how connect transistor tip142 to pic

Thread Starter

hertz.12

Joined Apr 25, 2015
41
hi
i m trying to interface tip142 and tip 122 to pic 16f628 to drive 10A load....the problem is i don't get 10A out..only about 7A out and the tip 142 get hot after 5minutes ..not too hot so it is ok but i need 10A..what is wrong?


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WBahn

Joined Mar 31, 2012
25,918
You are saying that your load is 1 Ω and that it is powered from 9 V. How do you expect to get 10 A into it in the first place?

Look at the data sheet for the TIP-142 and you will see that the Vce saturation voltage at 10 A (and Ib = 40 mA) is spec'ed to be less that 3 V. So even if you only got 6 A you would have nothing to complain about.
 

Thread Starter

hertz.12

Joined Apr 25, 2015
41
You are saying that your load is 1 Ω and that it is powered from 9 V. How do you expect to get 10 A into it in the first place?

Look at the data sheet for the TIP-142 and you will see that the Vce saturation voltage at 10 A (and Ib = 40 mA) is spec'ed to be less that 3 V. So even if you only got 6 A you would have nothing to complain about.
yes i want 9A not 10A.....

why i can't get 9A from tip141? now i get 6A no more...what is the wrong?
 

WBahn

Joined Mar 31, 2012
25,918
yes i want 9A not 10A.....

why i can't get 9A from tip141? now i get 6A no more...what is the wrong?
You start with 9 V. You have a transistor that saturates with as much as 3 V from collector to emitter. That leaves 6 V across your load, which is 1 Ω. How much current will flow through a 1 Ω load that has 6 V across it?
 

WBahn

Joined Mar 31, 2012
25,918
yes i think i know both Darlington transistor
So why are you using two Darlingtons in a Darlington configuration? The TIP-142 has a beta of ~500, meaning that to support 10 A you would only need 20 mA of base current. What can the PIC provide?
 

Thread Starter

hertz.12

Joined Apr 25, 2015
41
yes i think pic can provide 20-25ma but i prefer not to reach maximum pic output...i will use npn2222 instead of tip122

i thought that tip 141 can drive 10A load...there any way i can drive 9A with tip141?
thanks
 

Bordodynov

Joined May 20, 2015
2,628
From my pictures easily calculate the power transistor.
7.606A*1.394V=10.6W !!! We need a big heatsink!

8.933A*66.86mV=0.597W You do not need a heat sink.
 
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