For reverse engineering this week, I took a look at two different night lights – one that turns on and off with a button (and has a charged battery), and one that plugs into the wall and automatically turns on and off depending on the ambient light.
The IKEA night light (which retails for about $14.99 now) is comprised of a soft silicone outer shell, a hard three-part inner shell, circuit boards, LEDs, a button, various resistors, and a battery pack and power input.
1. Silicone outer – single piece injection molded $0.50?
2. Interior shell – three parts, injection molded rigid plastic $0.50?
3. NiMH battery 3/6V 550mAh – $11.99 on DigiKey
4. Class 2 Battery Charger $18.99 on DigiKey
5. Button $1.49
6. 9 Resistors+ $0.40
7. LEDs x4/ green $1.52
8. wire and circuit boards $0.50
TOTAL for parts vs. retail cost // $35.89 vs. $14.99
The photocell nightlight was interesting because it has a very simple sensor mechanism – and because once I took it apart, it was clear that there was an absolute economy of materials. For example, the copper clip that keeps the circuit board and photocell sensor in place also serves as the contact between power and the lightbulb.
There were delightfully few moving parts in this construction.
1. clear plastic cover/diffuser – injection molded $0.50?
2. Body – three pieces white plastic – injection molded + clear plastic lens for photocell $0.50?
3. candelabra-size small light bulb – clear $0.68 @ Antiquelampsupply.com
4. copper band / copper contact clip – $0.10?
5. 2 loose prongs for outlet – $1.28/digikey
6. 1 resistor – 27 ohm – $0.128/digikey
7. Light sensor/ Photocell – $1.58/digikey
8. circuit board/wire $0.50?
9. 1 screw – $0.02
TOTAL for parts vs. retail cost // $5.29 vs. $1.75