Outdoor Solar Lights

Newbies with circuits, want to make a solar powered night light for my room. (inc. photoresistor)

I agree that a relay is useless. Everything needs to be very low power (i.e. use MOSFETs). Capacitors might work if you use the new "ultracapacitors", or DLC’s, which have huge capacitance and tiny leakage.
Since it’s solar powered, you’ll have a photocell. You can use this also as the light detector. When the photocell is producing current, charge your battery or ultracapacitor. When photocell voltage drops below some threshold, turn on the LED.

A simple way to go would be to use two or three photocells in series, and run through a diode to your battery/ultracapacitor. THen, run the battery/capacitor positive terminal to the source of a p-channel MOSFET, and run the drain to your LED (with a series resistor to control brightness). Control the gate of the MOSFET with the positive terminal of the photocells.
When the photocell voltage drops a few volts below the battery, the MOSFET will turn on, energizing the LED. When the photocell is .7V more than the battery voltage, the battery will charge.

Related posts:

1. Looking for solar powered security light(s) at realistic price – where can I buy them? Thanks in advance?
2. How do i power 2 LED lights with one AA battery?
3. I’m making a solar LED light, can you tell me if this will work?
4. How can I power LED light strings with a solar panel?
5. Setting up a solar powered LED night light?

This entry was posted on Saturday, October 24th, 2009 at 9:43 am and is filed under led solar lights. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.