I’m designing a new control board that will combine the arduino mega and motor controller in a single board. I’m also adding three connectors for fans.
This is a brainstorming thread. I’m designing this circuit board from the ground up, so if there’s something you want added to the motor controller, speak now or forever hold your peace 
The idea is that this board, as well as other maslow parts and eventually kits, will be available for sale on my website.
why would you want 3 fans? one is enough isnt it?
also what is the point of having it all on one board? does it make it cheaper to produce? Seems like it would just make it more expensive, since now you have a bigger board with more components, minus all the connecting pins.
not trying to be pessimistic, but seems like a lot of work for not much added benefit?
All the fan connector is is a 12v power connector. They can all be used for fans, or one could be used for a fan and the other two can be used to power other things like LED strips for machine lighting.
I’m designing everything on one board to get away from having to buy Arduino Megas, plain and simple. The truth is, Maslow doesn’t use a lot of the peripheral functionality that a Mega has. A simplified version can be used with less parts, and, believe it or not, the entire board with h-bridges can be made smaller than just a mega because I don’t need to try to fit that form factor anymore. So yes, it will be cheaper and smaller than an Arduino Mega2560 + shield. It also prevents people from using questionable chinese Mega2560 clones.
huh? (wheels exist, use them.)
if you can save a lot of money go for it, but in quantites over 100 the Arduino and shield are about $30 or less. Wish I had the skills to redesign boards like that.
z axis zero
Router control (power for relay)
Vacuum control (power for relay)
Emergency stop
Welcome @ScottyWarpNine!
The most common failure has been thermal or over-current damage to the L298 H-bridge chips.
The TLE5206 variant of the PowerControl board was created to address this, by separating the motors onto individual controller chips, using controllers with built-in protection and offering a version that uses heat sinks attached to the board instead of adhered to the chip (a wood shop is a rough environment for a stick-on heat sink).
There is some concern that the stock 5A power supply might not quite handle the load of the three motors under high load conditions, adding fans and other accessories might make a more powerful supply advisable.
Look at the TLE5206 board’s use of gpios; it makes provision for expanded version detection and makes more of the IOX gpios available for AUX controls.
Awesome, thank you guys. I’ll add two relays, and built in E-stop support. What do you mean z axis zero? Could a limit switch on an adjustable mount be used to detect a zero position? If that’s the case then I’ll break out some unused I/O pins to some screw terminals.
I’ll look into using uprated driver ICs and better heat sinks. I understand how adhesive heat sinks might not be the best solution.
You wouldn’t normally use a limit switch exactly for a z axis zero, although it’s essentially the same thing. Usually you have some very thin conductive material that sits under the bit on the surface that you want to zero to, and then you have a wire that is grounded to the bit as well. Lower the z axis until the circuit completes. So, works pretty much just like a limit switch electronically, but it’s removed after the zero is set so that it isn’t in the way.
As for the board itself, if you do design it all on one board, I’d suggest making sure you have it designed in a way that the controller portion is easily modified and changed to a different controller. There are threads where people have been exploring porting the Maslow firmware to more powerful controllers. If you were to design this board and produce it in mass quantities it’d be a shame if a better controller option is then found and there is no easy way for you to modify it. I think this is one reason that it makes for a very good argument to keep the controller and power board separate.
I’d also suggest not making it to small. I think it’s a good idea to keep a bit of space between the H-Bridge chips, since those are big heat producers.
One other thing you might consider is having possibly vacant but easily added places for additional H-Bridge chips / motor connections. There has been talking and possibly some people playing around with adding additional motors, possibly up to 5 I believe (one for each corner and z-axis). If your board could readily be adapted to accommodate this that would be a bonus IMO. Heck if you wanted to go ahead and include the H-Bridge chips and motor connections, even if using more motors doesn’t become standard, you could design in some way to specify which motor the H-Bridge is for so that it could be failover chips if nothing else. Burn up one chip and move to another without having to replace the board hehe 
Don’t know if the additional cost would be worth it though.
the problem with relays is now you have high voltage wiring that people have to mess with and that is dangerous and a possible liability. better to make a complete box with a 110V outlet receptacle to make it more user friendly/ idiot proof.
