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sushmair
02-13-2010, 09:05 PM
Hi,

Can anyone suggest what are the best transistors for a transistor based h bridge? I have made one using 2n3904's & 2n3906's - I get just about 12 mA for the dc motor which is not enough for the motors I am having. I have scavenged all motors from kids toys so dont really know their ratings.

As an aside, are there motors that rub off 12 mA?

Rgds,
sushmair

Ulhas
02-14-2010, 01:00 PM
use transisors based on motor current
cheaper is 2n3055,BD139,Tip122-127
mosfet irfz44n,irf840,irf540 etc

all cost around Rs. 8

vikas
02-14-2010, 02:17 PM
How much current do you want to source !!!

sushmair
02-14-2010, 05:39 PM
Thanks Ulhas. I'll try the TIP option next time I go shopping...

@Vikas, I ran some tests on my motors - I guess at least 200 - 400 mA.


BTW, I plugged a cellphone vibrating motor (extracted from a broken Samsung SGH-X620) - its a tiny one just about bigger than a button cell. Even this tyke doesnt respect the 12 mA my h bridge puts out...

Rgds,
sushmair.

akshay66
02-14-2010, 08:58 PM
I once used TIP 122 for toy motors it works good.Its a darlington transisitor with more that 1A .

rao
02-15-2010, 03:40 PM
In your case, an L293D would perform much better and be more space efficient.

akshay66
02-15-2010, 04:19 PM
I also suggest L293D

sushmair
02-15-2010, 05:42 PM
@rao, @akshay66,

Yes - I did take a look at that option but costs are what hold me back. The end user is going to be my < 3 yr old son and I am pretty sure he will manage to destroy it. In the longer run, I am planning to add wireless comm capability to this and create multiple numbers of such bots/cars. In the immediate future I plan to spend money more on sensors than motor drivers.

sushmair.