H-bridge reverse problem help plz!!!

[Titeo]

Hi all, I'am making a H-bridge for my 300w scooter motor. I connect the H-bridge to an arduino for control. I can make the motor run forward without problem, but when i try to run it backward the motor doesnt run. I try to measure the voltage of the output 20v forward and -20v backward but the motor just cant run backward. If anyone can help plz thank you!!! Here is the sch of the H-bridge

 

[dr pepper]

Couldnt open your schematic, is it eagle format?
Anyway have you tried the motor drectly accross the power supply or battery, will it actually go backwards?
If its a brushless motor then it wont go backwards without mods.

 

[Titeo]

Yes it's eagle the file and yes I did try it directly from a power supply and the motor run forward and backward.

 

[ronv]

Not everyone has Eagle. You might want to post it as a .png file so everyone can see it.

 

[Titeo]

here is the file in png

 

[Boncuk]

Hi Titeo,

I've never seen an H-bridge using that many transistors.

Here is the schematic for an H-bridge serving one DC motor for CW/CCW and stop.

The example shown can be used for motor currents up to 3A.

Boncuk

 

[audioguru]

I cropped then added some contrast to your "hard to see" pastel schematic.

What are the input signal voltages?

 

[Titeo]

The input voltage is 24v and the signal input is from an arduino so 5v pwm.

I need an h-bridge capable of 25amps constant current and more. Everything is working good i think just that i cant backward the motor but if i split the signal input 1 for Nchannel and 1 for the transitor to drive Pchannel the motor can go backward. If i do this i have to use 8 i/o of the arduino, I dont have enough i/o on my arduino, only 4 i/o left. So if anyone can help me???

Ps: motor run forward but not backward and if I measure it with multimeter there 24v and -24v.

 

[MrAl]

Hi,

What you say about the motor not running in reverse and the output being either +24 or -24 doesnt make any sense. If the output went to -24v then the motor should be running in reverse or else it is not hooked up right or something else very simple is wrong.

Try reversing the leads to the motor and see if you can get it to run ONLY in reverse and see if it does not go forward anymore.

 

[audioguru]

The Mosfets will blow up if the supply is more than +12V and 0V.

 

[Titeo]

It have voltage but dont have enought current to run the motor in backward i think, when i send signal backward the motor make a weird sound, there something wrong but i cant find what. The mosfet wont burn coz vgs is +- 25v.

 

[MrAl]

Hi again,


Ok. There has to be something fairly simple wrong here, most likely in the wiring or one or more of the connections or the signal. The reason it must be simple is because the circuit looks completely symmetrical and since it works in one 'direction' it should work in the other exactly the same way except different transistors are turned on. There could even be a transistor burnt out now.

So what you would have to do is make some measurements. First, make sure your signals are the same for both forward and reverse. Make sure the levels getting to the transistors are the same either way.
Next, measure the voltage across each transistor Drain to Source and see that when it is supposed to be turned 'on' that it actually shows a low voltage drop across D to S. Make sure that when it is not supposed to be 'on' that it shows a higher voltage D to S.

You should be able to quickly find the problem that way. Once you find a problem, try to find out what is causing that. It may take a little work to troubleshoot though because so many MOSFETs are in parallel. Because of that, you may have to open up the gate lead (maybe remove a resistor) and tie the gate either to plus or to ground to turn the MOSFET off, and if you do that with 3 out of 4 that are in parallel then you can check each individual MOSFET to see that it works as it should. The one that isnt tied high (or low) should turn on and off with the drive signal with no problem. Once all 4 in that section are working the whole circuit should work as planned.