7-segment/calculator project

hi! im new here and i dont know if this is the right place to post this...if it's not, then im sorry, this was the closest i can find that relates to my problem. anyways...

my teacher gave the class a project which uses 7 segment displays to create a calculator. And the only specifications she gave was:
- use 3 7-segments; the first two will display the two numbers to be added. and the other one will display the sum of those two numbers.
(only addition)

..and i don't have the slightest idea how to implement this..can anyone help please..any suggestions or circuit diagrams will be very much appreciated...thanks!

Are these 7-segment displays a single digit each?

If they are single digit the total maximum you can display is 9 in decimal of 'F' in hexadecimal which doesn't use the full range of digits you could show on the first two displays.

The technique for handling just three digits is quite different to handling three different multi-digit displays.

Brian.

yes...they're single digit 7-segments.

How can the teacher give you a project were you don't have any idea.

Is this her fault or your fault ?

What you need to do is:

- Learn how the 7 segments work
- Decide what to use for the addition, this depens on you knowledge level and the purpose of your class. It could be done with microprocessor or logic circuits.

well, she gave it in advance coz we only hav about a 2 weeks to do it...and we havn't even discussed the 7-segments yet..we're still learning about the basic logic gates..and i can't w8 for her to finish all the discussions before doing the project.. coz then, i wont have anough time to do it..

i already know how the 7-segment works..now, im trying to find out how to implement the adding part..

what other interfaces you are using??
how you are receiving two numbers..??
First try to display basic number on seven segment display...

If you are at the stage of learning basic logic gates, this is what you should be thinking of:

1. adding the numbers is easy as long as they are in binary.
2. the 7 segments have to be turned on or off in combinations to make numbers appear.

So breaking your problem down, you first have two digital inputs which can carry a number in binary. Assuming you want to use at least the numbers 0 to 9, you need 4 binary inputs for each of the numbers you are going to add. So for the first input you have to convert the four bits into seven different segment signals. You have to do this again for the second four inputs so the second LED shows it's number.

Now you have two sets of 4-bit numbers and you want to show their sum, for this use a 4-bit adder circuit. The output of the adder also has to be decoded into the correct seven segment pattern so it shows on the third LED.

Hint - if you are using TTL logic, look at the data sheets for the 7447 IC which decodes 4 binary bits into the seven segment signals and look at the 74LS283 data sheet for details of a full adder IC. Even if you are not using these devices, their data sheets will help you understand the technique.

Brian.

thanks betwixt. that really helped me a lot.