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I need help setting up my H bridge for a motor design Answered

Please help me !

I am working on an electric motor design, and I am having trouble understanding the sizing of the resistors required to set up my H bridge. If you look at my diagram you will see each phase consists of four power coils wired in parallel . There are two sets of reed proximity sensors that turn the circuit on one way then the other.

I am using a TIP 35c & a TIP 36c for my Transistors
I am using a 1n4936 for my Diodes
I am using a PRX 8200 for my Reed Sensors

 You will find data sheets attached 

So far I have only been running my project at 12 volts DC . At 12v the transistors are running cold with no resistors at all. I have tried to apply OHM’s Law but I’m not getting it right. I am confused about a few other things as well.

The Data sheet for the Transistors tells me the Base- Emitter Voltage is 5v & the Base current is 5a .

Should I be running a separate power supply for the sensor feed to the base ? Or dose the resistor adjust the voltage for this?

When you buy Resistors they come in 1/4 watt ½ watt 1 watt 2 watt etc. How do you choose the wattage?

I would like to run my motor in 24, 36, 48, or higher voltage, to as much as the transistors will take , but until I understand this set up I fear I will only fry my transistors or sensors if I get it wrong.
  Can you help me turn up the power?



8 years ago

You should use Power MOSFET transistor.
They can manage more Amps without requiering base current.
They drop very few voltage CE generating less heat. I've made an H-Brigde with TIP122-TIP127 and 1,4 volts (from 12V) drop inside them. Then the motor only receive 10,6V and part of the power is disipated as heat by the transistors. MOSFETs are more efficient.


8 years ago

The circuit is one phase in my motor, as the motor turns at one time a pair of reed sensors trip the transistors to apply current to the circuit in one direction, as it turns further they shut down as it turns further the other set of of sensors line up and send current in the opposite direction.

My motor does work, I started with a mechanical switching system , it worked well but was limited to 12 volts or my contacts would burn. I want more power from my motor so I have gone to transistors for switching.

Do you understand transistor switching circuits?



8 years ago

I am baffled by what you are trying to do here, and can't see how what you have drawn in the transistor relay circuit can possibly work.

Tell me what you are trying to do in the system.