i am trying to use a EZtect plc 420 to automate a aquarium

I have a 100 gallon salt water aquarium that i want to use an EZ Automations EZtext PLC to automate the lights, pump and heaters with. I use plcs at work and have a little experience with manipulating data in them but have never wrote a program from start. Any help with writing the program would be appreciated. The inputs are 1-led light switch. 2- actinic light switch 3-daylight bulb switch 4- top of pump switch 5- low water float 6- full tank float. 7- over fill float. The outputs are 1-led lights. 2- actinic lights 3- daylight lights. 4- top off pump 5- over fill alarm 6-water heater 7 cabinet heater.

It has thermo card with a water temp thermo couple and a cabinet temp thermo couple.
I would like the lights to be automatic with the ability to turn them on manually with out interrupting the timers

EZtext plc 420

The EZ-420 from Auto-Dir is a viewing panel, not a PLC. For what you get, it is an overpriced viewing panel at that (opinion)! Seems that you might still need a PLC. What PLC?

what i have is a ez-series text plc system that has a plc built into the back of the display. it has slots for 4 modules i have 1 8 dc inputs card, 1 8 output dc card and 1 thermo input control card for it, the part# on ez automations site is EZ-420-PLC-E

OK. It might turn out to be as EZ as they say. Have you drawn an electrical ladder diagram to match physical devices with the PLC outputs? Low voltage switches may be fairly simple, but it is a little hazardous to start designing logic until a hardware design is in place. I didn't see sufficient speciications for the device online. for example, are the output relay outputs or npn/pnp outputs. It's makes a big difference to how things get wired. Also, some makers call the outputs relay's just because it is relay logic, but in fact they are sinking or sourcing outputs. You may already know and have a schematic drawn, but before you can get starting programming, these basic things need to be in place.

I have not used that brand of product but it does look like a good fit for your project based on what I found with google.

I would start with a wiring diagram to iron out exactly how everything will be connected. For your manual light operation, I would add that as a PLC input so that you can program the lights to behave how ever you want them to. Example: You push a momentary button and the lights turn on. Push it again and they go back to "Automatic mode" based on the daylight switch or a clock schedule (does your PLC have a real time clock?). If you forget to turn them off, after a predetermined or adjustable time limit they go back to the normal automatic mode at that time limit.

For your tank overfill switch, it might be a wise to have that hardwired to prevent a mess in case your little PLC "locks up" or suffers from a programming error while you are developing/polishing the code. If the switch offers only one set of contacts or one output, it would be wise to add a relay so that you can monitor it with the PLC and have a contact interrupt your pump.

The same sort of situation may apply to the heater system, since you don't want to cook your fish, and thermocouples can fail. When testing the stuff, and by reading the manuals, you can find out what happens to the value in the PLC from the T/C input if a wire breaks and perhaps program a failed T/C alarm, and maybe even go into a mode of operation for the heaters to limp along until the problem is solved.

When you design the wiring, think about what can (and will eventually) go wrong and plan accordingly.

Once the wiring diagram is all ironed out, then you can more easily plan how to write the logic to go with it.

i am in the process of doing a wiring diagram now and when it is done i will post it. the plc does have a built in real time clock and calender.

The test panel has 5 buttons on it that can be programed to be monetary or alternating switches and i was going to use them for the need switches for lights and pumps.

I will list the inputs (X) and outputs(Y) and what they will be wired to
X0 alternating switch for LED Lights
X1-alternating switch for actinic lights
X2- alternating switch for daylight bulb
X3- momentary switch for manual top off pump
X4-momentary switch for overfill alarm reset
X5- low water level float switch for top off pump
X6-full water level float switch for top off pump
X7- overfill float switch for all pumps

Y0- LED lights
Y1- actinic light
Y2- daylight bulb
Y3- top off pump
Y4- overfill alarm buzzer
Y5- water heater
Y6- cabinet cooling fan
Y7- return pump(always on unless x7 turns it off)


Also a thermocouple for water temp and a thermo couple for cabinet air temp.

Top off pump comes on when low level and high level are on and shuts off when they are both off

Overfill will set off a buzzer and turn off both pumps.

The water heaters are standard aquarium heaters internally set at 82 degrees F
I want the Plc to monitor temps and turn off the power if it raises to high.
And to turn on a cooling fan in the cabinet if the temps get to warm inside of it.

The outputs on my Plc are 110 volt relay out

Consider your code organization. Can you arrange to have a"main" routine that calls subroutines? The subroutines needn't be in separate files, that depends on the PLC coding architecture. Decide what subs you will want. For example, one might handle inputs and a separate one outputs. Yet another one might be prgm logic and another might be display maintenance. Once you have a grand plan, begin coding with testable lines of code. TrY to keep the main routine doing little other than calling the other subroutines.

My biggest hang up is the timer operation with the lights and making it so you can turn them on manually without interrupting the time sequence. I need the LEDs to come on at 6am go off at 7am. Then the actincs come on at 7am and stay on till 9 pm. While those are on, at 9am the daylight bulb will come on and stay on until 7 pm. At 9 pm the LEDs come on until 11pm. I need to be able to turn on the lights manually incase of a problem at night. I can control the overfill and the top off pumps with a set and reset line in the program.

Write your automatic timing sequence as an independent subroutine. Get it working. After that, manually switching any lights on or off should look a lot easier to you. if it doesn't, then show your code here and you will get lots of help.