Righty, doing my AS-level project at the moment and i've come up against this. I'm looking to input a 4bit binary code using four two pole switches and i'd like to display this number in decimal on two seven segment displays. I know how to wire a decoder and display so thats not an issue but the problem is that my binary word can go up to 15 and a single display can only do 9. Obviously i could connect the logic gates so that the tens display shows a one when the input is 10, 11, 12, 13, 14 or 15 but this would involve using a 5 input OR-gate and a load of AND-gates, which i'd like to avoid if possible. Any thoughts welcome!
A quick scan thru my chip books found TTL 7447 but the A-F characters are weird and the CMOS 4511 only decodes 0-9. There are hex displays (TIL311) that decode and display all 16 digits but "7 Segment Problem" is the title. I will look through a few more books and catalogs to see if there is a one chip solution to display HEX on one digit. 123456789AbCdEF is the way I would display it.
That PPROM (read article) is worse than his present solution. Another solution is to use a 8bit wide programmable memory. The smallest I could find was 32*8bits (74s188, 74s288). With 8 bit output you can drive the 7 segments and the DP. Either throw away (not use) the extra memory or use it as selectable character sets (fonts). The only problem is finding a programmer, but being in an AS course the school may have one somewhere.
The problem is that my sylabus only covers the use of basic seven segment displays and decoders, and of course logic gates. Will ask the head of department next week and post back with what he suggests . Thanks for the help guys
Feed the nibble through a 4-bit adder, with the second set of inputs set to 0000 when between 0-9. Then, use a comparator or 1337 logic to detect when above 9, which sets the adder input to subtract 10, and lights up the tens display to show a '1'. The adder output then drives the units 7-segment decoder. Cant remember offhand if you can do subtraction (may depend on which series you use) if not just add enough that it rolls over.
Great idea! It fulfils the original requirement "i'd like to display this number in decimal on two seven segment displays." and is more elegant than a bunch of simple gates. I don't know how we got sidetracked on one Hex digit. BjD - I am old so what is "1337 logic"?
4028 is a 1 of 10 decoder. The 4511 is for common cathode and the 4543 can be used for either common anode or common cathode 7 segments. Also dirtbiker has not stated which family of logic he is using.
Not entirely sure what you mean by "family of logic" but its just a four bit binary word. Our electronics dept. only has 7-segment displays that deal with binary, but i could probably order some that deal with hex, although i'd like to keep it in binary if possible! Finally, i dont understand what's meant by "nibble"? Cheers guys.
Family of logic refers to the type of chips you're using, 74 series is TTL, 4000 series is CMOS, etc. A nibble is half a byte (geddit? ), aka 4-bits And by 1337 logic i was refering to the whole hacker speak thing. Just me trying to be funny
You say "Our electronics dept. only has 7-segment displays that deal with binary". Do you mean that each of the seven segments has its own pin? Skylined - No harm, I just did not want to sidetrack dirtbiker again. Like with the whole single digit HEX display thing.
