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Old February 4th, 2018, 08:35 PM   #1
CaspianSage
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Arduino Sensors

I was looking at some Arduino sensors for a home project to interface with a PLC 5. Was wondering what is needed to connect them to a dc or TTL input card. I wanted to try a flame sensor first. So what options are there?

Are these 5 volt DO devices?
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Last edited by CaspianSage; February 4th, 2018 at 08:37 PM.
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Old February 5th, 2018, 03:19 AM   #2
cardosocea
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Opto-isolator would do what you want... but I'm not sure if you can find them for 24V to 5V reduction. You'd also require the power supply of 5V which would add to the complexity.

Do you have the specs for the flame sensor? If the output is digital, there's a chance that it may take a fair amount of voltage, although you'd have to power it and that is likely to be 5V.
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Old February 5th, 2018, 11:44 AM   #3
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For flame sensing looks like this will do nicely- Not going to be used for a safety device, just informative on a water heater.

I think I can de-solder the diode connect wires to it and insert it in a piece of tubing and aim it at the area of the main burner and use another to watch the pilot light. Might even be able to extend the wires long enough to mount the relay module in the PLC Cabinet. Not far from the heater.

They come in 5 and 12 volt models.
https://www.amazon.com/Alloet-Sensor...no+flame+relay


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Old February 5th, 2018, 07:12 PM   #4
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You have a PLC5 at home? You should interface it with a PDP-11
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Old February 5th, 2018, 08:22 PM   #5
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Wink

Surely you jest.....

Quote:
Originally Posted by Geoff White View Post
You have a PLC5 at home? You should interface it with a PDP-11
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Old February 6th, 2018, 01:16 AM   #6
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I think you need to handle voltage converting as a separate interchangable issue. Even if you still find 5v arduinos, most sensors have moved to 3v or lower.
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Old February 6th, 2018, 06:39 AM   #7
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Powering the sensors aside (easily done using cheap voltage regulators like the LM7805 or similar), if it's open collector output then you can just use a pull up resistor and 24V input card.

If you have a bunch of 3 or 5V level signals then I'd interface them to something like this open collector hex buffer.

http://www.ti.com/product/SN7407

If your inputs can be configured for "source" operation then connect directly. If they are only "sink" then add a pull up resistor and invert in logic.
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Old February 6th, 2018, 06:48 AM   #8
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Quote:
Originally Posted by Saffa View Post
Powering the sensors aside (easily done using cheap voltage regulators like the LM7805 or similar), if it's open collector output then you can just use a pull up resistor and 24V input card.
24 to 5V is a drop that although within the working range is likely to only be possible with really low currents (which could still be enough for this application).
For the same price of the 7805 (plus capacitors and board to connect it) I would go with one of these instead.

https://www.ebay.co.uk/itm/LM2596-DC...0AAOSwTzlZijCJ

No heat to worry about and little assembly/soldering required.
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Old February 6th, 2018, 08:33 PM   #9
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I think VCC on these is 5 volts, am I wrong ???? if that is the case all I need is a 5volt PS, pretty easy to come by.
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Old February 7th, 2018, 03:06 AM   #10
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Quote:
Originally Posted by CaspianSage View Post
I think VCC on these is 5 volts, am I wrong ???? if that is the case all I need is a 5volt PS, pretty easy to come by.
Not in my experience in industry. But perhaps there are some ready made for panel mount?
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Old February 7th, 2018, 03:52 AM   #11
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Quote:
Originally Posted by cardosocea View Post
24 to 5V is a drop that although within the working range is likely to only be possible with really low currents (which could still be enough for this application).
For the same price of the 7805 (plus capacitors and board to connect it) I would go with one of these instead.

https://www.ebay.co.uk/itm/LM2596-DC...0AAOSwTzlZijCJ

No heat to worry about and little assembly/soldering required.
That looks like a very nice little unit. Would certainly do the trick.

I'd have used a 9V plug pack to power my 5V DC regulator rather than from 24V. I don't have any PLCs at home so it's not normally an issue for me. 24V down to 5V is a bit steep for the 7805, you're right
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Old February 7th, 2018, 05:33 AM   #12
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I see you want to use a flame sensor, but what is your full application? If using the sensor that CaspianSage mentioned, you could just use an arduino alone. For more inputs and outputs you can use shift registers, and for higher level outputs, have relays. Simpler in some senses, but terrible for maintenance and troubleshooting..
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Old February 7th, 2018, 09:34 AM   #13
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Thanks everyone for jumping in here.

Quote:
Originally Posted by TL140 View Post
I see you want to use a flame sensor, but what is your full application? If using the sensor that CaspianSage mentioned, you could just use an arduino alone. For more inputs and outputs you can use shift registers, and for higher level outputs, have relays. Simpler in some senses, but terrible for maintenance and troubleshooting..


All I want is a binary signal - either I have it or I don't A flame relay of some sort will do fine but I want to keep the cost down. As I said in another post this is not for safety or anything critical. Just informative. ie, Main Burner ON or Off

I plan to watch the Pilot Light also and set an annunciator bit if the pilot goes out. A thermocouple that can turn on a relay will work.

These might do it. https://www.ebay.com/itm/BRAND-NEW-G...kAAOSwux5YQDs3











https://www.ebay.com/itm/Lot-Of-2-Om...pe!45801!US!-1
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Last edited by CaspianSage; February 7th, 2018 at 09:43 AM.
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