clsanchez77 (Customer) asked a question.
Hey everyone. I am a long time reef aquarium hobbyist and I am looking to upgrade my aquarium controller to a PLC. The standard aquarium controller has too many limitations and too many proprietary products that just don't work well or as advertised. The aquarium controller does use a modified ladder logic, so most of my programs would transfer over pretty intuitively.
The project does have a LOT of IO so the fact that it is just an aquarium can be miss-leading. Most of the controls are timer based and some require manual overrides.
I plan to start out small and build out over time. The full buildout plan will include:
- 12 Flow Meters
- 20 Discrete Inputs
- 6 Discrete Outputs
- 8 Relay Outputs (24vdc)
- 12-14 Relay Outputs (120vac)
- 1-2 Relay Outputs (240vac)
- 8 Analog Inputs (half current & half voltage)
- 12 RTD Inputs
- 14 Analog Outputs (all voltage)
- 5 PWM Outputs
A full Click PLC buildout would require two head units and 10 modules. The one feature that I cannot do on Click is the PWM output for fan speed control. I would compensate for this with an Arduino on Modbus.
A full BRX buildout would require the 36 point unit with 7 modules. The BRX option looks like it would cost about $300 more. Doing this on the proprietary aquarium controllers on the market would cost me about $2000, but severely limit my product options and take up far more cabinet space. The PLC option appears to be very similar in price.
The main input I am looking for is between the Click and BRX system, which is the more reliable for a casual user?
Interface will be a C-More HMI panel. The HMI panel will be a bigger learning curve for me than the PLC.
I appreciate your feedback on the project and PLC brand recommendation.
Also, a lot of my discrete inputs are float valve switches. On the aquarium controller, these wire directly in. From reading the manuals on the PLC, it appears I need to apply a control voltage to the float valves. Can someone confirm if this is correct? I plan to provide a 24vdc rail and a 5vdc rail. The 5vdc rail voltage looks like it is too low for this usage. So, to keep things simple, I will probably use the 24vdc rail instead of introducing a new voltage. My question is should I wire these in as either sinking or sourcing? Am I correct in assuming that a sinking wire diagram would be safer as I am wired on the 0v side. Also, are resisters required, or are these already integrated into the PLC units?
Thanks again.
BRX is hands-down a more capable controller. If you're o.k. with spending a little bit more money I would go this route. The instruction set with the BRX is vastly superior to the Click. You might want to look at the P1000 controller as well. Reliability wise you shouldn't have any issues with any of the AD platforms. Instead of using relay output cards, I would run all discrete outputs and use interposing relays to interface with your switched devices. Concerning the float switches, if they're mechanical you can wire them as sourcing inputs as shown in the link below if you want to switch 0v with the float switch (using 24VDC as common). You're correct in that 5VDC cannot be used with the majority of PLC I/O modules. If they're not mechanical (are transistor based) you'll have to match whatever wiring configuration is necessary for that specific sensor. Additional resistors are not needed with discrete PLC I/O modules.
https://library.automationdirect.com/sinking-sourcing-concepts/
Thanks. I did look at the P1000, but the lack of high speed inputs was the main negative. It also came out more expensive than both the Click and BRX options, with no apparent benefit. The Click gives me 6 HS inputs on the main with no add-ons. BRX gives me some on the main (could not determine how many are actually usable for frequency measurement) and then additional on the cards. P1000 looks like its only two on a card. My goal is to have at least 6 flow meters, but optionally up to 8.
I have considered using discrete outs with a Zip relay board and space is my biggest constraint. I am laying everything out now to see if it will fit. If I do not have the space, I may have to resort to the relay cards.
The float switches are mechanical and I am just curious if there is a preference on sourcing vs sinking in regards to wiring. If I understand the theory right, wiring them as sinking inputs would put the voltage across the switch as 0V when submerged (closed) and 24V when above the water (open). The water in the sump is also grounded so this is my preference.
