logic gate and other things

[-=GST=- Nemisis (cs/cz)]

hi im working on a pic program wich is a stop clock/24 hour clock/alarm clock with 6 chips (18 pin, it would have been soooo much easier with two more output and two more inputs grrrr :lol and 6 seven segments for my school GCSE project. i have alredy made the pics program and all i need to know is if there a logic gate that does

A|B|o(output)
1|0|1
1|1|0
0|1|0
0|0|0

i need this for the alarm part where i have the variables count 24 hours then to give an output from the first(or last depending how u look at it ) 7 seg that only counts one and two so i will use the normally unused out put to turn on a radio.

the other help i need is the radio, i have looked for a design but i cant find a useful one, really all i want is a fm radio with a llinear potentiometer to command the frequency.


also does any one have the design of a 7 seg, just so i know where the +/- go when i draw up my curcuit diagram.

if any one wants to see my finished desing ,just ask but i cant do the programming till im back at school.

 

[-=GST=- Nemisis (cs/cz)]

also, doesne one know where to get a TDA1554 Two Channel Audio Amp Chip in england (surrey/london area) as seen here https://www.aaroncake.net/circuits/amp20w.htm[/url]

 

[Nigel Goodwin]

You already seem to have far more chips than required, you can easily do the logic functions in the PIC software - no need for any extra chips.

One 18 pin PIC might be pushing it a bit, but certainly two (or one 28 pin) could do the job easily - I can't believe you used six!.

 

[-=GST=- Nemisis (cs/cz)]

erm, im using a spread sheet program and i dont know how to code, and i dont think it can be done on the one im using. its called pic logicator. also i can only get 18 pin ones. ne way how could you have all the 7 segs working at the same time using one or two chips, unless you have a 28 pin one with loads of outputs????? 6 pic, one for each seg.

 

[checkmate]

It seems that you are using an excavator to dig a hole where only a spade is required. Only one 18-pin pic is required if you bother to read up on coding. The 7-segment displays could be multiplexed, and the logic implemented easily in software.
As for the logic gate you are searching for, there's no such one. Pick up a book on elementary boolean algebra, and you could probably devise one after reading the very first chapter.
What you need is
A AND (NOT B) or equivalently, (NOT A) NOR B
This can easily be achieved using a NOR gate with input (NOT A) and B, where the NOT operation could be carried out using another NOR gate (With A and 0 as inputs). Since 2-input NOR gates usually come in quad packages, you would only need a single IC.

 

[-=GST=- Nemisis (cs/cz)]

im gunna have to do that, but i will have to make it out of NAND gates coz we cant get NOR ones at our school. the other thing is that i CANT code beacuse i have never been shown, and unless someone sows me i got to do it this way. is there anywhere i could have very simple toturials to code? last thing, what is mulitiplexed? if it means that the 7 segs stay on even when theres no constant input ot it which is what i have now, (ie. 7 outputs for each segment and the last to tell the next chip to start counting or whateva) then i could do that even with the poic logicator software very easy.

 

[Nigel Goodwin]

im gunna have to do that, but i will have to make it out of NAND gates coz we cant get NOR ones at our school. the other thing is that i CANT code beacuse i have never been shown, and unless someone sows me i got to do it this way. is there anywhere i could have very simple toturials to code? last thing, what is mulitiplexed? if it means that the 7 segs stay on even when theres no constant input ot it which is what i have now, (ie. 7 outputs for each segment and the last to tell the next chip to start counting or whateva) then i could do that even with the poic logicator software very easy.

Multiplexing is a common procedure, your existing design uses 7 pins per display, with 6 displays that's 42 pins required. Multiplexing the display would reduce that to 13 pins (7 + 6, rather than 7 x 6) - a massive difference!.

Multiplexing is short for "time division multiplexing", it means you select each display in turn, one after the other - so you have the seven segments all connected together, and use other PIC pins to select the particular display you want. By doing this fast enough it gives the impression of a permanently lit display.

One of my tutorials shows how to do this for a double 7 segment display.

 

[-=GST=- Nemisis (cs/cz)]

righti can see how that works but there another problem, how would i get the outputs to switch between each 7 seg?

like i can say, switch to seg1, do time 9 seconds, swich to seg2 show 1 switch to seg 1 again, do time 0.1 (or something stupidly fast) seg2 show 1, do time 0.1, and so on. is this what you mean?

 

[Nigel Goodwin]

righti can see how that works but there another problem, how would i get the outputs to switch between each 7 seg?

like i can say, switch to seg1, do time 9 seconds, swich to seg2 show 1 switch to seg 1 again, do time 0.1 (or something stupidly fast) seg2 show 1, do time 0.1, and so on. is this what you mean?

Yes, that's the way - in my tutorial I cheat somewhat, as I only use two digits I use one pin to toggle between them - I did this simply so it would connect to a single 8 pin port, in keeping with my tutorial design boards.

For your 6 digits you would use six pins, selecting them one at a time. You could use the same basic method as my tutorial, a timer interrupt generates the multiplexing frequency, and the interrupt routine displays each digit in turn, one each time it's called.

 

[-=GST=- Nemisis (cs/cz)]

that sounds very hard, or at least, very hard to get ot grips with coz im sure its easy once u get going. the only thing is i cant code, i already have a design. it alows me to have a stop watch cprogramable clock and programable timer, even if it does use alot of chips, hey im not paying for them also this is a gcse project, have a clock even if it does use 6 chips probably wont affecy me till im old. non the less i will look at what uve done and i will do my best to learn code, as electronics is a fuure carrer prospect for me i have plenty of time to learn, after all im only 15