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Step 2Printer Disassembly and Motor Control
We used an old Epson ink-jet printer for the horizontal motion of the printer and the print head mount assembly. First thing to do here was to carefully disassemble the printer. This required removing all non-essential components until all that was left was the track assembly, the motor, the print head holder and the drive belt. Be careful not to break this belt or its driving motor. It may also be cleaver to poke around with a volt-meter before you tear out all the power boards, but we were a little too excited for that. Note you don't need any of the page feed assembly, the actual print heads or cartridges, or any circuit boards.
After everything is disassembled, we must figure out how to drive this motor. Since we tore everything apart before testing anything, we needed to find the proper voltage to supply the motor. You can try to find the motor's specs online if you can find a model number, but lacking that, hook it up to a DC power supply and slowly increase the voltage to the motor. We were lucky and found our motor could run on 12-42V, but to be sure we tested it manually as described. We quickly discovered even at 12V the motor will be running way too fast. The solution here is to use Pulse-Width-Modulation (PWM). Basically this turns the motor on and off very quickly to spin the motor at a slower speed.
Our battery supplies 18V so to make life easy we will run the motor off the same. When using DC motors that must reverse in circuits you will experience a large back-current in your circuit when reversing the motor. Essentially your motor acts as a generator while it is stopping and reversing. To protect your controller from this you can use what is called an H-Bridge. This is essentially 4-transistors arragnged in an H-shape. We used a product from Acroname. Make sure the driver you choose can handle the current needed for your motor. Our motor was rated for 1A continuous, so the 3A controller was plenty of head room. This board also allows us to control the direction of the motor simply by driving an input high or low as well as brakeing (stopping the motor and holding it in position) the motor in the same way.
After everything is disassembled, we must figure out how to drive this motor. Since we tore everything apart before testing anything, we needed to find the proper voltage to supply the motor. You can try to find the motor's specs online if you can find a model number, but lacking that, hook it up to a DC power supply and slowly increase the voltage to the motor. We were lucky and found our motor could run on 12-42V, but to be sure we tested it manually as described. We quickly discovered even at 12V the motor will be running way too fast. The solution here is to use Pulse-Width-Modulation (PWM). Basically this turns the motor on and off very quickly to spin the motor at a slower speed.
Our battery supplies 18V so to make life easy we will run the motor off the same. When using DC motors that must reverse in circuits you will experience a large back-current in your circuit when reversing the motor. Essentially your motor acts as a generator while it is stopping and reversing. To protect your controller from this you can use what is called an H-Bridge. This is essentially 4-transistors arragnged in an H-shape. We used a product from Acroname. Make sure the driver you choose can handle the current needed for your motor. Our motor was rated for 1A continuous, so the 3A controller was plenty of head room. This board also allows us to control the direction of the motor simply by driving an input high or low as well as brakeing (stopping the motor and holding it in position) the motor in the same way.
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