Motor not spinning? - Electronic Circuits Projects Diagrams Free

Omar.M · 28th February 2007, 02:20 AM

Hello!
I've build a simple robot. I wanted to make a line follower, and I followed the diagram here to make the motor controller (disregarding the other schematics):
http://www.diylive.net/index.php/200...lowing-robot2/

So I assembled the robot and set up some test code. Basically, turn right motor on for 5 seconds, the left motor on for 5 seconds and loop.

When I run it, the left motor turns on fine as it is supposed to. When it is supposed to switch the motors, it seems the right one does not turn on. Both motors have the same motor controller components, and I've hooked them up the same way.

When the right one is supposed to go on, I gently spin it in and it seems to start running. I guess there is some kind of problem with it starting to spin. When I spin it manually, it starts to work.

It cannot be the motors, I've changed the motor to a different one and hooked it up. Same problem.
Any ideas?

Omar

kchriste · 28th February 2007, 04:19 AM

Quote:

followed the diagram here to make the motor controller (disregarding the other schematics):

I assume you mean the "circuit for a simple motor controller."
Well that diagram looks kinda blurry and wrong because they have a 83

hm: resistor in series with one motor and a 33

hm: in series with the 2nd, running off of a 5V supply. This might work (Not very well because the resistors are different OR is it the blur?) with VERY small 3V motors on a VERY small robot. Try it with 33

hm: resistors for both the right and left motors.
Your motors are not getting enough current and are stalling! You should really be using the circuit with the H-bridge as shown further down the page.
What is the current / voltage rating of the motors you are using?

Omar.M · 28th February 2007, 12:08 PM

Hm, I believe it is blurry. I just focused on the right part of the diagram (for his right motor controller). Basically, I made two sets of those (with the 33 ohm resistor) and hooked each up with the motors.

I understand I need a H-Bridge, but I don't have access to it right now. Can't buy online until parents say it's OK.

The motors, were just small ones taken out of a hand held fan toy (that I bought from the dollar store). I just popped it open and took the motor out. Is there something I can do? Or am I pretty much out of luck?

blueroomelectronics · 28th February 2007, 03:51 PM

You'll need an H-bridge of some form or other.
Here's a site that might help.
http://www.robotroom.com/

kchriste · 1st March 2007, 04:36 AM

Quote:

Originally Posted by Omar.M

The motors, were just small ones taken out of a hand held fan toy (that I bought from the dollar store). I just popped it open and took the motor out. Is there something I can do? Or am I pretty much out of luck?

It could be that you need to use a beefier transistor to switch the motor current. Short together the collector / emitter pins on each transistor and see how the motors run.

You could also try lowering the 33

hm: resistors to 5-10

hm: and see how they run. If the hand held fan had two batteries in it, then the motors are 3V types, so it would be best to check the voltage across them and make sure it is around 2-3V or so. Diodes and 0.1uF caps across each motor will also extend the life of the ICs running off the same 5V line. Better yet, source them from their own 3V (two battery example) regulator instead and eliminate the resistors.

Omar.M · 2nd March 2007, 01:02 AM

Thanks a lot for your help.
Well, there is so much glue in there, I can barely access the components =P, I think I will have to rewire everything anyway so I might just rip everything out. It seems I might as well just restart.

So my new question: Is it possible to use really tiny motors without drivers? I mean I have two very small motors...smaller than this:
|---|
| |
| |
|---|

I found these in those micro R/C cars, smaller than the palm of my hand. Is it possible to use this and cut the transistors, resistors and the motor controlling (after all, I just want to make it go forward)? I understand there may be too little torque to move anything, so I think I may set it up like this person has:
http://elm-chan.org/works/ltc/ltc02.jpeg

Any ideas... will I fall flat on my face again?
Omar

kchriste · 2nd March 2007, 02:09 AM

Quote:

Is it possible to use really tiny motors without drivers?

If you mean drive them directly with a PIC / microcontroller, then NO.

Quote:

I found these in those micro R/C cars, smaller than the palm of my hand. Is it possible to use this and cut the transistors, resistors and the motor controlling (after all, I just want to make it go forward)?

You'll still need, at a minimum, 2 transistors & 2 resistors to boost the current capability of the PIC. I think that those motors are designed to run on 1.5V so running them off a 5V supply will be very inefficient.

gramo · 2nd March 2007, 07:11 AM

Or 1 FET

A single logic voltage controlled FET is a great driver, and without delving to deep into this, a 'drive circuit' for the FET is not required for lower current devices (i.e. small motors)

Have a look at http://users.tpg.com.au/gramo/Site/irl2203.htm

Keep in mind that you just have to connect the output of the digital device directly to the Gate on the FET, and you should have a diode in parallel with the motor to minimize EMF generated by the windings of the motor

Omar.M · 2nd March 2007, 12:10 PM

Ah ok. Well I will just keep the set up I have, I think it might work with the small motors. Maybe I will hook the motors up to a separate 3V supply.

One question I had... for motor drivers, how important is it to use a MOSFET or FETS? Can you use an ordinary NPN or PNP transistor?

Omar

gramo · 2nd March 2007, 09:43 PM

The transistor used in the diagram under "circuit for a simple motor controller" is a 2N3904, these are rated at 200mA DC @ 40V.

I don’t see you using a motor that requires over 40V, so current is what we have to be concerned with here.

