Need help with a circuit.

{PMS}fishy · Aug 6, 2005

I need to create a circuit to display the numbers 1-6 on one of the 7 line LED displays.

I need to take the voltage or resistance from a wire, and display the apporaite number.

1 = 1.7v
2 = 2.2v
3 = 2.9v
4 = 3.6v
5 = 4.3v
6 = 4.6v

Thats the voltage for each number. Someone point me in the right dirrection.

Need to try to do it for less than $5 worth of parts, and I only have a 12v source.

kayson · Aug 6, 2005

My circuitry knowledge is very limited, but you could use voltage comparator chips. It's probably a very stupid way to do it, but it'll definitely be less than $5. If for some reason you can't get this accomplished, I'll provide some more details.

{PMS}fishy · Aug 7, 2005

Yea, I need more help than that.

sdwood · Aug 7, 2005

You will need 6 comparators (LM339 has 4 in one chip). Apply your signal voltage to all 6 "+" inputs. Set up voltage dividers (using 10K resistors and 10K VRs) to apply the trigger voltages to the "-" terminals.
Now you will have a digital output
0 - 1.7 -> 000000
1.7 - 2.2 -> 000001
2.2 - 2.9 -> 000011
2.9 - 3.6 -> 000111
3.6 - 4.3 -> 001111
4.3 - 4.6 -> 011111
4.6+ -> 111111
Now use these outputs and 7 Karnaugh maps (one for each segment of the display) to find the proper logic to build a circuit to drive the display.

{PMS}fishy · Aug 7, 2005

sdwood said:
You will need 6 comparators (LM339 has 4 in one chip). Apply your signal voltage to all 6 "+" inputs. Set up voltage dividers (using 10K resistors and 10K VRs) to apply the trigger voltages to the "-" terminals.
Now you will have a digital output
0 - 1.7 -> 000000
1.7 - 2.2 -> 000001
2.2 - 2.9 -> 000011
2.9 - 3.6 -> 000111
3.6 - 4.3 -> 001111
4.3 - 4.6 -> 011111
4.6+ -> 111111
Now use these outputs and 7 Karnaugh maps (one for each segment of the display) to find the proper logic to build a circuit to drive the display.

You've lost me.

Can you draw a digram that I can use to build one?

sdwood · Aug 7, 2005

This is the baic input circuit. You will need 6 of them. Download a datasheet for the LM339 for pin numbers.

This will get you the analog to digital conversion, but you still have to design a driver circuit for the display.

Need help with a circuit.

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