Another thing would be better connectors for the harnesses. A lot of troubles with harness connections in these posts. I think they are on and off many times, and a better connector for that type of use.
I would also like a totally enclosed “box” to come with it, suitable for shop dusty conditions.
Ok, I understand what you mean by Z axis zero, a similar thing is used for 3D printing. I’ll keep that in mind.
I’m planning on having two microcontroller footprints, one for the mega2560, and one for a 32 bit Atmel processor, maybe the same chip as the Arduino Zero, or Due.
I don’t know about having 5 motor outputs, but if there is space I could at least put in footprints for extra drivers.
I do agree that it would be a good idea to have everything in a self contained box.
I think one of the issues with the stock maslow h bridge is that most of the heat dissipation is through the pad itself. It might benefit from having some thermal vias and maybe a heat sink on the other side of the PCB in addition to fan cooling. Or maybe just using the other available package and a vertical heatsink.
I think you’ll find that the Arduino Zero doesn’t have enough gpios. The Due has lots of gpios but loses its stored settings during programming, so would need to be recalibrated or have those settings restored after programming.
Hm, I’ll keep reading forum posts, but do you have a microcontroller in mind?
I’ve looked at the ESP32 and PJRC’s Teensy 3.5 & 3.6.
The Teensy have plenty of gpios and porting the firmware is relatively straightforward. There’s an issue that those boards don’t respond to the USB-reset trick that the Arduino use, and the Maslow firmware/software rely on a soft reset when the connection is established. Not insurmountable, but to be addressed.
The ESP32s offer Bluetooth and wifi, which is interesting, see here for an example from the grbl/spindle world. The ESP32 doesn’t have as many gpio as the Mega or the Teensys though, so version detection and AUX pins would probably need to be though an I2C bus arrangement or something similar. Those are functions that aren’t time critical, so the bus delay wouldn’t matter.
All these offer real double precision floating point, something that the Arduinos lack and which bites us fairly often. The stock encoders work with 3V or 5V logic, so that’s OK. The firmware managing the encoders is interrupt-driven and critical to accuracy, so getting that right would be a high priority.
note that bluetooth and wifi both have potential lost connections ‘built right in!’
while I guess I see reasons for using other controller chips, I think the biggest improvement to any new hat (beyond the power changes already being applied) would be to bring through all the unused mega pins and let them be used as needed. otherwise, the existing structure certainly meets most needs and does so at an exceedingly reasonable cost.
Would there be any benefit to adding an SD card slot? It would be super easy to add if I use Teensy 3.6 as a model. I know a lot of 3D printer controllers use SD cards to eliminate the possibility of a lost USB connection issue.
if you use an sd card then dont’ you need a lcd interface to choose which files to cut? at least that is how my 3d printer works. good idea, but this is getting more and more expensive?
hwo would it be cooled if totally enclosed? I have put my electorncis in a square tube with one end having a fan and the other end being open. Seems to work ok.
As far as harness coming loose. ONe just needs to zip tie the cables for strain relief close to the motor shield and that should take care of that issue.
Not necessarily. You can connect a computer to a 3d printer with such an interface to upload and start a print, then disconnect the computer. Or there are other alternatives like Octoprint which I use at home. A raspberry pi stays connected and can be accessed via a web server to upload files and control the 3d printer. The files can sitll be put on the sd card so that if connection is lost to the raspberry pi the printer will still work off the sd card.
That should work fine in this case as well, as long as all the processing is being done by the Mega and the only thing the computer is doing is feeding it the gcode. The firmware might just have to be updated slightly to be able to read in the gcode from a file instead of off the serial connection. I haven’t looked at the firmware to see how it’s written currently.