Need tips to use PLC's in control board for many fans - newbie to PLC. 1

[Rollout]

I have 40 fans in a large warehouse. I need them to be controlled by temp, and humidity. When temp sensor 1 reaches a certain level fans 1-9 come on, if it goes to another level fans 10-19 come on.
Same with humidity. I also need these fans on timers, so when they kick on they will stay on for at least 5 minutes, and not just kick on and off right away.

Can someone please point me in the right direction, as to the PLC to use? Possibly some other tips?

Thanks in advance.

 

[IRstuff]

Is this for school

TTFN

FAQ731-376
Chinese prisoner wins Nobel Peace Prize

 

[Skogsgurra]

Even if there are 40 fans, you have only four outputs. So a very simple micro-PLC like the Siemens LOGO! can be used. It has analogue inputs for your temperature and humidity signals and a program like the one you need can be put together by yourself in hours.

There are also timers for scheduled on/off. Even a calendar for week-ends and such things.

The cost is almost nil (USD 200 - 300). All you need to invest in is the 'Comfort' program (usually included in the Starter package) and a couple of days to familiarize yourself with the hardware and software.

'Just do it!'

Gunnar Englund

http://www.gke.org

--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

 

[Rollout]

Thank you for the replies !!!

I will look into the Siemens LOGO.

This is not a project for school, it is an actual site I am working on, but am new to the electrical business, however have been an IT guy for 20 years. I am an apprentice electrician, but they are helping me to advance by letting me do some design work.

 

[Rollout]

One more question. With only 4 outputs how can I control the separate fans? Perhaps a dumb question, but I am trying to grasp the concept ...

 

[MiketheEngineer]

Wire them in parallel. Your "ON" output might need to activate a big relay to handle the loads.

 

[itsmoked]

Alternatively you can skip the PLC headaches, (which will start just trying to buy a LOGO!), and just use any two stage temp controller. Use the hysteresis setting to prevent short cycling of the fans.

Also a very inexpensive Humidastat can be used for the humidity control.

Or.

Just cut to the chase. You're describing everything several million greenhouses need. There is an entire market of that equipment and it's extremely cost sensitive, so a huge bang for the buck.

Here's an example:

http://www.littlegreenhouse.com/accessory/controls2.shtml

To drive a truckload of motors you will want to have anything you select drive a rack of relays. The relays will be what turn the individual motors on/off. That allows an individual failure to not bring the whole thing down. If you use the correct relays they will come with a little lever on them that allows you to manually turn any ON for testing or manual emergency operation.

Keith Cress
kcress -

http://www.flaminsystems.com