Does anyone recognize this hardware?

In our clean out of some old hardware we found two of these boards in a drawer full of IFI control system components. The only marking on the board is “JEM” on the bottom. There as a PWM cable soldered to the board.
Does anyone recognize them and can tell use what they are for? We have tried searching but have come up with nothing.


In my 17 years in FIRST Robotics I can say I’ve never come across that particular board. Perhaps something another student or mentor brought in to your team during a prior year.

Agreed. This wasn’t something in the kit or widely seen as a COTS item.

I didn’t see anything here that looked like that board: (which was a fun read).

A lesson to future board designers… etch or print a part number and the company name onto the board. It costs you nothing, but might save someone a bit of hassle a decade down the road.


you noticed the date code on the processor is over 20 years old, didn’t you?

If you look at this link it will tell you what the micro-controller does. I looked up the part number and found this:

What you’ve got there is a controller board for a Rockwell Automation Retro Encabulator.

Here a good technical overview:

The geek version of being “Rick Rolled”?

Gotta be careful of that Dingle Arm tho.

After looking at the picture(s) for awhile I’m going to hazard that it’s a driver board for stepper motors.

It looks like there are 6 sets of driver circuits (gate drivers) feeding into 12 power transistors, creating H-Bridges. The power and ground feed from each end of the terminal strip row.

The switches across the top are controlling if the bridges are to do a momentary pulse (so the stator can attract the rotor poles) or if it should toggle between N/S to pull/push the rotor.

The 6805 CPU in the center has enough grunt to manage the timings.

Dig in you teams past history and see if one of the designs had a stepper motor as part of it, you might find more hints there.

Variable reluctance stepping motors have three to five pairs of windings, creating several phases on the stator. It allows the motor to turn, but also have full torque in a stopped position. So this is some spiffy hardware. (If I’m right)

Were steppers ever legal in FRC? I don’t doubt that this is a stepper board, but I think it may more likely be from an old CNC machine or similar device.

Echoing what Foster said above. But to me, this looks to be a custom 2 layer board someone might have made (ordered) for a reprogrammable configuration setup (i.e. single board multi-motor tester?). So maybe someone with initial of JEM in your team past would ring a bell?

The main components are the MC68HC705 microcontroller. 6x dual photo-optocouplers and the corresponding 12 power transistors (no image so can’t tell which ones but just guessing), Atmel EEPROM and an Op Amp (hard to tell what its use for but that cap is clearly soldered on a cut trace).

I’m more curious what the Op Amp is doing. I would guess the Op Amp is setup as an oscillator for the microcontroller since I don’t see a crystal on the board. The 3 wires connected would be 5V, GND and maybe 12V (or whatever the motor power feed is). But the wire is way too small to use to carry large current though. So maybe 1 of those wire (white?) is the clock for the microcontroller, and the motor power is from the Pins and the Op Amp is used as some sort of power reference/or something to that effect.

I’d bet it’s some sort of PWM switch or lighting controller. You can probably control the outputs of the fets depending on the range the input PWM is in. The DIP switches control whether the output toggles on and off or is monetary.

The gray rectangle near the 68HC705 might be a ceramic resonator for the microcontroller’s oscillator.

My first thought was that this was a 12-channel solid state switch, but that PWM cable soldered to it makes me lean towards Foster’s idea that it’s a stepper controller, with a PWM signal delivering the speed. (MAYBE a unidirectional serial signal. The 68HCs did have a UART.)

There are no silkscreened legends on the board, like you’d find in something commercially produced or from a newer board house like OSHPark. The lettering is neatly etched. I’d say it’s a custom board, photo-etched from a template laser-printed to a transparency. That’s the kind of thing people did when I was in college (mid 90s.) But the surface-mount parts suggest a more recent design than that. The older date code on the MCU, maybe it’s out of somebody’s parts bin? Whatever the case, it’s beautiful work, especially with the green solder mask applied.

The Motorola 68HC11 and 68HC05s were common microcontrollers in the 90s and early 2000s, before the advent of the PIC and AVR series. Usually you had an external ROM for program storage, but some had small on-chip EEPROMs. No JTAG or SPI programming/debugging.

No, they have not. Only brushed motors until this year.

When these devices were new (date codes), FRC hardware was a pre-made custom controller running Pbasic. This was not part of that package.
It appears to me to be a simple serial controller with a number of simple contact closures. It may have been a relay/contactor controller for an industrial machine. Considering the power output devices, I would not be surprised that is was part of a three phase machine controller. It may have also been a lighting controller. The opamp could have been used a zero crossing generator so that lighting would be turned on at 0 volts on the sine wave of the power line. This was a common technique to prevent filament “singing” and transients that would interfere with other equipment.