Too much current into PLC

[j.sean.gg]

Today I was working on my project for school and we were using a power supply with 24V and we accidentally had the current at 0.9A. We heard a pop in the PLC and it started to smell a little bit. The PLC is a Micrologix 1100 series B 1763-L16DWD. We didn't try to power it on after that. I was wondering what may have happened, if we blew a fuse or a capacitor or something. I don't know anything about PLC's really so I was wondering if we can replace a part and get it back running or if its fine to boot up still.

 

[Bit_Bucket_07]

Today I was working on my project for school and we were using a power supply with 24V and we accidentally had the current at 0.9A. We heard a pop in the PLC and it started to smell a little bit. The PLC is a Micrologix 1100 series B 1763-L16DWD. We didn't try to power it on after that. I was wondering what may have happened, if we blew a fuse or a capacitor or something. I don't know anything about PLC's really so I was wondering if we can replace a part and get it back running or if its fine to boot up still.

I would say that it's not fine to boot up.

You don't specify to what you had the power supply connected, but the pop sound that you heard and the smell that you smelled implies that you damaged some electronic component(s). You may or may not have also blown a fuse, but if you did, it probably wouldn't help to replace it without first replacing the damaged component(s) that caused the fuse to blow.

 

[j.sean.gg]

So after talking to some people it sounds like the current wasn't the issue at all but we instead drove 48 volts into the PLC itself. In terms of over voltage for this particular model, does that mean we could have potentially fried the entire thing? I looked in the user manual and couldn't really come to a good conclusion on how bad it hurt the overall system.

 

[parky]

The fact is that ther PLC will only draw the amount of current it requires you cannot put more in so even setting your PSU to something like 5 amps when it only requires 1 amp it will only draw 1 amp unless the PLC is already faulty, however, 48 volts onto a PLC that is rated at 24 volts it probably will pop some components. it hopefully will only damage the power supply regulator circuit so could be a reasonably good chance of repair with luck the regulator or perhaps a capacitor & resistor will have burnt, however, there is no guarantee. once had an engineer connect 240v onto a PLC that was 24v, it blew the regulator & burnt a resistor everything else seemed ok, it worked for a while but it did fail at some point probably othe components suffered with such a high voltage so we replaced it.

 

[Tom Jenkins]

V = I x R. Applying twice the rated voltage puts twice the current through the load, We professionals call the result "letting the smoke out".

 

[Puddle]

The only thing to do here is to remove the plastic casing and see where the scorch mark is. If you're lucky, it could be something that can be replaced with some soldering skill. Most likely not though.

On the plus side, at least this is a school project and not something on a production line that a customer was expecting to run today.

You're not the first and won't be the last. I'm sure plenty of people here have seen enough people mistake a DH-485 port for ethernet and those don't mix well with laptops.

 

[dummy_bit]

Hopefully its not like a MicroLogix 1400... its an epoxy coated circuit board. Might need to get with an electronic repair company to remove the coating without further damaging the board.

I tried putting the magic smoke back in the 1400, but it didn't seem to work.

 

[JesperMP]

V = I x R. Applying twice the rated voltage puts twice the current through the load [..]

And twice the current means that the power dissipated in the load is 4 times more.
P = I² X R

 

[j.sean.gg]

Guys good news, my teacher looked at it and it looked like it just blew a zener diode. So thankfully it still works and we are able to continue with the project.

 

[danw]

Dodged that bullet . . . . .