Are you looking for a high speed counter or fast response inputs? The P1-16ND3 inputs have a 1ms response time.
High speed counter to measure frequency of flow meters.
High speed counter to measure frequency of flow meters.
I wouldn't use the ZipLink relay board (I think they're really bulky). I was thinking something more like the below. The 36 BRX has 10 high speed inputs.
https://www.automationdirect.com/adc/shopping/catalog/relays_-z-_timers/electro-mechanical_relays/slim_interface_relays/kpr-sce-24vacdc-1
Thanks BRPLC, that is potentially a perfect solution. Let me see how I can accommodate these into the build. What I really like is this eliminates two 8-pt relay cards as now I can use a single 16-pt discrete output. A 1/4" thick with LED is pretty amazing too.
Do they make a DPST, or can I just use two with a jumper?
Will these need any protection from inductive loads such as small motors? My largest load is only a 1/4-hp pump (3 of these). Other than that, I mostly have 10W solenoids and peristaltic pumps.
Below is a link to DPDT card relays. These could be used or you can use jumper bars for commons, which is the customary way to wire these (also linked below). I can't tell from the spec sheet if the AD 6mm card relays have coil surge supression built in to them. The Finder brand linked below does have a suppression diode so that they can be directly interfaced with the discrete output module. For the 1/4-hp pumps I would probably jump up to an ice-cube relay which will have a higher contact rating and will probably last longer. Suppression modules need to be installed for these. For the pumps you'll probably want to install some form of current limiting device as well.
https://www.factorymation.com/38-52-0-024-0060
https://www.factorymation.com/093-08
I plan to have panel breakers to isolate my larger AC loads. Pump failures are pretty rare in the hobby as I use industrial pumps (suck as Iwaki brand) and the loads on these are really small. The newer DC pumps fail often but I despise them. The hobby brands use proprietary drivers on Chinese built pumps and they are problematic. I await the day some one makes a saltwater safe 1-hp VFD submersible option...but then it will probably be too expensive for a hobby pump LOL.
"I can't tell from the spec sheet if the AD 6mm card relays have coil surge suppression built in to them."
I saw the AC models have it on the coil side, but I do not see any reference to it being on the load side on any model. I did see they have a 6A/30vdc (250vac) rating with a "dielectric strength" between the contacts of 1000vac. Would this be sufficient suppression if my largest inductive load is a 120vac/1.5A pump motor?
"For the pumps you'll probably want to install some form of current limiting device as well."
I plan to do so. One issue very common in the hobby is that we plug our tanks into a GFCI, one item (or a collective of items) causes it to trip and the whole tank goes dark. If this is not captured quickly in a reef tank, mass casualty is usually in only a few hours. One of my goals to address that was to create GFCI groups instead of the entire assembly using panel breakers. Then I would have current monitoring on the main line, and anticipated current demand calculated at the PLC. If there is a difference of say 1 amp, then I can have it notify that an item is de-energized (or potentially stuck on). Conveniently, most items of concern will draw approximately 0.75 to 1.0 amp with a single pump hitting 1.5A.
A ground probe is used to prevent the saltwater tank from turning into a capacitor for obvious safety reasons. But when you have a half dozen 120vac devices in the water and each one as a negligible amount of voltage leakage, it starts to add up and can easily generate false trips on a common GFCI. I have not decided how many I would use, but my thinking is to separate heaters from submersible pumps and from external pumps. Heaters would probably be split in half as well. So that is already 4 GFCI breakers. The rest of the system is 24vdc or 19vdc (LED lighting system) so the GFCI is not helpful on the power supply side and this is separated from the water anyway.
Ironically, over the years, I found my biggest shock hazard was when I put in 120vac LED lighting. I never located a direct contact between the lights and the water, but the I strapped the power line to the PVC pipe. I can only assume the voltage source was inductive. Oddly enough, this never tripped my GFCI, so again points to inductive. I will be switching these out to 24vdc.