Created Date: January 03,2018

Created by: WWorld

I have been research using a BRX plc to upgrade an older machine. I have a few questions if its possible for anyone to answer.

Is there a advantage to using a 12vdc BRX system over using the 120vac system that I am not seeing?

I will be using up to 5 festo 6211 solenoids on this machine. What I have managed to find on the coils that active the solenoid its 24vdc, 4.5 watts from my math that is 0.1875A per coil. The outputs can handle .5A per output. Reading some other posts some claim you can drive right from the output, some say freewheeling diode is only needed and others state to use a relay. I am not sure how using a relay changes much in this case as both are using a coil so wouldn't both be capable of transient voltages that could damage the PLC output? I don't know much on this subject but I am trying to learn it. What is the simplest and least costly options recommended to connect a solenoid to the plc to avoid damage to the PLC? One of the Solenoids is on most the time and the other 4 cycle depending on the step within the processing cycle. I haven't been able to find any video tutorials yet that have shown how most people wire a solenoid to the PLC. I was looking at maybe using RS6N-DE but I am not sure if that solves this issue the best way. If I did use a RS6N-DE I would need a sinking output PLC correct?

thanks

Created Date: January 03,2018

Created by: Do-more PE

You should always use snubbing. No exceptions. That CEMF pulse (which is hundreds to potentially thousands of volts) when the coil de-energizes has to go somewhere. If you don't use snubbing it is going to damage something. Maybe not immediately, but it is damaging something somewhere in the system and eventually that something will fail.

See The BRX User manual Chapter 1 Page 29 for more information. https://cdn.automationdirect.com/sta...xuserm/ch1.pdf

Created Date: January 03,2018

Created by: plcnut

I always snub even the smallest coils. Some coils have built in snubbers, and other times you can buy a connector with a built-in snubber. One way or another, make sure there is one on every coil.

One of my very first projects that ended up getting me started in the Industrial Automation industry, was troubleshooting a system that had multiple issues all caused by lack of snubbers. It took a while to figure out what was going on, but it has caused me to watch out for things that I have seen many other people overlook.

Created Date: January 04,2018

Created by: WWorld

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This is a picture of where the solenoids first terminate. Am I understanding this correctly for using a diode... The bottom of the terminal blocks go to each solenoid coil. The upper connection either go to another terminal block or to a connector on the plc. All the 12s are neutral and 13-17 are the positive connections to the plc. Would I place a diode from each connection on 13-17 to the 12 for each solenoid, or would placing the diode here not work? If this would work what type of diode would i need?

Thanks

Created Date: January 05,2018

Created by: Bolt

This is a picture of where the solenoids first terminate. Am I understanding this correctly for using a diode... The bottom of the terminal blocks go to each solenoid coil. The upper connection either go to another terminal block or to a connector on the plc. All the 12s are neutral and 13-17 are the positive connections to the plc. Would I place a diode from each connection on 13-17 to the 12 for each solenoid, or would placing the diode here not work? If this would work what type of diode would i need?

Thanks

If by neutrals you mean the 12's are negatives, then yes, in theory you would place the diode between 13-17's and back to a 12. In reality that will be a little tricky in the size of your enclosure.

I like these 2 videos that to me explain everything well, the necessity and the possible solutions.