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40A DC Motor speed regulator with BEC, KITS for sale or assembled

Updated September 21st. 2003.

Here is my homemade 40A regulator with cables and heat shrinking tube. Ready to fly,
You can make one just like this, read below to find out how

The schematic looks really simple.
R3 needs to be selected so the low voltage cut off will work best for the number of cells used.
R3 = 3k0 cut off at 5.4 volt, works good for 6 cells.
R3 = 3k9 cut off at 6.7 volt, works good for 7-8 cells.
R3 = 4k7 cut off at 7.8 volt, works good for 9-10 cells.
Test the cut off voltage is right, using a little light bulb instead of the motor, and a DC variable powersupply.

Top side with component placement. Seen from the top solder side.

Bottom side with component placement, seen from the bottom solder side.

The proffesionally made PCB is made using double layer copper in double thickness to handle the high current.
This regulator boards measures 29 x 36 mm.
The layout supports both SMD and DIL microcontrollers, lets see what the future brings about, what types are cheapest and easy to get.
SMD soldering instructions (Danish and English version)

Top side, with text in silkscreen print, this makes it easy to make it right.

Bottom side, has a few components placed.

Here is the information about where to solder your wires, batt+ and mot+ must be soldered at SAME place, so that high current goes directly from cable to cable.
Batt+ and mot+ use red wire, Batt- and mot- use black wire, 1mm2/10A the motor uses max.

Motor and regulator mounted as close as possible, the motor plus terminal is soldered to the motor case to minimize radio noise radiation.
Also remember to add a 100nF capacitor directly on the motor.
Battery and battery cables are to be kept short to minimize noise radiation into the reciever and antenna,
that is mounted as far away as possible from the regulator and motor.

See here the wires have been soldered.

Cost and performance:
This homemade regulator (8.5 grams) can be made for a really low budget.
I sell all the parts you need attached to one A4 size paper so you know you have got it all.
Kit Price is:
with 1 FET 10A 65 DKR
with 2 FETs 20A 75 DKR
with 3 FETs 30A 85 DKR
with 4 FETs 40A 95 DKR

Assembled and tested Price range:
with 1 FET 10A 140 DKR
with 2 FETs 20A 150 DKR
with 3 FETs 30A 160 DKR
with 4 FETs 40A 170 DKR
All prices are in Danish Kroner.
You need servo cable Red and Black power cable and some heatshrink tube to complete it.

I can sell to worldwide RC freaks no problem, I have a www.moneybookers.com account so you can transfer in advance fast and easy.
You will have to pay for postage extra off course.
Please contact me in advance for sorting out what you need and addresses and so on: thomas at webx dot dk

This regulator can be used from the smallest to the biggest DC motors ! It all depends on the fets used and the number of them,
just add one fet for each 10A peak current you need. The PCB has room for 4 of them normally so you can regulate up to 40 Amps !

More amps !?!?
If the demand is more amps or cooler fets, it is possible to mount 4 more directly on top of the first 4,
with 8 fets you will have a 80A regulator ! for only 40 DKR extra.

See 8 fets on the same board. (sorry this picture is of old homemade proto board, but the same can be made in the prof boards.)

The top mounted fets; bend the legs carefully into the fet so they will almost reach the bottom fet,
then apply plenty of solder to carry all the amps and transfer the heat better,
be carefull to double check all connections are good.

How it works:
First turn on your transmitter!
Then turn on battery power to this motor regulator that also supply the reciever,
When voltage is applied the PIC is reset, then the software will check for zero throttle,
if not it will make a beep beep beep sound (with motor) until zero throttle is recieved.
Normal operation is when IC1 pin 3 is over the threshhold voltage, then the motor speed can be adjusted from zero to 100 % of battery power,
The regulation is done in micro steps so it is really nice smooth PWM regulation, the main switching periode frequency is 1KHz.
When battery voltage drops to the low voltage threshhold the program simply goes to the reset state,
now the throttle must go to zero again before motor speed can be turned back on,
but don't give max throttle now then it will off course reach the low threshhold point again, due a flat battery.

Original design, schematic and program see this link:
Original ECS software:
Min servo pulse 1200uS (Motor PWM = 0%)
Max servo pulse 1800uS (Motor PWM = 100%)
PWM output pulse was lo active, so extra fets driver was needed.

Francisco Pantano Rubiņo helped me so I could modify the program,
The following program changes were made:
New ECS2 software:
Min servo pulse 1326uS (Motor PWM = 0%)
Max servo pulse 1734uS (Motor PWM = 100%)
Output is now active Hi to drive N-fets directly.
Programming the PIC12C508 was done using free software called IC-Prog, and home made parallel port programmer (propic style)
Fuses = Code protect off, Watchdog off, Masterclear off, Internal RC osc.

EMF Brake add on board
See here how I did it.

Made September 2003, Thomas Scherrer.