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Brushless Motor Controller

Speed control for radio controlled scale models

Brushless Motor Controller
This article mainly concerns enthusiasts using radio controlled scale models that include an electrical motor without permanent magnet brushes, usually called ‘brushless motors’.
massive interest in recent years for this type of propulsion system has made it possible to take electric motors to record levels in terms of efficiency and compactness, with the inevitable trade-off of increased complexity in control electronics. This article describes the basic theoretical principles linked to the operation of these motors, and a solution that is dependent on the ST7 microcontroller, recently introduced to the market and completely dedicated to this type of application.
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Gerber file

CAM/CAD data for the PCB referred to in this article is available as a Gerber file. Elektor Members can exclusively download these files for free as part of their Membership. Gerber files allow a PCB to be produced on an appropriate device available locally, or through an online PCB manufacturing service. Elektor recommends its business partner Eurocircuits as the company of choice for its own prototypes and volume production in selected cases.

Microcontroller board (050157-2)
Resistors:
R1,R4 = not fitted
R2 = 4k7
R3,R5 = 10k
R6 = 22k
R7 = 15k
R8 = 5,6
R9 = 5k1
R10-R15 = 6k8
R16 = 3k3
Capacitors:
C1,C2,C3,C5,C6,C7 = 100nF
C4 = not fitted
C8 = 10nF
C9*,C12* = 4µF7 20V low-ESR
C10 = 47µF 6V3
C11* = 2µF2 5V low-ESR
Semiconductors:
D1 = BAT54
IC1 = M24C01
IC2 = ST7MC1, programmed, Publishers order code 050157-41)
IC3,IC4 = L4941 BA05FP
Miscellaneous:
X1 = 8MHz quartz crystal
K1,K2 = see text
K3 = 3-way SIL header with 1 jumper
PCB, ref, 050157-1 from The PCBShop

Power driver board (050157-1)
Resistors:
R25-R30 = 270
R31-R36 = 1k
R37-R48 = 240
Capacitors:
C1,C11-C17 = 100nF
C2-C10 = not fitted
C18 = 470µF 6V3
Semiconductors:
D1,D2,D3 = BAT54A
D4,D5,D6 = BAT54C
T16-T21 = FDS6675
T22-T27 = BSS138, 2N7002
T28-T33 = PHK12NQ03LT
T34-T39 = BC817-40
T40,T42,T43 = BC807-40
T41 = not fitted
Miscellaneous:
K2,K3 = see text.
PCB, ref. 050157-2 from The PCBShop.
Generic library, file # 050157-11, Free Download, February 2006.
User Manual, file # 050157-13, Free Download, February 2006.
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