7 Segment LED display

Thread Starter

noltex

Joined Apr 18, 2006
15
I need a circuit that will allow me to display digits 0-9 on a 7 segment LED that it switched by a 10 position rotary switch. Each position on the rotary switch corresponds to a digit. Is there a simple way to do this?
 

techroomt

Joined May 19, 2004
198
a 10 line to 4 line encoder (74147 or equiv) and a bcd to 7 seg/decoder/driver (7447a or equiv) should do the trick. these can be had in ttl or cmos families.
 

SgtWookie

Joined Jul 17, 2007
22,201
Thanks. My skills are basic enough that I need a schematic. Theory won't do it for me.
I suggest you go with techroomt's recommendation.

You certainly could do it by using 49 diodes and seven current limiting resistors - but you would need to make a lot of connections.
 

bloguetronica

Joined Apr 27, 2007
1,359
I suggest a decimal to BCD encoder connected to a BCD to 7-segment driver by the means of an inverter. Use this scheme:
Decimal to BCD encoder -> Inverter -> BCD to 7-segment driver

Decimal to BCD encoders:
74LS147 (TTL);
74HC147 (CMOS);
74HCT147 (CMOS/TTL compatible).

Inverters:
74LS04 (TTL);
4069 (CMOS);
74HC04 (CMOS);
74HCT04 (CMOS/TTL compatible).

BCD to 7-segment drivers:
74LS47 (TTL);
4511 (CMOS);
74HC4511 (CMOS);
74HCT4511 (CMOS/TTL compatible).
 

lightingman

Joined Apr 19, 2007
374
That's why I sugested diodes....I was going to mention the use of a 74HC147 into a CD4511....O.K. I will post both schematics tomorrow, as I have been just a bit busy today...Daniel.
 

lightingman

Joined Apr 19, 2007
374
Hi,I am so sorry that I have not yet posted the schematics for you....I have had one hell of a day and am still working now at 21:53, and will still be at it until midnight.... I will post them tomorrow, as I have more or less a free day....You will be best of using CMOS, as it is less fussy about supply voltage, and is very low power.....Daniel.
 

lightingman

Joined Apr 19, 2007
374
O.K....Now I have just had time to sit and think about this one..... It is not going to work with just the priority encoder, as the zero will only be displayed when all the switches are off... I.E. each time a button is released, the display will return to zero.....This means that a latch arangenent would have to be added to hold the last number sellected, this would make it a lot more complicated.....It would mean the addition of a 10 input OR arangement to trigger a one-shot, and using the latch input on the CD4511 to hold the last digit sellected.....Do you wan't to go that far ????Daniel.
 

Thread Starter

noltex

Joined Apr 18, 2006
15
As I said in my original post, I'd like to be able to use a 10 position rotary switch to have a 7 segment led display digits 0-9. I don't know enough about the various options for any of them to make sense on how to do it. I'm just looking for a schematic.

Thanks for any help you can give me with this.

Jeff
 

Thread Starter

noltex

Joined Apr 18, 2006
15
a 10 line to 4 line encoder (74147 or equiv) and a bcd to 7 seg/decoder/driver (7447a or equiv) should do the trick. these can be had in ttl or cmos families.
That looks like it may work for what I need. Anyone have a schematic I can use? I just need to be able to turn a 10 position rotary switch to make a 7 segment LED display #'s 0-9.

Thanks for your help.
 
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