Anth's Computer Cave

HP CP1515 Teardown

I was planning on tearing down a cheap HP printer today, but I came across a couple of matching color laser printers so I think I will do those first.



This was the first time I had dealt with laser printers so I was keen to get into it. The fact that there were two identical units was awesome. I knew I would get some matching motors for starters, but it also meant I had two machines to study and hopefully a good chance to hack the motor controls.

The first thing I can tell you is that taking one of these printers apart is a lot of work. There are literally hundreds of screws, and dozens of tricky little things to remove. It took hours to do this, partly because I was intent on keeping the system alive for later hacking so I took a great deal of care. Each time I removed a component I would power the unit up again to check if it would initialize.

The first challenge was hacking the front and rear door sensors so the unit could still initialize with the doors removed. The front sensor was fairly easy to find, the rear one was more difficult to access. Eventually I had both sensors taped up and the printer powering on fine.

What's inside?

Inside the right-hand side panel are the DC controller board and another board (I think it is called a formatter). It has the Ethernet and USB connections, and also connects to the buttons and LCD panel. The DC controller board (left in the image above) is what I hope to hack to run and power the motors.

The left-hand side of the printer has a large board which has the front and rear photo-interrupter sensors for the doors. According to the service manual this is called the high voltage PCA. When I disconnected the ribbon cable to this board and powered the printer on, the brush-less motor no longer turned on and the LCD panel produced a warning that a non-Canon power supply was in use. I had got lucky, though because the stepper motor(previously dormant) was now turning for ten seconds on each restart. This means I have an opportunity to study both motors in action.

Quite a strange board, I would say. I hope I won't need to use this because it is too big for any of my projects..


I managed to get down to this stage with the printer still initializing but removing the rear fuser assembly changed things a little. The stepper motor now runs for about two seconds rather than ten. The LCD displays a warning that the fuser has a problem and tells you to turn the printer off and back on again. It still has enough functionality for what I need.

The Laser

This unit has a laser and four receivers, heaps of lenses and a tiny brush-less DC motor spinning a deflector. I plan to have a play with these soon. I want to use them on AAIMI to calibrate the measurement sensors.



Other goodies

At this stage I discovered another stepper motor towards the bottom of the unit on the left side. It is exactly the same model as the first stepper, but with a longer shaft. This means that from the two identical printers I will get four identical 24V steppers. That could be really handy.

The brush-less motor should be interesting. It actually has all the pinouts clearly marked so there will be no problems wiring it up, I just need to determine what type of motor controller it needs if I cannot hack the one that came with the printer.

The power supply is vital to one of my next projects. It is divided into two units for some reason which makes it a bit awkward, but I think it will work just fine. It outputs 24V and 3.3V. I am hoping it functions without the other large board I mentioned earlier, because I have no room for that in my project.

There were a couple of magnetic servos that are fun to play with and about a dozen optical interrupter sensors.

There is also a sensor attached to the left-hand board that appears to be a thermal sensor but I cannot find much info online. I would like to use it to monitor the heat sink on the motor controller I use for testing motors.

As usual, there were gears. I counted over forty, and many of them are quite large. They look more useful than the type you find in inkjet printers. Many of them have angled teeth that match the cogs on the steeper motors.

There are some good solid pieces of structural steel and tons of springs

The Downside

As usual, there is a lot of plastic waste. I am hoping to reuse the outer case from the printers to make a stack-able storage system so that will reduce the waste, but there is still a lot of junk left over. I am thinking of asking a welder I know to make me some kind of mulcher that can chew it into tiny pieces.

Summary

I would say I got about what I expected in the way of motors, although the big brush-less DC motor was a bonus, and the 24 volt PSU really tops it off. The laser diodes should be awesome and same with the gears.

How did this compare with a good quality inkjet printer? A lot more time intensive and more left-over waste are the main issues. Also there are none of the fancy print-head slides that I have been having so much fun with.

Stay tuned for my next teardown, a cheap and nasty HP printer. See you then.

Cheers

Anth


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Next: Teardown: Brushless DC motor



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