H Bridge Troubleshooting

Thread Starter

Dinel

Joined Mar 2, 2016
9
I checked all my data sheets and confirmed that all components were placed properly, which they are, yet my circuit still isn't working. I am supplying 5V from a 9V battery that is going through a regulator. The motor works if placed directly after the regulator, so my problem must be with the bridge. The PNP and NPN are in proper position, so it can't be them either. Any suggestions would be appreciated.
 

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Do you have a schematic of what you are trying to build?

Also, what is driving the bridge? You have resistors to the transistors that do not seem to be connected to anything. How are you turning the transistors on and off?
 

Thread Starter

Dinel

Joined Mar 2, 2016
9
Do you have a schematic of what you are trying to build?

Also, what is driving the bridge? You have resistors to the transistors that do not seem to be connected to anything. How are you turning the transistors on and off?
It is just a regular H Bridge, and I removed the other connections so that the rest of the circuit could be visible, I'm just trying to get it to work right now so I'm manually connecting the NPN bases to 5V and the PNP bases to ground
 
I was hoping the schematic might answer some questions as what parts are being used as transistors, resistors, and possibly motor. How much current is required by the motor?
 

ISB123

Joined May 21, 2014
1,236
Your motor maybe doesnt work because it's actually working at 3.6V since the voltage drop of PN junction.Try the circuit without the regulator.
 

Marcus2012

Joined Feb 22, 2015
384
If the low side BJTs are NPNs and 2N3904s then they are the wrong way around. pin configuration is the same as the 3906 (1-E,2-B,3-C). But do you also know the current for the motor as the collector current for these is only 200mA.
 
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If you saturate the transistors you should be able to get around 4.5 volts across the motor. This is very dependent on the motor being used and the transistors as well.

Also, just as a side note. The pinouts of transistor are not all the same. Check the datasheet for the transistor pinout for every new transistor you use.
 

Marcus2012

Joined Feb 22, 2015
384
Also, just as a side note. The pinouts of transistor are not all the same. Check the datasheet for the transistor pinout for every new transistor you use.
Actually I recall a PN2907 or something that was a complementary NPN TO-92 that had opposite pinout so I stand corrected. This is why a schematic would be useful please :)
 

GopherT

Joined Nov 23, 2012
8,012
A BC337 and BC327 have reverse pinout from 2N3904/3906. And these BC parts have much more appropriate current carrying capabilities than the 3904/6 parts.
 
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