H-Bridge doesnt work

Thread Starter

BenM825

Joined Mar 14, 2024
5
BA078880-592C-4027-BDD4-09EB168EFBBC.jpeg
I made this H-Bridge to reverse current in a heating/cooling system but no current is flowing. The transistors are 417-801, I am currently using another wire to connect the positive to either one of the outer red wires which is supposed to let current flow in each direction. I plan on using an spdt switch in the future for this, and the design worked in multisim. The alligator clips provide a 5V source, though no current is flowing.
 
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ronsimpson

Joined Oct 7, 2019
3,128
I see power in, red and black clips.
I see output, red & black wires going off the edge of the picture.
I do not see any signal going to the input of the transistors.
 

KeithWalker

Joined Jul 10, 2017
3,135
Did you measure the voltage between the output red and black wires when you connect an input?
What current is the load rated for? Is it a Peltier cell?
 
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Thread Starter

BenM825

Joined Mar 14, 2024
5
I see power in, red and black clips.
I see output, red & black wires going off the edge of the picture.
I do not see any signal going to the input of the transistors.
The base signal for the transistors is what the missing wire would connect to, planning on making it a switch once i find one
 

Thread Starter

BenM825

Joined Mar 14, 2024
5
Did you measure the voltage between the output red and black wires when you connect an input?
What current is the load rated for? Is it a Peltier cell?
Its a peltier cell, also i measured the full 5v from the source, but no voltage across the peltier cooler
 

BobTPH

Joined Jun 5, 2013
9,116
If your transistors have the same pinout, the top ones and bottom ones have a different pin connected to power. The power connections should be to the emitter in both.
 

Thread Starter

BenM825

Joined Mar 14, 2024
5
If your transistors have the same pinout, the top ones and bottom ones have a different pin connected to power. The power connections should be to the emitter in both.
The idea is that the emitter for the bottom row is fed by the collector of the top row
 
I dont have access to the computer at this moment but I should be able to get back on it tomorrow
I highly recommend the use of a pencil and an eraser to draw and modify schematics, at least in the first iteration. Easier to visualize and less spidery. Then take a photo and post it.

Not directly related, but Adrian Newey, the designer of the Red Bull F1 car doesn’t use CAD, he sketches ideas in pencil. He is far and away the best race car designer alive today. Using a computer to design a schematic can limit creative thinking
 

BobTPH

Joined Jun 5, 2013
9,116
The idea is that the emitter for the bottom row is fed by the collector of the top row
Okay, I assumed you were using PNP on top and NPN on the bottom. With NPN on top you need a voltage higher than the supply voltage to turn them on fully.
 

crutschow

Joined Mar 14, 2008
34,676
I highly recommend the use of a pencil and an eraser to draw and modify schematics, at least in the first iteration. Easier to visualize and less spidery.
..................
Using a computer to design a schematic can limit creative thinking
The complete opposite for me.
I stopped using pencil and paper as soon as I could do schematics with a computer, which made it much easer for me to do a design.
My difficult to do and messy paper schematics ended up being rather difficult to follow.
And then working with or modifying the resulting blue-print generated by the draftsman was a pain also.

To me, one of the best things that happened during my career, was when I could start using a computer for word processing and electronic design (of course that was initially just using an alpha-numeric monitor connected to a main-frame).
My main problem, is that I do a lot of changes on my circuits and my writing before they reach their final form, and that's a Royal Pain in the "you know what", when you have to use a pencil eraser or white-out for that.
Writing reports by hand was also a real chore for me, that I disliked intensely, but became relatively easy when I could do it on a word processor.
For me, a pencil and paper significantly limits my creativity (or makes it more difficult to do).

To each his own, I guess.
 

Reloadron

Joined Jan 15, 2015
7,543
I would just buy a cheap and simple H Bridge module as posted above or a newer H bridge module. The older L298 design is OK but there are newer better H bridge modules out there with little loss to worry about like basic transistor designs.

Ron
 

yahya123

Joined Apr 15, 2024
1
View attachment 317632
I made this H-Bridge to reverse current in a heating/cooling system but no current is flowing. The transistors are 417-801, I am currently using another wire to connect the positive to either one of the outer red wires which is supposed to let current flow in each direction. I plan on using an spdt switch in the future for this, and the design worked in multisim. The alligator clips provide a 5V source, though no current is flowing.
It sounds like you've designed an H-Bridge to reverse current in a heating/cooling system, but you're encountering an issue where no current is flowing despite your setup. Here are a few quick troubleshooting tips:

  1. Check Connections: Ensure all connections are secure and there are no loose wires or poor connections.
  2. Verify Component Specs: Double-check the specifications of the 417-801 transistors to ensure they can handle the current and voltage requirements of your heating/cooling system.
  3. Test Components: Use a multimeter to test the transistors and ensure they are functioning properly. Also, confirm that the diodes are connected correctly and functioning as intended.
  4. Power Supply: Verify that your power supply is providing the necessary voltage and current for the circuit to operate.
  5. Switching Mechanism: When you integrate the SPDT switch, make sure it's properly wired to control the direction of current flow in the H-Bridge configuration.
  6. Simulation vs. Real-world: While the design may work in simulation, real-world components and conditions can introduce variables that affect performance. Double-check your circuit against real-world constraints and consider any differences between simulation and reality.
 
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