4 ms·

In the article, it describes keeping an LED lit for 350 continuous hours. Lots of room for improvement too

by chabes 7y ago

kragen 7y ago
An LED with 0.5 mA going through it is definitely visually distinguishable from one that's off, but it's not “lighting” either, except maybe for Borrowers in a romantic mood, or ants.
- chabes 7y ago
  A single LED emits plenty of light. Just not compared to daylight. And this was for many days..
  - kragen 7y ago
    A single LED can emit enormously varying amounts of light. With some quantities of current, it can emit plenty of light. (Unless it's a low-power LED and burns up first.) With other quantities of current, it emits very little light, all the way down to no light when the current is zero. The brightness at a given current varies by the type of LED, but not all that much (unless you're dealing with infrared or ultraviolet LEDs). And at 0.5 mA, all LEDs are very dim, more like “barely visible”. I suggest you try the experiment. Grab a 7805 and a 10kΩ resistor; you can find these in any discarded electronic device (from 1980 to 2005, anyway) or you can buy them at any electronics store. Connect the resistor between the “output” and “ground” pins of the 7805. Do not connect the “ground” pin to ground. Connect an LED between the “ground” pin (not the “output” pin) and actual ground. (The negative pin of the LED goes to ground.) Connect a positive DC voltage relative to ground to the “input” pin of the 7805; any voltage between 10 volts and 35 volts will work. Now you have a regulated 0.5 mA going through the LED; if you want to confirm this, replace the LED with a 1kΩ resistor and measure the voltage across it with your multimeter. Try different LEDs. Do they emit “plenty of light”? No, they do not. None of them. If you want variable current regulation, you can use a variable resistor, but you should probably put it in series with a fixed resistor. You aren’t going to burn up the 7805 without great effort, but you might burn up whatever you're driving with it.

In the article, it describes keeping an LED lit for 350 continuous hours. Lots of room for improvement too

by chabes 7y ago

In the article, it describes keeping an LED lit for 350 continuous hours. Lots of room for improvement too

An LED with 0.5 mA going through it is definitely visually distinguishable from one that's off, but it's not “lighting” either, except maybe for Borrowers in a romantic mood, or ants.

chabes 7y ago
A single LED emits plenty of light. Just not compared to daylight. And this was for many days..
- kragen 7y ago
  A single LED can emit enormously varying amounts of light. With some quantities of current, it can emit plenty of light. (Unless it's a low-power LED and burns up first.) With other quantities of current, it emits very little light, all the way down to no light when the current is zero. The brightness at a given current varies by the type of LED, but not all that much (unless you're dealing with infrared or ultraviolet LEDs). And at 0.5 mA, all LEDs are very dim, more like “barely visible”. I suggest you try the experiment. Grab a 7805 and a 10kΩ resistor; you can find these in any discarded electronic device (from 1980 to 2005, anyway) or you can buy them at any electronics store. Connect the resistor between the “output” and “ground” pins of the 7805. Do not connect the “ground” pin to ground. Connect an LED between the “ground” pin (not the “output” pin) and actual ground. (The negative pin of the LED goes to ground.) Connect a positive DC voltage relative to ground to the “input” pin of the 7805; any voltage between 10 volts and 35 volts will work. Now you have a regulated 0.5 mA going through the LED; if you want to confirm this, replace the LED with a 1kΩ resistor and measure the voltage across it with your multimeter. Try different LEDs. Do they emit “plenty of light”? No, they do not. None of them. If you want variable current regulation, you can use a variable resistor, but you should probably put it in series with a fixed resistor. You aren’t going to burn up the 7805 without great effort, but you might burn up whatever you're driving with it.