at home, and you can purchase them online, for kits.

Anyways hope that helps.


#10

thanks mate. is it just me or the photo is cropped? Where’s the connection from FC?


#11

Hi Jtwalkz, old post but very interesting and actual to me! I am a noobie so from what I can understand from the diagram, you use all wires of ESC. Red and Black go to + and - at the pad (where he is putting a resistor) and signal go to Gate of Mosfet? Confirm this? And this is valid for other brushed based FC?
Thks


#12

Hi Airkaos , I am a noobie so I cannot understand well the diagram. The signal cable, I understand that goes to the gate of Mosfet but the Red and Black go where? To the pad where 100%epic was putting the resistor? Thks


#13

The red and black go connected directly to battery power. On the video he makes a daysi chain connecting all + together and the same with negative.


#14

Thks. I am not getting the result yet because, I think, battery is too weak for the 2204 2300kv I am using at tests! I will buy today one better or if the 1304 3100kv arrive today as I expect, I will change motor! Using 4in1 ESC but I think is the same! Note - to get it spinning I must do somethinh at BHHeli?


#15

I don’t know if a 4 in 1 will work, when i dis it I used separate esc’s and the where running older blheli, not blheliS. But i think it will work, you have to connect it directly to the leg of the fet on the oard, like Jtwalks picture


#16

See also:


#17

Hi, I had already seen your video but I thought it was for Eachine boards! Do you think I can do the same with this board of Hubsan? I will bridge the Source and Drain of Mosfet and remove the red x (must confirm 1 I have doubts). If are individual ESC (mine have a twisted par with white and black) The white/signal goes to motor pad + and the black goes to - . Is that for individual ESC? But I want to use the 4in1 ESC as pictured above. How I make the wiring here? Just

a noobie!


#18

After seeing better the video and after airkaos comment, if I connect signal to gate of mosfet I don’t need the bridge I assume! And resistors are removed or not in this case?
We are 4 that are trying several methods for the conversion of this board! At this moment the most advanced guy has managed to put the brushless motors spinning with the signal at gate of mosfet and no bridge, but he must keep the brushed motors at the original pads that spin at same time the brushless ones! One of us thought to replace each brushed motor with a resistor but not luck until now! These Brushed motors get from 4 to 7 volts 1 - 1.5A! What do you think?


#19

The way I did it, the motor is conected to the esc, the esc has 4 cables 1+, 1-, 1 signal, and 1 signal ground (standard on all esc) the + goes directly to battery positive, - goes directly to battery negative, signal goes to the gate on the mosfet like on the picture, signal - I did not use, I did not bridge anything just plugged directly to the mosfet (I did not even take out the mosfet), after all that I used a polulu to power the flight controller since the one I was using would only take 5V.


#20

thks. As is the first time I make a build, when you say that + and - goes directly to battery you wanna mean to the PDB + and -. Correct?