a Shiny led Blackboard post-it

[TucoRamirez]

hello

I was googling and i found this:

http://www.youtube.com/watch?v=EIyYmQhuMQs


but i find plugin the leds directly is not efficient and even dangerous for the life of the leds ...


I have an itchy bitchy question :

1:  if i use 2 or three leds for a little plexy postit (just to write quick notes!)  , what do you think about using a little pic for pwm and or sleep mode to reduce power and power the little gadget from  a 3V  mini battery    Do you think it's a good idea?

best regards!

[LabVIEWguru]

Look at Electronic Goldmine - they sell different types of UV LEDs at 405nm. Be careful though, some of them are dangerous to your eyes because they are very high power and you can't see most of the light output. But when you look at the specifications, they are very hungry. I used 10 of the more low powered devices for a prototype and it consumed 3.3V at about 400 mA - not so good for batteries. Even if we PWM two of them that is still a lot of current.

But, please try - maybe you will discover something new and make millions of dollars. Then you can buy toys for all your friends here on Sonsivri!

http://www.goldmine-elec-products.com/prodinfo.asp?number=G19287

3.6V @ 100 mA !!!

http://www.goldmine-elec-products.com/prodinfo.asp?number=G13533
4.5V @ 30 mA

[TucoRamirez]

what about this ones? 

http://docs-europe.electrocomponents.com/webdocs/0e77/0900766b80e77d25.pdf

anyway i need a little angle to iluminate because i'm lighting only the plexy...

[CocaCola]

but i find plugin the leds directly is not efficient and even dangerous for the life of the leds ...

A small series resistor although not efficient should keep the LED running withing perimeters...

1:  if i use 2 or three leds for a little plexy postit (just to write quick notes!)  , what do you think about using a little pic for pwm and or sleep mode to reduce power and power the little gadget from  a 3V  mini battery Huh   Do you think it's a good idea?

I would use 3 AAA batteries in this application, or one of the flat rechargeable 3.7V lithium packs or cells...  PWM and sleep if you want, but I'm not sure what good sleep is going to do over say a manual on/off switch unless you use additional sensors to toggle the sleep...

[TucoRamirez]

A small series resistor although not efficient should keep the LED running withing perimeters...

yes at least a resistor , in fact i was talking about the video, not about my personal choice of not putting any resistor

I would use 3 AAA batteries in this application, or one of the flat rechargeable 3.7V lithium packs or cells...  PWM and sleep if you want, but I'm not sure what good sleep is going to do over say a manual on/off switch unless you use additional sensors to toggle the sleep...

oki, i'll buy and test the components first ... i think i have plexyshit somewhere in my office ...

[pickit2]

I did something like this for exposure panel for Pcb work.
I used an old laptop screen and used UV-Leds 400nm to light edge of panel.
This was in turn taken from the idea, of using the laptop screen as a light-box for photographic work.

[Parmin]

I find laptop screens are usually not even enough in lighting exposure for photographic work.
OTOH they are good enough for PCB resist exposure.

[mike_au]

If you have a sleep mode, how are you planning to wake it up?

Apparently when light is shone onto an LED it produces a very small current, I saw a project a while ago where someone had an array of LEDs and by turning one on and looking at the current produced in surrounding LEDs it was possible to detect the reflection when something was in close proximity to the panel. Obviously the perspex would complicate things but I wonder if it might be possible to do something similar here. It would be quite cool to have it wake up when you touch the screen.

I don't imagine that sensing across the entire panel would be possible, the amount of reflected light would probably be too small, but the top edge (and maybe the sides) might be a possibility.

[TucoRamirez]

in fact i was thinking of use watchdog to make sleep the mcu in loop and use that to send pulsing signals to the leds ... otherwise just a button and pwm outs will be enough i think

[witsanukai]

I try to do something like this project too.
"Parmin" Would you advice about "OTOH", what is it's 
I have order 5mm UV LED with 400nm already

[solutions]

@witsanukai http://www3.sympatico.ca/n.rieck/docs/Internet-Acronyms.html

CUL8R

[TucoRamirez]

i received leds today and i'll do a  test w/ calculations tonite:

[pickit2]

@witsanukai http://www3.sympatico.ca/n.rieck/docs/Internet-Acronyms.html

CUL8R

FFS very limited

[TucoRamirez]

FFS very limited

when i read your post pickit i thought it the FFS ... was about my photo... it isn't?

[solutions]

https://sites.google.com/site/northwesternlightboard/home