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.......

Attached Images

single_supply_h_bridge.gif (9.9 KB, 2046 views)

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....)

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Ibrahim Kamal
check my electronics and robotics page: http://www.ikalogic.com/

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..

Attached Images

nch-brdg.gif (9.8 KB, 1954 views)

Oznog

What freq are you running it at?

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I thought what I'd do was I'd pretend I was one of those deaf-mutes.

Elektor

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.

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namnl_s.jpg (62.3 KB, 1833 views)

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when you post that reply, im just kidding.

Elektor

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 :-)
http://www.cadvision.com/blanchas/whiteleaf/index.html

Someone Electro

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

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Il give you shocking experience.

Elektor

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