The LED string has a sufficient number of LEDs to require 120V at 20 mA. The voltage across R 6 provides a means for indirect measurement of the LED current. Figure 3 This circuit achieves an ...

[youtube= Mad Scientist Labs brings us this easy to make LED blinking circuit. The idea is to put a LED in series with a small blinking incandescent bulb from a string of Christmas lights. The bulb… ...

For one open LED: Power Limit Circuit. ... If there is a low drop in the LED string D1 + D2, the voltage at V1 (Q1 collector) will be high and Q11 will turn on through R11 and R12.

The circuit works with any 1.5-V cell, even with a button cell. A good choice, though, is an alkaline AA-LR6 battery, which can power the circuit for several hours due to its 2700 mA-Hr capacity.

In production, this may be replaced with a zero Ohm resistor. The open circuit protection circuit shown utilizes R9, causing it to serve an additional function, in conjunction with Zener diode D2. In ...