Seven Component Regulated LED Lamp
(C) G. Forrest Cook 2001
Updated March, 2003
Introduction
This is a minimal parts lamp made with four white LEDs. It features regulated light output from 10V to around 20V and works well as a flashlight.
Specifications
Nominal Operating Voltage: 12V DC
Operating Current: 40ma
Theory
The LM317L and resistor act as a current regulator set to 40ma. Current flows from the battery through one pair of LEDs, through the regulator, through the other pair of LEDs, and back to the battery. The capacitor filters out noise on the power supply lines. The LED pairs must be matched so that the current through them is roughly equivalent. Small resistors could be placed in series with each of the four LEDs to improve the balance, but the parts count would go way up.
Construction
There is one trick with this circuit, matched pairs of LEDs must be used. Normally, a batch of LEDs from the same manufacturer will be matched close enough for this application. If unmatched LEDs are used, one LED per pair will be bright and the other one will be dim. It is best to first build the circuit on a plug-in proto board to verify that the LEDs light evenly.
A small circuit board was made using press-n-peel blue film, the board was cut into a circular shape using a nibbling tool. The parts were soldered in, and the board was mounted inside of the bottle cap. The bottle cap protects the LEDs and prevents bright light from coming out of the side of the assembly. The cap came from a 1 Liter "Aqua Fina" brand water bottle. The single screw can be used to mount the assembly to an external bracket.
The completed circuit board and cap assembly was mounted in an old automobile turn signal. The lamp head was mounted onto the end of an old fluorescent lamp base with a goose neck adjustable arm. The resulting lamp is quite effective for night reading, and it's not too ugly.
Alignment
If you have a variable power supply, it is best to bring the voltage up slowly the first time power is applied to the circuit. If any of the LEDs don't light, turn off the power and fix the problem. If all of the LEDs light up evenly, the circuit should work (for many years) on 12V.
Use
Connect this circuit to a 12V battery or power supply, be sure to observe the correct polarity. The LEDs should put out a bright white light. You can read by this light, and it is useful for emergency illumination. The low current draw allows it to run for many hours on a battery.
Parts
4x white LEDs (matched), T1-3/4 size
1x 30 ohm 1/4 W resistor
1x 0.1uF capacitor
1x LM317L adjustable voltage regulator
1x plastic bottle top from a water bottle (1 liter Aqua Fina brand)
1x 4-40 3/8" screw
2x 4-40 nuts
这是一个由极少元件与四个白色发光二极管级成的台灯，它具有亮度调节输出，用10 v至20v的变压器供电。
规格：
操作电压：12 v直流
电流： 40毫安
说明：
由lm317l 和电阻器作为电流调节器设定为40毫安。目前流入从电池透过一双发光二极管，通过调节，通过其他对发光二极管，并回电池。该电容器通过过滤噪声对电力供应线。领导对必须配合，所以说，目前通过他们大致相等的。小电阻器，可放置在同系列的每4个发光二极管，以改善平衡，但部分指望会去的方式。
制作：
有一招，与这条赛道，匹配对发光二极管必须用。通常，一批发光二极管从同一制造商将配合不够紧密，为这项申请。如果无法比拟的发光二极管的使用，但其中主导的每对将是光明和其他人都不会黯淡。最好是先建立电路的一个插件，在原董事会，以核实该发光二极管光均匀。
一个小电路板是靠了新闻氮-皮尔蓝膜，董事会被切割成圆形形状用nibbling工具。零件被焊，与董事会展开里面的瓶盖。该瓶盖保护发光二极管，并防止光线的强弱，从步出侧大会。帽来自1升"王水国际泳联"品牌水壶。单螺杆可用于摩大会，以一个外部支架上。
已完成的电路板和帽大会是装在一个旧汽车转向灯。灯泡的头部被装上月底老荧光灯基地，以鹅颈可调臂。由此产生的灯泡是相当有效夜读，这不是太丑陋。
说明：
如果你有一个变量的电力供应，最好是把电压缓慢第一次权力是适用于电路。如果有任何的发光二极管不轻，关掉电源和解决这个问题。如果所有的发光二极管灯均匀，使电路应工作（多年）的12 v 。
使用：
连接这条赛道到的12 v电池或电源供应器，一定要遵守正确的两极分化。该发光二极管应出明亮白光。你可以阅读这个角度来说，它是有益的应急照明。低电流消耗量允许它运行，为很多个小时的电池。
元件选用：
4 ×白色发光二极管（配对） ，在t1 3 / 4尺寸
1 × 30欧姆1 / 4瓦特电阻
1 × 0.1uf电容
1 × lm317l可调式稳压器
1 ×塑料瓶盖，（ 1升王水国际泳联品牌）
1 × 4-40 3 / 8 "螺丝钉
2 × 4-40坚果
