how to properly bias transistor?

Thread Starter

Man10

Joined Jul 31, 2018
163
You should put the motor on the collector of the transistor, and the base resistor should be calculated to provide 1/10th of the needed motor current.

You will probably want to use a Darlington, or a MOSFET.

Ok I see you are using a Darlington, in that case you might get away with a 1k resistor.
1 time I tried using a, 470 ohm resistor connected to the base of a tip110 transistor, it wouldn't turn on a mabuchi 555 motor. Why? I measured base current it was 16 miliamps.
 

BobTPH

Joined Jun 5, 2013
8,816
You have already been told why your circuit will not work. Did you try the suggested changes, or are you just going to ignore us?

Bob
 

Thread Starter

Man10

Joined Jul 31, 2018
163
You should put the motor on the collector of the transistor, and the base resistor should be calculated to provide 1/10th of the needed motor current.

You will probably want to use a Darlington, or a MOSFET.

Ok I see you are using a Darlington, in that case you might get away with a 1k resistor.
Why is mosfet better than a bipolar junction transistor?
 

dl324

Joined Mar 30, 2015
16,846
Why is mosfet better than a bipolar junction transistor?
A BJT is a current controlled device. A MOSFET is a voltage controlled device and the only current drawn from the driver is gate charging current.

If you use a MOSFET, you need Vgs to be low enough that you can drive it hard enough to have a low on resistance. When driving with an Arduino, you need a logic level (low Vgs) device.
 

Thread Starter

Man10

Joined Jul 31, 2018
163
A BJT is a current controlled device. A MOSFET is a voltage controlled device and the only current drawn from the driver is gate charging current.

If you use a MOSFET, you need Vgs to be low enough that you can drive it hard enough to have a low on resistance. When driving with an Arduino, you need a logic level (low Vgs) device.
By driver you mean the arduino?
 

sparky 1

Joined Nov 3, 2018
756
The motor has a voltage rating of 12 volts. I already mentioned I am using a 555 mabuchi motor
This video shows connecting arduino to a 12V device with mosfet.
The video shows a proper bias for an IRLZ44 mosfet for the application the motor can be the load that is shown.
If a 1Ω resistor was part of this it would be for sensing current, both speed and current can be addressed with pwm.
See demo in video for instructions on connecting, fast forward to 5 minets.
 
Last edited:
Top