Tronic's DIY dual Mosfet H-bridge (DSMhb)

@Stefano

That 169A represents the limits of the junction temperature. The mosfet will still melt/explode because the package limitation is 75A, which is very typical of TO-220 packages. Although, that is still better than the IRFZ44 50A max.

And at 100'C, which is probably just shy of the temperature prior to destruction, it is much better than the 44s 36A!

R-eng

thanks! another question. The DSMhb has two kind of mos, N and P. Can I mount the IRF1405 instead of each mos, or I have to choose 2 different tipe of mos?
sorry for my bad english..

thank you

Stefano

Ok, I have read now your last posts! I see that you guys are working together in the most efficient DIY h-bridge design up to date that will use only N-channel mosfets (IRF3207)!!! good luck on the sourcing of the parts!!!!

Thanos, Do you think that it will be possible to use some part of the old DSMhb, for the new one? :uups:


Stefano

The DSMhb must use both P and N channel mosfets as the design stipulates. The new HPMhb will only be able to use the 74HC08 for now. It is a very different design, and will be one dual-sided PCB per motor. It is still in early development.

R-eng

Hi,

I have the amc and h-bridge working... On motor 2 at I have full output on the red and green led.
But on motor 1 I have full output on the red led but not on the green.

Input: 15.3 volt
output motor2 : 16 volt on red and green
output motor1 : 16 volt on red 4,5 volt on green

What can this be?

gr. Jeroen

I had this issue as well. In my case it has been a defective mosfet.

regards

Hi,

Ok... Will try that.

Do I have to ground the amc and avr to the frame cause its all made
of metal?

gr. Jeroen

Hi Jeroen,

It might sound strange but the AMC doesn't have (and doesn't require) common ground with the power source of the motors!!!!! I'm not sure what happens in that case!!! On my joyrider everything is isolated from each other as they are mounted on the PVC pipes!!!

I recommending using a plastic or wooden base to host your boards. Another reason you don't want to connect the ground of the motor power source to the power source of the AMC is the EMI noise from the motor that may cause problems on the operation of the ATmega8535.

Regards, Thanos

Hi,
Had the same issue with my simulator (HB25 based) and the car wipers from Renault Clio.
Most (if not all) car wipers are negative grounded, and HB25 (like HBridge I suppose ) do not like to have a common ground.
Strange behavior on my configuration as either one or the other motor was working, but not both at the same time.
Motor needs clearly to be isolated. Not so complex with wipers motor. You need to open the box, cut the wire connected to ground, and sold a new wire to be used in place. Not sure about other actuators. Check if motor has one wire connected to ground or not.
Have a nice day.
OscarH

Hi,

Yes thought so... Because is I tried to run both motors on a battery nothing happend when I changed polarity of 1 of the motors.
When they ran the same direction I had no problems.

But where do I ground the cut wire?

gr. Jeroen

You have to solder a wire on it.

Here is a german tut. Perhaps someone will add an english tutorial to our wiki someday...
http://www.roboternetz.de/wissen/index. ... schermotor

Or use motors that have isolated GND ex factory.

regards

Hi again,

On the wipers motor, there are 2 wires. One is isolated and one is connected to ground. Check which one in connected to gnd with an Ohmmeter
The best I found is to cut the flexible copper wire connected to motor's brush. Cut as close as possible to PCB. Connect this flexible wire to a standard cable, then get this out of the motor, following the same path as untouched wire. Better glue the cable to avoid it moving in the motor, causing possible short circuit.
Test with a powersupply before you connect both cables to HB25 or HBridge. Don't forget to retest isolation with an Ohmeter.

OscarH

Hi,
First of all thank you for contributing this motor driver circuit as it was very intuitive and easy to build.. I am using this to control 2 12v DC motors from cordless drills. It is connected to an arduino board. When I test it with no motors connected it seems to work perfect, led status lights come on instantly and bright. They change when I change direction and everything is great.. Now the problem I have is when I connect the motor and turn everything on I get no status light initially and then after about 5 secs or so the status led will begin to brighten and the motor will begin to turn, gradually accelerating. At this time the mosfets begin to get extremely hot fast so I shut it down. I have tried both sides of the circuit in both directions with the exact same results. Further I have tried not using PWM on the driver but just tying PWM1 high. Any suggestions would be greatly appreciated. I don't want to run it and chance burning it up..

Hey, this h-bridge is meant to be used with PWM signals only. With duty ratio of 5% up to 95%. Using it with 100% ratio (PWM1 tied high) would be bad for the mosfets if used under load!!!!! If you switch on the motor with 100% duty cycle, the peak current will overheat and burn the mosfets! :no:

I think arduino has support for PWM output, why don't you use it? The PWM will set the speed of the motor, and the IN1 & IN2 the direction of rotation of the motor!



Regards, Thanos

tronicgr... I have for sure tried PWM from the arduino.. but as a test from one of your posts you mentioned tying the pwm pin high to see if the motor spins... But to clarify I am using pwm from the arduino and at about 50% duty cycle and yet when I power the system on there is no activity on the status led's for approx 5 sec then they gradually turn on with the motors and proceed to accelerate..

********UPDATE***********

Ok please forgive my lack of electronic knowledge... The short answer was I had to tie the ground from the arduino to the supply ground... Once I did that all went great.. Again I want to thank you for taking the time to create and share this great little circuit..

I'm glad you make it work!

Of course you have to use the GND and VCC signals on the connector of the DSMhb too. otherwise you will not power the 74HC08 chip that does the multiplexing of the PWM signals!!!! But keep this ground (as well AMC1.5 ground) separated from the motor power supply ground please!!!

Regards, Thanos

Question:Yesterday i solder my H.Bridge when i but it on a battery without a AMC what should it do?? Are the LEDs working or are they only work in connection with the AMC ?? HOw can i test my H-Bridge wothout the AMC ?? My ATMEGA is not on stock.

Thanx

Yet another update ... This one is not so positive but hopefully a little more informative.. Ok here is what is happening.. when I have no motors connected I can run it and the status lights flash back and forth and everything seems to be perfect, the status lights are bright and responsive..

When I connect a motor to the circuit is when it stops working.. The lights for the motor connected will both come on dim and the motor doesn't spin.. Does this make any sense? Do I have a problem with not supplying enough current to saturate the mosfets or what?

I spent the entire day yesterday trying to understand transistors and fets better and I am stumped at this.. Again I am sorry for my lack of electronic knowledge and really appreciate your help...

Anybody have any ideas as to why I can't get this to work ... ???