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how to get higher output.

i am making a robot using transistor as a switch .

i am using a bc693 transistor but want higher current output approxly. 200mAmp

i previously used a 2n3904 transistor also ,

my supply is 500mAmp.

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actually i want enough power to turn the chassis, The voltage is 5 volts and the i am providing is 500 mA to the cuircuit and i want higher power to produce higher torque in motors  currently i am getting 165mA ,

the tyres move if i lift them up but cant produce enough force to overcome the frictional force at ground

the chassis are ulta light. so can you now provide me some examples of available transistors

 

 

 

It really depends on your motors. What motors are you using? Are they gear motors? What is the stall current? What is the rated torque at the voltage you are using?

Pictures of your motors and setup, or a link to the website you bought them at or to their specifications are needed, or it is very hard to help you.

my motors are gearless low torque motors rated 100rpm and 5volts it look exactly like the picture below , but i have made very light weight bot for this it overall weight is 160grams only . can i increase the torque mannualy? with the help of gears?  

r

In most cases, even very light robots need some gearing to make the motors effective. I had a mouse bot projoect that was gearless, and I ran into the same problem as you.

You can find gear motors, which already have the gears built in. Another fine option is to modify a pair of servos for continous operation. Then you can use them as motors. If you insist on using your current motors, you would have to add some weight and complexity by adding external gearing.

You want a small gear or pulley on the shaft of your motor. As small as possible, just a bit bigger than the shaft itself. Then you want to mesh that with a much bigger gear to drive the motors. Practically speaking, you may need several gears to get an effective ratio.

I cannot find a datasheet for the bc693.

The 2n3904 will provide 200mA of continuous current, although that is its absolute maximum. See the datasheet.

http://www.datasheetcatalog.org/datasheet/fairchild/2N3904.pdf

The 2n2222A is another general purpose NPN transistor, with maximum continuous current rated at 800mA. Something like that would give you a lot of room for error.

Do you expect to drive the transistor continuously at 200mA? If so, I'd consider a higher capacity transistor just to be safe.