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Hbridge using TIP41C not working

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xynthian

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hbridge bjt

I need a little help here. I fixed up everything and my motor is not working.
I checked the current through the transistor and there is no current flowing through the emmiter. Can you tell me what is the problem?
Attached is my circuit.

Thanks
 

echo47

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h-bridge using tip41c

Tell us what voltages you measure around the circuit.
How much current are you feeding into the opto-coupler?
How much current does the motor require?
 

IanP

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all npn h bridge

Assuming all components are OK and connected in configuration as per your drawing, you will always have some problems because of unfortunate use of 4 NPN BJTs ..
It is impossible to "saturate" both high-side NPNs driving them from the same supply voltage ..
TIP141 is a Darlington BJT and to "saturate" it you will need at least 2V Vbe, and in the same time you want the emitter voltage to go as high as possible, ideally as high as the supply voltage ..

One option to avoid this issue is to drive the high-side NPNs of higher voltage .. see similar scenario (with N-channel MOSFETs) on the attached picture ..
Alternatively use two PNPs as the high-side switches and re-configure the bridge ..

Regards,
IanP
 

    xynthian

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xynthian

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h bridge 2npn 2pnp

echo47 said:
Tell us what voltages you measure around the circuit.
How much current are you feeding into the opto-coupler?
How much current does the motor require?

I supply 9 volts to the circuit. which means the opto-coupler have around 9volts.
The dc motor is a hobby one. So I guess around 9 volts should be enough.

What i meant is I measured no voltage drop at the emmiter side of the power transistor.

Added after 2 minutes:

IanP said:
Assuming all components are OK and connected in configuration as per your drawing, you will always have some problems because of unfortunate use of 4 NPN BJTs ..
It is impossible to "saturate" both high-side NPNs driving them from the same supply voltage ..
TIP141 is a Darlington BJT and to "saturate" it you will need at least 2V Vbe, and in the same time you want the emitter voltage to go as high as possible, ideally as high as the supply voltage ..

One option to avoid this issue is to drive the high-side NPNs of higher voltage .. see similar scenario (with N-channel MOSFETs) on the attached picture ..
Alternatively use two PNPs as the high-side switches and re-configure the bridge ..

Regards,
IanP

You mean I should change both the npn to 2 PNPs? Sorry I'm really a beginner in electronics. Thanks for your explanation.
 

IanP

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tip41c circuit

It's just easier to control H-Bridges build with 2 NPN and 2 PNP transistors ..

See example at:
**broken link removed**

Take a look at the TOP H-Bridge .. Q5 and Q6 can be BJTs from your optocouplers ..

Regards,
IanP
 
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xynthian

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pnp transistor h bridge

IanP said:
It's just easier to control H-Bridges build with 2 NPN and 2 PNP transistors ..

See example at:
**broken link removed**

Take a look at the TOP H-Bridge .. Q5 and Q6 can be BJTs from your optocouplers ..

Regards,
IanP

:D Thanks. Now I've connected my h-bridge as your circuit. But there's a problem. The positive and negative side of the anode give me a reading of 7volts. Because of this, my motor can't spin.

Why is this happening? I doubt that It's because both of the pnp transistor is on right? How to correct this problem?
 
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