motor driver power supply help!

hi,

I've been working on projects with arduino w/dc motors for the past year or so. I'm still finding my way through the fog but getting there..

I have a few quesitons:

I've been using the arduino board with 8 of these motors.

https://www.allelectronics.com/index.php?page=item&id=DCM-367&extra=a:2:{i:0;s:40:%2203823345592a403b2f4a37a59384e7ab28f02be1%22;i:1;s:0:%22%22;}

while using a circuit similar to this to regulate power etc. http://homepage.mac.com/joester5/art/digitalart2/dcmotor.html

I am now working on a large scale installation at a gallery using some of these techniques with 25 of these motors, patterened in on and off position.

I've been researching 'motor drivers', which I'm totally new to was looking at http://www.sparkfun.com/products/9457

to connect to eliminate the need for this circuit with the tip 120, but am unclear as to which one would work best, obviously I'd like to use as few of the drivers as possible and still be able to maintain individual control over each motor. I essentially am looking for on and off control.

any suggestions? :o

My second question would be about using a wallwart, what kind to use with the mystery motor driver and if there is a forum/post I am missing on how to connect a wall wart to the motor driver?

Lastly, the motors will need to be running on and off in pattern for 8 hours a day for two weeks, so it needs to be a safe 'cool' soloution, I don't know if I need to rethink things a bit.

But, any help would be greatly appreciated!

Thanks a million!

I am missing on how to connect a wall wart to the motor driver?

No just connect the ground to the arduino ground and the motor driver ground and the positive wire to the motor drives positive wire.

If you have 25 of these motors you will need at least 25 times the quarter amp current rating. Unfortunately the link doesn't give the motor stall current which is what you want to know for worst case. But you need at least 6.25 Amps so you are best going for a wall wart with a 10A capacity. That is a bit high for a wall wart, you might have to go for a PC power supply. I am not sure why you want to replace the TIP 120, they are cheap and as you don't want to change direction there is no point going for a motor drive.

the motors will need to be running on and off in pattern for 8 hours a day for two weeks,

You will have to pay particular attention to noise reduction and have adequately decoupled supplies to the motors. See:-

http://www.thebox.myzen.co.uk/Tutorial/De-coupling.html

However, are you sure those motors can last for that long?

You also need to have 25 PWM outputs, are you going to use a Mega?

I am not sure why you want to replace the TIP 120, they are cheap and as you don't want to change direction there is no point going for a motor drive.

I'm not attached to the motor driver, I just got the sense that they were safer for longevity/possibly time saving? Maybe I received some bad advice. anyways...

If I was to hook up motors, would each one need a tip 120 or could I rig them all up with one transistor to protect the arduino, I'm trying to use as few power supplies as possible.

I'm planning on using two boards (sorry should have said that in the first place) because of the space I need to split the design using two different boards, this would make it easier also in dealing with power supplies.

Quote: the motors will need to be running on and off in pattern for 8 hours a day for two weeks,

You will have to pay particular attention to noise reduction and have adequately decoupled supplies to the motors. See:- Quote: http://www.thebox.myzen.co.uk/Tutorial/De-coupling.html

However, are you sure those motors can last for that long?

Is there any motors of similar power and design you would suggest that might have better endurance, or is there some sort of guide to longevity that I'm missing?

Thanks! EK

If it seems safer I could also budget in getting individual power supplies for each motor and building the simple tip 120 circuit. Would this greatly simplify the project and eliminate the overheating concerns?

Sorry if I'm not quite understanding :-/

ek

You also need to have 25 PWM outputs, are you going to use a Mega?

If the motors only need to be on/off, then the transistor on/off control can be multiplexed via latching multiplex chips like the 74HC259.

would each one need a tip 120 or could I rig them all up with one transistor to protect the arduino,

Each motor that requires individual control requires it's own transistor. Have you read:- http://www.thebox.myzen.co.uk/Workshop/Motors_1.html

Is there any motors of similar power and design you would suggest that might have better endurance,

Not really as I don't know what you are doing with them but a small brush motor like this one is noisy and does not have a long life. I would test a few now and keep them going all the time to get a feel for how long they will last.

Great thanks all for the help!

I am attaching thin wires to the motors to use them as beaters for instruments, so they are bearing a little bit of weight. I have some funding for the project so could spend a little more on a better motor if you have any suggestions, on any sites?

If it seems safer I could also budget in getting individual power supplies for each motor and building the simple tip 120 circuit. Would this greatly simplify the project and eliminate the overheating concerns?

