I had this cheap, mono laser printer that I wanted to dedicate to my kids endless printing of internet garbage. I've scrapped every PC in favor of a Chromebook, Chromebox, and Chromebit. YES, I have a problem.
There is a ton of information about using the Pi to link your antiques to the cloud. So I'm not going to cover that in here. Here is a great step by step of you need help. https://davesteele.github.io/raspberrypi/2016/04/23/raspberry-pi-cloudprint/
I wanted to save space, reduce power supplies, and minimize the chance my kids would destroy anything.
For this project I embedded a Raspberry Pi B+ into the printer.
Step 1: Parts
I already owned all these parts....
Raspberry Pi B+
Printer USB (A-B)
Step 2: Open the Printer
The first thing I did was to open the printer near the power supply.
If I need to tell you to make sure it's unplugged, please stop reading. Better yet, please stop breathing.
My goal was to meter out 5v after the power supply board.
Step 3: My Lucky Day
I found an empty plug with DCV printed on the board. Yep, 5v has been found.
Step 4: Power Supply
I cut the USB end off the micro power supply for the Pi.
Stripped the wires, and soldered them onto the appropriate posts.
The worst solder job ever was a temp to make sure it worked, I did go back and do a respectable job.
Step 5: Printer Cable
I didn't want any cables, so I improvised.
I shortened the printer cable to about 4 inches. Just cut, splice, solder, and protect.
This printer had a blank in the spot where an either cable would go. (Wish I got the option)
It was a perfect spot for the USB to fit into the Pi.
Step 6: Add the Pi
I pulled a Bic Clic pen apart and cut the barrel in half.
Using double sided tape, I mounted the two pieces on the existing PCB. Next, I added a piece of double sided tape on top of each piece.
I connected the Pi to power, connected the USB from the printer, and pushed the Pi down on the tape.
The last picture makes me laugh. I wedged the pen tip in there to help secure it down.
Step 7: Close It Up
I put the back cover on.
Step 8: Thoughts
Obviously the cloud functionality was tested before the installation.
I originally wanted to use a Pi Zero. However, I would need a powered USB hub to get everything to work and that made it not worth it.
Speed is absolutely a compromise. The first day of use my girls were doing multiple prints because they didn't think it worked. Sure, a Pi 3 would help, but I'd still have the B+ sitting around. Oh, and it's not my problem, it's theirs. lol
I could not find a spec sheet or reason for the hub I stole 5v from. I did meter out 2 amps worth of LEDs and kept them on for 24 hours to ensure overheating wasn't an issue. Lastly, I did hook up a monitor to the Pi to confirm that the low power indicator was not on.