Two weeks ag0 I had an issue with the analog outputs on a BRX36 with sinking outputs. I thought the analog outputs would be sinking too because there was no polarity indication on the diagram for analog outputs. I also didn't realize the analog outputs didn't need an external voltage source. I got past that and it is working fine. I think a little more information on the analog output diagram would make things clearer. A simple plus sign on the output channels would have helped. a note that these are active outputs not passive would have helped too. I've been doing this a really long time and it makes me feel really stupid to get caught on something like this.
So moving onto another project that was wired by a helper about 6 months ago I found out I did the exact same thing on the same PLC for both the internal analog outputs and the external analog outputs, putting a -24vdc to the commons and a plus 24vdc through a 32ma fuse to the load and the output. The output isn't sinking it's sourcing so it blew the fuse. Realizing the problem (experience lets you recognize a mistake when you make it again) I unplugged the connectors. The outputs are all set up for 4-20ma and this time I can't get anything other than 4.0 ma out of any channel even on the internal ones. I was able to get correct variable voltage out of the internal analog though when set for 0-10 output.
Simple test. Outputs are scaled 0-18000 to 4-20ma. Use a move instruction to put a value in RY0, RY1, RY2 and there is no change in the outputs. So maybe I damaged the I/O but it seems surprising that all channels put out 4ma if there was damage. So are the internal analog sharing circuitry that would disable both if damaged?
Been a bad week, I blew the direction inputs on 4 Yasakawa Servo drives when a year ago I missed a warning note in the 647 page manual that the pulse and direction are the only inputs that can't handle 24vdc and need dropping resistors!
Topic: BRX Analog output problems (Read 8542 times)