how to properly bias transistor?

Thread Starter

Man10

Joined Jul 31, 2018
90
hypothetically if i connect the base of a tip110 transistor to a 1 ohm resistor and the base recieves input from an arduino uno, any possibility, the tip110 transistor will get damaged?
 

Thread Starter

Man10

Joined Jul 31, 2018
90
but on another forum someone said the output pin of an arduino generates, almost no current, so where is the high current coming from?
 

Thread Starter

Man10

Joined Jul 31, 2018
90
the output pin of an arduino uno sends signals to a tip110 transistor, which turns an electric motor on and off, and the electric motor pulls on a wire, which raises or lowers an arm. i don't know what value of resisor, to connect 1 end to the output pin of an arduino uno and connect the other end to the base of a transistor. i am using a mabuchi 555.
 

Wolframore

Joined Jan 21, 2019
2,273
but on another forum someone said the output pin of an arduino generates, almost no current, so where is the high current coming from?
this might be a misunderstanding or mistake. The output pins are not able to sustain current over 20 mA for any extended time, in fact you should read the ATMEGA328 datasheet.

a 1 Ohm resistor connected to the base of a transistor with no other biasing would burn out the output pin. It does not limit current.

I can only guess at what was meant.
 

Wolframore

Joined Jan 21, 2019
2,273
Please draw a circuit diagram so we can be on the same page, please include the entire circuit including power supply and what you intend to switch.

it sounds like you need more than a transistor, you may need an H bridge so it’s reversible.
 

ElectricSpidey

Joined Dec 2, 2017
1,655
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.
 
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Thread Starter

Man10

Joined Jul 31, 2018
90
The rated current of a mabuchi 555 motor is 2 amp. The no load current is 180 milliamp. The stall current is 11.8 amp.
 

Audioguru again

Joined Oct 21, 2019
3,188
When a load is connected to the emitter then the load gets about 2V less voltage than the base voltage. The motor gets only 3V or less. The darlington transistor gets VERY hot.
 

MrChips

Joined Oct 2, 2009
23,528
Why not the emitter side I really want to know?
Because you will have to bias the base with a voltage that is higher than the voltage on the load.
If the motor is on the collector and the emitter is grounded you only need less than 1V to turn on the transistor, independent of the supply voltage.
 
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