Troubleshooting/motion products

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Troubleshooting T-Series Motion Devices

Symptom Check
After the device finishes a move command, it starts moving again on its own. The potentiometer knob is probably not centered. Make sure the knob is set to the middle position. You can feel a slight detent in the middle of its rotation.
Two or more devices both respond to commands sent to device 1. Most devices are shipped with their device number set as 1. If you connect the devices through Zaber Console, you will be prompted to renumber them. If you aren't able to install and open Zaber Console, send the Renumber Instruction (command 2) in the software you are using to set all of the device numbers to different values.
Device starts turning as soon as the power is on or amber LED blinks all the time The potentiometer is probably not centered. Turn the knob slowly until you feel the center detent.
Nothing happens when I turn the potentiometer knob either way. Manual control may have been disabled. Issue the Restore Settings Instruction (command 36) or enable the potentiometer using the Set Device Mode Instruction (command 40).
Nothing happens when I send a move instruction. The device needs to be "homed" first. You must issue the Home Instruction (command 1) after power up to home the device.
When I try to move the device it just makes a noise and vibrates. There may be too much load that the device is trying to push. The actuator stalls in this situation. Try removing the load and see if the problem goes away. You can achieve higher thrust or torque by lowering the speed of the device using the Set Target Speed Instruction (command 42).
Stall condition: The device makes noise but does not move. Try removing all external loads. If the device now extends and retracts normally, the problem is excessive load. Try to reduce the load or change step time and acceleration parameters to ensure the load is less than the maximum thrust. If a linear motion device is stalled in its fully extended position and remains stalled without any external load applied it means the lead screw has been over extended and is stuck. You can usually get the lead screw unstuck by pushing on it after issuing the home command. If a device is stalled (with no external load) in a position that is not fully extended then it requires servicing.
There is no communication between the computer and my Zaber device, the amber light does not come on or flash. There are several things you should check:
  1. Make sure you have the correct serial port selected. Try selecting other serial ports in the software. To ensure that your serial port is working properly, you can connect the send and receive pins of the serial adaptor without connecting any devices. Use a wire to connect pins 2 and 6. Your software should echo a reply every time you send an instruction. You can view the pinout diagram here.
  2. Check the baud rate, hand shaking, parity, stop bit, etc. when configuring your serial communications software. The required settings are listed in the Control Through The RS-232 Serial Port section above. Also make sure that your serial port is not configured with a termination character (it often defaults to linefeed).
  3. Make sure there are no bent pins in the ends of all the data cables
  4. Make sure the power supply is working. Check the voltage over the DC plug to see if it measures close to the rated voltage for the supply.
  5. Make sure the power plug is plugged in all the way. If your device has LEDs, the green LED should light.
  6. If your device has a manual control knob, make sure it is centered (you should feel a detent in the center position).
  7. If your computer is a laptop running on batteries, try plugging in the power. Some laptops disable the serial ports when running on batteries.
  8. Make sure you do not have a null modem adaptor or cable in the line.
  9. The serial to mini-din adaptor comes in many varieties and many have different pin connections. Check the adaptor for continuity on the proper pins by consulting the adaptor pin-out diagram above.
  10. If you encounter the problem when trying to control the device with your own software, try using one of the demo programs from our website to verify that the hardware is functioning properly.


My device is behaving strangely. It responds to some commands as expected but not to others.
  1. Send a Restore Settings Instruction (command 36). A setting might have been inadvertently changed. If you have a T-MCA or T-CD series stepper motor controller, note that a data value should be entered with the Restore Default Settings Instruction corresponding to the Peripheral Id of the device you are controlling.
  2. Your computer might be set to Unicode. This is common for languages that use non-Latin based characters. Go to Control Panel/Regional and Language Options/Advanced. Select a language for non-unicode programs. This should be English or another Latin based character language.
The device is moving very slowly. It used to behave differently. The speed settings may have been changed inadvertently. Send a Restore Settings Instruction (command 36).
The device is not communicating or responding to computer control. The yellow LED may be blinking. If the actuator has a manual control knob, make sure the knob is centered. Turn it back and forth until you feel a click or detent. Leave the knob at the center detent position. Then turn device off and on, and try again.
Green LED does not come on Check the A/C wall plug, the voltage adaptor and its connection to the device. If the power is coming over the data cable, check the mini din connector for bent or broken pins.

