I was bouncing around various projects in various stages of maturity. At the time, I was thinking of building a micro-quadcopter to test out some ideas on the cheap.
I crashed my little store bought toy and had to re-order some motors. So, I thought I would play with the ones I had. Turns out the controller I wanted was in my Erco box!!!
I got just that far, when I also found in my box a nice collection of NRF NL01+ another Erco special which caught my flight of ideas and crashed my schedule. And of course, now I am back to my robot wheelchair.
I spent a lifetime wishing I could do this kind of thing and now that I have the time and Parallax has been so kind as to put it all right in front of me, my biggest problem is setting a course and seeing it through.
The "problem" is that there is something interesting and worthwhile every time I come here:) This kind of problem, I can live with.
The "problem" is that there is something interesting and worthwhile every time I come here:) This kind of problem, I can live with.
Is there some sort of 12 step program for this? If so, let me know.
To go along with Bill's L293D suggestion, SN754410s are drop in replacements for the L293D and can handle higher currents.
I've read a lot of debates about whether or not the L293D and SN754410 need external flyback diodes. From what I've read, it seems like they're a good idea.
Make sure you pulse the enable pin and not the direction pin. As erco showed in one of his test videos, if you pulse the direction pin, you cause the motor to break between on pulses rather than coasting.
If you don't need the ability to use the break feature, you can use one less I/O pin per motor by using an inverter with each pair of the direction pins.
Is there some sort of 12 step program for this? If so, let me know.
To go along with Bill's L293D suggestion, SN754410s are drop in replacements for the L293D and can handle higher currents.
I've read a lot of debates about whether or not the L293D and SN754410 need external flyback diodes. From what I've read, it seems like they're a good idea.
Make sure you pulse the enable pin and not the direction pin. As erco showed in one of his test videos, if you pulse the direction pin, you cause the motor to break between on pulses rather than coasting.
If you don't need the ability to use the break feature, you can use one less I/O pin per motor by using an inverter with each pair of the direction pins.
I notice the HG7881 and L9110 controllers don't have an enable pin. Doesn't using these drivers with a normal DC motor cause the motor to break with each down pulse when using PWM?
I'm wondering if these should be limited to small stepper motors?
Erco you should know Ebay. I found some small H bridge assemblies. Some use LM 393 or LM 398 and some unknown. I picked up a small board (less then 1" square) that will drive 2 motors for around $4. I plan to show a LEGO robot using a BS2 board at the maker faire in Detroit in July. The LEGO format is perfect for small robots with lots of gearing and add on options.
Good Q, DD. I guess you meant brake, not break... Although one might lead to the other, worst case.
Dunno, didn't find a data sheet quickly. That might be the case, otherwise braking might not be an option and coasting is the default mode.
Normally it's me singing the benefits of dynamic braking. Do I have a convert on my hands?
Hey spell check didn't complain about break so I don't know why you should?
I'm not apposed to dynamic braking except when I want to coast rather than brake.
I keep intending to do a bit of studying about the whole drive/coast vs drive/brake issue. I just don't see how drive/brake during PWM would be a good strategy but the guys over on Pololu seem to think it's a viable option. I've been impressed several times with how helpful the Pololu guys are. They even started listing the teeth on their gear motors when I pointed out an error in one of their ratios. This makes it easier to calculate the exact encoder pulses per revolution.
If drive/brake is ever a good idea when using PWM, I think it would only work well at high PWM frequencies. At 200Hz drive/brake sounds more like drive/break. It makes an awful racket and pulls a lot more current than drive/coast. I haven't tested drive/brake at higher PWM frequencies yet but it's on my robotic todo list.
Good question. I have one of those L9110's on Elf, maybe I'll do some experiments next week. Heck, maybe even tomorrow if I can sneak away from family for a bit (hope wifey is not reading this...)
