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Sadly, no.

Typically inkjets only have one positional reference point, a microswitch at the right hand edge of the carriage's travel. Sometimes they have an optical or microswitch leading -edge -of -the -paper detector too. There are usually no other positional encoders.

The rest is done with two stepper motors, one to control the sideways movement of the carriage, one to control the up-and-down movement of the paper.

They don't ususally use ball/leadscrews either. Toothed belts on a cog rotated by one of the steppers controls the sideways motion, and a paper roller controls the up/down motion.

:(

They're ok for used cheap low-power steppers though, but you can buy them new for a few pounds each, and if you buy them they will match and have known performance (the two steppers in one inkjet are usually different).

Used scanners tend to have slightly more interesting bits, but again they will have no grey-type encoders.

The reason I mentioned it was because the last "£90" HP Inkjet I had did have an optical "gray code" strip, it looked like a long loop of 16mm film (without the sprocket holes!) the width of the carriage. The printer failed because this strip had a dollop of gunk on it, causing the printer to lose correct position. Having resolved this I donated it to the local school.

How can I tell determine stepper type when looking for salvage?

Steve

What's a "£90" printer? A cheap inkjet costs £30 these days.

I haven't much experience with HP, mostly Epson, but I haven't seen one of those in an inkjet printer before.

Count the wires, and measure the resistance between them. Very occasionally the case is also connected, best to check that too.

is a bit old but is still a good online reference to stepper motors, and will give details of the wirings of the different types. Most of the ones I have come across in printers are bipolar.

Assume that any stepper fram a printer will take less than 500 mA. They will most likely be either 5V or 12V, you have to take the size and weight and resistance together to guess which - or just try it, and see if it gets hot.

Steppers from printers are not high power or high torque. They will operate a X-Y -(Z) for a Dremel (just) or a film or foam cutter, but no more.

"Bob Minchin" wrote: [snip]

Would you mind awfully waiting a moment while I beat you senseless with this Ikea boingy armchair thing?

Tim

I guess as most inkjet printers are colour now they won't be able to use Gray code?

Sorry about that - i'll get my coat and go now

Bob

I have built a foam cutter with motors from Epson dot matrix=20 printers. The source was a pile of 80 column printers en=20 route to the skip. The 132 column printers have bigger=20 steppers and would doubtless do a mini CNC setup. I=20 couldn't get 4 of these though. As for inkjets the print=20 head and paper feed motors are different.

Discussion and software for foam wings....

Regards,

Steve Salisbury

Bad form to reply to oneself, but:

I just took a real cheapie Lexmark apart, it has a "filmstrip" about 6 mm wide with lots of lines on it. The carriage traverse motor is not a stepper. The strip is not an encoder, just a lot of lines. Perhaps the electronics just counts the lines crossed, perhaps they do how-far-between-the-lines as well (the strip is grey overall; but not Gray).

I haven't seen the like before (well, not recently), it's a weird mix of stepper counting and encoder feedback technologies. Maybe I'm just out-of-date!

The 'film strip' is used to generate a trigger signal that unloads the buffer holding the 'stripe' of data to be printed by firing the print head pins. The motor drives the head across the carriage and pins fire as and when a line is recognised on the film strip.

Put a mark on the film and you will generate a corresponding white space on your print-out. This (and also dust on the sensor) used to be quite a common fault on Centronic 101 and 101AL printers 25 years ago when I used to look after them.

Andrew Mawson