Can you hook the photo sensors to one 12 volt out??

[RyanN]

What we did is used the terminal strip.

For the 12V power:
I used a butt connector and had basically one input, and three outputs, 2 on each side. So we had our positive and negative wire going to a yellow butt connector, then 3 loose ends.

For the Digital Input Cables, we got the 5V power, and the signal and brought them to the terminal strip. We put a resistor between the 5V DIO power, and the signal.

So, if you do the math, that's 4 spots on the terminal strip used by every sensor, and 3 sensors. You just so happen to have 12 terminations on the terminal strip.

With the resistor between the 5V and the signal, what you did is create a pull-up for the circuit using a pull-up resistor.

I then used the white signal wire from the photo sensors. The white is the D.O. connection, meaning that when it sees the dark, it turns on. When it turns on (aka sees the dark), it pulls whatever is on it to ground. You wire the white wire to what is usually the white signal wire from the Digital Side car.

So, when it's dark, the white signal wire going to the sidecar should be at 0V when tested to ground. When it sees the tape, the signal goes out, so the pull-up resistor should pull it up to ~5V.

As for what resistance to use... I didn't do the math. We're using a 1K Ohm resistor. We haven't checked it to see if works yet. We hooked it all up at the last second, and the programmers had some code in to read it, but it didn't work. It's the first thing we'll look at when we get back.

Just remember that you're probably using 1/4W resistors. What this means is that they can keep their rating when only pulling through 1/4 of a watt.

With a 5V power supply, you don't want to go with a resistance lower than 100 ohms. At that point, you may have some toasty resistors. You may not want to go that low. I don't know what the sensors can handle (like if they can pull down the 5V supply).

[Vikesrock]

Originally Posted by RyanN

For the Digital Input Cables, we got the 5V power, and the signal and brought them to the terminal strip. We put a resistor between the 5V DIO power, and the signal.
.......
With the resistor between the 5V and the signal, what you did is create a pull-up for the circuit using a pull-up resistor.

The Digital Sidecar DIO pins are internally pulled up to 5V using 10K resistors.

[RyanN]

Originally Posted by Vikesrock

The Digital Sidecar DIO pins are internally pulled up to 5V using 10K resistors.

Sweet! Always a cool thing to learn something. So do the sensors work fine with the internal 10K ohm?

[Alan Anderson]

Originally Posted by RyanN

So do the sensors work fine with the internal 10K ohm?

They work perfectly. It's almost as if the Digital Sidecar was designed to handle open-collector sensor outputs directly.

[Al Skierkiewicz]

Please be advised that the PD terminals work best and most reliably with #18 AWG wire or larger.

[KHall]

No matter how you wire it, you might want to think about including a quick and easy way to swap out a sensor in your design. Just in case of field damage.