You should already have the nominal voltage of the motor (i.e. 6V or 3V, not sure what one your using), and now grab a multimeter and find the resistance of the winding on your motor, should be a rather small figure.

Divide the nominal voltage by the resistance of the winding, e.i.

V / R = I (Max Current)

If I is >200mA (0.200) then you will have to use a larger switching device..

Omar.M · 3rd March 2007, 07:14 PM

Thank you very much for your help! I really appreciate it.

I was also wondering about wheels. It seems they really affect the way the robot moves. Since I am moving on to small motors, should I make them out of cardboard, or use the REALLY small wheels that I got with the miniture R/C car?

For torque, I was thinking of setting it up like so... how well does it work?:
http://elm-chan.org/works/ltc/ltc02.jpeg

The motor spins and it is pressed against the wheel, which makes it spin...
Thanks.

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28th February 2007, 02:20 AM	(permalink)
Omar.M	Motor not spinning? Hello! I've build a simple robot. I wanted to make a line follower, and I followed the diagram here to make the motor controller (disregarding the other schematics): http://www.diylive.net/index.php/200...lowing-robot2/ So I assembled the robot and set up some test code. Basically, turn right motor on for 5 seconds, the left motor on for 5 seconds and loop. When I run it, the left motor turns on fine as it is supposed to. When it is supposed to switch the motors, it seems the right one does not turn on. Both motors have the same motor controller components, and I've hooked them up the same way. When the right one is supposed to go on, I gently spin it in and it seems to start running. I guess there is some kind of problem with it starting to spin. When I spin it manually, it starts to work. It cannot be the motors, I've changed the motor to a different one and hooked it up. Same problem. Any ideas? Omar

28th February 2007, 12:08 PM	(permalink)
Omar.M	Hm, I believe it is blurry. I just focused on the right part of the diagram (for his right motor controller). Basically, I made two sets of those (with the 33 ohm resistor) and hooked each up with the motors. I understand I need a H-Bridge, but I don't have access to it right now. Can't buy online until parents say it's OK. The motors, were just small ones taken out of a hand held fan toy (that I bought from the dollar store). I just popped it open and took the motor out. Is there something I can do? Or am I pretty much out of luck?

28th February 2007, 03:51 PM	(permalink)
blueroomelectronics	You'll need an H-bridge of some form or other. Here's a site that might help. http://www.robotroom.com/ __________________ Bill Smart Kits build Smart People http://www.blueroomelectronics.com

2nd March 2007, 01:02 AM	(permalink)
Omar.M	Hmm Thanks a lot for your help. Well, there is so much glue in there, I can barely access the components =P, I think I will have to rewire everything anyway so I might just rip everything out. It seems I might as well just restart. So my new question: Is it possible to use really tiny motors without drivers? I mean I have two very small motors...smaller than this: \|---\| \| \| \| \| \|---\| I found these in those micro R/C cars, smaller than the palm of my hand. Is it possible to use this and cut the transistors, resistors and the motor controlling (after all, I just want to make it go forward)? I understand there may be too little torque to move anything, so I think I may set it up like this person has: http://elm-chan.org/works/ltc/ltc02.jpeg Any ideas... will I fall flat on my face again? Omar

2nd March 2007, 07:11 AM	(permalink)
gramo	Or 1 FET A single logic voltage controlled FET is a great driver, and without delving to deep into this, a 'drive circuit' for the FET is not required for lower current devices (i.e. small motors) Have a look at http://users.tpg.com.au/gramo/Site/irl2203.htm Keep in mind that you just have to connect the output of the digital device directly to the Gate on the FET, and you should have a diode in parallel with the motor to minimize EMF generated by the windings of the motor __________________ Spency. PIC Micro's - Your mind is the limit PIC's and interfacing with other devices - a PIC Basic Guide @ digital-diy.net

2nd March 2007, 12:10 PM	(permalink)
Omar.M	Ah ok. Well I will just keep the set up I have, I think it might work with the small motors. Maybe I will hook the motors up to a separate 3V supply. One question I had... for motor drivers, how important is it to use a MOSFET or FETS? Can you use an ordinary NPN or PNP transistor? Omar

2nd March 2007, 09:43 PM	(permalink)
gramo	The transistor used in the diagram under "circuit for a simple motor controller" is a 2N3904, these are rated at 200mA DC @ 40V. I don’t see you using a motor that requires over 40V, so current is what we have to be concerned with here. You should already have the nominal voltage of the motor (i.e. 6V or 3V, not sure what one your using), and now grab a multimeter and find the resistance of the winding on your motor, should be a rather small figure. Divide the nominal voltage by the resistance of the winding, e.i. V / R = I (Max Current) If I is >200mA (0.200) then you will have to use a larger switching device.. __________________ Spency. PIC Micro's - Your mind is the limit PIC's and interfacing with other devices - a PIC Basic Guide @ digital-diy.net

3rd March 2007, 07:14 PM	(permalink)
Omar.M	Thank you very much for your help! I really appreciate it. I was also wondering about wheels. It seems they really affect the way the robot moves. Since I am moving on to small motors, should I make them out of cardboard, or use the REALLY small wheels that I got with the miniture R/C car? For torque, I was thinking of setting it up like so... how well does it work?: http://elm-chan.org/works/ltc/ltc02.jpeg The motor spins and it is pressed against the wheel, which makes it spin... Thanks.