DL240 Pots for more then one timer each.

So I've got this project where I need a LOT of adjustable timers (each with different times). So I was thinking of using the 4 Pots on the DL240 to adjust up to 12 timers (some fast timers also). My idea was to use a spare input or two to switch between one set of timers and another. It seems doable to me but I'm wondering how complicated it's going to be to program, and for the operator.

Any comments, or suggestions appreciated...

Thanks, Mike.

Wouldn't it be less complicated to use an inexpensive HMI panel?

With a pot, all you can tell the operator is "clockwise is more time, counterclockwise is less time". With the HMI, the operator can both set the time he needs and see the value.

Steve, I guess your right, but I need to make it REAL simple for the installers... Besides it's a NEMA 7 job, and that opens a whole new can of da-worms.. Additionaly Port 1 must be left open, and Port 2 is for the modem...

The insatllers have NO PLC expierance so giving them a laptop is really not a good answer either. Many of the timers will be used for the 2 speed AC motor/brake action, so the idea is to allow adjustments between the brake, motor, and start and decell transitions and such. In this case the simple act of turning a pot would be much better.

How about a MOBILE PU (for Programming Unit). They hook it, setup, and bring it back at the shop?

The HMI that is.

I did something very similar to that and had nothing but problems with the operators. I used switches (actually one selector switch) to change which timers would be used but used pots on the control station to set the times, I did this because I only had one analog card to connect my pots too. The operators had a "cheat sheet" to show what did what but never got it right, always had the switch in wrong position for the process and/or set pots wrong.

After about 3 months I converted it to use an HMI to set the variables, actually developed a batches which would set default values for that batch that minimized the need for changes made. The HMI allowed me to setup more options for batches.

I guess alot depends on the operators abilities plus how well they get trained. I know it will work but how well depends entirely on the operators.

Just a thought, if using the pots ON the DL240 which I assume will be in a NEMA 7 cabinet why couldnt you mount an HMI inside the cabinet...either way they would have to go to the PLC to make the modifications.

Are these adjustments strictly for setup or will the machine operator need to tweak them after the installers have gone back home?

Let's say that pot number one controls the preset for three timers. When switches X0 and X1 are both on, the pot setting is moved to timer number 1 preset.
When X0 is on and X1 is off, the pot value is moved to timer number 2 preset.
When X0 is off and X1 is on, the pot value is moved to timer number 3 preset.
Now, once you've set all three timers to the preset you want, and the pot is in the position corresponding to the preset setting for the last timer you set. You change the X0 - X1 switch positions and the current pot value gets loaded to a different timer preset. What sort of problems does this cause?

You might be better off doing the whole thing with discrete inputs. Four switches to determine which timer you're adjusting and two more to INC and DEC the preset value by a fixed increment.

We'll Ive got some OP panels in stock, so that's really an option. Our guys wont be maintaing the equipment, and the guys that will be..well sometimes they like to push buttons indiscrimitly to see what happens... I really need the modem, so that makes the HMI/OP panel issue a little more diffucult. You see this panel cover has somthing like 40+ bolts in it. Also the job is a confined space, hence the modem, so you can see whats going on before durmming up the Haz team to go to the job for repairs etc... The Pots/timer adjustments are to be used just for inital setup, and VERY infrequently thereafter. I need a way to adjust the timers that would be very intuitive to a non-plc type tech.

Ron bring up some very good points, that's what I'm afraid of.... What may seem simple to you and me likely wont be to others with less expierance.. So KISS is the keyword.

I guess I should just start playing with it, and seeing how it turns out.. I actually have a good idea of what I gotta do. It's as to wheather or not it's a good idea is really the question..

Thanks for the input. Mike.

Budget allow adding an ECOM or COProcessor module? This could eliminate the port issues.

As the cost of the equipment is a smiggin of the total project cost, I really dont have a problem adding another com module, and HMI of some sort. I'm going to play with the pots for a day and maybe then if it dosnt work out go and get another DCM and go with the OP module, OR get an analog card and a few pots from the local electronics shop.

We'll see... Thanks, I'll keep you posted..

Mike.

Technically your idea is certainly do-able. However, I tend to agree with Ron that it could get confusing for some. As odd as this may sound the fact that people will need to make adjustments infrequently will tend to work against you. Doing something that isn't extremely intuitive is OK if you do it all the time. If you have to do it once every few years it gets a bit tougher to remember what you need to do.

At the very least I would use something like a DV-1000 or some type of display only device just to tell them what they are adjusting and what the value is. You could leave this ijn the cabinet and plug it in only when needed. Using the pots as an adjustment device isn't a bad thing. They just need to know what they are influencing.

Keith

Mike

I thinking about something like EZ220/240 you can pre program it in your office with label for each timer and with the limitation you want for each timer.
They can connect it to the free port or the modem port during the installation.Them return the modem back and return the unit back to you.
I made someting very similar to my customer to set up mashine with out any PLC knowlage.

In my opinion, Mike, you will be dollars ahead adding a DCM and a small operator interface like the mono EZ-Touch. By the time you get done with programming, training, phone calls, service trips, and general BS it will be much less $$$.

As for the Explosion proof issue, you can use a deadfront panel inside a windowed enclosure - they are available from several sources. I believe you can also get serial converters that include intrinsic safety barriers. I'm not in the office now, so I can't give you the names. This would let you put the O/I in a safe area.

Ok so I guess it's a small HMI. I've got some OP Panels so I'll use one of them.

Thanks a bunch for your comments...

Mike..

Sorry to chime in late on this topic, Mike. The consensus seems to be to use an HMI, which is what I would recommend also. The onboard pots can be handy, but as Keith mentioned, adjusting them without seeing the value would be confusing for the operators.

I have used them in the past on occasion, but in conjunction with an HMI. Back then, I was using the Optimate panels, and providing timer adjustments was a chore. What I did was simply let the user display the pot's value on the screen so they could SEE the setting.

I have also used them as discrete switches to turn options on and off. With the min/max values set as 0 and 1, fully CCW = OFF, and fully CW = ON. Eliminated wasting an input for rarely changed selections...

elevmike said:

The Pots/timer adjustments are to be used just for inital setup, and VERY infrequently thereafter. I need a way to adjust the timers that would be very intuitive to a non-plc type tech.

Click to expand...

Here's my low-cost, operator-friendly solution...

Optimate OP-420 display and cable to port 1 - $145 (that's the low-cost part). I would use an Optimate over an EZ-Text because they get their 5V from port 1, so it's a cinch to connect/disconnect while the machine's running. No separate power supply connections. They can just plug it in whan they need to, freeing up port 1. Also much more comfortable for handheld use. No A-D 'bat wings' getting in the way...

Create a simple menu of timers that the operator can navigate with the function keys (F1 - Previous, F2- Next). This will display the names of the timers and their current setting. If an operator wants to make a change, they scroll to the respective screen and press F3 to request the change.

Now the display shows the current setting on the top line (for reference), and the value from the pot on the lower screen. The operator adjusts the pot to get his new setting and presses F4 to 'enter' the new value. This writes the pot's current value to the timer preset.

If the operator decides not to 'enter' the new value, they can press F3 again to abort the change, and return to the timer menu. Always give them an 'oops' choice!... :nodi:

This would require minimal programming in the PLC.

beerchug

-Eric

Hey, Thanks Eric! I've got a OP 420. I had no idea about the power supply thing though... Anyway I'll get to work on that in the AM.

Thanks again..

Mike