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I have a 512 pulses encoder with four wires: +5V, ChannelA, ChannelB, GND and I'm using it as feedback for my motor position (max 80 RPM) on Arduino UNO. Everything works fine, but I need also to generate a +5V signal everytime ChannelA is HIGH since I need to use it to trigger further actions.

I was thinking to read ChannelA by using an optocoupler in order to split the signal and use it both for feedback and for the +5V signal. Is it possible?

Is there any other easier solution to do that?

EDIT: I try to explain better what the additional device must do.

The device is a video camera system that takes a +5V signal from the encoder to trigger some actions by software (create key frames or more) and we need it for our computer vision system. I just need to use the encoders both for the motor feedback and to trigger the video camera. The signal is always +5V so I do not have problems with voltage levels. What do you suggest? I do not have to drive loads from channelA output, I just need the +5V signal to trigger the video camera. Can I split the channelA output and use it both for the motor controller and the video camera inputs?

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    Possible, yes. But you may get it easier. For what do you need that 5V signal from channel A? – chrisl Oct 16 at 7:13
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    Can't you just split the channelA encoder output, to go to both the Arduino and your other mystery device? Please tell us more about what it is you are trying to do, and what the actual problem is. – Gerben Oct 16 at 12:02
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    Thank you for all your assistance! The mistery device is a video camera system that takes a +5V signal from the encoder to trigger some actions by software (create key frames or more) and we need it for our computer vision system. I just need to use the encoders both for the motor feedback and to trigger the video camera. The signal is always +5V so I do not have problems with voltage levels. What do you suggest? – Marcus Barnet 2 days ago
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A simple cheat is to place the LEDs of the two opto couplers in series and then modify the current limit resistor to bring the current back to where it should be.

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People sometimes use optical couplers when anticipating large voltage differences or the potential for large voltage differences. This may always be the case as in a light dimmer. Or may preventative as in ground loop mitigation for MIDI connections. If you anticipate these types of situations then an optical coupler may be a good design choice.

Alternatively if the signal is changing between 0 volts and 5 volts and the fan out of the signal is larger then the existing load and the new load combined and the new load is 5 volt tolerant then the signal might be able to drive both loads.

You might seek out the specifications of the 3 connected devices in question. At the very least, discover the current the encoder output will support. Then measure the resistance to ground of the input to the motor controller and the resistance to ground of the input to the video equipment. Find the parallel resistance of these two resistance and calculate the current at 5 volts. If the current is substantially less then the specified capacity of the encoder, the encoder might be able to drive the 2 loads. This assumes many things such as no ground loops being present. There are so many variable it is difficult to be predict the outcome.

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  • The fan out is very limited, I just need to catch the +5V signal to trigger some events on my video camera system so I do not have to drive high loads. The video camera system is 5V tolerant. – Marcus Barnet 2 days ago
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    Thank you for making your question more complete. It is still a mystery what is inside the video equipment. It may be a high impedance device like a MOSFET with a load resistor to ground to mitigate noise problems. But that is just a guess. Also, your video equipment may be only inches away. Or may be across the lab. Logic level signals can be adversely affected by long wires. This is turning into a complex problem. – st2000 2 days ago
  • I can't check what's inside the video system unfortunately. For sure, the maximum distance between the encoder and the video system is 100 cm. In case it has a high impedance, what would be a possible solution? I think we have to check the worst case.. – Marcus Barnet 23 hours ago
  • Hi @MarcusBarnet, we are getting into a situation where we can not assure success. It is at these point I start to consider what risks I am willing to take verses the effort to discover everything about everything involved. For example I would ask myself how much would a new encoder cost if the current one failed. Keep in mind you are asking this question in the Arduino forum where parts very rarely cost more then $50. That said, 1 meter isn't that long in a quiet environment. Did have a prof w/a pulsing ruby laser in a lab once. That didn't go well. Hi impedance isn't a bad thing ... – st2000 18 hours ago
  • ... unless there's a lot of noise. Guessing, what I would do is to make sure there are no ground loops. That can blow out connected devices quickly. Make sure the input impedance to ground is high for both loads. Scope the output of the encoder w/no load. Scope it w/the motor controller only. Scope it w/the video equipment only. If both look good then connect them both and verify the signal from the encoder still looks good. If you are iffy about doing this, then I would suggest you find a tech or eng that is more familiar w/your setup who can do this for you. – st2000 18 hours ago

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