How to control these 24v motors

I'm continuing my "please help identifying motor" thread in a new thread, because my question has evolved.

So it looks like I won't be able to identify the motors, so am now going to move on to controlling them. They're 3 24 volt motors being fed by a 24 volt 2.5 amp power supply. There are also two other motors in the machine that I need to control, but I haven't looked at them yet. They would use less power than these three.

So a total of 5 motors that I have to control. I think what I want to do is to start with a shield(s) for my prototype. But I may end up making a bunch of these, so may ultimately want to build my own circuits for controlling the motor. And keep in mind that I'm an electronics newbie.

People seem to recommend this one:

This can only control two motors, so I'd need three of them. This is pricy!

Here are my questions:

  1. These "high power" motor shields can handle my 24 volt motors, but they're also designed for MUCH higher amperage than I will use. Again - my entire power supply is only 2.5amps. So do I really need a high power shield? Are there any cheaper options available?

  2. Do you think it would be possible for an electronics newbie like me to build my own motor control circuits for these motors? Again, I'll probably start with a shield but will want to do a one-board solution at some point.

Thanks!

  • Dave

Do you need to reverse the motors?

Yes I do, at least 2 of them.

Ok, I went ahead and ordered 3 of these:

I hope they will fit my needs! Please let me know if you think I made the wrong choice. I decided that I really need to break this project up into manageable pieces, and with all the other work I have to do and things I have to learn, learning how to make a motor controller was something I could "outsource".

But I'd still really appreciate the answers to my questions. For phase 2 of this, I will want to make several of these control boxes for other people, and I'm hoping there's a cheaper way to do it than to have to have three $60 motor control boards in each control box.

You might try the below type h-bridge.

http://www.ebay.com/itm/390908373242?_trksid=p2060778.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT

Thanks zoomkat! Those certainly are a lot cheaper than the Poulu controllers. Could somebody explain the difference, whether the ebay ones are good enough for my application? I notice that they have large heat sinks, while the Poulu ones do not...

The heat sink is because that e-bay module claims to be good to 43A. It's cheaper because it's from China and it's only ONE channel.

The Pololu controller appears to be an actual "motion controller" since you can tell it what to do over a serial link. I thought I read three channels? http://www.pololu.com/product/767

Wow now that I further read about it, you can control two bidirectional and one unidirectional motor which you can control from an R/C interface from the radio or over a serial link. With the R/C interface you can have a remote joystick just by having a radio. Obviously an Arduino could send commands out the serial interface to it.

That's nice , but I don't need any of that. I need to control 3 24 volt 1.5 amp (ish) motors and am looking for the cheapest way to do it. I'm happy to use the analog outputs of the Ardunio. The Poulu seems way cool, but maybe a bit over-engineered for my needs. It feels like paying for something where half the functionality wouldn't be used.

So if anyone has any other suggestions let me know. I did order a couple of the ebay ones to check out. The other thing I'm wondering is if there are any circuit diagrams available in the public domain that I could cheat off of. My first choice would be to build the whole thing myself on one PCB.

An older discussion about the ebay H-bridge.

Ok, so I'm thinking ahead to when I get this all working. Once I have it all working, I will want a custom PCB. And to make it more cheaply, I'd much rather not be buying controller cards like discussed here. But designing my own motor controller from scratch is probably over my head. So can't I just use a design I find? If I google 24v motor controller, I get a lot of hits, such as this one:

What's wrong with that? Being new to this stuff, I'd think there was a standard source to find free (or to buy) circuit diagrams to solve common problems. Isn't there?

  • Dave

What's wrong with that? Being new to this stuff, I'd think there was a standard source to find free (or to buy) circuit diagrams to solve common problems. Isn't there?

You said you found a lot of Google stuff, so you should be good to go.

dptdpt:
Being new to this stuff, I'd think there was a standard source to find free (or to buy) circuit diagrams to solve common problems. Isn't there?

Well my Google is the same as yours, and I found 13M hits when I Googled "electronics circuit library".

This one for example, claims to have 40k examples in 500 categories.

Ok, I've wired up the Pololu TRex motor controllers and can't get them to work. The flashing LEDs are indicating that "safe start" conditions aren't met. As far as I can see I'm doing everything right. I emailed Pololu support and haven't heard back. If anyone has suggestions, please let me know. Details of how I have it set up are here.

But I've already decided that these controllers are way too much for what I need. They have RC input, serial input, steering stuff, software configuration, yada yada. They seem mostly designed for RC cars and robots. They also have a linear voltage regulator built in. They're big and expensive too.

So if anyone knows of a simple motor controller that can handle 24 volts and just does analog input, let me know. I'd still rather not have to build my own. It seems like somebody should make one! Ideally it would only need to handle about 1.5 amps per motor, so I don't need big heat sinks. And I can give it 5 volts, so it doesn't need a voltage regulator either. Those nice little Pololu stepper motor controllers are more like what I have in mind. I wish they'd make a DC motor controller like that.

This link may help with what you are attempting.

Thanks! That looks like it could work, although it is designed for only about 2/3 of the power I need and still has huge heatsinks. Do you think they're necessary? The Pololu boards, even with the aforementioned issues for me, don't have heatsinks.

In any case, although I think I eventually will want to redesign this board with custom motor controllers, I'd still like to do rev 1 with off the shelf motor controllers, just simpler and smaller than the Pololu ones. Take the Pololu ones, remove the RC and serial interfaces, remove the software control, and the linear voltage regulators and I'd be all set.

If anyone else knows of a more simple prebuilt motor controller, please let me know!

Here is a useful datasheet for DPDT relay boards they do a 24v version:

http://www.audiowind.com/pdf/D-128.pdf

They have RC input

That makes things simple, you use the servo library to control them.