integer to 7 segment
- Thread starter roxusa
- Start date
How do I separate the integer into 1's 10's & 100's to write less program.
My display is 3 digits old school 24 vdc lamps configured with 4 lamps per segment.
I am running 503E RIO with a SN, I can fire the segments with a relay out put if needed.
My display is 3 digits old school 24 vdc lamps configured with 4 lamps per segment.
I am running 503E RIO with a SN, I can fire the segments with a relay out put if needed.
You need to write logic for a BCD to 7-segment Decoder. For each of your 3 digits, "XXX" you can have segments lit to produce numbers 0 to 9 for each of the 3 digits. So for each number, figure out which segments have to be ON, then write rung logic: IF Input 0 is equal to "1", then OTE outputs for these segments 1 to 7 needed to light up a "1". If Input 0 = "2", then turn on the segments needed to light up a "2", and so on for the 9 0-place digits. Repeat for the 10's and 100's place.
For a complete 3-digit decoder, you would need logic for each digit 0 to 9 for the 4 outputs for each digit (9 x 4) = up to 36 rung branches for each of your 3 digits, but some segments will not be lit for some digits so the total branches will be less.
It should have 7 lamps per segment, but only 4 inputs per those 7 segments, make 1 digit from 0 to 9. Your 4 inputs to each digit should be labeled the power of 2 for that position - 0,1,2,3 (because 2^0 =1, 2^1 = 2, 2^2 = 4, and 2^3 = 8). To light up any digit, say "9", turn on bits that add up to a BCD 9 (inputs 3 and 0).
For a complete 3-digit decoder, you would need logic for each digit 0 to 9 for the 4 outputs for each digit (9 x 4) = up to 36 rung branches for each of your 3 digits, but some segments will not be lit for some digits so the total branches will be less.
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Are you assuming that his BCD to 7-segment decoder is outside the PLC? I read it that he is driving lamps from PLC outputs to illuminate each segment. That would mean 7 outputs per digit.
No, I did not have to assume here, but only believe what he said:
If these were internal display LEDs, he would not be able to fire them with PLC outputs (no access to each segment). Except I think he meant 3 digits and 7 lamps per segment BUT 4 Segment Inputs per digit. He mistook the number of input terminals (4) on the digit for the number of segments.
Roxusa, do you really care if your segment decoder logic is the least expensive, or do you just want to get it programmed? Does your digits turn on a segment (go high) when the inputs are high, or do the segments go low when the inputs are high (inverse logic)?
I believe that your old 7-segment display digits are old-school just like you said, and look like the ones in this picture, with 4 inputs per digit.
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My Display is an old COPAR speed & Downtime Display.
Each of the 7 segments consists of 4-24vdc mini lamps
It displays the speed from an encoder wheel on machine and shows accumulative downtime when stopped. I wanted to write this logic into
the SLC I already have running other functions on the machine. I could run another Blue Hose up to it with Flex I/O
I have the Speed & down time already configured in the ladder in Integer File
Just not sure how to fire segments with out writing a mile of ladder logic
I am not firing a 7 segment display driver with BCD, I would like to fire them (each digit) with a 1794-ow8
Each of the 7 segments consists of 4-24vdc mini lamps
It displays the speed from an encoder wheel on machine and shows accumulative downtime when stopped. I wanted to write this logic into
the SLC I already have running other functions on the machine. I could run another Blue Hose up to it with Flex I/O
I have the Speed & down time already configured in the ladder in Integer File
Just not sure how to fire segments with out writing a mile of ladder logic
I am not firing a 7 segment display driver with BCD, I would like to fire them (each digit) with a 1794-ow8
Okay, I get the picture now. Each number of your display has 7 segments, but each segment is made up of four 24 VDC lamps.
No problem. Use ONE of your 1794-OW8 Outputs to turn ON/OFF ONE segment of 4 lamps. For each digit, you will need 7 OW8 Outputs. All you have to do is write logic for each set of 7 outputs, so they they work as shown in the Truth Table of my Post #5. You can ignore the "Segment IN" column and instead ONLY use the "DECIMAL NUMBER" AND the "SEGMENT OUTPUTS". For each Decimal Number, write PLC logic to produce the Segment Output. For example, suppose you assgin your first 0's place digit to your first 1794-OW8 module. (You will need a module for EACH of you display digits, with one spare output per module, unless you want to get into complicated multiplexing). You should use OW8 Outputs 0 to 6 for your first 0's-place digit segments A to G. Your logic for these 7 outputs would look like this: (later).
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Your logic for these 7 outputs would look like these rungs, 1 rung each for numbers 0 to 9. You will need similar logic for each digit in you display. I will leave it to you to figure out how to pull out each place digit (0's, 10's, and 100's) from your numbers to be displayed.
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I would probably save each new set of 3 digits as a String (use AIC to convert Integer to String). Then use 3 versions of the RSLogix instruction AEX, with Indexes of 1 (0's digit), 2(10's digit), or 3(100's digit), and a Number setting = 1. Pull out these 3 new extracted 1-digit strings for each digit, convert to a back to an integer number using the "ACI" instruction, then run each integer number through the 7-Segment Decoder routine, then send the chosen Output Word to the PLC output module for that number position. That's all!
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