This wonderful post thanks to the great minds at http://buildyourcnc.com
February 5, 2008
Update! Here are the files you have been waiting for. Click on these links to download the Eagle files (Schematic) (Board Layout). A word of caution. The CNC stepper motor driver schematics are very complex. Use the board file to create the gerber files if you want to send it out to get fabricated from a PCB fabrication house.
Another Update: I will be making assembled driver electronics and motor systems available for $499.00 on Saturday. If you have special requirements, please contact me with your wish list.
Brief Elplanation of the Circuit
The circuit is very straight-forward. (I will add this information to the website) There are two typical components in the functionality of the circuit: The translator (L297) and the Driver/Amplifier (L6203). The translator receives step pulses and direction signals and “translates” the step pulses to coil combination signals and the direction signals is used also to determine how the coil combinations are sent. The coil combination signals are then sent to the L6203s. There are two L6203s for each L297, since each L6203 drives a single coil. The benefit to using these drivers is that the amount of amperage that can be drawn is 4 amps per coil. That will provide a greater amount of torque at high speeds. This explains the elements of one axis. The schematic replicates this three times, with the necessary companion components such as the vref trim pot that adjusts the amount of amps for each axis. Also contained on the board is the parallel port with pull up resistors to protect the computer. Other components not mentioned are simply components required by the L297 chip for daisy chaining, power current sense resistors, and for the L6203 there are resistors and capacitors that are not worth mentioning in the greter discussion of the functionality, but important non-the-less.
January 30, 2007
The Printed Circuit Board (PCB) finally arrived in the mail today. I can’t believe it took so long, but I’m excited regardless. I spent about 4 days non-stop… Driving my wife and kids crazy designing this thing. It was so bad that when I got up from the continual sitting position, my back had some serious hurtin’. I fit 3 axes in an extremely small footprint. Not that I really had to work in such a confined space… I mean, I could have just purchased the Eagle license to work with a larger board area, right? The board is about half the size of a slice of bread. Yep, that’s why it took me four days, and the signal routing was especially fun?!?
There was a suggestion from a user to add a few more features to the board, like a charge pump and spindle controller. I am very intentful in doing that in my next version, which could be soon. If the board works like expected, I will start on my next version, while offering this board as a kit for those who don’t need that extra functionality.
This board will be able to handle 4 amps per coil, which is above average in the hobby world, but it does come with a price, unfortunately. For that extra punch of amperage, I suspect the kit will cost around $250 for the PCB and the components alone. With power supply and motors, the price will come to around $699.
For those of you who are wanting the electronics now and with a top draw of 3 amps per coil, I’m offering a complete plug and play system in the range of $499. Wait to see that made available in the stuff for sale soon.
As I mentioned in a previous post: The new electronics kit will contain the L298 chip (shown below) that serves as the translator for the L6203 (shown to the left) driver chips. A translator simply accepts the step and direction signals and translates them into coil combination singnals to tell which coil combination to fire so the motor shaft will rotate one step (or half step depending how the board is configured). Once I get the board populated with all of the components, I will add the image to this page. These are only a couple of the multitude of components needed for the board shown. In terms of complexity, I would rate this kit for the advanced user. Speaking of advanced users, I also intend to add the Eagle files of the schematic and PCB layout if anyone is interested in producing this from scratch.
I welcome any suggestions as I trudge along this path. Tell me what your requirements would be in a perfect world for these electronics. Would you like to see more explanation on the workings of the electronics?