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Author Topic: How to connect Arduino to "Volt Free" teminals on an input module.  (Read 495 times)
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Azeroth
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I'm looking for a bit of help with a wee project I have.

I'm trying to control 4 inputs on a Digital Input Module from my Arduino Uno

The DIM is here: http://www.titanproducts.com/categories/5_198_62/Digital_Input_Multiplexer__DIM4_.html

pdf datasheet here: http://www.titanproducts.com/download/datasheets/62.pdf

From the pdf, the unit in question is the one to the left and as you can see it mentions Volt free inputs of which there are 4 and it is these 4 that I wish to connect to my Arduino Uno output pins.

Although the sheet says “volt free”, I am measuring them at 5v.

At the moment, I'm looking at two solutions.

1) Make a shield with 4 5v relays onboard and connect this way. (or buy???) (completely isolating the voltfree/5v)

2) Take the ground from the Arduino and connect it to the ground of this DIM, then using the 5v from the Arduino output pins, connect one to the negative side of each of the 4 inputs on the DIM

All help and comments are appreciated...

Thanks in advance.
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Rapa Nui
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It seems to me those IO/DIM4 are opto-isolated inputs. So there shall be no connection from those IO/DIM4 to ground (mind "Link5") or 5 volt on that module, imho.
In order to connect it to arduino you need most probably to drive those opto-isolator's LEDs through a resistor . The other side of the opto-isolators drives a 4bit DAC with 9V max output (my understanding). No waranties of any kind smiley
« Last Edit: June 03, 2013, 10:50:09 am by pito » Logged

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You call that a datasheet? More like a sales brochure. It says nothing about what "volt free" inputs are.

Is anybody forcing you to use it? It seems like a complicated way to read 4 digital inputs.


Although the sheet says “volt free”, I am measuring them at 5v.

Maybe they have pullups on them. Put a multimeter (showing voltage) on the "DC Output" pin and try shorting the pairs of pins together.

« Last Edit: June 03, 2013, 11:01:52 am by fungus » Logged

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Azeroth
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Here's what we got. This module was meant to be an easy way for me to get a 0-10v output to control a piece of plant, this module gives a 0-10 or 0-9v output based on different combinations of the 4 inputs.

If I "close circuit" any of the 2 pins on the 4 inputs I change the output voltage, which is exactly what I want to do.

I thought I could just connect an output pin on the Arduino and the other to ground on the Arduino and when program dictates, change the state of the output pin and this would be enough to close cirction the input on this module but this does not seem to be the case.

The module I have is the one on the left which does not have the optoisolated inputs.

With the Arduino in another room, 24v applied to this module, I'm measuring 5v across any of the 4 DI's and between the positive side of said inputs and 0

I want to close circuit the 4 DI's on this unit from my Arduino, nothing more fancy than that.

Thanks for the replies so far...
« Last Edit: June 03, 2013, 11:43:11 am by plisken » Logged

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Valencia, Spain
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Here's what we got. This module was meant to be an easy way for me to get a 0-10v output to control a piece of plant, this module gives a 0-10 or 0-9v output based on different combinations of the 4 inputs.

I see...

If I "close circuit" any of the 2 pins on the 4 inputs I change the output voltage, which is exactly what I want to do.

I thought I could just connect an output pin on the Arduino and the other to ground on the Arduino and when program dictates, change the state of the output pin and this would be enough to close cirction the input on this module but this does not seem to be the case.

That would seem logical, yes.

Can you measure the voltage on the output pin when you change it? Does it go from 5V to 0V like you expect it to?
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If I "close circuit" any of the 2 pins on the 4 inputs I change the output voltage, which is exactly what I want to do.

There are 6 possible ways to connect 2 pins out of 4. How many of those do you want to use?

I suspect that, internally, there's a resistor chain and by connecting two pins together you're shorting out one or more of the resistors to adjust the output voltage. That would indicate that directly connecting the Digital Input Module to arduino pins wouldn't work. The only way I can see is to use relays.
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