I notice the HG7881 and L9110 controllers don't have an enable pin. Doesn't using these drivers with a normal DC motor cause the motor to break with each down pulse when using PWM?
I'm wondering if these should be limited to small stepper motors?
Comments
http://forums.parallax.com/showthread.php/144881-2.86-L298N-Motor-Driver-Module-(Must-Try-to-not-Buy...)?p=1242398&viewfull=1#post1242398
Or get away for just $1.72 if you can live with piddly current (800 mA): http://www.ebay.com/itm/H-bridge-Stepper-Motor-Dual-DC-Motor-Driver-Controller-Board-For-Arduino-HG7881-/261335267186?pt=LH_DefaultDomain_0&hash=item3cd8cbb772
Jim
Thanks saved me money.
twice:)
If this is to control low current motors on a 4WD robot, I often parallel the motors on each side and use one L298 channel per side.
L293D dip chips are another option - trivial to drive.
I was bouncing around various projects in various stages of maturity. At the time, I was thinking of building a micro-quadcopter to test out some ideas on the cheap.
I crashed my little store bought toy and had to re-order some motors. So, I thought I would play with the ones I had. Turns out the controller I wanted was in my Erco box!!!
I got just that far, when I also found in my box a nice collection of NRF NL01+ another Erco special which caught my flight of ideas and crashed my schedule. And of course, now I am back to my robot wheelchair.
I spent a lifetime wishing I could do this kind of thing and now that I have the time and Parallax has been so kind as to put it all right in front of me, my biggest problem is setting a course and seeing it through.
The "problem" is that there is something interesting and worthwhile every time I come here:) This kind of problem, I can live with.
Many regards,
Rich
Is there some sort of 12 step program for this? If so, let me know.
To go along with Bill's L293D suggestion, SN754410s are drop in replacements for the L293D and can handle higher currents.
I've read a lot of debates about whether or not the L293D and SN754410 need external flyback diodes. From what I've read, it seems like they're a good idea.
Make sure you pulse the enable pin and not the direction pin. As erco showed in one of his test videos, if you pulse the direction pin, you cause the motor to break between on pulses rather than coasting.
If you don't need the ability to use the break feature, you can use one less I/O pin per motor by using an inverter with each pair of the direction pins.
The L293D's work fine in the board.
The SN754410's don't.
Now I buy only L293D's...
RoboAxe: http://www.mikronauts.com/robot-zoo/roboaxe/
I notice the HG7881 and L9110 controllers don't have an enable pin. Doesn't using these drivers with a normal DC motor cause the motor to break with each down pulse when using PWM?
I'm wondering if these should be limited to small stepper motors?
Dunno, didn't find a data sheet quickly. That might be the case, otherwise braking might not be an option and coasting is the default mode.
Normally it's me singing the benefits of dynamic braking. Do I have a convert on my hands?
Hey spell check didn't complain about break so I don't know why you should?
I'm not apposed to dynamic braking except when I want to coast rather than brake.
I keep intending to do a bit of studying about the whole drive/coast vs drive/brake issue. I just don't see how drive/brake during PWM would be a good strategy but the guys over on Pololu seem to think it's a viable option. I've been impressed several times with how helpful the Pololu guys are. They even started listing the teeth on their gear motors when I pointed out an error in one of their ratios. This makes it easier to calculate the exact encoder pulses per revolution.
If drive/brake is ever a good idea when using PWM, I think it would only work well at high PWM frequencies. At 200Hz drive/brake sounds more like drive/break. It makes an awful racket and pulls a lot more current than drive/coast. I haven't tested drive/brake at higher PWM frequencies yet but it's on my robotic todo list.
Do you have a link? Have you tried them yet?
Here is a data sheet I found:
http://nvhs.files.wordpress.com/2013/02/datasheet-l9110.pdf
It has internal diodes, dead easy to hook up.
It does look like it breaks on HH or LL input.
@erco - you are the deal finding man. You are a one man stimulus project.