Introduction: Auto Brightness Adjusting LED Strip
This project is an automatically dimmable LED strip light. This project is aimed towards beginners in electronics, or those who have some electronics knowledge or experience. This project will provide an opportunity to learn about PWM (pulse width modulation) and the 555 timer IC in order to regulate the dimming of an LED strip light.
The purpose of this project is to provide adequate lighting no matter the ambience of the room. The brightness of the LED strip would be determined based on the lighting situation of the room it is in. For example, if the time of day is morning and the room is already well lit, the LED strip light would remain off or at very low brightness. However, if it is late at night and there is little to no light in the room, the LED strip would be near 100% brightness.
Supplies
All supplies can be purchased from https://leeselectronic.com
- JST XH 2 pin jumper wire #28602
- LDR photoresistor 1K-3M #71862
Step 1: Wiring the Breadboard
Before soldering onto a PCB, it is always a good idea to build the circuit on a breadboard and test. Build the above circuit using the schematic shown above. Connect the LED strip or a 12V LED from the 1K resistor to GND. To test, plug in a 12V 1A (center positive) AC/DC power adapter into the 2.1mm DC power jack, and try waving your hand over the LDR to make the area darker. If the LED brightness changes, then the circuit is working.
Step 2: Soldering the Circuit
Once the breadboard circuit is working, it is time to solder it onto a PCB. Solder the 8-pin IC socket onto the board rather than soldering the 555 timer directly, in case the IC needs to be replaced at any point. Solder all the necessary connections. You may need to use a short length of solid wire to join components that are further away. Use the above picture as an example of how to solder the connections together. Leave 2 wires (VCC and GND) disconnected on one end, these will connect to the LED strip.
Step 3: Connecting the LED Strip
Using the JST 2 pin jumper wires, solder the leads onto the leads of the LED Strip. Then crimp or solder the JST pins onto the 2 wires left disconnected on the soldered PCB circuit. Push these pins into the male end of the JST jumper wire. Plug in the 2 ends of the JST connectors together to connect the LED Strip.
Step 4: Powering the Circuit
Power the circuit using a AC/DC 12V 1A power adapter. Make sure the adapter is center positive. LED strips typically use about 1A per meter, so if you wish to use a longer LED strip, simply use a 12V power adapter with a higher current rating.
Step 5: Video Demonstration
Disclaimer: Flicker is caused by camera capturing faster than PWM signal
Step 6: Wrapping Up
The LED strip dims using PWM and the 555 timer.
By pulsing the voltage being sent to the LED strip, it gives the effect that the LED strip is dimming, although in reality it is flashing at a rate which the human eye is unable to see. This circuit can be used in multiple situations. Some examples include lighting for a staircase or lighting for clothing at night.
