As with a 3D printer or a CNC, to control the stepper motors specific electronics are required.
The first aproach was to use 2 Arduinos Mega with RAMPS shields to control the robot steppers, endstop and tool signal using GRBL firmware. The communication with both boards at the same time was a bit tricky and far from the ideal solution.
At that time, there were not commercial boards nor DIY designs capable of controlling up to 7 steppers separately, that’s why a custom electronic board was designed for Thor. The board designed was based on the schematics of the RAMPS v1.4.
The Control PCB designed had the following features:
- Control up to 8 stepper motors simultaniously
- Connection for up to 8 endstops for motors homing
- 1 Output PWM signal for tool controlling
- 12V Aux pins
- 5V Aux pins
This board is an arduino shield, being connected to the arduino via the digital pins. The complete wiring diagram is as follows:
⚠️ Note that the PDIG1 connector is not connected to pin 41 of the Arduino Mega, but to pin 7. This connection is made by unsoldering the male pin of the Control PCB and soldering a jumper wire in its place ⚠️
Making your own
As this is a custom board, you will most likely not find a shop that sells it and you will have to make it yourself. Anyway, take a look at the Buy & Sell section of the forum, where you may find other users offering already soldered boards.
In the Bill of Materials you will find all the necessary components, as well as the PCB references so you know where to solder each one of them.
Probably the most complicated component to obtain is the PCB itself. There are manufacturers that make PCBs very cheaply (about 10$ per unit) but there are minimum quantities that you have to order (5-10 units).
If you decide to order several boards, you are invited to post an announcement in the buy and sell section of the forum to get rid of all your leftovers!
It may sound difficult, but it’s pretty simple once you know what you have to do. There are two options:
- Easy one: Go to the ControlPCB project created on the PCBWay site and order it from there.
- The also easy one: Download the Gerber files and order it from your favourite manufacturer.
Most manufactures will ask you for the Gerber files and for the properties of the board on which the circuit will be printed. The gerbers are the files needed to manufacture the PCB (something like STL files for 3D printing) and you can find them on the Downloads.
The board properties usually match with the cheaper ones: