fried my power supply... maybe my plc?

I don't know much and I'm just getting involved in this world. I want to turn this into a learning experience than just replacing things

As a learning project I'm playing with a small conveyor, run by relay's. I have a Click PLC C0-00DR-D, and a Rhino power supply (apparently it's a switching type).

I was getting some feedback from the relay's when they closed that was preventing communication and was trying to put in a snub diode to see if that solved my problem.

I didn't do it right and got some sparks (yes, I should have turned/unplugged things before doing it, I was stupid).

All the lights died on both the power supply and PLC. My dad who is a electrical engineer, said to check the fuse on the power supply. The Fuse is fine.

How do I fix this?
What can I learn from this? (besides fixing things with the power on)

The power supply has overcurrent shutdown. You need to power off for a minute or so to allow it to reset.
Your snubber diode is most likely shorted. Check with Ohmmeter.
Choices for diodes are UF4004, 1N4934, 1N4004.
Band goes to positive side of coil.
Learn about diodes here.

Sounds like your power supply doesn't have good short-circuit protection.

The first week on my current job I put the terminal labels into a MicroLogix upside down, put 120VAC to the the wrong terminals, and fried the Ethernet port (I call this PLC "Sparky" now, that's how it shows up in RSLinx). Anyway, your takeaway should be to always double-check your wiring and don't power anything on unless you're 100% sure everything is right. This time it was a cheap PLC and power supply, what if it was a $10,000 ControlLogix rack?

Thanks kiethkyll
that seems to have been right, though you knew that anyways.

My thinking has been that I get feedback for my communication cable when the relay turns off. I don't suspect that will be the case, mainly because the software says it disconnects when the first relay turns on in the program. Not when the magnetic field collapse when the relay contacts open.

Without a diode, there will be a large spark across the relay contacts as it opens. It won't be long before the relay fails.
The noise from the spark radiates through the air, because it's RF. It doesn't matter whether software is communicating or not.

you are right it doesn't matter whether I'm communicating to run the program, however I was using the click software to track the progress of the program as it was operating, for general diagnostics.

do you mean by RF?

RF = radiofreqency (electromagnetic interference)

jcollins said:

I was getting some feedback from the relay's when they closed

Click to expand...

The problem is when the coil is de-energized and its magnetic field collapses (which is the principle which creates the high voltage in your car's ignition coil).

jcollins said:

that was preventing communication

Click to expand...

What did the comm break down look like?

jcollins said:

snub diode <snip>. I didn't do it right and got some sparks

Click to expand...

If the diode is installed the wrong way, it will conduct when the power side of the output is turned on and connect the power to ground in a near short circuit. The diode has to be installed in the correct direction/polarity.

Take a look at this application note. It should tell you a bit more about what you are experiencing.

I set up the program to start running the conveyor to run 5 seconds after the start of the program. It's at that point that My connection get's cut. I could up until this point change the specific addresses as well as track the "green on the screen". At this point I get a red bar above my ladder logic window that says it can't communicate. I can't immediately reconnect. I hadn't figured out what combination but I've rebooted my computer, let the PLC be powered off for like 15 minutes, and unplugged everything before I can start the process again. I've done it on another desktop that ran windows 8 (I'm running windows 10 as a virtual machine), that's even worse as unplugging the com cable causes the whole computer to crash.

I'm not sure if the coils are causing a large draw that would tie up the power supplies capacity (unlikely IMO), or if it's the feedback from the coil fields, or if the RF which I didn't think about until this post.

To me this sounds like a USB converter issue. What happens if you connect to the PLC and run the logic but leave your outputs unwired. Do you still get the same fault?

it works just fine.

jcollins said:

... unplugging the com cable causes the whole computer to crash.

I'm not sure if the coils are causing a large draw that would tie up the power supplies capacity (unlikely IMO), or if it's the feedback from the coil fields, or if the RF which I didn't think about until this post.

Click to expand...

All of the USB converters I've used will cause the computer to crash with the Blue Screen Of Death (BSOD) if it's pulled while communicating. Any laptop, Win7, ,8, 10. Thank Microsoft when you get a chance.

There is a large current draw when you first energize a coil. Does it fail when you turn the coils on, or when they turn off?

it would appear that after having added in the diodes I no longer have the issue of the communication error. so I'm not sure if it was happening when the coils turned on or off.