The Philips PM5139 is not famous. It won no great victories on the battlefield, nor was instrumental in changing the political landscape. It was just a useful function generator that you might find on a workbench somewhere, doing its job quietly and relatively accurately. [doctormord] has been doing the work to reverse engineer this humble piece of hardware.

The PM5139 is poorly documented; the only existing service manual out there is for the PM5138A, a less-capable sister model. Hence, there was some value in reverse engineering the device to understand it better. Work started with two EPROM dumps capturing what Philips put in the box all the way back in the early 1990s. From there, the code was examined and tinkered with until [doctormord] felt confident to modify it and improve upon what was already there. This was achieved with the aid of an 8051 emulator that could run the code to make it obvious what was going on. The result was a custom “V2.0” firmware that adds six arbitrary waveforms to the function generator and the ability to play simple music, amongst other tweaks.

We love to see old hardware given new functionality, even decades down the line, and we love some good reverse engineering, too. Video after the break.

Having access to a planer opens up a lot of options for woodworking. It enables a craftsman to work with much rougher lumber and the finished results generally have tighter tolerances. But as [DendroLabsDev] found out, the height adjustment wheel on a planer needs a lot of turns to go from its lowest to highest position, and this gets tiresome when greasing parts during maintenance. So what started as a quick hack to quickly perform this single maintenance task eventually resulted in this programmable height adjustment that’s in use on the planer full-time now.

The motor attached to the height adjustment for the planer is a stepper motor, capable of around 1000 steps per inch. Since revolutions on this tool with the stock wheel adjust only a small amount per revolution, this can in theory enable very small tolerances to be dialed in consistently. Not only that, but [DendroLabsDev] has programmed it with a few different modes, the first of which allows a board to be planed to a certain thickness by making several passes, mimicking the workflow of a human-controlled machine. Then a device to zero the position was added, and then the ability to save the height adjustments to make replication across different boards was added, and then a mode to step through set amounts per pass.

What [DendroLabsDev] has essentially made is a high-dollar planer control that is actually available in the most expensive planers, but adapted for a DeWalt planer easily available and semi-affordable at many local hardware stores. It is also theoretically adaptable for any planer with an adjustment wheel, and [DendroLabsDev] has some plans to improve the control system and package it with a PCB and enclosure that would allow it to be a more accessible product for other woodworkers. Adding electronics to woodworking tools other than routers is a popular pastime, take this CNC-controlled scroll saw for example.