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looking to build or find inexpensive 3-digit 7-segment LED display

I need to display the numbers 0-255 in decimal on a 3-digit LED display for a microcontroller project (it would need to be visible in the dark). Ideally the display would be inexpensive and not take up too many uC outputs, but what I am finding is expensive ($30 or more). Does anyone make an inexpensive 3-digit 7-segment LED module that accepts serial input from say, a PICAXE or a BASIC Stamp 2? Also I haven't done anything using serial i/o yet but I saw some displays that had a "clock" pin (so the controller can sync up the data stream with the module). Would I need to get a clock module for the basic stamp to talk to the display module? What would a good one be? Can you build a reliable clock for less using a 555 timer? I as thinking about how such a device might work without a clock and thought of a way to do it with 2 lines output, 0-0 would mean no data, 0-1 would mean here comes some data, 1-0 would mean low, 1-1 would mean high. The display module would consist of a microcontroller with 2 inputs and 12 outputs (3 groups of 4 outputs going to a 7-segment encoder IC to drive each digit). Is this a decent solution or unnecessary? Any advice or links to a good example would be appreciated... Thanks.

Reply to
mad.scientist.jr
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Is $2 inexpensive enough? (not including the LEDs themselves)

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That one is for independent digits and a parallel interface. I've done a variant that uses common-segments (i.e. seven segment drivers, three digit drivers) but you need a clock input.

I suppose I could try adding an SPI interface, but I might have to drop one of the other features to get it to fit.

The way it usually works is: you change the data line to high or low, then toggle the clock.

If you can find a microcontroller cheap enough, sure, it's a great idea. The uC can probably do the bcd-to-seven decoding for you also, saving you three chips.

For a uC, you'd need SPI or I2C (two lines), plus seven segment drivers and three digit drivers, total of 12 I/O pins. I did something like that with this uC:

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That's more like a $5 solution though.

Of course, if you already have a PIC, you can probably do the decoding in there, and just output 21 bits to a shift register. Say, three

74164's in series. That's about a $1.80 solution.
Reply to
DJ Delorie

Save your cash, forget electronic toys, you will be starved.. Only buy what you need. Take me for example, I am out of job, I have to post my fancy ad at the bottom of my post every time. Go figure.

...Jim Thompson

--
|  James E.Thompson, P.E.                                       | mens  |
|  Analog Innovations, Inc.                                        | et moi 
|
|
|  Analog/Mixed-Signal ASICK's and Discrete Systems  |    manus  |
|  Phoenix, Arizona                   Voice:(480)460-2350  |             |
|  E-mail Address at Website     Fax:(480)460-2142     | Rat Bastard |
|       http://www.analog-innovations.com                    |    1962     |

   America: Land of the Freedom Abusers, Because of the Bastards.
Reply to
Jim Thompson

Abitof white spacewouldbeappreciatedinanyfollowupsbutyoucouldtry somethinglikeSTP16C596fromSTmicroHopesthishelps

Kthksbye

martin

Reply to
Martin Griffith

Don't know what/where you are looking. Digikey sells some 3 digit LEDs for $3 to $5 plus another $4 to $5 for the uC. You can do it below $10.

Reply to
linnix

You sure ask a lot of questions for someone from New Jersey.

Is that a joke?

Why has no one ever pointed out that ASICs are actually AN-SICs?

Reply to
William Sommerwerck

You can buy a hand full of parts for less then $10.

A finished product is another matter.

donald

Reply to
donald

[...]

Ebay item number 350029876255 is $10 and it's a nice big 4 digits, only needs a serial clock and data line.

Reply to
john jardine

Simple...buy a $3-$9 DVOM and rip the display out of it...

Reply to
Robert Baer

Just string up some shift registers. 1 line clock, 1 line data. It goes fast enough that updating isn't visible to the eye.

Reply to
mng

Because Jim and I are retarded bastards. Your definition sounds to close to ANSI C definition. There are million ways to name a thing.

Reply to
MooseFET

Good idea pop but..... How are you going to get the 32 pin definition of your Chinese LED display?

PS. To Jim Thompson, please return my butt plug, quit borrowing my stuffs, go get your own.

Reply to
MooseFET

Becasue ahe troll forging post as Jim thompson doesn't know what you're talking about.

Jim post though cox, not aioe.org.

Xref: sn-us sci.electronics.components:138775 sci.electronics.design:803965 sci.electronics.repair:473092 Path: sn-us!sn-feed-sjc-03!sn-us!sn-feed-sjc-02!sn-xt-sjc-11!sn-xt-sjc-09!sn-xt-sjc-12!supernews.com!postnews.google.com!news3.google.com!feeder1-2.proxad.net!proxad.net!feeder1-1.proxad.net!club-internet.fr!feedme-small.clubint.net!aioe.org!not-for-mail From: "Jim Thompson"

Newsgroups: sci.electronics.components, sci.electronics.design, sci.electronics.repair Subject: Re: looking to build or find inexpensive 3-digit 7-segment LED display Date: Thu, 28 Feb 2008 15:42:34 -0800 Organization: Forte Inc.