The amber light should turn off.

Green LED flashes The power supply voltage is outside the specified range for your device. It may either be too low or too high. Some unregulated adaptors may produce voltages significantly in excess of their rated values. If the number of devices connected on a single power supply exceeds its current capability, the voltage may drop below the required minimum voltage. You may experience this problem when many motors on a single supply move together. The load may exceed the maximum current available, causing the voltage to drop too low. If you experience this problem with a single device on a single unregulated supply rated at over 300 mA, then the problem is probably that the supply voltage is too high.
Turning the potentiometer causes no motion. You may be at the end of travel. This can happen due to missed steps even if the device does not appear to be fully extended. Turn the knob the other way. If the device makes noise but does not move you may be in a stall condition (especially if the device appears to be fully extended). See “Stall Condition” below. The amber light should blink when turning the knob, if not, try turning the power off and then on again. You may also have set the Target Velocity (command #42) so low that it doesn’t produce any visible motion. Try using command #36 to reset the device to default settings and try again.
The amber light comes on briefly when sending a command, but the device does not move and does not return codes. Check baud rate, hand shaking, parity, stop bit, etc. Make sure that your software does not transmit any control characters like line feed, spaces or something else. The device numbers may not be what you think they are. Issue a renumber command, make sure that the computer does not transmit anything else while the devices renumber. Check that you transmit 6 bytes and that the device number and command are valid. If you encounter the problem when trying to control the device with your own software, try using one of the demo programs from our website to verify that the hardware
The device does not send replies but otherwise works. If you encounter the problem when trying to control the device with your own software, try using a demo program from our website to verify that the hardware is functioning properly. Make sure that the receiving part of your code or commercial package is correct. Check baud rate, etc. Check connectors for bent or broken pins.
The device sometimes returns fewer than 6 bytes. This problem usually indicates a problem with the settings for your serial port. Some serial ports are set to automatically recognize and remove specific control characters such as carriage returns when they appear in the RS232 receive buffer. When this happens, it appears as though the device has not sent enough bytes, but really the controlling computer has just removed some before you could read them. You will need to change the serial port settings to fix the problem.
Poor repeatability or the device does not extend or retract smoothly or makes louder than normal noise during travel. You may be skipping steps. When skipping, the device will lose position in increments of 4 full steps (not microsteps). This condition happens if the thrust needed is more than the thrust available from the device. Check that the force on the device is less than the maximum thrust. Check the voltage using the voltage command. Voltage less than the rated or recommended voltage will reduce the device’s maximum thrust. Try a slower target velocity (command #42) as stepper motors produce more thrust when moving slowly. Lead screw conditions greatly affect the performance of linear motion devices. Dirt, damaged threads, no grease or too heavy grease will degrade performance and may contribute to a stall. A black residue appears on the lead screw after extended use. This can increase friction and reduce thrust. Clean the screw and re-grease it. In general if you try to move a large payload or have a large static axial load (like lifting something vertically) you will have more problems. For vertical motion the use of a counterweight, spring or rubber band can help reduce the static load and improve the performance of the device. The default value of the acceleration and target velocity are good for small to medium loads and medium speeds. For very light loads and higher speeds, or heavy loads at lower speeds, these parameters can be tuned. Trial and error is the best tuning technique.
The device has repeatability errors smaller than 4 full steps. If you're not skipping steps, friction may still cause some variation when returning to a position. Depending on the exact cause, there are a couple of device modes that can reduce these errors. See the Set Device Mode command's sections on the anti-backlash and anti-sticktion routines.
A linear motion device extends and retracts smoothly but will not retract to the home (zero) position. The device will not retract below what it believes to be the zero position. If the device has missed steps due to a previous stall condition or if the device has been set to an incorrect position, the device may incorrectly believe it is at the zero position. You can solve the problem by issuing the home command, or by turning the device on and off and manually homing it.
The device does not behave as expected when software sends it a series of commands. It can be challenging to track down problems in a complicated script or other software. In addition to the standard techniques of debugging any software, it's also helpful to see exactly what bytes are being sent and received on the serial port. There are several tools available to display the raw data from a serial port, and stackoverflow.com has a list of some.