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Old Apr 04, 2012, 08:11 PM
Crash and learn
United States, PA
Joined Dec 2011
1,605 Posts
DH9104 NOTES - Motor FETs and Motor Amps

DH9104 NOTES - Motor FETs and Motor Amps
fly4fun6719 pulled a part number off one of the DH9104 motor switching FETs.
Part number is: CEP73A3G

N-Channel Enhancement Mode Field Effect Transistor
30V, 62A,
RDS(ON) = 9mW @VGS = 10V
RDS(ON) = 16mW @VGS = 4.5V.
Super high dense cell design for extremely low RDS(ON).

"Purchased a IRF1405 mosfet from the local electronics store and fitted it..I tried it with the receiver out of the helicopter and it appears to work ok.The only problem I had was removing the original mosfet. I haven't done this sought of work for some years and I am a bit rusty."

IRF1405 should work as a replacement for any Syma or Double Horse receiver board.
Note: Input control Voltage Gate to Source is 5.0v for 20 amps motor current, though it does start switching ON between 2.0 and 4.0 Volts.

VDSS = 55V
RDS(on) = 5.3mΩ
ID = 169A


IRFZ44N IRFZ44 Power MOSFET N-Channel International Rectifier - Banggood

DH9104 tail motor was 2.99 amps full speed off 7.4v 1300mah Li-Ion stock battery.

Main motor 5.72 amps full speed off 7.4v 1300mah Li-Ion stock battery.

Non-motor load = 23ma = receiver and forward white floodlight LED (Transmitter turned off)
Receiver without LED and motors = 16.1ma (Transmitter turned off)
Receiver without LED and motors = 17.6ma (Transmitter turned on)
Receiver without LED and motors, Servo disconnected = 9.6ma (Transmitter turned off)
Receiver without LED and motors, Servo disconnected = 11.2ma (Transmitter turned on)

7.4v 1300mah Li-Ion stock battery = 7.67 volts no load after running tests (needs recharging).

I had expected main motor around 10 amps. It may not have been running full speed due to the test leads, but the main blades were bending upwards, so 5.72 amps is at least close.

Motor ampere measurements were by shorting motor switching FETs to ground through ammeter. Kids, don't do this at home!

DH9104/9100 TX schematic drawing
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Last edited by Ribble; May 13, 2012 at 10:42 PM.
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