LED Passenger Car and Building Lighting Constant Voltage with Current Regulating Chip
Joined: Sep 25, 2010
Topics: 32 Replies: 39
Current regulating chips are relatively new. Instead of a resistor the chip limits current flow to 20ma (.02 amps) the current that many LEDs run on. This approach eliminates the need for resistors or resistor calculation. The chips cost about 50 cents each from Mouser. com and come in several packages. I used the TO92 without problems. The leads are brittle so only bend them once.
One or more LEDs can be put in series with the chip. As always series wiring is more efficient.As many LEDs can be put in series as voltage input allows. 20 volts will drive 6 for example. However for conventional each LED will need a chip since 5 volts,the minimum throttle setting will only drive 1. However for building wiring LEDs in series is practical. A good use for this chip is circuiting a constant voltage headlamp. The circuit is not practically dimable.
A small capacitor is recommended on the output but I do not use it. I corresponded with an engineer from the company and he said not to worry about it.