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hardware:piezos [2016/10/28 20:25]
Jon Daniels [Troubleshooting] |
hardware:piezos [2020/02/13 20:29] (current)
Jon Daniels [Caring For Your Piezo Objective Movers] |
| 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. |
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| 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. |
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| 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 them down when not in use. There are a few related strategies for this: |
| | * Shut down the Tiger controller when the system will be idle for a few days. |
| | * Use the auto-sleep feature if possible. 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 Micro-Manager the sleep delay is set by the property "AutoSleepDelay(min)". The firmware-default delay setting is 5 minutes for piezo objective movers and never for piezo top-plates. |
| | * 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. This is available beginning in firmware v3.00. This is not usually necessary if you use the auto-sleep feature. |
| | * In external input mode, 2 volts is a good input voltage to use when the piezos are resting for long periods. |
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| ==== Troubleshooting ==== | ==== Troubleshooting ==== |
