I tried to construct the h-bridge circuit im wondering if this is correct.

MrAl

Joined Jun 17, 2014
9,158
Can you please check if this is correct and if not where are the errors i may have overlooked
Hi,

I looked at your schematic and it looks right but you dont show what is driving these transistors.
Driving transistors in a H bridge requires a little more care than just driving one transistor so you should show the drivers too and any timing generation circuit because the timing is more important also when you have two transistors arranged in a sort of totem pole right across teh power supply. If they both turn on at the same time the transistors either blow or get too hot and then blow. Since the storage time of bipolar transistors is longer than the turn on time, it is easy to inadvertently turn on an upper while a lower is still on, or turn on a lower while an upper is still on. Both of these can cause immediate destruction of the bridge.
 

dl324

Joined Mar 30, 2015
14,689
Can you please check if this is correct and if not where are the errors i may have overlooked
For being "very new" to electronics, that's one of the cleanest breadboard layouts I've seen from anyone. The symmetry makes it easy to follow. When I breadboard circuits, I place the components to minimize the number of wires needed.

You have the connections on Q2 wrong. The emitter isn't connected to ground and the base appears to be connected to ground.

You could simplify the wiring a little by using the bottom ground rail for the NPN emitter and D2/D4 anode connections.

Since you're using switches to control the transistors, you need to insure that Q1/Q2 and Q3/Q4 are never on at the same time. That will put a short across the power source and at least one of the transistors will die. During normal operation, either Q1 and Q4 or Q2 and Q3 would be on (or all would be off).
 
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dl324

Joined Mar 30, 2015
14,689
I need to recheck the wiring for the NPN transistors on your breadboard. I used a P2N2222 datasheet and the pinout is different than PN2222.

EDIT: If the NPN transistors are PN2222/PN2222A, both are wired incorrectly. Q4 would be wired correctly if it was P2N2222A.

This is a breadboard I made for your circuit:
hbridgeBB2a.jpg
I used 3 pin headers to emulate the switches. I used 1.5k resistors because I happened to have some with cut and formed leads. Transistors are 2N3904 and 2N3906.

EDIT: better picture
 
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