5V PWM Ports on RAMBo (Taz 4)


I’ve installed the Hexagon hotend on my Taz 4, and I noticed that it was plugged into a PWM pin on the RAMBo. Is there a way to directly access and control those pins to adjust the fan speed or turn it off, as it currently appears to always be on 100%?

I’m actually looking for a way to control the brightness of some LEDs, and I’d like to be able to do it through those pins.

Also, is there a place to get some always-on regulated power to power a Raspberry Pi, even when the Taz is switched off? And to power the aforementioned LEDs while I’m at it? I expect to use transistors to control them, unless those PWM pins can handle lots of current (around 100mA per channel, possibly more).


For starters, a cooling fan on the Hexagon barrel isn’t optional. That needs to be on all the time the hotend is in operation, pretty much full blast. SO if you take those pins, you would have to replace them with a different source.

I have tapped into power two ways on my Taz. I actually ran a second 12v lead direct to power lighting and accessories. Mine just has an on / off switch, but you could control brightness with a dimmer in line too.

The other way was using a buck converter to drop 24v direct off the mains down to appropriate voltage to run the status indicator blinky RGB lights and it’s mini controller.

Your other option would be the 24 volt output that goes to the optional Cooling fan. you could use that to run lights instead if you don’t want to cool filliament.

Thank you, Piercet!

After reading another thread, I agree that the fan should be on whenever the hotend is on. I do want to be able to turn it off when it isn’t, though. Perhaps it’s just best to turn off the whole Taz after a job is finished. That way I don’t screw things up if I neglect to turn the fan back on. I plan to upgrade the fan to a more powerful front-mounted one using some plans I found, anyway.

I’ll look at those power options. I want to be able to control them remotely, and programmatically, through OctoPrint. This is mostly so I can record time-lapse videos and monitor it when the sun is down, but it might be nice to alter the colors to reflect different print stages. I’d like to be able, ultimately, to be able to analyze the exposure of the time-lapse stills and adjust the lighting to compensate. That might be overkill, of course, but it might be fun to try.

Since the Raspberry Pi only has one PWM pin, I thought I might be able to use the PWM pins on the RAMBo, but I could use a shift register on the RPi instead. If I can find a good library that works on the RPi 2 for neopixels, I might just use a strand of them instead, but I’m currently planning to use several individual RGB LEDs. I’m sure there’s a better solution, though.

Here’s an idea. Duet/Duex supports commanding an ATX power supply on/off with G-Code. Maybe something compatible could be set up for the supply used by Taz machines with an opto-isolated MOSFET.