# Current Limiter

Discussion in 'The Projects Forum' started by chrismightsmile, Sep 17, 2013.

1. ### chrismightsmile Thread Starter New Member

Sep 17, 2013
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Hello, is this circuit correct? I am limiting a current from 6 A to 3 A. I need help. Thank you.

Input: 12 V, 6 A
Output: 12 V, 3 A

2. ### t06afre AAC Fanatic!

May 11, 2009
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1,222
I am not sure why and what you want to achive here. I think this thread need more information. Where on net did you find that circuit you posted

3. ### R!f@@ AAC Fanatic!

Apr 2, 2009
8,791
771
U need to show the complete circuit.
If those transistors are used to supply 3A, they will blow.

4. ### chrismightsmile Thread Starter New Member

Sep 17, 2013
5
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This a current limiter circuit. I have a battery charger that supplies 6 Amps and i need it to go down 3A without changing its voltage. Do you guys have other suggestions or different circuit suggestions?

5. ### #12 Expert

Nov 30, 2010
16,703
7,341
It doesn't matter where you found this. It is a concept drawing and it won't work at practical levels.
First, use transistors that are bigger. That will make them smoke less.
Second, understand that a 12 volt charger does not apply 12 volts. It applies more than 12 volts.
Third, the limiting circuit will use up a little bit of the voltage. Probably not enough to matter in this case.

Judging from the way you write words, I guess you are in a country where you could buy Radio Shack parts or Maplin parts. An NPN transistor that starts with "TIP" could be used for both of those 2N3904's.

Make R1 = 39 ohms, at least 8 watts in size, and R2 will be about .22 ohms of at least 4 watts of size. Those are not Radio Shack parts. Better have some more discussion before you lay your money down.

I have to go to the dentist now. Sorry, gotta go.

6. ### wayneh Expert

Sep 9, 2010
12,388
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Is the problem is that your battery charger is too large for your battery? You need to prevent it from supplying a full 6A into a battery that can only tolerate 3A?

Sep 17, 2013
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yes, wayneh.

8. ### t06afre AAC Fanatic!

May 11, 2009
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1,222
What kind of battery is this?

Sep 17, 2013
5
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lithium-ion