Using 12 V motor with propeller

CharlieT

Hi,

I am new to propeller, and am working on my first project.

My setup: I am working with one of the Propeller Platform USB boards by Gadget Gangster. I have a 12V (200ma) gearbox motor that I would like to operate programmatically -- i.e. if certain conditions are met, run the motor for X number of seconds.

I am aware that the Propeller board is 5V. However, I am not sure what type of add-on module I should get in order to operate my 12V motor.

Would a 12V power step-up module such as this one be appropriate? http://www.revolution-robotics.com/solutions/micro_power_module_24w_12v_step_up

Or would I be better off getting a motor driver board, perhaps like this one? http://www.pololu.com/catalog/product/1212

I am of course open to using other modules if someone can recommend a superior or more appropriate one. As I mentioned, I am a novice, so any assistance is greatly appreciated.

Thanks,

Charlie

Jonathan

Charlie,

Go with the second option, it will allow you to spin the motor in both directions and is easily capable of providing your motor's current requirements.

Have fun!

Jonathan

Peter Jakacki

As long as it's in one direction then a simple transistor will handle that easily. What you have to watch is the peak current at start when the motor is stopped (or any time it is jammed). But this might depend upon your 12V power source, if it's a car battery then it will melt a spanner if you short that across the terminals whereas a small power-pack (wall-wart) will be self-limiting. If in doubt then just use a way over-rated IRF3708 rated at 62A which might sound like a lot but I have the IRLB3036PBF which is the same sized (TO220) transistor and it's rated at 195A which I haven't been able to destroy as yet. However in most case a much smaller device will work, just depends whats available and easy for you.

CharlieT

Jonathan and Peter, thank you both for the replies and advice.

Jonathan, I actually only need the motor to go in one direction. Given that information, are there any advantages to using a motor driver board, rather than the 'simple transistor' approach that Peter suggests? Would either approach be easier for a novice like me to implement?

Again, thank you both for the advice! I really appreciate it.

Charlie

Jonathan

Charlie,

The controller you listed will be plug and play and the transistor approach will be cheaper. Here is a link with good info about using tansistors and mosfets with microcontrollers.
http://www.bristolwatch.com/ele/transistor_drivers.htm

The only thing is bi-directional control with transistors is a little more complex, look up "h-bridge". I know you said you don't need it, but things have a way of changing...

Jonathan

Duane Degn

Charlie,

First off let me say I don't know nearly as much about transistors as the other guys on the forum (particularly Peter and Jonathan) so I'd suggest you give more weight to their advice than mine.

The motor driver board you linked to is overkill for this.

I'll suggest another solution that's also overkill but only costs a couple of dollars.

The L298N is a motor controller I really like. I'm using it in this project. Even if you don't use the L298N for this project you ought to keep it in mind for future motor driving needs.

Rayman

I think I'd use the ULN2003. It's basically a transistor array, but it has a built in base resistor and also transient protection.
Plus, you could drive 7 more motors, if you wanted to...

jmg

Peter Jakacki wrote: »

As long as it's in one direction then a simple transistor will handle that easily....

and I see in the recent news, Fairchild has a new series of High-Side drivers, that somewhat redefine that 'simple transistor' - prices look quite good at Mouser.

http://www.fairchildsemi.com/news/2012/1205/050212_Smart-High-Side-Switches.html

100mOhm 3A TO252 model, is 89c/100+.
9mOhm 48A TO263 model is 1.43/100+

These are not fast switching devices, so are not for PWM, but are ideal for "run the motor for X number of seconds"

The smaller part looks to have a 3V compatible control pin, but the larger parts data is more confusing.
The larger variants have a current sense pin as well.

CharlieT

Thanks for the advice everyone.

I noticed that some of the motor controllers are listed as being for single brushed motors. Others controllers are listed for brushless motors.

I am unsure as to which category the motor I am using falls into (i.e. single brushed or brushless). It's an inexpensive gearbox motor I ordered from China, so what does not have any part number identification.

Since I am new to working with motors, I'm not sure how to determine if the motor is single brushed or brushless -- or if it matters. But I thought perhaps someone here might know:

http://www.virtualvillage.com/high-torque-electric-motor-4-rpm-12v-dc-gear-box-motor-37mm-001480-106.html

Thanks for all the help.

Charlie

Duane Degn

It matters a lot!

It's probably brushed unless it says "brushless". A brushless motor has three power connections a brushed DC motor usually just has two.

I just looked at the link. It's a brushed motor.

CharlieT

Thanks Duane!

PJAllen

Peter Jakacki wrote: »

If in doubt then just use a way over-rated IRF3708 rated at 62A which might sound like a lot but I have the IRLB3036PBF which is the same sized (TO220) transistor and it's rated at 195A which I haven't been able to destroy as yet.

At >$4 each, I'd hope that destroying one would come with a good *bang!*, just to make it worthwhile.

I was wondering, their having this extraordinary drain current, there must be some hitch: the input capacitance on those guys is tremendous, > 10,000pF (that's 0.01uF). I don't think I've seen one so great as that.

You're using a MIC4427 or something, too, yes?

Duane C. Johnson

I love the IRF3708 and others in this class.

Yes, they have fairly high gate capacitance. However, a Prop pin has about 100 Ohm output driver FETs. With a 10nF gate capacitance the RC time constant is about 1uS. At 5 time constants this is about 5uF. A good portion of this time is delay so the drain rise time is more like 2uS.

I would be a bit careful switching faster than about 1KHz directly from a Prop pin.

Don't consider the extreme over current capabilities as a problem. I read the "high current" as "very low resistance" instead. With low resistance the MOSFET will dissipate low power and doesn't need a heat sink in most applications up to 10A or more. Cool huh.

Duane J

CharlieT

I ended up getting the motor driver board as Jonathan suggested, just in case I require additional functionality from the motor down the line.

http://www.pololu.com/catalog/product/1212

As I mentioned, I am a novice when it comes to wiring electronics. Thus far, I have been able to build my project by following some of Gadget Gangster's step-by-step tutorials that are available online.

However, I am unsure how to connect the motor driver board (see link above) to my project. Can someone advise me?

I am trying to connect the motor driver board via the breakout board that comes with the Gadget Gangster touchscreen module:

http://gadgetgangster.com/find-a-project/56?projectnum=209

Any assistance would be greatly appreciated (and thanks again for all the help thus far).

Thanks,

Charlie