DIY LED-Illuminated Sleep Chamber

Bulldozer2003 writes "'Finally something both nerdy AND sexy engineers can do.' It sounds like an oxymoron but this guy took a cue from The Vos Pad and decked out his own dorm room bed with Light Emitting Diodes. They're even fully adjustable 'allowing me to create every color of the rainbow.' Total cost, according to him in an email: 'Around $25, the LEDs cost me about $0.25 a piece in bulk, and the potentiometers cost about $6 a piece from digikey. I got the LM317 voltage regulators as a free sample from Texas Instruments. Lots of companies will ship you free samples, its a good deal for college students.'"

Reminds me...

[flatface]

Reminds me a lot of this guy's [demon.co.uk] projects. He made some damn cool things out of LEDs there, complete with howtos.

Re:"sexy engineer" (with working link)

[JaJ_D]

the link [thefacebook.com] wasn't working so I'll try again!

Pot signing out

Jaj

Re:Electric bill?

[spdt]

Most LEDs operate at a relatively low current (~20mA) and voltage (~3V). This amounts to maybe .06 Watts (60mW) per LED. It looks like he has 5 panels of 4 LEDs and a 6-LED reading lamp, from the pictures; this makes 26 LEDs, consuming around 1.5 Watts in total. This is 1/40th of the power consumption of a single 60-Watt light bulb. If we say that electricity costs $.06/kWh ("US Federal Average"), then it would cost approximately $.09 to run these lights for 1000 hours.

The kinds of LEDs will probably have different operating characteristics than those I have in my head (like those UV LEDs, which are higher frequency -and energy- than I'm used to).

Whatever it is, it will not exceed the power output of the wall wart he's using.

Re:Samples

[Lisandro]

Actually, most semiconductor companies are very liberal when it comes to sampling. TI, for once, ships three samples of almost anything on their catalog, to anywhere over the world, as long as you fill some personal info and state what are you intending to do with the devices (or atleast they used to). They once shipped me a very high quality opamp IC that i turned into a beautiful headphone amp. I can't recall the price, but it's surely wasn't cheap, if not unavaiable.
Maxim does the same, and i got from them a couple of LCD display drivers that would've costed me a sum here in South America.

Of course, they don't want the service to be abused. But for them it's a neat way to do advertising amongst designers (i sure regard both companies better after that) for cheap. Anwyay, 90% has no use for electronic parts anyway, it's not like it's free T-shirts.

Re:Haiku

[DJCF]

Ok, no way is that a haiku.

1. A Japanese lyric verse form having three unrhymed lines of five, seven, and five syllables, traditionally invoking an aspect of nature or the seasons.

2. A poem written in this form.

Re:Electric bill?

[Hognoxious]

The big problem is, they throw a narrow beam of light.

There's these things called lenses that can affect the width of a beam, and some other things called diffusers that you can use to, well, diffuse the light. Oh, and there's reflectors too.

Re:Electric bill? -- Burnin' down the house

[Anonymous Coward]

If doing that burns down the dorm room he needs to take a course in EE! :-D

Nothing spells CHEAP like CARDBOARD.

I came close to burning down the house once when I left the soldering iron plugged in next to the drapes. My parents (thankfully) forgot something and we headed back to the house, discovered that it was filled with smoke and the curtains were smoldering.

This was thirty years ago. I remember to unplug the soldering iron to this day.

posting Anon, as I am an adult Nerd.

Not bad but...

[Len Budney]

Interesting! This guy's project basically connects a dimmer switch each to red, green and blue LED strings. The colors sorta mix, sorta producing colored light, but as you can see in his pictures there are major fringing effects (multicolored bands of light). The howto on this page [demon.co.uk], suggested by another poster, gives a much cleaner result.

The link above uses a microcontroller and pulse-width modulation to vary each color's intensity, producing a much more even color effect.

Now, of course, I want to redo the apartment with them. Eternal lighting with no more power consumption than a couple of flashlights...yum...

Re:Haiku

[Anonymous Coward]

Of course you haku-jin get it wrong.

The syllabic form is not so rigid as that. Buson, Bassho, and Issa all wrote haiku that deviated from 5-7-5.

That definition also fails to mention the "cutting word" that links the two separate ideas of the poem.

Also missing is the mention of the customary poetic reference to "classical" Japanese poetry i.e. from the compilations made in the 13th century by various courtiers.

Re:LEDs for Barbie house?

[sifi]

You can use any sort of LED you like - It basically comes down to:
a) The colour you want.
b) How bright you want it.
c) How big you want it.

You shouldn't connect LED's straight to a battery.

You need a series resistor (In between the battery and the LED). The value of the resistor is calculated using

R = (Vb-Vf)/I.

Vb = Battery Voltage
Vf = Forward Voltage (On Data Sheet)
I = Current (On Data Sheet)

so for this [ledsupply.com] 5mm white LED using a 9V battery Vf = 3.6, I = 30mA => R = 180 Ohms.

Make sure that you connect the LED the correct way round (The long lead should be connected to the '+' terminal on the battery, the short lead to one end of the resistor and the other end of the resistor to the '-' terminal on the battery. If you get it the wrong way round it don't worry the LED won't blow up, the LED just won't work!

Good Luck.

Re:LEDs for Barbie house?

[ajs318]

Don't use batteries, they pollute the environment something shocking. Use a mains adaptor instead, possibly even an old phone recharger or similar. Note that the voltage ratings quoted on the label are only for show and don't reflect what your trusty AVO will indicate.