Sorry if I’m not quite understanding

ek

If it seems safer I could also budget in getting individual power supplies for each motor

No I would go for something like a 2 to 4 amp power supply and use one to power several motors. I don't buy a lot of motors so I am not familiar with what is out there at the moment.

Hey mike,

thanks very much for all the help again---

So if I was to use a single power supply to work with several motors, the amp power needs to to be within the range of all the motors combined, and the voltage doesn't have to be added together correct? Then I would set up a parallel circuit to power all the attached motors?

Is there any reason besides equipment saving to do this? The motors will be spread out and may be just as easy to use a power supply per individual motor?

Lastly, unless I'm missing something is there any indication for 'noise' on motors --

here is a motor for example similar with a product sheet.

http://www.allelectronics.com/make-a-store/item/DCM-345/12-24VDC-MOTOR/1.html

thanks thanks!

ek

I've been using the arduino board with 8 of these motors.

You can use a multimeter to measure the current being used by the motor when in use, and calculate from that the size power supply you need.

Sorry forgive my ignorance---

Is this more reliable then looking at specs? Is there a tutorial or some sort of site explaining how to test current being used. Would I set up the whole circuit to test this?

Best, EK

Then I would set up a parallel circuit to power all the attached motors?

Yes that is it you would use a common supply for all the motors.

unless I'm missing something is there any indication for 'noise' on motors

Data sheets do not usually give information about the noise generated by a motor. This is because :- 1) It looks bad 2) It depends on how they are powered 3) It is dificult to measure and will change from motor to motor.

But they all generate noise some more than others.

Is this more reliable then looking at specs? Is there a tutorial or some sort of site explaining how to test current being used. Would I set up the whole circuit to test this?

http://www.google.com/search?q=multimeter+measure+current&hl=en&num=100&lr=&ft=i&cr=&safe=images

I guess what I’m asking is once I come up with a combination of motor/power supply that works well- Is there a way of testing or calculating the noise level/ rate of error etc.

thanks!
EK

The motors will not be so noisy as to cause serious problems, and you can take some basic precautions: include a forward rectifier in series with each motor, a 1 microfarad cap and reverse rectifier in parallel with each motor, right at the motor.

Use an old computer power supply for your PS. Run the motors directly off the 5V rail. Run the 12V into the Arduio's VIN and let its regulator and filter work.

Finally, I think I would use 5V reed relays to control the motors. That way the motors are further isolated from the Arduino. And finally the circuitry for controlling relays from Arduino is well documented.

The motors will not be so noisy as to cause serious problems

Well there are lots of people on this forum that run into these problems.

include a forward rectifier in series with each motor

How can that help? Reverse polarity diodes yes but not forward.

Is there a way of testing or calculating the noise level/ rate of error etc.

Measuring noise takes some very special test equipment in a electrically noise free chamber, but the value will not tell you much except if it conforms to various emission standards. There is no way to calculate it.

/ rate of error etc

Again no. It is a matter of using good design techniques and testing the finished installation.

I'm sorry, I understand all the components but not quite clear on how to assemble them for this particular project, is there any documentation beyond this?

The motors will not be so noisy as to cause serious problems, and you can take some basic precautions: include a forward rectifier in series with each motor, a 1 microfarad cap and reverse rectifier in parallel with each motor, right at the motor.

Use an old computer power supply for your PS. Run the motors directly off the 5V rail. Run the 12V into the Arduio's VIN and let its regulator and filter work.

Finally, I think I would use 5V reed relays to control the motors. That way the motors are further isolated from the Arduino. And finally the circuitry for controlling relays from Arduino is well documented.

Interesting we raised a little debate, so you think that errors of noise would reveal themselves after an 8 hour test or something like this?

Would the fact that they are running with breaks effect there longevity?

I guess we are running circles a bit here, but if I was to upgrade to a more expensive motor it would most likely help the situation?

thanks ek

Quote: You also need to have 25 PWM outputs, are you going to use a Mega?

I was planning on using the displayduino

http://mondomatrix.com/info/?page_id=311

I don't understand why i would have to use all pwm's--I couldn't just use the regular out pins if Im just using on/off?

best ek

So hopefully this is my last post…for now :wink:

It seems that if I combine something similar to this http://itp.nyu.edu/physcomp/Tutorials/HighCurrentLoads

and add on there 0.1uF capacitor, I should be in good shape? or at least take the safety precautions?

thanks!
EK

If you run an arduino for 2 weeks, I strongly suggest you heatsink the regulator.