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Topic: Arduino DIY motor shield (Read 4886 times) previous topic - next topic

polishdude20

Mar 08, 2011, 08:04 am Last Edit: Mar 08, 2011, 08:07 am by polishdude20 Reason: 1
So 'm planning on making  a motor shield for my arduino which basically will be controlling 2 small sized DC motors. I want it to run off of a 9 volt battery AND have that battery also run my arduino through a voltage regulator. So far  I was thinking of using  the SN754410NE Quad Half Bridge as my H-bridge and incorporating that into EAGLE and making the shield.

Now my question is : what other parts should I consider using or maybe should I use a different H-bridge?  

Lastly, would I even NEED an H-bridge to make motors JUST move forward like in a line following robot?

MarkT

You need H-bridge if you want to reverse the motors, or if driving a bipolar stepper motor.  Incidentally 2 H-bridges are needed for a stepper, so a single-stepper controller can double as a dual motor controller.

There are hundreds of H-bridge chips out there - you need to nail down your requirements before choosing one.  Voltage range, current, current limiting, fault handling, heat sinking, SMT v. thru-hole  etc etc.

Its also worth looking at what other people have done - that way you can build on a known working design.  Easy with open hardware designs!
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keeper63

Lastly, would I even NEED an H-bridge to make motors JUST move forward like in a line following robot?


You only want an h-bridge if you intend to reverse the direction of the motor; if you don't need this ability, then a simple NPN transistor or N-channel mosfet (plus a diode, and maybe a resistor) is all that would be needed.
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polishdude20


Lastly, would I even NEED an H-bridge to make motors JUST move forward like in a line following robot?


You only want an h-bridge if you intend to reverse the direction of the motor; if you don't need this ability, then a simple NPN transistor or N-channel mosfet (plus a diode, and maybe a resistor) is all that would be needed.


Okay thanks for the helpful info. Yeah I think that's what I'll do then, but Im using a 2N3906 transistor to drive a small DC motor I think it's normally rated at IDK around 5-6 volts. But, the transistor keeps heating up alot. I have a 1K resistors between it's ase and digital pin, and I have a diode connected in parallel with the motor which goes to the transistors collector and then down to ground. Then the emitter is connected to +5 volts. What can I do to stop it overheating? Also if you have the time can you tell me how I can get the motor to adjust it's speed with PWM?

MarkT

Motors take more current than a 2N3906 can easily provide.  You want a medium power transistor (current rating several amps).

BTW people often mistake absolute maximum ratings for working values.  A transistor with a max current rating of 0.5A might saturate at 1.5V drawing max current due to stray resistance, rather than the nominal 0.1V of a saturated transistor in its 'comfort zone'.

You can parallel several identical transistors for more current if they each have their own base resistor.
[ I will NOT respond to personal messages, I WILL delete them, use the forum please ]

polishdude20


Motors take more current than a 2N3906 can easily provide.  You want a medium power transistor (current rating several amps).

BTW people often mistake absolute maximum ratings for working values.  A transistor with a max current rating of 0.5A might saturate at 1.5V drawing max current due to stray resistance, rather than the nominal 0.1V of a saturated transistor in its 'comfort zone'.

You can parallel several identical transistors for more current if they each have their own base resistor.


I've decided to use MOSFETs and they work very well now, they don't heat up and they provide enough current for the motors. thanks for the advice anyways.

polishdude20

well I just made my new shield PCB design and it looks great! Now I just need to iron transfer it in class and etch it. Once I get it together and get it running ill post a video and some pictures and schematics, maybe even an instructable.

BTW It's a line follower and not JUST a motor shield.

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