Various White LED Lighting Solutions
Now that 5mm White LED's with high light output are economically available, they can be a good solution for various 'background' lighting, both indoor and outdoor.
Many commercial implementations are very crude (if you're lucky, there will be just a single resistor between supply and the LED's; one "lantern" I saw had pairs of white LED's directly connected across a 6V SLA battery) so I've ended up with a few circuits for my use. All are capable of operation on a nominal 12V supply, and will work from 10V to 20V (and more if additional heatsinking is provided).
|
Disclaimer: Whilst information on this page is given in good faith in order to help others, no responsibility for this information is assumed and all liability in respect of such information is disclaimed. |
The first circuit is a simple 20mA current limiter for powering 3 white LED's . Almost any NPN transistors can be used:
If you've got lots of PNP transistors instead, or want ground referenced LED's, use this version:
If you only want the LED's to come on when it's dark, add a CDS photocell as shown; you might need to change the value of the 1M resistor for different light levels. Note that the LED's come on gradually as it gets darker!
|
Disclaimer: Whilst information on this page is given in good faith in order to help others, no responsibility for this information is assumed and all liability in respect of such information is disclaimed. |