**That is an ingenious idea. **
That is an ingenious idea. Naturally, I never considered doing it that way. I like that idea and will work that into the design.
Thanks a lot
Cheers,
Curtis
Oh that is a good video. I
Oh that is a good video. I wonder how much liquid courage it would take to get Frits to shoot a video grooving like that. The guy in that video definitely had coordination
Grog is a very competent
Grog is a very competent person!
(Just for the record)
I agree with you. That is
I agree with you. That is why I took his advice and added the alternate circuit. Thanks to all who is/has helped with this circuit. I have received all of the components and will be testing the circuit and designing a PCB shortly.
Sob
Yes, I’m feeling a little teary-eyed myself that this has been such a success.
Are you able / confident to follow through on this and make it an I2C slave device with positional and current feedback?
When I made the Big Chaser controller (I’d like to think of it as the great-grandaddy of LMR motor controllers), my vision was that LMR should be host to a series of free (we’ll you’d have to buy the components yourself and build it yourself) pluggable designs and software which would be the backbone of any robot project, such as:
- A motor controller
- A range of distance sensors
- temperature sennsors
- Displays
and that they should all have a common protocol, such as I2C behind them. In this fashion, one could take a handful of the components and all we’d really need is an I2C controller to script them all together.
I’m still massively keen to see this through, so if anyone feels like picking up the gauntlet and mking this design into an I2C slave, please do…!
You sorta read my mind on
You sorta read my mind on this. Although I am not a big fan of the Arduino I am impressed with it’s pluggable design. That is sort of what I invisioned for the projects that I am working on. This is just a prototype and will have current and positional feedback. The I2C protocal would be simple to add as the finished design will have its own controller on board so that you’ll only have to send it a set of commands. I’ll be posting all schematics, PCB’s, code and test applications as I go along. I’m also working on a more traditional H-bridge design but, for this one, using the relays and the opto-isolotion made for a simple to build/implement project. The relays I used for this project are rated up to 14V @ 20A.
Looks great
Your finished product looks like a work of art! Can’t wait to see the robot it will go in!
Thanks for the kind
Thanks for the kind comments. I like to add a finished look to all my projects. I consider it a gift and a curse as the end product is well thought out and put together but it tends to cause me to spend more time to accomplish it. I have big plans for the Robot and ofcourse I will release all designs/code for others to learn from and to offer suggestions for improvement.
So what are the specs for
So what are the specs for this? I bought two wheelchair motors and 2 12v 18aH sealed lead acid batteries, is this a suitable motor driver? What is the voltage supply max, as well as amp? Does it have pwm/speed control?
This design is rated up to
This design is rated up to 14V @ 20 Amps. The voltage/current constraints are based on the ratings on the relays that are chosen. There is a PWM/speed controller designed for this controller. The next revision of the boards will have the PWM controller integrated on the board. They will also include positional feedback, current/voltage monitoring and I2C. I am considering designing the relay boards as separate plugin attachments so that different values can be swapped in based on needs.
This design should handle your wheelchair motors with no problems. I will be uploading the board files, schematics, PIC code and test applications shortly.
Alright I am looking forward
Alright I am looking forward to that! Does a relay with amp max that exceeds the amp of the motor incredibly make it bad? For example, say I have a motor rated at 25A and I provide a relay rated at 40A, is this detrimental to the motor? Also, does the Ah/voltage of the batteries I use affect the chosen amperage of the relay?
Actually, that is better as
Actually, that is better as it leaves some room for stall current of the motor. The Ah/voltage of the batteries will not affect what relay you choose. Hopefully I can get some video up soon. I need to get one of those YouTube cameras instead of the DV camera I have.
Thanks! I didnt know they
Thanks! I didnt know they made youtube cameras.
Edit: what is the part # of the relays you used thats the only part # you didnt include, it might be hard finding relays for the board I base off of your schematic, so I’ll just wait for you to upload your .brd file.
I’m looking at getting the
I’m looking at getting the following camera from Action-HD GVS www.aiptek.com
Edit #2: I also noticed
Edit #2: I also noticed there is no fuse, do you plan on adding a 40+ amp interrupt rating? With a 24 volt voltage rating, some kind of circuit protection would be useful, unless you already have one and I dont see it :D.
The fuse is not shown in the
The fuse is not shown in the pictures but is built into the test power cables. The fuse is a 40 amp 24V rated spade type fuse. The same type that is used in cars and audio equipment. I plan on adding it to the board for the final design. I’m going to finish up the current Build of Materials with the prices/vendors. I have an extra board if you would like to test this design. You would need to furnish your own components. Let me know if you would like to have it and I can send it to you.
That would be great!! I will
Hmmm if you have forward and reverse headers, then what is the PWM header for?
The FWD and REV pins are
The FWD and REV pins are just for direction control. The PWM pin is to pulse the DC voltage that is applied to the motor so the speed can be controlled.
For those that want to save an extra pin, the last schematic I posted incorporates a NOT-gate so that the FWD/REV pin will operate from one Output pin. The second Output pin is for the speed control. If you look at the way the NOT-gate is wired you will notice that the output of the second gate also feeds the input of the first gate. This is so when a high is placed on that input pin it will be inverted low on the output of that gate which places a low on the input of the first gate. The first gate inverts the low input to a high output. Therefore, when the input is high, the forward direction is selected and when the input is low, the reverse direction is selected. The only hangup with this circuit is you will not have dynamic breaking. The only way to stop the motors is by setting the PWM pin to 0.
The FWD and REV pins are
The FWD and REV pins are just for direction control. The PWM pin is to pulse the DC voltage that is applied to the motor so the speed can be controlled.
That makes sense, but does that mean this controller doesnt allow for individual motor speed control?
Also, looking forward to the .sch or .brd files, I really don’t want to find a library for all the parts you used :D.
The controller as feature
The controller as feature here will control a single motor and thus, allow for individual motor speed control. I’ll go ahead and upload the current schematic and board files so you can play around with the design. I created them using ExpressPCB. The next design will include a 8 pin PIC on the board that will provide the direction/PWM control. All you’ll have to do is send it serial commands from the microcontroller of your choice. I’ll also upload the current test application and PIC source code as well. Be advised, the PIC source is minimum as I wrote it for testing functionality. I think I’m going to shoot some video with my current digital camera and upload. That may take a while as I’ll have to import the video afterwards.