Things you can do with a current source

[Th3_uN1Qu3]

I've just built myself a 20A current source using a BD139 and two 2N3055s (in the schematic there's only one figured, i use two in parallel for Q2). I feed it with a 9.5Ah SLA battery, just the thing for getting a boatload of amps.

I built it to use it along with my inductance measuring multimeter to check DC saturation current of inductors for SMPS supplies. But soon i figured there's more things it can be used for.

• Testing fusing current of wire (for replacing fuses with a piece of wire without tripping the breaker or setting my house on fire)
• Testing current capability and voltage drop of diodes

What other uses can you think of?

[kikkoman]

Re: Things you can do with a current source

4-wire resistance testing!

[Th3_uN1Qu3]

Re: Things you can do with a current source

Eh, i don't think it's that accurate... It drifts quite a bit.

Btw, the circuit is only meant for brief operation, it won't do >10A for more than 20-30 seconds. Up to 10A it's alright, higher and the BD139 gets crispy. If you put a beefier transistor in place of the BD139 then the 1N4148 dies. And you can't use a more heavy duty diode because the whole circuit depends on the high voltage drop of the 1N4148.

There are more elegant ways of making a current source. But for now, this one serves its purpose.

[skystormfarms]

Re: Things you can do with a current source

i built a t-former 150a @12v(: