Lowest powered LED ?

akalati

Greetings all,

What's the lowest-powered LED that you've seen (specifically, a surface-mount component, but if needed, can use anything)? Have an application where we don't have too much power at our disposal, so everything counts. Currently using 1.5mA in a bicolor LED. I know Digikey has some LEDs that are rated 0.5mA. Anything less out there? Is there any other technology that will give visual feedback at a fraction of the power requirements (LCD is one example, but need something more visible)?

Any other ideas? Thanks much.
Andy

groggory

LED's that are being fed a PWM signal should do a pretty good job. Maybe have a button you have to push in order to complete the circuit to see the visual feedback LEDs?

erco

I use these http://www.junun.org/MarkIII/Info.jsp?item=62 and http://www.junun.org/MarkIII/Info.jsp?item=63 rated "bright" at 2 mA, but it sounds like you're drawing less than that already.

Unknown

I looked up 1 ma led on google and found the link:

http://parts.digikey.com/1/parts-kws/low-current-led-1ma

Look for the part that says this:

LED 3MM 645NM RED DIFF LOW CURR - HLMP-K150
http://parts.digikey.com/1/parts/684192-led-3mm-645nm-red-diff-low-curr-hlmp-k150.html

AJ-9000

What about flashing a LED.

Try doing a Google search; "Improved LM3909 replacement". Here is one circuit I found that claims it uses only 40 uA average current.

http://www.imagineeringezine.com/PDF-FILES/1vled3.pdf

Phil Pilgrim (PhiPi)

Any LED can be driven at low current, as long as you meet the forward voltage requirements. So the trick is not to find an LED that has a low current rating but one with a very high brightness rating at, say, 20mA. An LED that's very bright at its nominal current rating will still be plenty visible at a lower current or PWMed at a low duty cycle.

-Phil

Humanoido

http://forums.parallax.com/showthread.php?124495-Fill-the-Big-Brain/page11

Akalati: In my Brain Project
I found a solution to the problem of the LED drawing too much current on the PPPBs. After trying several complex PWM programs, I decided to write a simple Spin program that takes the power drawn down from 19-20 mA to 3-5 mA by pulsing the LED-resister combination in two disparate cycles. The code is easily modifiable to include more than one data LED. This is a very simple solution to the original power problem and does not require any extra objects from the OBEX and the code is very small - only 7 lines. (it could be made smaller) Propeller Spin code is available for download at the link. If the LED brightness does not go too dim, you should be able to reduce the 1.5mA to some lower value. I use this program on the 19mA stock LED but never tried it on the ext 1mA LED. This is something I can try next time the Brain is turned on for testing.

Humanoido

Have you tried a higher value dropping resistor? What are you currently using? On a 5v or 3.3v circuit?

Humanoido

I just found another link here for reducing LED power.

akalati

Thanks all for your valuable feedback. Trying to digest the options. One question re PWM, since I'm not at all familiar with it: Will an LED PWMed yield a visible blink, or will it look solid on? If it's a function of the duty cycle, is there an approximate point at which a blink is visible to the naked eye?

marksmith

You can run the 3.2 volt LED directly with 3 volts power source without need a current limitting resistor. The old type LED is 1.6 volt, some is 2 volts.

Spiral_72

akalati wrote: »

Thanks all for your valuable feedback. Trying to digest the options. One question re PWM, since I'm not at all familiar with it: Will an LED PWMed yield a visible blink, or will it look solid on? If it's a function of the duty cycle, is there an approximate point at which a blink is visible to the naked eye?

IMO it's right at 5ms for the blinking to occur

akalati

Humanoido:

Does your setup produce any visible blink on the LED or does it look solid on?

Humanoido wrote: »

http://forums.parallax.com/showthread.php?124495-Fill-the-Big-Brain/page11

Akalati: In my Brain Project
I found a solution to the problem of the LED drawing too much current on the PPPBs. After trying several complex PWM programs, I decided to write a simple Spin program that takes the power drawn down from 19-20 mA to 3-5 mA by pulsing the LED-resister combination in two disparate cycles. The code is easily modifiable to include more than one data LED. This is a very simple solution to the original power problem and does not require any extra objects from the OBEX and the code is very small - only 7 lines. (it could be made smaller) Propeller Spin code is available for download at the link. If the LED brightness does not go too dim, you should be able to reduce the 1.5mA to some lower value. I use this program on the 19mA stock LED but never tried it on the ext 1mA LED. This is something I can try next time the Brain is turned on for testing.

Humanoido

akalati wrote: »

Humanoido: Does your setup produce any visible blink on the LED or does it look solid on?

You can vary the rate from blinking to something that's hardly noticeable. For the lowest current values that I quoted, you can see some high speed blinking. For my app, solid on is consuming too much current per unit time. I found a happy value and compromise that I can live with. Besides, I think the slight blink effect is very unique. I can notice the "on" LEDs much easier. I don't know why I didn't adopt this approach in the past! Try the program. Set it to your board's LED pin number. Adjust the on/off rates. You can get some very good results!