Hi! I made an H-bridge with 4 tip122,4 1N4007 diodes. It's working but I noticed that the Output Voltage seems like coming from the arduino 5V pins and not from my External Battery, my Input batt is 3s lipo, but the output is Around 5v, so i assume its coming from the 5v pin? Anything I should check? this is my first hbridge.
You need to be aware of the voltage drops through transistors and diodes. What is your circuit ?
If you H-bridge supply is around 9 volts, you might only get 5V out, for this reason.
michinyon:
You need to be aware of the voltage drops through transistors and diodes. What is your circuit ?If you H-bridge supply is around 9 volts, you might only get 5V out, for this reason.
my supply is 3s lipo, around 12V. changing the input voltage has no effect on the output. I can increase output by increasing the voltage on the base but I need it to work on 5v for Arduino. 
Pls check the schematics, I did exactly like it, its working but increasing batt voltage more than 3V and it'll overheat, too hot to touch, can melt a gluegun.
anyone know why? thanks!
did you put the diodes in the right way ?
Tamulmol:
Pls check the schematics, I did exactly like it, its working but increasing batt voltage more than 3V and it'll overheat, too hot to touch, can melt a gluegun.
anyone know why?
Yes. The drive to the TIP122s is OK, however if you are running the H-bridge from a voltage higher than the Arduino, then you need to level-shift the drive to the TIP127s. For example, if the supply is 9V, then to keep the TIP127 turned off, the voltage on the base resistor needs to be 9V, not the 5V you get from the Arduino.
Darlingtons like the TIP122 and TIP127 have high voltage drops, which is why everyone uses mosfets instead. But you would have exactly the same level-shift issue if you used mosfets.
michinyon:
did you put the diodes in the right way ?
I checked it, I forgot to change diode position when I changed npn to pnp. Transistor isn't overheating now but now my Voltage regulator is overheating even without a Load, just a voltmeter. lol another problem.
dc42:
Tamulmol:
Pls check the schematics, I did exactly like it, its working but increasing batt voltage more than 3V and it'll overheat, too hot to touch, can melt a gluegun.
anyone know why?Yes. The drive to the TIP122s is OK, however if you are running the H-bridge from a voltage higher than the Arduino, then you need to level-shift the drive to the TIP127s. For example, if the supply is 9V, then to keep the TIP127 turned off, the voltage on the base resistor needs to be 9V, not the 5V you get from the Arduino.
Darlingtons like the TIP122 and TIP127 have high voltage drops, which is why everyone uses mosfets instead. But you would have exactly the same level-shift issue if you used mosfets.
Adding another transistor to TIP122/127 base is what I need to supply higher voltage right? too many components just to reverse a motor heheeh. Thanks you!
One way you can drive an NPN--PNP H-bridge is with cross-connected pre-driver transistors, which both level-shift
and drive two output drivers simultaneously, something like this:
You get two control lines, one for each direction, do not turn both on simultaneously or you short the
power supply out.
lol You make it even more difficult, I can't even make a simple Hbridge hehe.
Can too small wires cause voltage regulator to overheat? Im just testing my hbridge on a breadboard with small wires.
Another DIY h-bridge project that might be worth reading.
Tamulmol:
lol You make it even more difficult, I can't even make a simple Hbridge hehe.Can too small wires cause voltage regulator to overheat? Im just testing my hbridge on a breadboard with small wires.
The simple solution is an IC, not a discrete bridge.
I still can't make this work,overheating either the regulator or the transistors lol. I don't have this problem making 2n2222 hbridge.
Is it normal for the TIP122 Emitter to Collector to be always connected? I tested it, I can turn on a Led without any connection to the base, just E and C.
Tamulmol:
I still can't make this work,overheating either the regulator or the transistors lol. I don't have this problem making 2n2222 hbridge.Is it normal for the TIP122 Emitter to Collector to be always connected? I tested it, I can turn on a Led without any connection to the base, just E and C.
No. It sounds like you've blown that TIP122.
Hi, question, Tamulmol in your schematic you do not show the negative or ground of the motor supply connected to the ground of the arduino.
Is this a diagram error or is ground connection not made.
If not, then your drive signals to the transistors will have no reference.
Tom... 
If you have made changes to this circuit can you please post another up to date circuit., thanks.
dc42:
Tamulmol:
I still can't make this work,overheating either the regulator or the transistors lol. I don't have this problem making 2n2222 hbridge.Is it normal for the TIP122 Emitter to Collector to be always connected? I tested it, I can turn on a Led without any connection to the base, just E and C.
No. It sounds like you've blown that TIP122.
Aww I bought 40pcs, all have emitter to collector connected.
TomGeorge:
Hi, question, Tamulmol in your schematic you do not show the negative or ground of the motor supply connected to the ground of the arduino.
Is this a diagram error or is ground connection not made.
If not, then your drive signals to the transistors will have no reference.
Tom...
If you have made changes to this circuit can you please post another up to date circuit., thanks.
I made a voltage regulator, It has two outputs, one for arduino and another for hbridge. their grounds already connected.
I tried:
All TIP122 = regulator overheats and Output doesn't change even if I increase/decrease supply voltage.
2 TIP127 and 2TIP122 = Transistors overheat.
IF Emitter and Collector shouldnt be always connected. I think ebay seller sent me 40pcs of broken transistors
Thanks all for the Help
Tamulmol:
dc42:
Tamulmol:
I still can't make this work,overheating either the regulator or the transistors lol. I don't have this problem making 2n2222 hbridge.Is it normal for the TIP122 Emitter to Collector to be always connected? I tested it, I can turn on a Led without any connection to the base, just E and C.
No. It sounds like you've blown that TIP122.
Aww I bought 40pcs, all have emitter to collector connected.
How have you tested them? Don't forget that the tab is probably connected to the collector (centre pin) internally.
dc42:
Tamulmol:
dc42:
Tamulmol:
I still can't make this work,overheating either the regulator or the transistors lol. I don't have this problem making 2n2222 hbridge.Is it normal for the TIP122 Emitter to Collector to be always connected? I tested it, I can turn on a Led without any connection to the base, just E and C.
No. It sounds like you've blown that TIP122.
Aww I bought 40pcs, all have emitter to collector connected.
How have you tested them? Don't forget that the tab is probably connected to the collector (centre pin) internally.
I Attached a schematic. I noticed that using BJT the current will not flow without the base but I tried using mosfet on Icircuit App and it's same as mine
Led lights even when base isn't connected. Is a TIP Mosfet? lol I also used multimeter. Meter set to Diode sign. 600+ reading when multimeter Positive to E and Negative to Collector.
thanks for your time
The TIP122 has a built-in diode between collector and emitter. Therefore, if you connect collector and emitter the wrong way round (as I suspect you have), current will pass and the LED will light. Likewise, a multimeter used in diode test mode will read about 600mV with multimeter positive to emitter and negative to collector.
Thanks all. It's working now