I just programmed a timed filtration system, and was very pleased at how simple the code is to handle a simple on/off timer with selectable day-of-the week:
Pretty neat, huh? I coupled that with a simple screen letting the user set start and stop times and select the days to run:
and the lion's share of the job was done.
But there's much more to Unitronics timekeeping than just simple timers. In the forums, there's been some discussion of the difference between RTC and UTC, the use of U
If you were to look over my shoulder while I'm working at my desktop or laptop PC, you'd probably notice pretty quickly that my computers don't look quite like most. Firstly, my keyboard doesn't have its letters in the usual "QWERTY" layout - I use the Dvorak layout, optimized for faster typing with minimum finger movement. I credit that (along with the refusal to use a trackpad) with curing my carpal tunnel syndrome - it took a month or so to switch over, but I've never regretted it. There's
When Programmable Logic Controllers were first introduced, their programs were geared toward the replacement of simple relay circuits. Logic statement 0 was processed first, then logic statement 1, and so on until an END instruction was reached. Then the PLC's supervisory software, or "Operating System", would do some housekeeping - update timers and counters, send outputs to the physical devices, read inputs from the physical devices, and run the user's stored program again. Logic statement fiv
One of the requirements I frequently find in customer specifications is that Operator Terminals shall have eight hierarchical levels of password protection. The idea there is that an operator, for example, enters the level 1 password to do operator things, and a supervisor can enter a level 2 password to do anything the operator can do, plus supervisor stuff. I have yet to actually see an application where all eight levels were used for anything, but somebody somewhere once decided that eight
So I'm easing my way back into VisiLogic land, in-between phone calls from TV trucks. The other morning I get a call from one of our techs on a startup somewhere in Texas, telling me that the customer is requesting that all the panels on the "A" side of the facility have their primary power feeds fed from the "A" side breaker panels, and that on the "B" side, "A" side breakers should go to the secondary power inputs. For this they wake me up? Just swap the feeds on the "B" side, right?
It's been a couple of weeks since I've run VisiLogic - that's a bit unusual for me lately, since I generally don't go a day without doing something or other on a Unitronics system. The reason is that I've been spending my time on two of the nation's newest mobile HDTV production trucks, installing control systems which combine an embedded Linux computer with networked frames of Mitsubishi PLCs and a cross-platform PC GUI written in Perl/Tk.
Working as a controls systems integrator has its bene
I'm Phil Salkie, Lead Engineer for Howman Controls in Edison, NJ, USA ( http://www.howman.com ). We're a small distributor and manufacturer of industrial controls products, and a UL-508A panel shop. Howman has been in business for about 30 years, and I've been here for 25 of them - if you've watched a sporting event on TV, dealt with a large bank, had a wound sewn up, or bought a banana, a gallon of gasoline, or a computer chip, there's a good chance that some of our hardware or software