This is a multi-part message in MIME format. --===============63782423822065648== Content-Type: multipart/alternative; boundary="------------040609030107000404050601" This is a multi-part message in MIME format. --------------040609030107000404050601 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Hi Martin: You might want to look into the Allegro 6276. http://www.allegromicro.com/sf/6276/ It's designed to drive 16 Common Anode LEDs with a constant DC current that's set with either a resistor or you can control it using a signal form a PIC. One chip will drive 2 each 7-segment LED digits or 1 each 14 segment alphanumeric LED character. The input takes 2 or 3 PIC I/O pins: data, clock, and optionally enable. It has a shift register and outputs so you can cascade as many as you need. Since the LED drive is DC the LEDs are very bright and there's no software concern about muxing. It can handle the higher voltage needed for the large LED digits. Since the 6276 is on the ground side of the LED it can be driven conveniently from the PIC while a higher voltage source is connected to the LED common anodes. You do need to pay attention to the power dissipated in the 6276 since it can handle up to 17 Volts and 90 ma per LED segment. To this end the anode supply voltage should be just higher than the LED on voltage. carries the 4" 7-segment digits for less than $11. Another option for very large LED displays is to make your own using inidvidual LEDs. For this you want wide viewing angle LEDs and connect all those for each segment in series. Have Fun, Brooke Clarke, N6GCE -- http://www.PRC68.com http://www.pacificsites.com/~brooke/PRC68COM.shtml http://www.precisionclock.com From: "Martin McCormick" To: "Microchip PIC microcontroller discussion list." Sent: Saturday, August 28, 2004 9:03 AM Subject: [EE]: Display possibilities >> I want to have a lighted display in a clock in which the >> digits are in the general range of 2 to 4 inches high. If > > someone >> makes individual digits like that then I will need to build a >> controller for them, of course. >> >> If there is a display module that fits this general >> description, then I need to be able to connect it using DIP > > headers or >> something similar that I can accommodate with wire wrap > > technology. >> >> The idea is to make the clock work first and add the display >> last such that the clock treats the display like a peripheral > > and >> updates it but doesn't concern itself with lighting up this or > > that >> segment. It would just send out BCD or ASCII digits to a second > > PIC >> that managed the display itself. >> >> What I don't desire is what I have seen in some devices I have >> salvaged in which there is a ribbon of 4 score and 7 tiny > > stranded >> conductors wave soldered to the surface of both the display > > board and >> the main board. That is not my idea of fun. I am sure it works > > fine >> in a mass-production environment, but not here.:-) >> >> Thanks for any useful ideas. This is a one-of-a-kind project, >> but one never knows where these things can lead. >> >> Martin McCormick WB5AGZ Stillwater, OK >> OSU Information Technology Division Network Operations Group > --------------040609030107000404050601 Content-Type: text/html; charset=us-ascii Content-Transfer-Encoding: 7bit Hi Martin:

You might want to look into the Allegro 6276. http://www.allegromicro.com/sf/6276/ It's designed to drive 16 Common Anode LEDs with a constant DC current that's set with either a resistor or you can control it using a signal form a PIC. One chip will drive 2 each 7-segment LED digits or 1 each 14 segment alphanumeric LED character. The input takes 2 or 3 PIC I/O pins: data, clock, and optionally enable. It has a shift register and outputs so you can cascade as many as you need. Since the LED drive is DC the LEDs are very bright and there's no software concern about muxing. It can handle the higher voltage needed for the large LED digits. Since the 6276 is on the ground side of the LED it can be driven conveniently from the PIC while a higher voltage source is connected to the LED common anodes. You do need to pay attention to the power dissipated in the 6276 since it can handle up to 17 Volts and 90 ma per LED segment. To this end the anode supply voltage should be just higher than the LED on voltage.

<http://www.jameco.com/webapp/wcs/stores/servlet/CategoryDisplay?storeId=10001&catalogId=10001&langId=-1&categoryId=11324>
carries the 4" 7-segment digits for less than $11.

Another option for very large LED displays is to make your own using inidvidual LEDs. For this you want wide viewing angle LEDs and connect all those for each segment in series.

Have Fun,

Brooke Clarke, N6GCE

-- 
http://www.PRC68.com
http://www.pacificsites.com/~brooke/PRC68COM.shtml
http://www.precisionclock.com

From: "Martin McCormick" <martin@dc.cis.okstate.edu>
To: "Microchip PIC microcontroller discussion list."
<piclist@mit.edu>
Sent: Saturday, August 28, 2004 9:03 AM
Subject: [EE]: Display possibilities

> I want to have a lighted display in a clock in which the
> digits are in the general range of 2 to 4 inches high.  If

someone

> makes individual digits like that then I will need to build a
> controller for them, of course.
>
> If there is a display module that fits this general
> description, then I need to be able to connect it using DIP

headers or

> something similar that I can accommodate with wire wrap

technology.

>
> The idea is to make the clock work first and add the display
> last such that the clock treats the display like a peripheral

and

> updates it but doesn't concern itself with lighting up this or

that

> segment.  It would just send out BCD or ASCII digits to a second

PIC

> that managed the display itself.
>
> What I don't desire is what I have seen in some devices I have
> salvaged in which there is a ribbon of 4 score and 7 tiny

stranded

> conductors wave soldered to the surface of both the display

board and

> the main board.  That is not my idea of fun.  I am sure it works

fine

> in a mass-production environment, but not here.:-)
>
> Thanks for any useful ideas.  This is a one-of-a-kind project,
> but one never knows where these things can lead.
>
> Martin McCormick WB5AGZ  Stillwater, OK
> OSU Information Technology Division Network Operations Group

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