Project: motorcontroller for electrical bike

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Roderick Young

Joined Feb 22, 2015
Courtesy of Google translate:

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The motor controller of the electric bike sparta pharos did strange and new costs a lot, therefore yourself cobble something together.
First experiment with a microcontroller tiny13, everything worked well until the engine was connected, the power surges disturbed occasionally the controller and this was not just betrouwbaar.Dan but analog pulse width modulation control a fet and pulse width as a function of trapsensor.Dit worked but the bike jumped as young
horse up so not good .The surge was more than 20A.
So we made a flow control and it works perfectly.

The schema is fairly simple, it is made up of a comparator U2A, the inverting input receives a voltage in function of the motor current.
The non-inverting input receives the signal from the kick sensor.
The stair sensor provides a resting voltage of 1.2V, if one force on the pedals turn the output voltage increases to 2.5V.
With the potentiometer RV1 can choose the support arbitrarily.
In order to prevent the motor from rotating is at a standstill, a second comparator U2B, communication of the switch as soon as the input voltage is greater than 1.5V.
Both outputs of the comparator forms an AND function (open collector output) .The fetdriver is formed by Q1, the diode D2 will discharge the gate capacitance rapidly
when one of the comparator outputs are low.
The LM7805 is the stairs of the sensor supply.
The opamp U3A is used as battery indicator, if the voltage drops below 21V, the LED will blink uitgaan.Vooraleer the LED goes out completely, he will first because the
battery voltage by the load is just below the 21V.
The battery is switched off by a double pole schakelaar.De 24V constant on the battery indicator, but the flow is negligible.
Instead of the 24 V, the motor is interrupted by SW1, this to be able to easily move the bicycle, passes through the motor to move this work as a generator and the generated voltage is short-circuited by the diode D3.
The second part of the switch is used to interrupt the 12V branch.
The reason for this method is that voltage regulators like 7815 die after a short time, himself a 2A 35V regulator not hold it for long.
Probably due to the surge of motor.Het placing snubbers and capacitors delivers more disadvantage than advantage, therefore, but the simplest way.
The batteries used are 2 X 12V 7Ah and 12Ah 2X12V. These batteries are housed in the panniers.

Motorcontroller for electrical bike (SPART PHAROS)

Because the original controller was broken,i decide to design an simple and easy controller.
The bad NiCad battery is replaced with an leadbattery (cheaper but more weight).
The circuit is an switching currentcontroller.Then current depents off the force on the pedals,this is an hall-sensor.The output varies from 1.2V to 2.5V.
With the potmeter RV1 ,you can set the current.
The opamp U2B is an comperator that switch off the motor when there is no force on the pedalsensor.
The fetdriver is Q1 and the diode D2 is for fast discharge the gate.
De comperator U3a is use for battery indicator.


Joined Mar 24, 2008
I'm not sure how this was in this area. I will be reviewing it.

OK, there were several old posts that would not have passed muster by modern standards. I have locked them, and this thread, to prevent further necroposting.
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