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  1. #1
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    Multiple AC inputs relay (light PLC)

    Hi,
    I have a circuit like in attached diagram (multiple switches associated with light bulbs in different rooms). I'll like to add a new device (the green one with question marks) that has the following "specs":
    - 230V AC powered
    - 10 to 16 230V AC inputs (the same AC phase, but will be nice to have different phases too)
    - 1 to 3 relays (classic NO/NC) outputs
    - it should trigger based on how many input lines have active power (the number of active inputs to trigger should be adjustable from outside (jumpers, switches, etc)
    As a practical implementation example will be to trigger an actuator which closes a window if there are more than 3 lights turned on and to open the window if there are 3 or less light switched on.
    Most probable I need a PLC / PLR, but I hope there are other devices to do this in an easier way. So the question is: Are there such devices? If yes, what is their name?
    If I have to go with PLC, can you please recommend some to me? (So far I've seen that there are very few relays, PLCs or actuators running native with 230V AC inputs).
    Notes:
    -I'll like to keep the light part in existing form (so no Dali/KNX/similar switches)
    -It will benice to be able to associate different "weights" to different inputs.
    Click image for larger version. 

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  2. #2
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    Re: Multiple AC inputs relay (light PLC)

    Quote Originally Posted by my_name View Post
    nice to be able to associate different "weights" to different inputs.
    This can be done by putting resistors inline with the input signals. The weighting proportions are achieved by making differing ohm values. Mix them through a final resistor, to produce an output voltage. When the voltage is sufficiently high (when 3 lights are on), it energizes a switching device which turns on the relay.



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  3. #3
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    Re: Multiple AC inputs relay (light PLC)

    Hi,

    PLC .., I have not much experience.. but a Siemens LOGO! with an I/O extension should work.

    There are different types available. Some run with 230V AC power, with/without display, with/without Ethernet.

    Klaus
    Please donīt contact me via PM, because there is no time to respond to them. No friend requests. Thank you.



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  4. #4
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    Re: Multiple AC inputs relay (light PLC)

    Quote Originally Posted by BradtheRad View Post
    This can be done by putting resistors inline with the input signals. The weighting proportions are achieved by making differing ohm values. Mix them through a final resistor, to produce an output voltage. When the voltage is sufficiently high (when 3 lights are on), it energizes a switching device which turns on the relay.
    I had a similar idea at the beginning, but I removed it from the list. Let's assign numbers to my rooms, so the left pair will be switch-1, resistor-1 and light-1. Similar to the second room: switch-2, resistor-2 and light-2.
    If I'll mix output of resitor-1 and resistor-2 (we'll ignore the other rooms) when switch-1 is closing the circuit (with switch-2 open) then a new circuit will form via switch-1 -> resistor-1 -> resistor-2 -> light-2 and will turn the light-2 on (with lower voltage, but still on). I can work around tsis issue in DC with diodes, but I'll like to avoid a 230 VAC to 24VDC conversion.

    Quote Originally Posted by KlausST View Post
    Hi,

    PLC .., I have not much experience.. but a Siemens LOGO! with an I/O extension should work.

    There are different types available. Some run with 230V AC power, with/without display, with/without Ethernet.

    Klaus
    Siemens LOGO looks nice at first glance (a light PLC, similar with what i need), but it seems that their analog inputs expect max 10VDC. Please correct me if I'm wrong.



  5. #5
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    Re: Multiple AC inputs relay (light PLC)

    Hi,

    You never mentioned analog inputs before.
    What do you need them for?

    Klaus
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  6. #6
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    Re: Multiple AC inputs relay (light PLC)

    Quote Originally Posted by KlausST View Post
    Hi,

    You never mentioned analog inputs before.
    What do you need them for?

    Klaus
    My bad. I was thinking that analog inputs are for "free range" AC input and digital inputs are for 3-5-12VDC. Meanwhile I've found out that the input accepting 230VAC is actually "digital input". So I don't need analog inputs anymore. I need 230VAC inputs :)



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