looking for help AVR or ISP for making 7-segment display

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dacflyer
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looking for help AVR or ISP for making 7-segment display

Post by dacflyer » Fri Mar 13, 2015 11:24 am

i have seen 7 segment led displays work with 3-4 pins for use with Arduino and addafruit etc.
i am looking to build my own.
i am looking to operate 1 7-segment at a time, if they are daisy chain-able that would be a bonus.

i am wanting to make my own 10" digits.

basically input to a chip, then a buffer that can drive 12v segments.

is there anything off the shelf or will i need a pic for this ? would like something i can make for AVR use.

any suggestions ?

i found this, wondering if this is what i am searching for..
http://www.kmitl.ac.th/~kswichit/Led/schematic.pdf

cae2100
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Re: looking for help AVR or ISP for making 7-segment displa

Post by cae2100 » Fri Mar 13, 2015 2:11 pm

I would look into using the 74hc595 shift register, you can do all 7 segments per IC and they are fully daisy chainable. They use SPI protocol with latch that pretty much every microcontroller that Ive seen understands quite easily.

The link you posted is using a bunch of LEDs to create a massive 7 segment display, but this will show the wiring and if you looked up AVR 595, you should easily find code to control it:
It also has the ULN2003 buffer IC like you want to buffer it up to 12v, and I think they'll do up to 500mA per output.

From your description, that's exactly what you are looking for.

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Re: looking for help AVR or ISP for making 7-segment displa

Post by dyarker » Fri Mar 13, 2015 3:52 pm

The shift register is clever. One chip per digit, 2 uP pins (serial data and clock) but binary to 7 segmant decodeing has to be done software before sending to shift register. The eigth bit could be used for decimal point.

4 uP pins out would be 0 to 9 for decimal, or 0 - F for hexidecimal. That would feed a BCD or binary to 7 segment decoder IC. That will control 1 digit.

One more pin out from uP could multiplex 2 digits. Two additional pins (now 6 total including the 4 segment pins) to multiplex 4 digits. Three pins mux pins uP, up to 8 digits; etc; etc;

Cheers for now,

(ps forgot to say schematic you linked to looked useful too)
Dale Y

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Re: looking for help AVR or ISP for making 7-segment displa

Post by dacflyer » Fri Mar 13, 2015 9:57 pm

i already have dumb 7 segments ( salvaged from pedestrian count down modules )
they have multi leds per segment.
i want to make them useable for projects.

cae2100
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Re: looking for help AVR or ISP for making 7-segment displa

Post by cae2100 » Sat Mar 14, 2015 1:31 am

why do you need the bcd to two or 3 wire anyways? If you are just controlling it with a microcontroller, you dont need anything to do the bcd outputs, just go directly from the microcontroller to the 2/3 wire setup. Also, If you use a standard shift register, that's going to be 3 wires, clock, data, and latch, only a few that Ive seen dont use latch, and for 7 segment applications, it makes it garble the letters when updating the display, hence why I stick with ones like 74hc595 that has the latch, then there's no flicker or anything when the digits change.

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Re: looking for help AVR or ISP for making 7-segment displa

Post by dacflyer » Sat Mar 14, 2015 4:51 pm

i had my tech speak mixed up... did not need BCD control...
just needed something to make larger 7-segments work.

what "cae2100" said will be what i will use.. easy enough to implement. and the 2003's will easily drive
the large multi leds (12v series strings )

the arduino can control the 595's easily directly and the communication to each one should not be a issue..
i remember using them earlier when i built a 8x8x8 cube for a customer over a year ago.

i am still trying to learn code, but it is very hard for me to grasp..but i will get it sometime soon.

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