Measure the output voltage, subtract the forward voltage of the LEDs {add together if wiring several in series} to get the "excess" voltage {guess 2V if you don't know it, 3V for blue or white diodes} to find out the excess voltage.

Select a suitable resistor to give about 20mA of current, it is not critical that this be spot on or anything, using the formula R = V / I -- where V is the excess voltage that needs to be dropped, I = 0.02 {because we said 20 milliamps but the formula wants whole amps} and R will be in ohms. Now resistors are made only in certain values, usually multiples of 10, 12, 15, 18, 22, 27, 33, 39, 47, 56, 68 and 82, so choose the nearest; eg. if your power supply is putting out 4.9V and your LED wants 2V, you have to drop 2.9V at 0.02A so R = 2.9 / 0.02 = 290 / 2 = 145, so use a 150 ohm resistor.

Finally, work out the power rating required, by multiplying the voltage dropped across the resistor by the current through it. In this case, P = 2.9 * 0.02 = 0.058 watts, so a 0.25W resistor will do fine.

Each room will need a separate switch and resistor, but if you have the volts available you can put multiple LEDs in series from the same switch. Watch the current consumption doesn't exceed the power supply rating: as you get close to it, the voltage will start to fall and the LEDs will get dim. But power supplies of this kind must be short-circuit-safe by law, so you won't burn your house down even if you do actually overload it.

Re:LEDs for Barbie house?

[B1ackDragon]

I'm rather suprised nobody has said anything here yet.

Basically you just need to put a resistor in series with the LED and battery, to keep the LED from burning out. LED's are a type of diode, which means that one side of the LED must be connected to negative, and one to positive or the current just won't flow.

To find out the resistor value you need, you can use the formula descibed on this Diyaudio page. [diyaudio.com] It also has some info for using multiple LED's in serial. If you have any more questions just leave a reply - I'm no electrical engineer but the Doll house lights thing isn't too big a deal, particularly considering the amount of enjoyment your daughter will get from such a simple hack!

Oh by the way, your local radio shack (if you have those) sells LED's and resistors individually, the forward voltage referred to on the diyaudio page will be listed on the back of the package.

Re:Not bad but...

[Bishop]

For LED control pulse width modulation is the proper way to do it. A dimmer switch is a poor hack, as LEDs are really only on or off. There is very little in between.

You can also make a quick adjustable PWM controller with a 555, a potentiometer, and a comparator like an LM111. (and a few caps, and other resistors) Hook up a 555 in ocsilator mode. Aim for a frequency faster then 120Hz. I would start with 1kHz and see what it looked like. That might be too fast for the LEDs to properly turn off. Connect one input of the comparator to the RC circuit on the 555. Connect the other imput to the sweeper pin on the pot. Connect the pot between Vcc and ground. Adjusting the pot will change the duty cycle of the comparator output from 0% to 100%. You could drive the leds directly from the comparator, but it is better to use a bjt or fet.

Obviously there is some fine tunning that you can do, but that is the general idea.

This circuit is nice because you only need one 555 which can drive many comparators. You only need one pot and comparator per colour of led. The microcontroller is nice because you can preprogram a number of pleasing colours, as well as automatically sweep throught those colours.

CF power factor

[name_already_taken]

You work for an incandescent light bulb company, don't you?

Several manufacturers are now making high power factor compact fluorescents (power factor >0.9).

I agree that LED lighting may not be terribly efficient and there will have to be some clever work with diffusing the light but its saving grace is that the lamps will last a very long time and the lamp packages can be made very flat which will allow some interesting design changes in products which use lights (like motor vehicles for example). Applications like street lighting and traffic signals and other public space lighting are probably ideal for LED retrofit; even if the lamps cost a lot more the savings in not having to replace them anywhere near as often will pay off quickly.

The problem of getting the illumination pattern even will be solved quickly. Take apart an LCD monitor. Who would believe that that thin cold cathode lamp could illuminate an entire screen so easily? Someone will solve the problem even if you can't see how.

Re:Electric bill?

[Phreakiture]

Of course, as we all know, "low energy" compact fluorescents are a waste of time *anyway*, because their power factor is so awful that twice as much energy again must be dissipated at the substation to compensate...

1. Even if you count VA instead of watts, a compact fluorescent bulb still draws half the VA of an incandescent bulb.

2. If that's not good enough for you, high power factor compact fluorescent bulbs are available.

3. You probably pay for Watts, not VA. Your electric meter will not charge you for reactive power.

4. If 3 is not the case in your case, you can install a power factor corrector. An active one would be preferable, but a passive one should get you some improvement.

5. There should be power factor correction at the substation, assuming that there isn't some somewhere along the line. I can point out several locations in my neighbourhood where there are power factor correctors on the poles.

Re:Not bad but...

[kzinti]

Just what I was thinking, dude, but you shouldn't need the external comparator. Look at this page: http://www.williamson-labs.com/555-circuits.htm, in particular the astable configuration with the diode across R2 to get a more variable duty cycle. Do that, but instead of separate R1 and R2, use a linear pot. Hook pin 7 up the pot center tap. The RC frequency stays constant, but by twisting the pot, you vary the duty cycle from low to high.

Re:what, who, how?

[msim]

And if you look at the pics at this link [uiuc.edu] you can read something written in his girlfriends yearbook, and if you look *REALLY* carefully you can see her name is Michelle, AND you can find out the email address of her friend.

*sits back and watches the geek frenzy*