I am much more comfortable in software than hardware, but I'm working on a home automation project to track water usage. I have a Dinel AFP-966-S fiber optic sensor positioned over the water meter - and that works. It changes state when the needle moves. I also have a Hobby Boards dual 1-wire counter. If I manually jump the C-A or C-B input to +5v, I see the counter rise in software. Perfect so far.

But I don't know exactly how to connect them because the Optical sensor requires 10-30VDC and the Dual Counter wants 5VDC. The dual-counter has an internal pull-down resistor, so I presumably have to send it a +5v signal to count. How? Surely I can't just connect the +5V and the +12V to the sensor because the dual counter will get +12v.... I guess here is where I'm stuck. Or do I have to tie in an opto-isolator between the two?

My guess is the internal pull-down resistor is working against me? Otherwise wouldn't I just tie a pull-up resistor to +5V and then tie all GND together? The sensor would pull down the logic pin instead of trying to pull it up? (If this is the easiest solution, I could remove the pull-down resistor, but that's a permanent move.)

Basically, I'm hoping the diagram below just needs one more wire, but where to PUT that wire?!enter image description here

  • \$\begingroup\$ do you have 12V and 5V supplies available for these devices? You can simply use 2 resistors from the output of the 12V device to make it ~4.5V so the 5V device is not damaged, but will still get the logic HIGH and logic LOW that you need etc. \$\endgroup\$ – KyranF Oct 3 '14 at 5:57
  • \$\begingroup\$ the pull down resistors are only there to stop the pins from floating and to protect them from false triggers in an electrically noisy environment \$\endgroup\$ – KyranF Oct 3 '14 at 5:58
  • \$\begingroup\$ Would you say my only two options are (A) power everything from a single source, stepping down the voltage for the 1-wire system, or (B) use an opto-isolator (or some other intermediate components) to fully isolate the two components? \$\endgroup\$ – Adamlive Oct 3 '14 at 6:32
  • \$\begingroup\$ And if I'm not mistaken, a standard PC power supply has +12v and +5v already? I have a few of those around, I could just dedicate one to the 1-wire system and that'd be more than sufficient. \$\endgroup\$ – Adamlive Oct 3 '14 at 6:33
  • \$\begingroup\$ You say the optical sensor needs 10+ VDC, so power that from 12V. What is the output from the optical sensor? It might actually have 5V outputs, do you have a datasheet link for it? \$\endgroup\$ – KyranF Oct 3 '14 at 6:35

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