multiple pH meters, solenoids, PLC and IOs

Request new hardware or ideas for the controller
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dave w
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Joined: Thu Nov 29, 2012 10:34 am

Re: multiple pH meters, solenoids, PLC and IOs

Post by dave w »

Roberto, I may end up using a number of float valves and probably should set up some water leak sensors. What type and how many I/O devices should we look at? And I told the solenoid valve company to send the first 30 solenoids as 12VDC.
rimai
Posts: 12881
Joined: Fri Mar 18, 2011 6:47 pm

Re: multiple pH meters, solenoids, PLC and IOs

Post by rimai »

We can have several inputs for your floats and water leak detectors.
How about 16? Will that be enough?
They would be digital input at TTL level only. Usually they are used only to detect switch closures, like reed switches, float switches or relay switches. Would this be sufficient for your needs?
Roberto.
dave w
Posts: 14
Joined: Thu Nov 29, 2012 10:34 am

Re: multiple pH meters, solenoids, PLC and IOs

Post by dave w »

Roberto, if another 16 inputs for floats can easily be upgraded in the future, then 16 is enough for now. Please let me know the price difference and I may go with 32 rather than 16. Thanks.
rimai
Posts: 12881
Joined: Fri Mar 18, 2011 6:47 pm

Re: multiple pH meters, solenoids, PLC and IOs

Post by rimai »

We can make 32... no problem.
Roberto.
rimai
Posts: 12881
Joined: Fri Mar 18, 2011 6:47 pm

Re: multiple pH meters, solenoids, PLC and IOs

Post by rimai »

Do you think you would need these inputs to be optically isolated?
Optical Isolation would create an isolation barrier which prevents the inputs to be burned up should you have any electrical discharge of any sort and also help with noise immunity a lot, especially when you are talking about so many inputs.
Roberto.
dave w
Posts: 14
Joined: Thu Nov 29, 2012 10:34 am

Re: multiple pH meters, solenoids, PLC and IOs

Post by dave w »

Roberto, how do we take care of the GFI requirements for these relays? I would assume that I will just wire up a bunch of GFCI outlets into large gangs for protection. Alternatively, I can plug a power strip of a dozen outlets into a GFCI outlet to save a little money. Please let me know if there is protection built into your board like reset buttons or fuses.
rimai
Posts: 12881
Joined: Fri Mar 18, 2011 6:47 pm

Re: multiple pH meters, solenoids, PLC and IOs

Post by rimai »

Like we've talked before, the relays are not going to be powered relays.
So there is not going to be any protection on the board.
You will use jumper wires on the headers, so you can come up with your own power board with breakers/gfci for each block of relays.
Check the attached picture.
It will be a relay with the contacts brought to the header.
So each pair in the header will be use on the hot phase of the AC coil.
All neutral phases will have to be jumpered out together by you either in a ground terminal block or with twist-on nuts. Whichever way you prefer. That's going to be your side of the project. Then, if you want to place gfci on the AC circuit, it is also up to you.
I hope it's a little more clear to you.
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Roberto.
dave w
Posts: 14
Joined: Thu Nov 29, 2012 10:34 am

Re: multiple pH meters, solenoids, PLC and IOs

Post by dave w »

Thanks, now it is much more clear. I will take care of pulling power to the device and protecting the circuits.
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