The fastest and least expensive solution to learn PLC technology is with a mini controller. There are several brands out there that are reputable and will do the job. For this project, I went with the Click PLC because it is cheap, easy to use, has a good selection of accessories, and is readily available. A few notes about this solution:
- Please consider this a working document as I plan to update it in the future with additional controllers and useful, relative information.
- *Disclaimer* I am not an expert and I'm still learning new things about this technology every day. My goal with this is to share the positive takeaways from the time I've put into this and the frustrations that I've experienced along the way.
- For this to be a cost-effective solution for all schools, you are responsible for purchasing these components at your own risk. If you experience technical difficulties, please refer to the manufacturers' websites.
Automation Direct - www.automationdirect.com
(1) 24 VDC power supply. If you have a Festo Meclab, you can use the power supply that came with each of the modules. Otherwise, you purchase one similar to this on Amazon: EMITEVER 24V DC LED Power Supply, 60W LED Power Adapter, Lighting Transformers, Input AC 100-240V UL-Listed,Class 2
- Once you have all your components, begin by attaching PLC to din rail along with I/O terminal blocks, end caps and end brackets.
- At this point, a good practice will be to label each of the I/O terminal blocks, keeping Inputs separate from Outputs. I place a piece of masking tape across the blocks after they were all assembled, starting from left to right with 24V, 0V, X1-X8, Y1-Y6.
3. Reference the wiring diagram as shown below. A few notes about the wiring:
- The nice thing about this model of the Click is that it only requires 24VDC, which is not only safe for students to handle, but it's also the same power required to operate the Festo MecLab system.
- If the below wiring diagram is a little confusing, just be sure to make the common for your inputs 0VDC and the ouputs 24VDC.
- Use individual strands of wire from the multi conductor cable purchased. Keeping your 24V red and 0VDC black is a good wiring practice.
- There is also the subject of sourcing versus sinking related to your I/O components, which may complicate matters. Festo provides a good explanation within the Festo LX curriculum as shown here. However, if you're still confused, just wire your controller the way I have. It should work fine if you're applying it to the Festo MecLab.
4. There are numerous strategies for how best to manage your wiring. Feel free to follow my method. For wiring, you'll need to jump wires from the power supply on the I/O block to the input power of the PLC. Be careful to take note of the 24VDC and 0VDC connections.
5. The next step is to connect the data cable to the MecLab terminal block. If you purchased the ANMBEST DB15 cable, you'll need to reference connection guides for the Anmbest Cable pinouts and the Festo multipin connector on the MecLab. Connect the corresponding wires to the corresponding terminal block connections on the opposite side, as shown below:
6. For this next step, you will need to be on your own since it requires a download of software from the Automation Direct website:
7. Once you have software and drivers installed, it's time to become familiar with the Click programming software. The fastest way I learned this software is through their series of 10 YouTube videos. For anyone who has a short attention span, these videos are for you! (I think the average time for each is 3 minutes long, so you can learn how to create a program in under 30 minutes! Your students will probably be doing it even faster than that.)
The software developed by each PLC manufacturer has its own nuances. Micro controllers like the Click and the Siemens Logo are very different, but both will help build skills in controller logic.
With everything connected properly, your PLC with MecLab application should look similar to this. By following the YouTube videos, you'll create a simple program which defines a few inputs and outputs for a total and 2 rungs of code. Using that simple program, you can make the conveyor move!
Now, have your students program the PLC to get the conveyor to stay on for 5 seconds. Then have them figure out how to sort the different material types. From there, you can apply it to the other Meclab systems. If you have an expansion kit, you can add other components, such as switches, lights, and other pneumatic valves to control more air cylinders, to do crazy out-of-the-box projects and so on!