Micrologix Timer

Hello,

With your help I have built a PLC trainer to learn PLC's and have now built a small machine with the knowledge I have gained from this forum. Thanks for that.

I have a question, about micrologix timers. I am wondering if it is possible to control the timer amount with a thumbwheel. If you have any information you can offer it would be much appreciated.

Thanks alot.

hmmm... I have never used a thumbwheel to control the preset to a timer, however, one way to do it is search for an analog thumbwheel or a thumbwheel switch with position locks that outputs a 4-20 or 0-10V signal based on the position of the thumbwheel, you would need an analog inout card for the micologix series to get your analog data in. Then scale the 0-10V signal or the 4-20ma signal in your PLC to your desired allowable timer preset value.

Im sure someone else has done this before so be patient and someone will surly have some info on this.

Billhc83,

you didn't state whoch model, so here goes.

you can use a 4 digit thumbwheel. each digit will have 4 inputs, you must wire them to the inputs the exact same way.
you will also need a pushbutton.

assign your value on your thumbwheel, press the pb.
use the FRD or TOD command (i can't remember which) to convert from bcd to decimal. assign a min / max limit to your logic.
then move the number to the preset register, t4:23.pre for example.

regards,
james

I have used thumbwheels to send data words to a PLC. Usually I used a TTL-Source Input module to bring in the thumbwheel setting as a Binary-Coded Decimal number. Once in PLC memory, the word of data can be used however desired, as a timer Preset or counter Preset, or some other program variable. As James said, you can also bring in the data with a standard digital input module by adding a few rungs to create a number from the bits.

Wire your thumb wheel to input 0 thru 3
Mask move that input word into an integer
I'm out of time. Maybe that will get you started.

Billhc83 said:

Hello,

With your help I have built a PLC trainer to learn PLC's and have now built a small machine with the knowledge I have gained from this forum. Thanks for that.

I have a question, about micrologix timers. I am wondering if it is possible to control the timer amount with a thumbwheel. If you have any information you can offer it would be much appreciated.

Thanks alot.

Click to expand...

Shouldn't be a problem. In order to do so, you will need to get a number into the PLC (either analog or digital). Scale it to your time base, and place it into an integer file. From there move it to your Timer.pre. Remember that both the N (integer file) and the timer preset is limited to a 15 bit number or 32,767.

If you need to buy a analog card only for this, or depending on your resolution and number of inputs for the digital binary coded decimal you may find that it is more cost effective to purchase a small HMI.

Hi Thanks so much for the replies, I am working with a ML 1000 L32BWA, so I am only able to work with discrete I/O's. I have only a few inputs used at this point so it sounds like to me from some of the info you have supplied that it is do-able. Wire the thumbwheel to the inputs then convert that to an integer and move that to the timer preset. I will look for a thumbwheel and test it out. Am I on the right track or not?

Thanks again,

Ok first rung, place only a MVM
Source I:0.0
Mask 000fh
Dest N7:0
Next 10 rungs
Place an EQU
Source A N7:0
Source B 0
Then on the same rung place a MOV
Source, what ever you want the preset to be
Dest T4:0.PRE
Then copy the second rung and paste it 9 times
On the first paste, add 1 on the source B of the EQU
And your preset value on the source of the MOV
That should work. But their may (most likely) be a better way

Caveman said:

Ok first rung, place only a MVM
Source I:0.0
Mask 000fh
Dest N7:0
Next 10 rungs
Place an EQU
Source A N7:0
Source B 0
Then on the same rung place a MOV
Source, what ever you want the preset to be
Dest T4:0.PRE
Then copy the second rung and paste it 9 times
On the first paste, add 1 on the source B of the EQU
And your preset value on the source of the MOV
That should work. But their may (most likely) be a better way

Click to expand...

Depending on the timebase selection of the timer, a series of MULs would be more appropriate than MOVs.
If the processor you are using supports SCP, then that would be even easier, done and dusted in one instruction.

Thanks so much for the replies, I am working with a ML 1000 L32BWA, so I am only able to work with discrete I/O's.

Click to expand...

Then you should have 20 digital inputs. If you use all of the possible 5 digits for a timer Preset value (32767 maximum), that would require all 20 of your inputs to input the Preset with a 5-digit X 4 inputs-per-digit thumbwheel switch. If you limit your timer setting to 3 or 4 digits, it would be more doable, leaving a few inputs for other purposes.

There is a way to use regular on/off switches to send binary numbers into your PLC. You use a PLC timer to read all input switches, say every 1 second or every 2 seconds, then convert the switches into an equivalent binary number. 10 on/off switches allows inputting all decimal numbers from 0 to 1023.