# Circuit that takes a pulse from a 555 chip

1. Nov 17, 2004

### Tom McCurdy

We currenlty have a circuit that takes a pulse from a 555 chip and goes through two divide by ten 7490 switchs to create a binary counter that counts up to ten. We are trying to figure out how to convert this binary which we have displayed in regular leds into a 7 segment LED - (LN514rk)

any help would be great.

2. Nov 17, 2004

### Averagesupernova

Don't remember the number but there is a seven segment driver made specifically for this. If you cant find this, set it up using gates to get 10 separate outputs and then diode or those to drive the 7 segment display.

3. Nov 17, 2004

### dduardo

Staff Emeritus
You'll need to convert the binary number into BCD and then use a 7447 to convert BCD to 7 segment.

The easy way to convert binary to BCD is to find a 74185 but it has been discontinued. If you can't find that chip you can always program a ROM to do the conversion.

4. Nov 17, 2004

### NoTime

You could set up the 7490 to do a carry-reset on A(hex).

5. Nov 18, 2004

### Tom McCurdy

How would we set up the 7490 to do a carry-reset on A(hex)?

6. Nov 18, 2004

### Tom McCurdy

So the 7446 isn't the way to go on this circuit? We were debating between it and the 7447

7. Nov 18, 2004

### Tom McCurdy

Alright So what would I need to do if I can't find the 74185 circuit--- Right now again I have a 555 going to two 7490 integratded divide by 10 circuits--- and then I have access to 7447 and 7446 chips is there anything I can do with those to hook up to a 7 segment LED (LN514rk).

8. Nov 18, 2004

### NoTime

Use an AND gate or two. There are a few ways to wire this, depending on the specific behavior you want.

The 7447 should be ok. IIRC the 46 takes a higher output.
The two numbers are much the same. Look up the specs.

9. Nov 18, 2004

### Averagesupernova

BTW, is this counting 0-9 or 1-10?

10. Nov 18, 2004

### GENIERE

You can display a "10" on the 7 bit display if you mentally rotate it. A 0 to 11 sequence is possible. I learned this by laying down on the job.

..

11. Nov 18, 2004

### NoTime

Laying down on the job :rofl: :rofl: :rofl:
10 can be just about any value you can imagine.
Depends on the base you select.

12. Nov 18, 2004

### Tom McCurdy

ok i just now got acess to a 4511 integradted circuit so I am trying to figure out how to use it...