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I am trying to drive a ThorLabs piezo controller (https://www.thorlabs.com/newgrouppage9.cfm?objectgroup_id=2421&pn=KPZ101) with an external +3.3V TTL signal provided by a microcontroller (using an ARM Cortex M4). I configured the controller to be edge triggered: the controller would increment the voltage output by a step size after each trigger. I managed to drive the controller at very low frequencies (up to 5Hz), but for higher frequencies the controller stops incrementing the output voltage. I tried the same thing with a TTL function generator with a proper +5V output and the problem persists. When the controller is driven by the ThorLabs software on a separate PC, it can handle frequencies up to 1kHz. I feel like I am missing something about the proper use of the external TTL trigger inputs of the controller. Any ideas?

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  • \$\begingroup\$ What makes you think it will go faster than 5 kHz? Have you spoken with Thorlabs? \$\endgroup\$
    – Andy aka
    Jun 8, 2018 at 9:34
  • \$\begingroup\$ I want it to go faster than 5Hz, ideally 40Hz. I have written applications with the drivers that come with the controller that handle 1kHz through USB. I thought it would do the same with the TTL trigger inputs. \$\endgroup\$
    – probably45
    Jun 8, 2018 at 9:38
  • \$\begingroup\$ Oops I did mean 5 Hz. Where is the document that describes the TTL interface? Have you found one? \$\endgroup\$
    – Andy aka
    Jun 8, 2018 at 9:43
  • \$\begingroup\$ The only section describing the TTL interface is found in the manual:(thorlabs.com/drawings/…). At section 6.2.3. However it does not contain a lot of information on the TTL interface, more on the settings for the edge triggering. \$\endgroup\$
    – probably45
    Jun 8, 2018 at 9:48
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    \$\begingroup\$ I think that because it says that the input can also be used with an external manually operated switch it probably has debounce features and they will resist any rapid changes even though they may come from a TTL drive. \$\endgroup\$
    – Andy aka
    Jun 8, 2018 at 9:55

1 Answer 1

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The data page that you linked says specifically that the external trigger inputs are meant to operate at 5V. There is a good possibility that your inability to get the performance that you desire is related to your trying to trigger the input with only a 3.3V signal.

I suggest that you try prototyping a simple 3.3V to 5V logic level translator that uses an active push-pull drive output to the controller to see if that improves the performance. If you can get your hands on a 74HCT125A chip it offers an extremely convenient single chip way to convert a 3.3V signal to a 5V drive signal. Power the VCC of the chip from 5V and ground the OE pins.

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  • \$\begingroup\$ Thank you for the reply. Indeed this is what I first thought, that is why I tried using a +5V TTL function generator, and the same problem appeared... \$\endgroup\$
    – probably45
    Jun 8, 2018 at 11:27

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