Inkjet printer technology

I disassembled a broken Epson C80 inkjet printer the other day. They nearly always clog if you don't use them constantly, if you use them constantly but have low humidity, or if you look at them the wrong way. It was a useful exercise, and I learned a few things about the state of printer engineering and how things change over time.

The engineers have decided that the principle of "imprecise positioning with a cheap motor, but with feedback", is a better/faster/cheaper approach than "precise positioning, assume the motor goes where commanded". Instead of stepper motors, with their high torque and their ability to hold them at a defined angle, they used standard DC motors, and read what they're doing via optical encoders, both rotary and linear, on the axles they move (aka servos). In the telescope world, most people prefer to use steppers for positioning. http://www.cs.uiowa.edu/~jones/step/ is a full overview of steppers. I got into learning about motors from the king of converting telescopes into computer-controlled monsters: Mel Bartels

You can tell you have a stepper in your hand if the motor has four or more wires going into it. When you turn the shaft of them, they should feel like they move into defined positions as you rotate it.

I've taken apart a number of inkjet printers, starting with old HP Deskjets from 1990. They used encoders and standard motors too, but the printer was designed to last. Canon Bubblejets from the mid-90's used steppers; and I had always assumed all printers would from now on. The HP Deskjets also used a Z80 CPU; I'd always loved that an ancient processor was still being used in embedded stuff. Keith tells me it's a great processor.

In addition to the DC motors I get some encoders, a beautiful aluminum heatsink, and a 1/3Farad backup capacitor. I would have had a huge absorptive sponge too, but it was full of ink.