Motor Wiring / Recommended Hardware Engineering
|Most of these practices are only recommended engineering practices, not gospel.|
Optical Printer Motors
Use anything from an MO61 to an
MO63 to control the fader.
Often motorizing an optical printer's fader is the hardest axis to engineer. Some folks rebuild the entire assembly, some folks just mount a motor to the fader dial. Good luck.
For optimal results, gear the fader such that it swings from open to closed in 2 to 3 rotations of the motor shaft.
Mount home sensors such that it triggers at or near the closed position.
You will need to mount the sensor somewhere where it only triggers once during the entire travel of the fader. (If you mount the sensor on the motor shaft, you'll get two or three triggers throughout the full travel of the fader, which is not very useful)
FYI, the OPCS software has the ability to customize home sensing so that, once home is found, the motor can be moved an additional known distance to the actual 'closed' position. This means the sensor does not have to be positioned at exactly closed, if that makes your life easier.
If your fader involves sensing linear motion, see the section on mounting home sensors to detect linear positions.
It is best to use TTL voltage level home sensors, such as the Omron PhotoMicrosensors.
|Animated diagram shows slot and flag type home sensor mounting.
Triangle indicates home sensor position.
'E' circle turns green when the software detects the homing edge of the slot (or flag), empty circle turns green when home sensor is not being blocked by the slot mask or flag.
Attach a disk with a slot cut into it on or as close to the motor shaft as possible, to avoid linkage slop from affecting homing. The slot does NOT need to be thin; the OPCS software will always home to one edge of the slot, not to the width of the slot, making for highly accurate homing, regardless of slot thickness. Also, if the slot is too thin, the sensor could miss it during rotation.
Mount the sensor to the motor bracket. This way the bracket can be removed with the motor and sensor all as a single assembly.
It is sometimes nice to have an led to give a visual indication when the sensor is in the home position. Some Omron sensors have a light on them already.
In this case, it's best to mount the sensor to the moving base, and mount a bar of steel that is half the length of the track to the stationary base, such that one end of the bar is flush with one end of the track, and interrupts the sensor for that entire half of the track.
|Animated diagram shows how to mount a home sensor on
a linear axis, where home is at the center of travel.
Gray bar of metal is mounted to bed, running half it's length. Right edge of bar is the 'homing edge'.
Sensor (triangle) is blocked by bar during half the travel of bed, which software uses to determine which direction to move bed to find home.
While bed moves, software monitors the sensor (S) until it changes state, detecting homing edge (E).
This way, the computer knows which end of the track the channel is sitting just by looking at whether the home sensor is triggered or not. The computer can then know which direction to run the motor to seek home. Then it just runs the motor until the sensor changes state, which will always be at the home position.
The software is normally configured to approach home from only one direction, preventing mechanical slop from affecting homing accuracy.
Use trip switches protect your linear axes. Should the operator accidentally tell a channel to run off the end of the track, the trip switches will prevent crashing the hardware.
Since trip switches are rarely activated, it is okay to use mechanical switches, but you should probably use optical sensors instead.
Wire all trip switches in series. This way interrupting any one triggers a single bit on the computer. Then configure the tripswitch command in the opcsdefs.opc file to monitor this bit. Tripping any switch will have the same effect as hitting the ALLSTOP key.
Put trip switches at either end of each linear channel, and mount them to allow for at least some amount of overrun, since stopping motors involves slight overtravel just to ramp the motors down to a stop.
It is recommended you use localized LEDs at each trip switch, to indicate which trip switch is the cause of the problem.
Superior Electric Motors
Superior Electric steppers are the most common motors
you'll see used on Optical Printers. Here are the most
The first digit indicates diameter, the MO-6x's are small, and the MO-9x's are large.
The second digit indicates length:
Customers must purchase motors from motion control distributors or motor manufacturers; see the links page.
|Superior Electric Motors - Models/Sizes|
|© Copyright 1997, Greg Ercolano. All rights reserved. To report documentation errors, send email to|