LED display drivers??

[tarantulataramasalata]

I can find plenty of LCD display drivers, including Rev-Ed, but I would like LED ones. The LCD ones hook up to a pic chip and can be programmed very easily; using seven segment displays involves lots of messing around with driver chips etc. Ideas?

 

[manuka]

7 segment LEDs are virtually obsolete I'm afraid, as their current demands alone are intolerable now compared to ultra efficient LCDs. Each segment takes ~5-10mA so a single 7 seg can take 35-70mA, & an array more like 100s of mA. This means battery powering not suitable = mains transformer costs etc. Sure- multiplexing is possible, but that adds further complexity.

This is not to say they've totally gone, since a few applications may still call for large bright numeric readouts - queue numbers etc. However these take even MORE current to drive !

LCDs not only allow a full alpha numeric ch. set,but take orders of magnitude LESS energy to drive, an important feature with today's portable electronics. They can often be rescued from old laser printers etc, & driven "Hippy style" via an 18X etc. Stan


Edited by - Stan. Swan on 12/11/2005 6:02:58 PM

 

[kranenborg]

Hi,

You may want to use (depending on the number of leds): MAX6955,MAX6956,MAX6959 that have led brightness control or equivalents without led brightness control(MAX7300 etc); all controlled via i2c, and should work flawlessy with PICAXE. These chips do require some proper initial settings, for an example of working picaxe code for the MAX6956 see the following link on this forum (I assume similar operations & type of code for the other parts):

http://www.rev-ed.co.uk/picaxe/forum/Topic.asp?topic_id=3080&forum_id=18&Topic_Title=MAX7300%2B20%252DPort%2BI%252FO%2BExpander&forum_title=No+new+posts+please%21+12

Hope this gives some useful hints. All very nicely comtrolled via just two i2c lines. Maxim also provides a lot of useful application notes concerning these chips (in particular brightness control approaches) and led use in general ...

Best regards,
Jurjen
http:/www.kranenborg.org/ee/picaxe

Edited by - kranenborg on 12/11/2005 8:03:28 PM

 

[MartinM57]

MAX7219....

 

[tarzan]

MAX6956ANI & MAX7300ANI PCBs Here:
http://groups.msn.com/picaxe/max7300ampmax6956.msnw?Page=1 <A href='http://groups.msn.com/picaxe/max7300ampmax6956.msnw?Page=1' Target=_Blank>External Web Link</a>

 

[tarantulataramasalata]

Yes, I read about the Maxim displays; are they as easy as the LCD ones from Rev-Ed?...and can I get them in the UK? got a URL?

 

[manuka]

Guys I'm not quiting yet! Just what do you want to display with these power hungry LEDS that LCDs couldn't handle? Scolling text? Numbers (maybe game scores- see the great SiCh recent article)? Letters ? How many ch.s at once? Budget?

As a guide for power needs, I've a $$$ Jaycar LED &quot;Times Square&quot; display here that runs off C cells at a most enthusiast rate- battery life is ~4 hours. Even multiplexed hence the drain is ~1/2A. We're in the age when &quot;energy out of thin air&quot; should be the challenge - ZigBee modules take so little that 5 years off an AA cell is being quoted.

 

[Michael 2727]

There's still life left in 7 Seg displays yet.
I have a 2 digit and a 3 Digit 7-Seg Display
project, (waiting, waiting, waiting, for
Silicon Chip magazine to decide if they
will publish it or not) which can display many of the functions of a PICAXE&#8482;.
The PCB was made to directly interface to
the Schools Experimenter PCB or as a Stand
Alone display with onboard PICAXE&#8482;.

http://www.porepunkahps.vic.edu.au/home/jef01/display-teaser.htm

I may buy Stan a Transformer for Crissy,,~ ;o)

 

[MartinM57]

http://www.maxim-ic.com/quick_view2.cfm/qv_pk/1339

 

[manuka]

In 1000 up quantities (!),these are US$3.99 each, so allow ~ twice that for 1-offs. You may have some joy requesting a free sample from Maxim?

Extra: I've crates of plugpaks &amp; transformers, &amp; also a long memory for the first LED watches &amp; calculators(~1975)&amp; their GREEDY enthusiasm for batteries. We have a responsibility to use the most energy efficient technology (c.p)


Edited by - Stan. Swan on 12/12/2005 5:41:47 PM

 

[evanh]

Don't you go lecturing on power savings by a few LEDs. You do realise that when running a small circuit like this from the mains that the tranformer will burn more power than the circuit it's powering. And that goes for every soft-powerswitch you get on modern appliances including ya average PC.

Besides, some people like to be able to read it from a distance or just be able to read it at all is nice too.

Evan

 

[Michael 2727]

Don't use the listed x 1k price guide too
closely, as the resellers etc, want their
cut as well.
I have a couple of ID iButtons and
Temperature iButtons I decided to have a
look at the Thernochron iButton&#174; (Logger).

With a listed 1k units of $14.25 which is
around $19.60 AUD, I rang the local agents
who quoted me a price of $38.00, the RS-232
or UBS adaptors are even dearer. You also
need to find someone who will sell them to
you as a 1 off item.
Both the Thermochron or adaptors are not available as samples. There are software
variations available as a free download.

 

[Michael 2727]

Stan, please look away,,!!

I have been looking into a NIXIE&#8482; Display
for my circuit as well,,~ ;o)

I have been buying all kinds of cheap LCD
toy, gadget whatever to find a suitable
low power display, but there is not much
around with the requirements I need.

Yes Evan, agreed, I can tell you the
Temperature at midnight from 10 meters away
with the lights out. All this for a total
consumption of 5V 40mA @ 25 C, digits.