EK032 Night Light USB
Part.no: 41023942
EK032 is a simple light-controlled lamp that turns on when it gets dark. The kit contains few components and is suitable for beginners.
The circuit consists of a photoresistor, a driver transistor, and an LED. The photoresistor together with the three 1 MΩ resistors forms a voltage divider that controls a transistor. When the transistor begins to conduct, it draws current through the LED, causing it to light up.
The protruding section of the PCB forms a simple USB-A connector that can be used to power the finished lamp, for example by inserting it into a USB port on a computer or directly into a USB charger in a wall outlet. The two diodes allow the board to be inserted into a USB connector in either orientation.
The board can also be powered from another voltage source via the holes marked "+" and "−".
To adjust the sensitivity, a different number of the three 1 MΩ resistors can be installed. One resistor gives high light sensitivity, two resistors gives somewhat lower sensitivity, and three resistors gives the lowest sensitivity.
- Supply voltage: 5 – 15VDC
- Current draw: ~5mA (5V)
- Dimensions: 25.4 x 38.75mm
Component list
| RefDes | Value | Qty. | Part.no. | Marking |
|---|---|---|---|---|
| C1 | El.lyt capacitor 47uF | 1 | 41017676 | 47uF |
| D1 | LED 5mm white | 1 | 40307039 | |
| D2, D3 | Diode 1N4148 | 2 | 40310010 | |
| LDR1 | Photo resistor 4-7kohm | 1 | 40850001 | |
| R1, R2, R3 | Resistor 1Mohm | 3 | 40811610 | |
| R4 | Resistor 100ohm | 1 | 40811210 | |
| T1 | Transistor NPN BC547 | 1 | 40320001 | BC547C |
Assembly guide
Before beginning assembly, check that the PCB is free of damage and scratches. Verify that you have all components to be installed by comparing against the component list. This kit contains few components, and aside from the resistors, each component has only one possible placement location. Pay attention to the markings for the capacitor, transistor, and diodes. These must be installed in the correct orientation for the circuit to function.
Interactive assembly guide ↗
Schematic
Drawing
