I'm trying to run a higher powered DC motor with an h bridge- is there some way to add a transistor or second h bridge so it could work?
You should be able to put H-bridges in parallel. They might not share current exactly equally but they should share pretty well if they are the same types of two devices (e.g., two L293's).
Just be careful not to have one configured in one direction and the other configured for the other direction as that will draw a huge current and burn up the devices. Test out your setup with a current-limited power supply to start.
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The Gadget Shield: accelerometer, RGB LED, IR transmit/receive, light sensor, potentiometers, pushbuttons
I've seen examples of people literally stacking L293D's on top of each other. Sure saves on board space and routing troubles. Don't neglect heatsinking though if you do this!
G.
Tried two h bridges- still seems like too much power- it works for a bit then drags. Can't seem to wrap my head around this.
Well, how about some details? How much current? Which H-bridge are you using?
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The Quick Shield: breakout all 28 pins to quick-connect terminals
I'm trying to power the motor with an external supply- 12v, 1amp, now with two L29s. It goes through the first arc (the dc motor is controlling an lever) fine and then stalls.
Got any pics or schematics of your setup... easier to give feedback when we can see what you have in front of you...
G.
why not try l298n ? it has a current rating of two amp per channel dc and is also equal to the cost of two l293d semms a better option!
in case you want to have a look at the datasheet
http://www.st.com/stonline/books/pdf/docs/1773.pdf
12v, 1amp,
So how much current is your motor drawing? If it is greater than 1A then that is your problem get a better supply.
Is anything getting hot when it stalls?
A H-Bridge will share current if it is constructed from FETs rather than transistors.
My setup is identical to this http://itp.nyu.edu/physcomp/Labs/DCMotorControl
except I have an external power supply hooked up to p8 of the l29 h bridge. The motor is a 12v dc power window motor, I'm pwm'ing the h bridge itself to control the speed but with my power supply (a 5v 1amp) the arm of the window motor is not strong enough to support any weight. Sorry if it's confusing, I am, of course, just starting out.
Basically the motor is drawing too much current for your power supply, so change one of them.