Jon Elson, Author at Pico Systems

Purpose of the Pico Systems Universal Stepper Controller

Jon Elson — Fri, 23 Jan 2026 02:39:33 +0000

The Pico Systems Universal Stepper Controller is able to provide a better train of step pulses than can be achieved by software step generation. Using software through the parallel port of a PC computer, it is quite difficult to get good step timing above about 20,000 step pulses per second. Our Controller can easily deliver up to 250,000 steps per second with very smooth timing of the pulses. It uses a 10 MHz clock, so that at 250,000 steps /second, the granularity of step rates is only a 5% change. Since the steps are generated separately from the CPU’s clock, the steps produced can be counted by the board so the machine position can be read by the CPU at the LinuxCNC servo rate (nominally 1000 times/second.) This position counter can also be selected to read from an actual encoder on the motor or axis to get more reliable position control, and to detect lost steps or motor stall. The board also has 16 digital inputs that can be used for home and limit switches. One input is dedicated to emergency stop. The others can be assigned as desired in the HAL file, for instance to use with a jog pendant. It also has places to mount 8 solid state relays for coolant, spindle control, etc.

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retrofit of X2 minimill to CNC

Jon Elson — Mon, 19 Jan 2026 01:46:12 +0000

I wanted a portable mill to demonstrate my CNC control hardware at shows like NAMES. I bought one of the ubiquitous minimills and started in. First, there were some things that needed to be fixed for proper operation. First, the Z axis was a horrible mess of backlash. So, I fitted a small ballscrew. It had to be small to fit between the vertical slide and the column. Then, I had to adapt motors to the X and Y handles. After some use, I discovered the Y leadscrew did NOT have a bearing at the crank, but the X axis DID! I carved away a round pocket at the front and behind the bracket to fit a pair of ball bearings there. The nut that holds the handle on also preloads the bearings.

Here’s a close-up of the Z axis mods:

This machine has a mixture of brush and brushless motors on it, it was a testbed for various developments. I used the Pico Systems Universal PWM controller and Pico Systems PWM servo amplifiers to move the motors.

Here is the CNC control box. The power supply is in the front, the servo amps are along the back on a heat sink, the Universal PWM Controller is on the right.

And, here’s a view of the controller board :

This system has an encoder on the spindle so it can do rigid tapping. The spindle motor can be connected to a servo amplifier so it can be reversed to bring the tap back out of the hole. The software keeps the Z axis in sync with the spindle rotation so as not to bind the tap or damage the thread.

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Case Study Bridgeport R2E3 (Boss 8) mill to CNC

Jon Elson — Sat, 17 Jan 2026 21:51:15 +0000

A friend was going to scrap an R2E3 Bridgeport mill with a dead control. I gladly gave him the scrap value of the machine. After some cleanup, I found the original servo amps were working, but those Contraves NC400 amps made a HORRIBLE whine that could be heard a block away! So, I got some eBay AMC servo amps, installed them and tuned them up. I used the Pico Systems PPMC analog servo interface (I make these) and configured the whole system. The Y axis encoder had gotten some coolant into it, I was able to clean it, but decided they should all be replaced. I got some 2500 line encoders on eBay, but had to make mounting adapters to fit them inside the motors. I fitted a shaft encoder to the top of the spindle so I can do rigid tapping. I regularly use 4-40 combo drill taps at 1000 RPM when making the mounting plates for my own brand of servo amps. The machine now works AMAZINGLY well! The silver box on the front of the head is an optical interface to my 3-axis touch probe. I created routines to find the center of holes and the coordinate of any inside or outside corner of a part. Very convenient.

Here’s a picture of the servo cabinet:

Top left is the PPMC card cage, with 2 encoder boards at top, then DAC below that and then the DIO below. There are 3 axes on this system, but then another encoder channel is used for the jog dial, and so I needed one more encoder board for the spindle encoder. The PPMC power supply is mounted to the bottom of the card cage. 3 AMC servo amps are mounted to the right of the PPMC card cage. Above the servo amps are a bunch of 120 V power outlets for servo amps and accessories (fans, lube pump, etc.)

Here’s the left side air and lube cabinet:

I got rid of all the air accessories, as I didn’t want to have to have the noisy compressor running when using the machine. I can very well turn the crank to adjust the varispeed drive, but I took out the first stage worm gear and mounted a little crank knob where that gear and air motor went. I also removed the brake cylinder and fashioned a steel wire hook that can hold the brake engaged if I need it. Mostly, I leave the varispeed at 4200, and adjust spindle speed with the VFD through LinuxCNC.

Above, you can see the hand crank and varispeed dial, to the top left is the brake crank and the wire that can be used to hold it on.

I removed the massive electrical box on the back of the machine base, and mounted the VFD back there so it won’t get showered with chips. The green and brown rods are the braking resistors.

Here’s the jog pendant and trackball mouse that I use to operate it.

And, here are work lights I made for the machine. I bought a cheap 3-petal LED lamp at Menard’s, and took 2 petals off and powered them from a DC supply so there would be no strobe effects on rotating spindle/cutter parts.

If you have any questions on this retrofit, or need more details on our other products, feel free to contact me at :

elson@pico-systems.com

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