Recommendation

I was wondering if it is possible to purchase a PLC, input sensor, and software in order to simply “play” with the setup. If so, can someone recommend a simple unit, sensor and software that I can order?

I want to learn more on how to use these for automating my greenhouse and I think the best way for me to learn is to have something in front of me. If it doesn’t work, I can pitch it. If it does, I can either upgrade the unit or implement what I have.

Thanks for any help and for your patience.

Michael

If you want something thats simple and cheap with free software then look at http://www.fujielectric.com/distr/elc.htm

They even advertise as useful for greenhouse temp and watering control.

You have to email them to get the password to download the free software.

Michael,

Most PLC manufacturer's offer a starter kit that is comprised of a "basic" PLC, cables and software. These starter kits start at approximately $200+.

Automation Direct would cost $217.00 (for the PLC, software and cable.) Manual sold separately. Sensors available as well.
Triangle Research has an offer of $259.00
Allen Bradley offers starting kits (Ken Roach would be able to provide you more information)
Omron offers starting kits as well (I think?) Jay Anthony would be able to provide you more information.

That is to name just a few. There are probably 30-40 different PLC brands.

Another approach you may want to consider is with what they call a "smart relay" This device programs using a form of ladder logic, but offers limited capabilities and flexibility than a PLC. Just about every PLC manufacturer offers a "smart relay" There is very little differentiation between them.

Your decision will depend on your requirements - number of inputs and outputs. Type of inputs and outputs (digital / analog) (AC / DC). You will also need to consider the complexity of your application as well as the number of internal elements in each controller.

Regarding the sensors, just about any distributor or catalog house will be able to help you. There are so many different types, you will need to know what. I was looking at DigiKeys recent catalog and they offer a wide variety to select from.

We have a customer that uses one of our controllers for automation of green house irregations systems. They operator and control the position of the watering heads (I think they are called boons?)

Entertron does offer an introductory offer for first time buyers. It is posted in the buy/sell section of this web site. To help you learn programming, we provide you with a programming manual and 32 programming examples to get you started.

Please note that I work for Entertron.

I hope this will help you,

God Bless,

Stephen Luft

I suspect you are going to want some analog inputs for temperature etc. My first suggestion would be the AutomationDirect.com DL-05. As Mr. Luft points out, it is very inexpensive, and you can add analog I/O for under $100.00. The A-B MicroLogix also has a nice unit with built in analog I/O, but the programming software is a little pricey. GE has a 90 micro that would meet your needs to, but again the software is more expensive than the DL-05..

Basics questions

Would like to find out from experts in this forum on how to know whether my power supply for the PLC is able to support the whole circuit with the sensors and limit switch from the same DC 24 V 1 amp power supply?

That is indeed a very basic question. I simply create a spreadsheet for each project. I total the current requirements of each device, including lamps, the switches and sensors, and the PLC inputs. Then compare it to the total current available. I try to stay at or below 75% load to allow for contingencies, expansion, and inrush. If the rating of the device is given in watts, such as a lamp, just use W = V x I.

basics again

hope you can answer some more basic questions. How can I know how much electricity my machine use per hour? If the amphere is not enough, the devices will work abnormally or not work at all?

You maybe in over your head, Ken. However, the answer to this is the same as the answer to your other question. You have to take all of the loads in your machine that use electricity, and total them. Power requirements are usually provided in the manufacturer's literature for each device. Your power source must be capable of supplying the total load at the voltage and current specified for each device. Your machine probably needs several sources of power - three phase AC for motors, single phase AC for some devices, and DC for sensors etc.

If you don't have enough capacity in your power supply the machine's needs it might work OK lightly loaded but not at full load. It might not work at all. It might work abnormaly. It all depends on the characteristics of the device. A motor, for example, will operate at reduced load and only draw a percentage of ful load current, but if the load equals full rated load it willl trip breakers, blow fuses, stall, or possibly burn up.