operater-adjustable timers

jonton · Aug 1, 2002

I made a small ladder for a PLC to be installed in an plastic moulding machine. It interupts some outputs, does some outputs of it's own using timers and limit switches, then permits machine to carry on. Simulation works well on my laptop but machine operater needs to be able to vary the timers using a pot or similar. How to I achieve this?

Dave Williams · Aug 1, 2002

Try a small HMI, Panelview, Panelmate, etc.

jonton · Aug 1, 2002

OK thanks. Suspected there might be a thingy just for this. What is an HMI?

Steve Meisel · Aug 1, 2002

Human Machine Inteface - usually a screen with some sort of keypad.
Check with the distributer of the plc you are using and they can help you out.

jonton · Aug 1, 2002

Thank you Steve. Will check this out but sounds a bit expensive. I could just by some timers for $70 au ($35 US), but now cost is defeating the idea of using a PLC.

Steve Meisel · Aug 1, 2002

What plc are you using?
Brand/Model#
Someone may be able to help you find fairly inexpensive way around buying a bunch of timers. How many timers to adjust?

longshot · Aug 1, 2002

Thumbwheel

You can use a thumbwheel, a typical input device, to connect to your PLC if there are some input points left or if you can put a expansion module(block) into the PLC.

Each digit use 4 points input. Convert those BCD data into a integer and move to the present value of the timer you want to set.

Refer to the other thread for the connection diagram.

jonton · Aug 1, 2002

PLC is Pharao 21 and is the 1st software I have played with. Nice drag & drop ands and ors etc. I would only use 2 timers for basic system but can do twice as much with 4 on some. This unit has its own display already and some programmable front panel buttons, but operators are best kept away from there.

jonton · Aug 1, 2002

Just remembered I may have seen a PLC with pots or ajustments on it's front panel. Has anyone seen that?

longshot · Aug 1, 2002

A PLC with a pot

Yes, you are right.

I was just about to say that. Mitsubishi's FXon has a pot on its front panel. If you can extent a cable to put that pot away from the PLC, your operator can use the pot without open the control panel to access the PLC.

Eric Nelson · Aug 2, 2002

And Automation Direct's DL-240 has 4 pots on the CPU... Very handy!

I didn't investigate much, but it looks like this Pharao is one of those "Smart Relays". Why not just use the built-in interface to adjust the timers? I really doubt you'll find an HMI that will interface with this unit.

beerchug

-Eric

gbradley · Aug 2, 2002

Operator Adjustments

If you have a spare input, you can adjust the time without using an HMI.
Hook up the input to a push button, then every time the button is pressed increment the counter by 1 second. after 10 or 15 increments, you can automatically return to the starting point.
You will have to use one shots.
The down sides to this scheme is knowing how close you are to the wrap around. If you have a spare output, you can blink an indicator led.
Good Luck

jonton · Aug 4, 2002

Well this is certainly the place for some good advice. Much appreciated. I guess the Direct unit with 4 pots sounds easy and worth checking out. Thanks Eric. Thanks all.

operater-adjustable timers

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