Large (I mean large) Display

crazynight

Senior Member
I have been searching high and low over the last few months for some sort of large display; all I need to display is 2 sets of 4 numerical values. i have looked for both 4x7 segment displays and also large alpha numeric screens and both i2c and serial.

Ideally they need to be about 4"-6" high any ideas? I have considered making my own 7 segment display from LED strips but no idea where to start and defiantly not as simple as sending a command to a screen or down a single serial cable.!
 

Hemi345

Senior Member
Large single digit displays:
https://www.sparkfun.com/products/8530

Not I2C or serial but they're large!
 

graynomad

Senior Member
I would need a picaxe with 28 output pins
Or one with 11 pins if you multiplex (Either way you will also need transistors and/or driver chips.) or 3 pins if you use a driver like the TPIC6A596.
 

Hydroid

Senior Member
I have been searching high and low over the last few months for some sort of large display; all I need to display is 2 sets of 4 numerical values. i have looked for both 4x7 segment displays and also large alpha numeric screens and both i2c and serial.

Ideally they need to be about 4"-6" high any ideas? I have considered making my own 7 segment display from LED strips but no idea where to start and defiantly not as simple as sending a command to a screen or down a single serial cable.!
What about this: http://www.sureelectronics.net/goods.php?id=136

I bought two of them to make a clock for my garage. The digits are 4" high and only require 3 Picaxe pins to control (2 if you don't want to adjust brightness). It operates in serial format. I used a 28X2 as the Picaxe and the spiout command made controlling it super simple.

They used to sell a 7" version (DE-DP005), but I don't see it on their site anymore - although the PDF documentation is available.

Regards, John.
 

graynomad

Senior Member
That display appears to use a 74HC595 shift register which is generally considered not suited for the job and that would explain the low current ability of 10mA (10mA x 7 segs == 70mA which is the max for the package).

They say

Only need to feed two signals (Clock and Data)
did you use it like that, surely that would have terrible flicker as you updated the display because they aren't using the latch pin.
 

Goeytex

Senior Member
I like the way you think Buzby,

Along those lines .... 4D systems has the uVGA=III module. Can display 800X 600 graphics on a standard/flat screen monitor. Either use serial commands from the Picaxe or use the integrated processor. Lots of of features.
 

crazynight

Senior Member
Another option is a nice big 56" LCD monitor, driven by something like Tellymate. ( http://www.batsocks.co.uk/products/Other/TellyMate.htm )

Some simple BASIC routines will let you build digits any size you want, up to the limit of your screen size !.

( If a 56" monitor is too big, smaller sizes are still available. )
Thats great will have a look and do some rough plans, my only concern is the PSU as everything needs to be 12v (or less) as mains power will not be available.
 

Hydroid

Senior Member
They say

Only need to feed two signals (Clock and Data)
did you use it like that, surely that would have terrible flicker as you updated the display because they aren't using the latch pin.
Yes, I used it like that. My clock is only four digits (Hours/Minutes) so it only updates the display once per minute. There is a bit of flicker, but it's not too bad.

Just thought I'd throw the idea out there - Sorry it didn't meet your needs....
 

crazynight

Senior Member
Another option is a nice big 56" LCD monitor, driven by something like Tellymate. ( http://www.batsocks.co.uk/products/Other/TellyMate.htm )

Some simple BASIC routines will let you build digits any size you want, up to the limit of your screen size !.

( If a 56" monitor is too big, smaller sizes are still available. )
Buzby do you know which Tellymate I will need to work with a picaxe there seems to be 3 different types with an education (not) guess I think its TellyMate Tiny or TellyMate TTL Kit. Cheers John
 

marzan

Senior Member
I did some experimenting with 3" 7 seg displays using a driver chip that worked reasonably well in the end. Look up "code woes " and also "SAA1064" in the forum search. It should work on bigger 7 segs from ebay. Make sure you get the right ones though.. I think they were common anode that you need.
Marz.
 
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4 numerical values may be displayed neater on four separate lcds.... four small cheap ones for instance ...... need chip with four ser out pins
 

crazynight

Senior Member
4 numerical values may be displayed neater on four separate lcds.... four small cheap ones for instance ...... need chip with four ser out pins
If you have any suggestions on a source it would be appreciated. Played around with a 7 segment common cathode tonight, no picaxe interaction just plan and dirty battery and resistor to get my head around how they work surprisingly simple. Plus with it being common cathode did not know how to wire it up to the picaxe.
 

graynomad

Senior Member
CC and CA are connected pretty much the same. Of course the common pin goes to +V or GND depending on the type but the segments can still connect to the CPU pins (through resistors of course). The other difference is just in the code, a logic high will turn on a CC segment whereas a logic low is required to turn on a CA segment. So with CC you write the value to be displayed directly to the pins, for CA you have to invert the bits before writing.

BUT, for these large displays the Vf (forward voltage) of each segment will be more than the 5V the CPU can supply (because they have several LEDs in series) so if you use CC you will have to organize high-side drivers to switch say 12V, this is a pain, but if you use CA all you have to do is switch segments to GND which is easy.
 

marzan

Senior Member
If you use a SAA1064 the Picaxe dosen`t need to do all the work. The less work the Picaxe has to do the better. It uses I2C . It also multiplexes so you don`t use as much power .Also can sink up to 15V.

Marz
 
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