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7 Segment Display

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Tythus

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I need to make a 6 digit 4 inch tall 7 segment display. I have been looking around for ways to do this and while I am quite handy with a soldering iron I have absolutely no idea how I would and where I should start.

I need it to be connectible and for it to converse to a computer and be able to take instructions from it via either a Serial Data Port or a Universal Serial Bus. the reason why I require this is I am making a defuse the bomb game with a timer involved and as part of this I want the player to be able to see the timer go down in big shiny letters.

Any help in this matter would be most useful so I shall thank before hand for all the amazing responses I shall receive.

Thanks,
Karl
 
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Rusttree

Member
The same company that sells the item mneary linked to above also has a how-to guide to buidling their 12 foot digital wall clock:

SparkFun Electronics

That'll get you 75% of what you're trying to do. Instead of the GPS signal, you'd probably just use binary counter ICs. As for the computer control side of it, the "outb" and "inb" functions in c++ will give you control of the pins on your PC's parallel port. Google "parallel port programming".

I recently built a large digital clock similar to the SparkFun design to use as a race timer. I can help with some of the specifics if you run into any roadblocks.

-Dan
 

Tythus

New Member
The same company that sells the item mneary linked to above also has a how-to guide to buidling their 12 foot digital wall clock:

SparkFun Electronics

That'll get you 75% of what you're trying to do. Instead of the GPS signal, you'd probably just use binary counter ICs. As for the computer control side of it, the "outb" and "inb" functions in c++ will give you control of the pins on your PC's parallel port. Google "parallel port programming".

I recently built a large digital clock similar to the SparkFun design to use as a race timer. I can help with some of the specifics if you run into any roadblocks.

-Dan

Do you have any part lists that you used for this project as I've been trying to the the diagram correct to no avail.
 

Rusttree

Member
Do you have any part lists that you used for this project as I've been trying to the the diagram correct to no avail.

Sure. The basic concept is to generate a 1Hz pulse into cascading binary counters. The first counter takes the 1Hz pulse as an input. It increments until it reaches 10, at which point it triggers the second binary counter (through an AND gate or similar logic) and clears itself. It's up to you to design the circuit to do all this. This cycle repeats for as many counters as you have digits to display. The 4-bit output of the binary counters are used as input to binary-to-7-segment drivers. These drivers are internally wired to drive a traditional 7-segment LED display.

I just remembered in your original post that you wanted to count down, not up. Therefore, you'd want to get down-counting binary counters (as opposed to up-counting).

As for the parts list, here are some ideas:

1 Hz pulse generator - You've got two easy options. First, you can write a routine on your computer that pulses a parallel port pin once a second, which probably won't be the most exact method, but timing probably isn't critical for you. Or, for more precise timing, crack open an old wall clock. Analog, not digital. Inside, you'll find a small PCB with a crystal soldered on it. All you need is the PCB, not the coils of wire or any of the mechanical linkages. If you apply between 1.5V and 3.5V DC to the positive and negative connectors of the PCB, you should get alternating 1Hz pulses out of the two leads coming out of the PCB.

Binary counters - I suppose you'd want decade down counters. I've not used one before, but it looks like 74HC192 would work.
CD74HC192EE4 Texas Instruments Counter ICs

7-segment driver - I've used the CD4511BE before.
CD4511BE Texas Instruments Encoders, Decoders, Multiplexers & Demultiplexers

If you're using large LED segments like these:
OVM12F3R7 Optek LED Arrays, Modules and Light Bars

You'll want hi-power darlington transistors like these:
ULN2003A STMicroelectronics Darlington Transistors

Hope this helps!
 
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