Need Help on High Current H Bridge

[pidot]

hi....

my project is to build a mobile robot consists of 4 brushed dc motor whereas 2 for the left side that will be running together and 2 for the right side. my problem is with the motor driver.

i wish to build a h bridge that can drive 2 dc brushed motor (usually used as a car power window motor) and connected the h bridge to a servo motor circuit (after removing the small dc motor inside). the gearing system from the power window motor being removed, so the shaft of the motor will be directed to a tyre.

ive built some h bridge but most of them using both p and n channel mosfet. the problem is, i cant find a high ampere p channel at my place. but its not a problem for a n channel mosfet.

attach is the one of it that ive built. but it cannot last for long. after 20 minutes running the mosfet will burnt out. do not know how. i used a very big heat sink.

thanx for helping me.......

 

[pidot]

additional info...

i connect the forward and reverse point to a small servo motor circuit that ived removed the small dc motor inside. the brand of the servo is sanwa, and it has ground pin. so i connect the ground pin to the h-bridge ground point.

thanx.

 

[ikalogic]

how much current do you need?
have you tried the l293D load driver ic? it can drive, in ceratin conditions, up to 4A... (if you connect the 4 channels in parallel....)

 

[panic mode]

i wouldn't consider 4A high current. dc motors used in car seats and doors draw easily 5-6 Amp with no load,
8-12 Amp with light load and stall current can be much higher (25Amp or more).

we build machines for automotove industry and as such we get lots of
samples of power seats, power windows etc. since we get them as surplus, we used to play with them. note that these motors are light duty, they are designed to run for only few seconds. they can be ok but they are far from perfect. one guy was using them to motorize toy car that originally was peddal-powered. it worked great... for about 15-20minutes.
if you want something that will run much longer, look for better quality motor such as windshield wiper. they are much better, designed to work continuously.

 

[pidot]

thanx for the help...

just to detail what im doing....

i want to build a mobile robot driven by 4 power window motor....
i haved remove the gear from the motor...thats mean only the shaft that directly from the motor being used....it is as my theory to make it run faster....

my plan is to control 2 of the modified motor with 1 h-bridge....
another thing is, my robot would be plus minus 18kg.

im using lead acid battery, 12v 7500mAH...

any comment on it...

 

[pidot]

ive done building this circuit using 1rfz44. firstly it work perfectly. but the second time i tried it, it cannot work..... why? the mosfet is very hot...

thanx..

 

[Oznog]

What freq are you running it at?

 

[Elektor]

use Maxim motor driver

you can use maxim motor drivers which are available upto 6 Amp of current capacity,which I think is quite enough to drive motors

 

[dav es tech]

I dont see what turns off the mosfets, suspect they turn off too slow
try totem pole driver or high side driver chip

 

[pidot]

hi

dav es tech

just dont get what u saying....and other thing, it is hard to find a high current mosfet driver at my place.
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[danielsmusic]

do you need a h bridge do somthing more simple.

sorry turn 2 on to turn off.

 

[Elektor]

increasing speed

I dont see what turns off the mosfets, suspect they turn off too slow
try totem pole driver or high side driver chip

there speed can be increased by using schotky diodes att output.see
www.robotroom.com

 

[panic mode]

interesting circuit... i wonder what was the guidline in sizing
of the circuit - 50Amp transistors and 1A diodes, 24V source to turn on mosfets...
according to datasheet, absolute maximum for Vgs is only 20V.
the same document also shows that Vgs of only 3V is going to turn the
transistor fully on. Fortunatelly these transistors have built in diodes so
presence of puny 1N4001 is purely cosmetic.

But i sure liked his review of Whiteleaf Hotel in London
**broken link removed**

 

[Someone Electro]

That hotel was suposed to be a 3 star?!? :shock: :shock: :shock:

 

[Elektor]

h bridge

you can try one from maxim --- 6A H bridge driver belonging to max 626to max 628 series.

 

[Elektor]

h bridge

you can try one from maxim --- 6A H bridge driver belonging to max 626to max 628 series.

 

[Sputnik]

Since you are using the servo driver circuit it may be frying FETs because the driver may actually be keeping the line that is supposed to go LOW above ground, keeping the FETs that are supposed to turn off, on just a bit and creating a short circuit through the FETS.


Try the IRFB4410's 10v sat and 96A. I have use them on 200 amp loads for surprisingly long periods and they have held up fine.

Also, try NOT using a heatsink and using a fan only on the fets, they cool much better this way as long as its cool air being blown on them.

 

[Frankels]

There is another problem with some windshield wiper motors: mine were internally grounded.
This means that when the casings are electrically connected (for instance if you mount them on a steel chassis !!!) and you are trying to run them in different directions you are shortcircuiting the system. My solution was to isolate the circuit from the casing.

 

[blueroomelectronics]

Thread is 3 years old.

 

[Frankels]

@blueroomelectronics
people still use it for reference