[Noisebridge-discuss] A simpler circuit for ... [driving multiple LEDs with minimal batteries]

T t at of.net
Sun Jan 16 10:08:10 PST 2011


Here's another idea in the thought of not getting overwhelmed by building
complex circuits.

You can get a device called a "Constant current diode (also called CLD,
current limiting diode, constant-current diode, diode-connected transistor
or CRD,current-regulating diode)"

 https://secure.wikimedia.org/wikipedia/en/wiki/Constant_current_diode

As long as your battery has a higher voltage than your string of diodes (add
up the voltage drops if you run them in series as others have advised) and
is capable of producing the current (milliamps), picking a constant current
diode that has a current rating at or below the rating of your LEDs should
do the job in a very simple circuit:

 --- - battery + ---- CLD |> ----- LED ---- LED ---- LED .... ---
|                                                                |
 ----------------------------------------------------------------

So something like a 12V camera battery should be able to drive up to 3 white
3V LEDs or a few more of the lower-voltage colored variety, a 9V "transistor
battery" should be able to drive 2.

And it lends itself to experiment too... you can hood up the battery and the
CLD and one LED, and it should work fine (since it's current-limited it will
limit voltage too), and you can hook up two, and you can hook up three, and
if you hook up too many they just won't light up, no harm done.

Best Regards.



On Thu, Jan 6, 2011 at 12:17, meredith scheff <satiredun at gmail.com> wrote:
> Thanks everyone!
> It's the booster that I was thinking of, i'm looking forward to trying it.
> It's a big hurdle in wearable electronics.
> M
>
> On Thu, Jan 6, 2011 at 5:11 AM, Christoph Maier
> <cm.hardware.software.elsewhere at gmail.com> wrote:
>>
>> On Wed, 2011-01-05 at 21:30 -0800, T wrote:
>> > > Now, what's all this SEPIC stuff, anyways?
>> >
>> > SEPIC is a particular type DC-DC converter such as buck, boost,
>> > buck-boost, can cuk
>> >
>> > http://en.wikipedia.org/wiki/SEPIC
>>
>> SEPIC is what Dr. Foote calls a boost converter
>> http://en.wikipedia.org/wiki/Boost_converter
>> in last November's Five Minutes of Fame,
>> http://www.ustream.tv/recorded/10946425 ,
>> beginning at about 49 1/2 minutes.
>> (Can anyone, by any chance, post the slides somewhere,
>> Nudge nudge. Nudge nudge. Know what I mean?)
>>
>> Unlike the two-component solution
>> [ http://www.diodes.com/datasheets/ZXSC380.pdf
>> page 1, "Typical application circuit",
>> and page 6, "Application Notes", Fig. 2],
>> with a current regulation and efficiency that is so-so
>> [see the graphs on page 3],
>>
>> Jonathan draws some serious power,
>> so he needs a little more than 2 components,
>> probably even more than the 5 components in Fig. 5,
>> to control current and efficiency more accurately
>> than the ZXSC380, which is more optimized for blinkenlights
>> (well, ok, 200kHz blinkenlights,
>> so it looks continuous to the human eye)
>> running off a single 1.5V-ish battery.
>>
>> An LT3092 is the [Norton] equivalent of a waffle iron,
>> as presented in
>> http://www.ustream.tv/recorded/10946425 , 51:40 minutes.
>>
>> [ http://en.wikipedia.org/wiki/Emperor_Norton ,
>>  http://en.wikipedia.org/wiki/Norton_equivalent ]
>>
>>
>> HTH
>> Christoph
>> --
>> Linear current sources are easy,
>> [
>>
http://reference.kfupm.edu.sa/content/c/m/cmos_current_reference_without_resistanc_122569.pdf
>> ,
>>  http://www.eelab.usyd.edu.au/andre/publications/BiasgenAICSP.pdf ]
>>
>> getting sufficient control over the necessary means of production,
>> however ephemeral, is anything but.
>>
>>
>> _______________________________________________
>> Noisebridge-discuss mailing list
>> Noisebridge-discuss at lists.noisebridge.net
>> https://www.noisebridge.net/mailman/listinfo/noisebridge-discuss
>
>
>
> --
>
> Ladycartoonist.com
>
> ___________
>
> A human being should be able to change a diaper, plan an invasion, butcher
a
> hog, conn a ship, design a building, write a sonnet, balance accounts,
build
> a wall, set a bone, comfort the dying, take orders, give orders,
cooperate,
> act alone, solve equations, analyze a new problem, pitch manure, program a
> computer, cook a tasty meal, fight efficiently, die gallantly.
> Specialization is for insects.
>
> -Robert A. Heinlein
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://www.noisebridge.net/pipermail/noisebridge-discuss/attachments/20110116/97c0c555/attachment.htm 


More information about the Noisebridge-discuss mailing list