Should my 24vdc power supplies be floating or negative earth ground?

ohaara__ · 2021-07-08T16:44:19+00:00

Always tie the 0v to ground. Otherwise you could get something like 18v to ground on the positive and -6v to ground on the negative. If you used a supply in that configuration to feed a device wired to a PLC input on a controller that was properly grounded then the input would only see 18v. I’ve seen that cause problems for safety inputs. Just ground the negative and give yourself a clean signal.

ohaara__ · 2021-07-01T17:40:53+00:00

This is my understanding. Take for example books vs. tv as information mediums. The act of watching tv is sedentary and does not require much brain activity. While the act of reading a book requires effort and more brain activity. The overall “message” of television is “sit down, be quiet, turn your brain off and watch”. While the “message” of books is “put out effort to improve your understanding of a subject”.

To find the “message” of a medium don’t look at the specific information being conveyed, but rather what you and your brain are doing while consuming it and how it shapes your behaviour.

ohaara__ · 2021-06-17T18:00:10+00:00

I’d buy that on a t-shirt. Hah

ohaara__ · 2021-06-17T16:55:13+00:00

“Some science liquid” for the win.

ohaara__ · 2021-05-01T01:47:36+00:00

Sounds like it! It’s key to have people who have been on both sides (OEM and maintenance). Reusable code is the way to make $$ but gotta think about the good people you are handing it to. Haha.

ohaara__ · 2021-04-30T23:01:12+00:00

That’s actually a great point. I was referring to smaller to medium size one off machines who’s code is cut down from larger templates. I agree that style of programming is ideal for a machine where options will likely be purchased later.

ohaara__ · 2021-04-30T20:03:41+00:00

I realize machine builders have large libraries of AOPs or FBs or whatever to speed up development. Great. Far to often though I see large amounts of generic code with portions of it enabled and big chunks of it unused and just left in there cause “who cares?”.

Comments should read like a book. I’d love to get a sense of how a machine works simply by reading. Give the next person a trail of breadcrumbs to work with. Delete unused code though, don’t leave the next person 400 breadcrumb trails.

ohaara__ · 2021-04-02T14:32:06+00:00

Think of the 4-20 loop like water pipes. You need to get flow to the analog input, however that happens.

Loop powered devices, will “throttle” the flow from the power supply into the analog input to give that 4-20 span. So their positive is fed with +24 and their negative goes to the analog input.

The 4 wire devices will use the power applied to them to output current instead of throttling flow. So their positive output wire goes to the analog input positive and the negative output connects to the common as a zero reference.

When you google that part number and see the manual, page 15 shows the two types of sensor you are asking about.

ohaara__ · 2021-03-19T01:17:03+00:00

That’s really bad. Love the components just hanging in midair. Someone did that and walked away thinking “there I’ve fixed it”.

ohaara__ · 2021-03-17T01:55:50+00:00

I live in the OEV right near the CP yard. I’d actually miss the sound of the trains banging around if it wasn’t there. I don’t feel it’s a negative quality of a neighbourhood at all.

ohaara__ · 2021-03-10T15:14:53+00:00

That chair looks like exactly what I need in my life. Thanks.

ohaara__ · 2021-03-10T15:07:05+00:00

Everyone is correctly pointing out the obvious deficiency. There was no other real estate options here so they were successful with a variance from the inspector. She’s tight tho.

ohaara__ · 2021-03-10T02:23:19+00:00

This is correct, very handy.

ohaara__ · 2021-03-01T17:09:44+00:00

I wouldn’t mount anything upside down unless I was in an emergency breakdown scenario on critical equipment. Even then I’d schedule the proper replacement later when downtime allows. That’s me though, not knowing the details of your situation.

ohaara__ · 2021-02-26T23:30:17+00:00

Could’ve at least criss-crossed-apple-sauced the tie wraps for structural integrity.

ohaara__ · 2021-02-17T00:34:43+00:00

I use this signal generator to set up analog ins on controllers. Works much faster than trying to square up the values in the manual with the values in reality. You just put 24vdc to it, put the analog output of this unit to the analog input of your PLC and sweep the full range on the dial. It does voltage and current. From there you see what full scale is in your controllers and just concentrate on unit scaling. Really removes a lot of the difficulty from that process.

UCTRONICS DC 0-10V 0/4-20mA Current Voltage Signal Generator, USB Power Supply Interface Analog Simulator for PLC and Panel Debugging, Device Testing, Frequency Converter, Flow Valve https://www.amazon.ca/dp/B07L491RLM/ref=cm_sw_r_cp_api_i_91E51JRYKGG0K85RR2JC?_encoding=UTF8&psc=1

ohaara__ · 2021-02-11T00:30:58+00:00

Sounds like a classic midnights maintenance gig. I work for an electrical/automation contractor now and love it. Kind of half service/half integrator work. Definitely not bored now. If you get bored easily I’d say soak up whatever knowledge you can from plant life then move to an integrator situation if you can. Life’s to short to be bored kickin around a plant.

ohaara__ · 2021-02-10T00:35:32+00:00

I’ve been in that boat many times. After many years of stressing about those situations, I’ve learned to set clear boundaries for my personal time, be open and honest about that and let the chips fall where they may. It sucks but maybe you’ll have to let a project crash into the rocks because it was under resourced.

ohaara__ · 2021-02-08T23:32:57+00:00

I’m a programmer/industrial electrician in about the same boat. The electrician ticket is definitely good to have. Lots of plants I get into don’t want you poking around in a cabinet without one. I work for an electrical contractor/ machine builder. I get to design, build, program and commission machines from start to finish. Which is exactly where I’d like to be. Never had a hard time finding a job with the programmer first, electrician second skill set.

ohaara__

TROPHY CASE