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Trigger pins

Nghia Huynh
Prodigy 80 points

According to pg 31 of the User Guide:

Table 4-1. Trigger Connector Pins

DESCRIPTION PIN SUPPLY RANGE
Trigger Supply 1 3.3 V
Trigger Input 2 3.3 V
Trigger Output 3 3.3 V
Ground 4

3.3 V

Are these 4 pins physically like this:

If I have a circuit look something like this: Pin1------------switch-------------Pin2

Would closing the switch issue a trigger signal?

In the software, under the "Pattern Sequence" tab, "Input trigger" is set to "External (Positive)." Shorting pin 1 and 2 produces no result but shorting pin 2 and 3 causes the pattern to change. Could someone help me explain why?

Also, "Exposure time" is set to 0 which according to the user guide would cause a pattern to be displayed until the next trigger signal is received. However, after shorting pin 2 and 3 briefly to change to a pattern, (at this point, pin2 and 3 are no longer shorted) that pattern only stay displayed for a few seconds and then the screen goes dark. Could someone help me explain this as well?

Thank you



 

  • 0
    TI__Expert 4500 points

    Hi Tommy,

    I apologize for delayed response. The physical placement of the pins is correct in the above mentioned image.

    If you are providing an active high external trigger ( "External (Positve)" input trigger setting in the GUI) at 3.3V, then you need to connect the trigger generator (or pulse generator) between Pin 2 and GND (Pin 4).

    This enables the display of pattern when each trigger signal is issued. If you are attempting something different, please let me know.

    Best Regards,

    Divya

  • 0 in reply to Divya Reddy
    Prodigy 80 points

    Hi Divya,

    I am thinking about one of these options:

    So if the pulse generator outputs a voltage square wave with amplitude = 10V, freq = 0.5 Hz, then the pattern would switch every 2 seconds. Is that correct?

    By the way, I measured the voltage difference between these pins (directly on the LightCrafter, without the circuit above):
    - V1 - V4 = 0 V
    - V2 - V4 = 3.3 V
    - V1 - V2 = 0 V

    Could you help me explain why this is the case? I thought V1 - V4 = 3.3V

    Thank you,

    Tommy

  • 0 in reply to Nghia Huynh
    TI__Expert 4500 points

    Hi Tommy,

    Sorry for the delayed response.

    First, I recommend not to apply 10V amplitude to the pulse generator. In the figure below (Lightcrafter System Board Schematic), R285 is not connected on the board by default. So, you are able to measure 3.3V between Pins 2 and 4. You need to connect a 0 ohm (R285) resistor, to use the set-up with the amplifier. Else, supplying a positive trigger (pin2 and GND) with 3.3V amplitude would suffice your needs.

    You can change the voltage levels to either 5V or 1.8V by removing R282 and installing R281(for 5V) or R283(for 1.8V). Please note that 3.3V is recommended for proper operation.