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

[[email protected]]

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.

 

[DJ Delorie]

Does anyone make an inexpensive 3-digit 7-segment LED module

Is $2 inexpensive enough? (not including the LEDs themselves)

http://www.delorie.com/electronics/bin2seven/

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.

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

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?

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:
http://www.delorie.com/electronics/r8c-27-adapter/

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.

 

[Jim Thompson]

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.

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 Voice480)460-2350 | |
| E-mail Address at Website Fax480)460-2142 | Rat Bastard |
| http://www.analog-innovations.com | 1962 |

America: Land of the Freedom Abusers, Because of the Bastards.

 

[Martin Griffith]

On Thu, 28 Feb 2008 15:20:36 -0800 (PST), in sci.electronics.design

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.

Abitof white spacewouldbeappreciatedinanyfollowupsbutyoucouldtry
somethinglikeSTP16C596fromSTmicroHopesthishelps

Kthksbye


martin

 

[linnix]

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).

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.

 

[William Sommerwerck]

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

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.

Analog/Mixed-Signal ASICK's and Discrete Systems

Is that a joke?

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

 

[donald]

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.

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

A finished product is another matter.

donald

 

[john jardine]

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).

[...]

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

 

[Robert Baer]

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.

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

 

[mng]

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

 

[MooseFET]

in message

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?

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

 

[Fred Bloggs]

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.

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|----------------------------------' |
.. -------------------------------------------------------
..

 

[William Sommerwerck]

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

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".

 

[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.

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.

 

[MooseFET]

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".

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

 

[MooseFET]

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.

Shut up imposter. Get fucked if you have anything better to do.

 

[William Sommerwerck]

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

Again, you miss the point.

 

[John Fields]

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.

 

[JosephKK]

in message

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?

Responding to some name faking twit i see. Check the headers.

 

[JosephKK]

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".

Talking up the to the sewer rat still? Check some more headers.