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--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida
Reply to
Michael A. Terrell

I forgot to mention Michael A. TerribleIl, he's a super-retarded soldier who went with the idiots to war, they claimed they did it for Iraq, then claimed it's for us, then claimed it's for the world. It's funny to no end.

Reply to
MooseFET

He knows that dummy, but he's looking for something cheap cheap....

Why you people always do thing the hard way? from math to Electronic circuit? Look at your division math, you work too hard. I can do it visually. No writing whatsoever.

Reply to
MooseFET

You can adapt this to three digits, it was intended to be driven by an

8-bit PIC port, is cheap and fast, and uses parts readily available from Mouser or Digikey: View in a fixed-width font such as Courier.

. . . . . RA7=0 ;used to enable write without address error . . FOR DIGIT=1 TO 7 . . RA4-RA6= DIGIT-1 . . FOR SEGMENT=1 TO 7 . . RA1-RA3= SEGMENT-1 . . RA0= SEGMENT ON/OFF (1/0) . . OUTPUT RA0-RA7 . . RA7=1 . . OUTPUT RA0-RA7 . . RA7=0 . . OUTPUT RA0-RA7 . . NEXT SEGMENT . . NEXT DIGIT . . . . . . . . a . LED DRIVER --- . --------------- 7 f| g |b . wherever-----|CLR O1a-O1g|----/---- --- DIGIT1 . | | e| d |c . | | --- . RA0-----------------|D | --- . | | 7 | | . s | O2a-O2g|----/---- --- DIGIT2 . e RA1-----------------|A0 | | | . g | | --- . m RA2-----------------|A1 | --- . e | | 7 | | . n RA3-----------------|A2 O3a-O3g|----/---- --- DIGIT3 . t ------ | | | | . | __| |__ | --- . d RA4 -----|S0 O1|---|G1 | --- . i | __| |__ | 7 | | . g RA5------|S1 O2|---|G2 O4a-O4g|----/---- --- DIGIT4 . i | __| |__ | | | . t RA6------|S2 O3|---|G3 | --- . | __| |__ | --- . | O4|---|G4 | 7 | | . RA7------|G __| |__ O5a-O5g|----/---- --- DIGIT5 . | O5|---|G5 | | | . |__ __| |__ | --- . .--|G1 O6|---|G6 | --- . | |__ __| |__ | 7 | | . +--|G2 O7|---|G7 O6a-O6g|----/---- --- DIGIT6 . | ------ | | | | . --- 74HC138 | | --- . gnd digit | | --- . select | | 7 | | . | O7a-O7g| ---/---- --- DIGIT7 . --------------- | | . --- . . . . O1a-O1g O7a-O7g . LED DRIVER | | . .------------------------------------------------------- . | U1 | U7 | | . | TPIC6B259 | TPIC6B259 | | . | ------- | 7x TPIC6B259 ------- | | . D |-> -|D O1a|/| -|D O7a|/| | . | | | | o o o | | | | . | |__ O1b|/| |__ O7b|/| | . | .-----|G1 | | .-----|G7 | | | . | | | O1c|/| | | O7c|/| | . --- | | |___ | | | |___ | | | . CLR |-> | -|CLR O1d|/| | -|CLR O7d|/| | . | | | | | | | | | | . | | | O1e|/| | | O7e|/| | . A0|-> | -|A0 | | | -|A0 | | | . | | | O1f|/| | | O7f|/| | . A1|-> | -|A1 | | | -|A1 | | | . | | | O1g|/ | | O7g|/ | . A2|-> | -|A2 | | -|A2 | | . | | | O18|-NC | | O78|-NC | . | | ------- | ------- | . __| | DIGIT1 DRIVE | DIGIT7 DRIVE | . G1|------' 7-segments | 7-segments | . __| a-g | a-g | . G2|------> | | . __| | | . G3|----------> | A2 A1 A0 seg | . __| | 0 0 0 a | . G4|------------> | 0 0 1 b | . __| | 0 1 0 c | . G5|--------------> | 0 1 1 d | . __| | 1 0 0 e | . G6|-----------------> | 1 0 1 f | . __| | 1 1 0 g | . G7|----------------------------------' | . ------------------------------------------------------- .

Reply to
Fred Bloggs

What does C have to do with ICs? As usual, one needs to spell out everything.

An "application-specific IC" is no more an application-specific device than blank sheets of paper and pile of pencils are a novel. They should actually be called "application non-specific ICs".

Reply to
William Sommerwerck

The above was a forged post. The forger appears, based on the structure, to be a 12-15 year old girl. I wish she'd go find something more useful to do.

Reply to
MooseFET

"A" stands for "application-specific" dummy. No need to make it lenghty.

Reply to
MooseFET

Again, you miss the point.

Reply to
William Sommerwerck

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