PLC as water valve timer

Completely new to PLC's but need advice on what to buy and program to activate a 1", 24v water valve for 4-6 seconds every 10 minutes.
I thought of a simple inline water timer but the minimum they open/spray is one minute and thats far too long.
Thoughts on something simple to time a valve?

Can you open and re-close a valve in 4-6 seconds anyway?

Aside from that, what's your budget? A micro PLC / "Smart Relay" could be had for around $100 or slightly less. If that's too steep, you might want to think about a simple little "cube timer", something like this for about half the price, but less flexibility:

The function you want to look for is called a "recycle timer" or "repeat cycle timer", where one cycle will be 10 minutes, the other will be .1 minute (6 seconds).

If you want to keep it compact and easy to use, you could get an Arduino with a relay shield and do a simple program to accomplish this task.

The electronic valve should be almost instant.
This really looks like what I need but as I expand to more valves (4-5) would this handle all of them or would the mini plc be better suited for that?

http://www.amazon.com/SainSmart-16-CH-16-Channel-Relay-Module/dp/B0057OC66U/ref=sr_1_7?ie=UTF8&qid=1431032395&sr=8-7&keywords=relay+shield

This relay module will control up to 16 different circuits. It's $25 and the price only goes down depending on whether you want 2, 4, or 8 relays on the board. The controller itself can be found for around $10-25 such as this one.

http://www.amazon.com/Atmega328p-Atmega16u2-Version-Board-Arduino/dp/B00SF28U7A/ref=sr_1_12?ie=UTF8&qid=1431032439&sr=8-12&keywords=arduino

The wiring is fairly simple, and I'm sure there is someone out there that can help you program it.

This relay shield http://www.amazon.com/Seeed-Arduino-Relay-Shield-V2-0/dp/B00BOZ7V02/ref=sr_1_1?ie=UTF8&qid=1431032598&sr=8-1&keywords=relay+shield , has the added perk of fitting directly on a standard Arduino Uno, so that cuts the wiring WAY down, as you wont need a breadboard. The only downside is that it's limited to 4 relays, unless you stack them.

haha, wouldnt know where to begin...

You'll also need a 24v power supply to power the valve, and a small project box to put everything in. If you decide to go that route, let me know when you get everything and I'll give you wiring info and write a program for you.

What about a Pico smart relay
It has 6 outputs.

gbradley said:

What about a Pico smart relay
It has 6 outputs.

Click to expand...

The Pico is going away, the new one is the Micro800
Software (Connected Components Workbench) is free now. If you can wait, order the CD and install it from that. the download takes about 3 hours sometimes.

This would be for 5-6 valves. If you only need 4, you could use the smaller one.


(not to scale)

...but as I expand to more valves (4-5) would this handle all of them or would the mini plc be better suited for that?

Click to expand...

Those little cube timers are for one unit, so you would need another one for each valve. After the 2nd one, you have paid for the Micro PLC...

You can get repeat cycle timers pretty cheap: http://www.newark.com/wcsstore/Exte...cas/catalogs/catalog_132/index.html?page=1923

For one to three devices max, I would go with an electronic multifunction timer. I had to do something similar in a tiny spot and used an electronic timer from Omega. It handled 2 valves with separate on and off timers for each, and had a tiny little keypad and display for programming. The instructions were terrible, and I had to just play with it (for about two hours) to figure it all out. I had to set one for an 8 hour delay and a 15 minute on time if I recall, and the other one was about half that for the off time.

For more devices than that, I would lean toward a PLC. If you don't already have an in-house brand preference or recommendation, I would go with the Click by Automation Direct. Get one with retentive memory a battery, a cable, a handful of relays and bases (for isolation) for about $200 give or take. Software is free, a small download, and is very good.

Add a relay for each solenoid to isolate it from the actual PLC outputs. Do this with any choice you make. Some of the multifunction timers may be robust and cheap enough and your solenoid may not be a terribly harsh load, but in general relay isolation is going to save time and money when something goes poof.

I have nothing against the Micro800 but the 2 gigabyte download of CCW is a pita. I have downloaded it just to gain access to a PVc. I installed it and glanced around but did not try to really use it yet. I will probably encounter a use for the Micro800 in the next year or so and may give it a whirl.

Hmmm, allot of good information.
Ok, lets say I order a micro 800.
I would get the CD, 120 to 24v power supply and with my personal computer could program the micro to turn the valves on/off as I want them? OR would I aslo need relays between the Micro and the valves?

The Micro is the relays.
Once you program it, it will be able to turn on and off the valves with no computer or other relays.

Ahhh, ok.
I think I'll go for that.
Micro 800, power adapter and 24 vac 1" water valve.
Not if but when I run into trouble I'll post for advice hahaha
Thank you all for the advice.

Just a few words on the relays.
In any relay output of a micro PLC or other similar device, valve solenoids are something that is hard on them. If one relay fries, the entire unit is toast (unless you have another spare unused relay). I like to use what are called "interposing relays", where the PLC relay drives an external interposing relay, and THAT relay drives the valve. If that interposing relay fries or welds from the inductive kickback of the valve solenoid, you unplug the relay from its socket, toss it and replace it. Cheap.

It's not necessary, it's just a common practice on things with high duty cycles, as yours will be. Once every 10 minutes, if it's 24/7/365, is 52,560 cycles per year. Mose relay contacts are good for 10 million mechanical operations, but under rated load, the contact life will be about 50,000 cycles. Your valve may be under rated load and/or your operating time may be less (you didn't provide details) that will help, but I would not expect the contact life to be more than about 2-3 years at best. So if you want to only have to plug and unplug cheap little relays instead of replacing the entire controller, regardless of what you use, go that interposing relay route. You can get small thin versions that look like terminal blocks if you don't have a lot of room, but there are less expensive versions if you can live with then being about 5/8"" wide. But pay attention to the INDUCTIVE current ratings for use on a valve, it's important.

Narrow (6mm) "TB style" interposing relays:


Lower cost plug in relays, base not shown but it is 5/8" wide: