LED Question

[Ofek Deitch]

Hi everybody

My question is how to wire my LEDs if I want them to create together something like this:



I'm not sure if I should put them in series or in parallel.
Also, will 18 LEDs take a lot of power? Because I'm planning on putting these on my ruby amp, which is powered with a 9V battery.

Thanks!
Ofek Deitch

[Mark Hammer]

18 (chai!) LEDs can take a lot of current, depending on the LEDs you use and how bright you need them to be in order to see them.  Indeed, they can easily require more current than the Ruby itself under some circumstances!

So, two recommendations:

Suggestion echad:  Use superbright LEDs, rated at 2000mcd or higher.  These will require less current for any given level of brightness, often 1/10 of what the average Boss pedal LED uses.  Blue are nice, but what colour is "best" would depend on the enclosure and what offers the maximum visibility against the background.  If they are set against a very light background, you may need them to be a bit brighter in order to be visible, and that will require more current.

Suggestion shtaim: Lose the 9v battery, if you can, and opt for an 8-pack of either AAA or AA batteries to get 12v.  This will give you more headroom and power out of the Ruby, and last noticeably longer.  Remember that the volume of electrolyte in the battery is proportional to the current capacity: bigger = longer lasting.  While 12v is better than 9v, at least try and use a six-pack of AA or AAA.  (I have a 2W battery-powered practice amp, that I power with 8 rechargeable C-cells I found cheaply, and that thing goes for months without needing a recharge.)  At 9v you can also get away with drawing less current for the LEDs.

[LucifersTrip]

http://www.instructables.com/id/LEDs-for-Beginners/step7/Wiring-up-multiple-LEDs-in-series/

[Tubebass]

The number of LEDs you can wire in series will depend on the colour of the LEDs and the voltage they will be powered from. For example, my Tiny Giant amp has a lighted border using 3 blue LEDs in series on 12v. Just look up the junction voltage for the colour of LED you intend to use, or even better, measure it on your actual LEDs.

[Gurner]

18 leds off a 9V battery ....not a fine idea.

Even choking the current right off ...say 8ma per chain , if you use anything but red LEDs, then thats 9 'strings' (2 leds per string) - therefore 9 x 8ma = 72mA ....constantly!

Get a wall wart .....and wallow in the nirvana that is mighty blue LED glow.

[G. Hoffman]

THIS WEBSITE has a good series/parallel LED array wizard, which I have used in the past to design large LED circuits (my 200 LED UV light box for circuit boards, for instance).  You'll need the LED's datasheets, or at least you'll need to know their forward voltage.  Unless you need maxi brightness, you can estimate the current.  15mA will probably be fine.  Heck, 10mA will probably be fine.


Gabriel

[gritz]

Why do some people require their led displays to be visible from space? One of my audio interfaces has a blue led to indicate power_on and it's soo bright that it casts shadows when the studio lights are off. Uggggghhh. Remember that a lot of commercial pedals are fitted with low current leds that are run at a milliamp or two and they're plenty bright enough (imo) to be seen on stage (unless someone has gone overboard with the smoke machine...)

Anyway, some time ago I built an led tail light for my dirtbike (the original incandescent was fragile and I needed to divert some watts to the uprated headlight). I just dug out one of the leftover leds - a red Superlux high brightness job and lit it up on my 9V breadboard through a 4k7 resistor. Forward voltage was 1.8V at the (very low) current of 1.5 mA. It was bright - much brighter than the low current led that's already on the board as an activity indicator in the gate circuit that's on the board already.

So conceivably one could run four leds in series (7.2 volt drop in total) in series with a 1k2 resistor (it would also act as a low battery indicator!). Certainly one could run three leds in series which for Ofek Deitch's requirements in his original post would mean 6 stacks of 3 leds = 9mA, which isn't the end of the world for a battery powered circuit. What's the capacity of a good PP3 these days? 500mA hours? It just depends on how bright you want your array to be, Ofek.

If you want a red display I'd recommend lookig for superbright leds with a wavelength of around 620 nm - the human eye perceives them to be brighter than typical red leds that work at longer wavelengths. You may also consider greens as the human eye is very sensitive to 550nm, but while they appear bright it's psychologically not as distracting / fatigue inducing as red. Green leds will have a slightly higher forward voltage, but you will still be able to run groups of three leds in series at 9V. I'd suggest getting hold of some high brightness leds and experimenting to see what works for you.

[deadastronaut]

joule thief...

http://www.youtube.com/watch?v=Vm2TGOtdVYM

[Gus]

You might want to search "DIY edge lighting plexiglass"
some links
http://www.instructables.com/id/Edge-Lit-Displays/
http://www.evilmadscientist.com/article.php/edgelitcards
http://blog.makezine.com/archive/2010/06/how-to-edge-lit-display.html

You might use a drill to make the shallow holes in the pattern you show in the first post and edge light it from the side with one LED

[deadastronaut]

^ cool ideas...i might try that for kids stuff...

[scratch]

check out this thread ... http://www.diystompboxes.com/smfforum/index.php?topic=68095.0

you could just use the 'ON' side and not use the 'OFF'

[EATyourGuitar]

also this 15ma 5v regulator comes in handy when you require low power consumption. I use it in video game controllers so I don't pull massive amounts of current from my +5v rail down through a 470R resistor. it also creates my 5v rail from 9v or 12v or whatever. only a 2 wire hook up. the 3rd pin is NC