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hardware:piezos [2015/09/21 23:34]
Jon Daniels [Piezos]
hardware:piezos [2019/06/21 13:00]
Jon Daniels [Caring For Your Piezo Objective Movers]
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 Mechanically, avoid applying external force to the piezos.  When assembling or disassembling the microscope, be sure not to set down the SPIM head resting on the piezos.  With pre-2015 piezos (not on dovetail), exercise caution not to screw in the bushings too tightly, and note the [[docs:manual#with_pre-2015_piezos|manual's instructions]] regarding inserting/removing the objectives.  As of 2015, the piezos can be removed from the SPIM arm mount on dovetail easily (see [[docs:manual#with_2015_piezos|manual]]) and it is impossible to over-tighten the bushings. Mechanically, avoid applying external force to the piezos.  When assembling or disassembling the microscope, be sure not to set down the SPIM head resting on the piezos.  With pre-2015 piezos (not on dovetail), exercise caution not to screw in the bushings too tightly, and note the [[docs:manual#with_pre-2015_piezos|manual's instructions]] regarding inserting/removing the objectives.  As of 2015, the piezos can be removed from the SPIM arm mount on dovetail easily (see [[docs:manual#with_2015_piezos|manual]]) and it is impossible to over-tighten the bushings.
  
-Electrical stresses on the piezo objective movers are inevitable during normal use.  However, applying extreme and/or static voltages to the piezo actuators for long periods can pre-maturely degrade performance and ultimately can lead to actuator failure.((The piezo actuator is a stack of thin dielectric layers of piezoceramic material with alternating electrodes across which a voltage is applied (generally -20V to 120V).  The main failure mechanism is electromigration of the electrode material through the piezoceramic leading to shorts.  Electromigration is proportional to at least the square of the applied voltage and worsens with humidity.  It is believed that fixed voltages are worse because self-heating during movement prevents the build-up of moisture.))   To maximize piezo lifetime they should to be turned off when not in use, or else apply only a small voltage across them.+Electrical stresses on the piezo objective movers are inevitable during normal use.  However, applying extreme and/or static voltages to the piezo actuators for long periods can pre-maturely degrade performance and ultimately can lead to actuator failure.((The piezo actuator is a stack of thin dielectric layers of piezoceramic material with alternating electrodes across which a voltage is applied (generally -20V to 120V).  The main failure mechanism is electromigration of the electrode material through the piezoceramic leading to shorts.  Electromigration is proportional to at least the square of the applied voltage and worsens with humidity.  It is believed that fixed voltages are worse because self-heating during movement prevents the build-up of moisture.))   To maximize piezo lifetime they should to be turned off when not in use, or else apply only a small voltage across them.  Reducing the humidity of the operating environment will also prolong piezo lifetime.  
  
 The simplest way to turn off the piezo actuators is to power down the entire Tiger controller when not in use.  Beginning in firmware v3.00 you can turn off the piezos using the **''MC <axis>-''** command to explicitly disable the axis and turn it back on with **''MC <axis>+''** (in Micro-Manager use the property "MotorOnOff" to do this).  For ADEPT Rev M cards or later (approx. August 2015 or later) the **''MC –''** command works whether in internal or external mode, but for earlier versions of the card it only has an effect in internal mode. Beginning in firmware v3.11 there is an auto-sleep function to automatically put the piezos in a good (low-voltage) position after a specified time being stationary; the auto-sleep function only works in internal input mode.  In external input mode, 2 volts is a good input voltage to use when the piezos are resting for long periods. The simplest way to turn off the piezo actuators is to power down the entire Tiger controller when not in use.  Beginning in firmware v3.00 you can turn off the piezos using the **''MC <axis>-''** command to explicitly disable the axis and turn it back on with **''MC <axis>+''** (in Micro-Manager use the property "MotorOnOff" to do this).  For ADEPT Rev M cards or later (approx. August 2015 or later) the **''MC –''** command works whether in internal or external mode, but for earlier versions of the card it only has an effect in internal mode. Beginning in firmware v3.11 there is an auto-sleep function to automatically put the piezos in a good (low-voltage) position after a specified time being stationary; the auto-sleep function only works in internal input mode.  In external input mode, 2 volts is a good input voltage to use when the piezos are resting for long periods.
  
 ==== Troubleshooting ==== ==== Troubleshooting ====
 +
 +If you need to know how to send serial commands see http://www.asiimaging.com/docs/tech_note_rs232_comm.
  
   - Make sure the piezo is set to be internal closed-loop input mode (or external if you are using external control mode).   - Make sure the piezo is set to be internal closed-loop input mode (or external if you are using external control mode).
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   - If you have a diSPIM, exchange the drive electronics to isolate a card vs. actuator problem   - If you have a diSPIM, exchange the drive electronics to isolate a card vs. actuator problem
     - Power the controller off.     - Power the controller off.
-    - Exchange the two piezo cables on the front of the controller.((Each card has been calibrated or paired with the corresponding actuator, but any working card will basically drive with any working actuator))+    - Exchange the two piezo cables on the front of the controller.((Each card has been calibrated or paired with the corresponding actuator for optimal performance, but any working card will drive any working actuator))
     - Turn the controller back on.     - Turn the controller back on.
     - Use the **''PZINFO''** command as described above to see if the high voltage is still low on the original problem card/axis.  If not, check the other one.  If the problem stays with the card then the problem is likely with the card.  If the problem moves with the actuator then the problem is likely with the actuator.     - Use the **''PZINFO''** command as described above to see if the high voltage is still low on the original problem card/axis.  If not, check the other one.  If the problem stays with the card then the problem is likely with the card.  If the problem moves with the actuator then the problem is likely with the actuator.