# Homework Help: How to conect 7447 in circuit board to make 7-seg desplay workin

1. Nov 12, 2008

### dubai boy

hello everybody i am glad to find this websit and hope its gona help i am student in my last year in betec deploma course and have to do my iva wot is my graduation project so i am willing to do wind speed indactor and i am stuck kn in converter to change the 8bits to 7-seg then to display screen ,,,

i got two 7447 wana conecte it to the circuit board bt do no how to make it work and give me the digit number?

is that all wot i need or its som staff missin to make it work?
1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

2. Nov 12, 2008

### Staff: Mentor

I'm not sure I understand your question (it is not worded clearly), but I'll try to offer some help nevertheless.

You want to make a wind speed indicator with a single 7-segment display? You will display wind speed as 0-9kph? Or will you use two 7-segment displays to be able to display a wider range of speeds?

What are you using to sense wind speed? You say you get an 8-bit quantity -- how are you making that? 8 bits gives you a 0-255 number....what is the calibration to wind speed in kilometers per hour?

There are ICs that convert 4-bit binary numbers directly into the 7 segment drive lines -- do a little google searching to find those ICs. If you want to make your own instead, writre out the truth tables for each of the segments based on a 4-bit input number, and design the logic based on a Karnaugh map for each of the segment truth tables.

3. Nov 12, 2008

### dubai boy

sorry 4 my writing or nt make it clear i got a fan which is spining by wind conected to mini motor which is change to generator to prduosing voltage so the voltage gona go thrught the a/d convertor so the convertor gona give me the reading in 8bits i did some reasirch and find the 7447 gona change the 8bits to 7-seg deget then i can read it in display screan so far i am stuck in how can i conect the two 7447 chip in circuits board and i gona read the wind speed by k/h then i gona add m/s mile knots so if i miss somthin could are u ppl be kind enugh to aske and thanx aloot

4. Nov 12, 2008

### Staff: Mentor

Okay, so it sounds like the initial problem is how to make a 2-digit 7-segment display from an 8-bit number. Well, since a 2-digit display can display 00-99 (assuming you don't do a HEX display), then you only need 7 bits from your ADC. The typical way would be to ignore the lsb of the 8-bit ADC output, and convert the upper 7 bits to the drive for the 7447 chips. The easiest and quickest way to do that, is to use a microcontroller (uC) to read the 7-bits of the ADC output and do the code conversion to form the 8 drive lines for the two 7447 chips. Alternately, you can do it in discrete logic, it will just take more work. You will need to write the truth tables for the two digits (the tens digit and the ones digit), and show how to convert from the 128 possible 7-bit codes to the 100 decimal codes for driving the displays. Be sure to pin the number at 99 for all readings over 99.

binary to decimal converter IC "2-digit"

and look around at some of the hits. Have fun!

5. Nov 12, 2008

### Staff: Mentor

BTW, keep in mind that we do not do your work for you. So we will not post circuits and papers that will help you short-cut figuring this all out for yourself. The hits you will see from that search will help you with some background information, but there are no exact implementations of how to do it. That is up to you to figure out and build.