Before you go an a salvage rampage consider the following hints:
RULES OF THUMB
- The older the printer the better.
- The newer the scanners the better.
Scanner stepper motors are often superior to printer steppers. They do have more steps in general.
The newer the printer, the lesser is the chance of getting steppers out of it.
All scanners have stepper motors. The older the more likely you are getting a unipolar stepper which we can’t use in this project.
Identifing the parts of old devices is often a pain but I had luck with at least the scanner stepper. For the printer I had found a service manual. But this didn’t helped me alot.
Scanner / X-Axis
The scanner is an old Tevion 2400 dpi scanner. Equivalent to a Microtek Scanmaker 5800.
The stepper is a 96 step bipolar stepper motor. It’s description is NEOCENE 2T354207.
Do not believe anyone other that says this is a 100 step motor. It is not ! It has 96 steps. Not more not less.
I used the bed of the scanner as the basis of the whole construction.
The rail and the timing belt aswell as the sled which carried the photoelectronics is used.
Though the sled needed to be trimmed to give more space for the laser.
There is something special about the stepper. It has a 4 gears mounted on its foreplate.
The gear ratio is luckly negligible.
If you are still curious how to calculate a gear ratio have a look at this page.
It is in german but the math shown there is a universal language (or use the google translator)
The scanner stepper serves as the x-axis.
Printer / Y-Axis
The printer was an old Epson Stylus Photo 925.
The stepper I salvaged is oddly described in the Service Manual.
It says it is a 4-phase 48 pole bipolar stepper motor for 42V (??) but as it is a bipolar stepper there must not be 4 phases but 2.
Turning the shaft by hand and counting the steps I came up with 48 steps.
This motor (and plates for printer head) serves as the y-axis.
In the end I realized that the 48 steps or the motor itself are the weak spot in this built. It moves slower than the scanner stepper and clatters on the rod. No brass fittings here. Vaseline should dampen the negative effect.
Stepper motor specifications:
|Tevion 2400 dpi / Microtek 5800||Epson Stylus Photo 925|
|Step angel||3,75°/Step = 96 steps||7,5°/Step = 48 steps|
|Voltage||5 V||5-12 V|
|Resistance||5,5 Ω||7 Ω|
Later in the process I found out that both motors draw less then at least 300 mA.
The Easydriver V4.4 still has the bug with the silk print on it mixing MAX and MIN of the poti.
So in V4.4 they switched the print on the PCB but simultaneously replaced the poti with a reverse poti.
At least this is what I have read in some forums or the comments over at Sparkfun.
So long story short:
The poti is set to a low resistance that means the steppers get a fraction of the current the Easydriver can deliver. Max 750mA per coil. The poti is set to roughly 25%. Just so that they dont scream in pain.
Stepper motor pinout:
On my journey through the endless deepth of the internets I often stumbled over question as how to get the correct pinout from the steppers.
You just need to take a piece of wire and connect the pins. If you connect the correct pairs you should feel a resistance when turning the shaft of the stepper.