GPIO cable extend length
Answered
Hello,
I am trying to set up a system for 3D motion capture using a series of 7 CM3 machine vision cameras. To that end I have soldered the tips of some of the GPIO cables and made them attachable to a breadboard or stripboard.
I have connected the green input cables of the cameras to the ~3 pin of an Arduino Uno to send the voltage triggering pulses and the black ground cables to the GND pin of the Arduino Uno.
When they are connected to the breadboard like this, they appear to record properly as a result of external triggering by the Arduino,
However the cables are too short to set up for a 3D motion capture of an arm. I tried to extend the lengths of the GPIO cables by simply attaching extra lengths of cables to them but this resulted in the cameras somehow not being triggered at all.
Are there any ideas for how to increase the lengths of the cables so that the camera positions have more flexibility?
Thanks.
Varun
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Official comment
Hello Varun,
It seems like there is too much voltage drop when you add the longer cables, or the arduino can not provide enough current.
The proper solution would be to use a higher voltage/current pin, or to add a circuit to increase the current the pin can provide.
This can be done with an opto isolator or FET and supplying and external voltage. We have an article on doing this from the output pin of a camera (Buffering a GPIO pin strobe output signal using an optocoupler to drive external devices | Teledyne FLIR) but there is no reason you can't instead do this to buffer the output signal of your Arduino.
If you can not add any circuitry and there is no extra pins you can use, you could try a thicker wire (less resistance) to see if that helps, or removing the breadboard and other connections in case that contributes to the extra loss.
I expect if you take a scope and measure the voltage at the camera end, it will be too low to trigger the cameras.
Please let me know if any of these suggestions work for you.
Thank you,
Demos -
Hi Demos
Thank you for that. I have used different resistors to enable a higher voltage drop and and the cameras are getting triggered best I can tell.
However, their recordings are not synced up.
Sometimes, although rarely, they all have identical durations and play the video in real time.
Sometimes some of them are half the duration of others and play the recording as if fast forwarded 2 x
Sometimes even some of them play the video as if it is slowed down by 1/2.
I think it has something to do with the exposure settings or the frame rate that I am using on my mocap software or even the square wave frequency on my Arduino IDE.
Do you have any ideas on how to treat this problem?
Thank you,
Varun
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Hello Varun,
For your new question, I will answer in a new post that you created so we can keep the issues separated.
Demos
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