Battery Level LED Indicator
This LED Indicator uses a LM339, a quad comparator. LM339 can work on single or dual supplies, it has a open collector output that can drive 15mA, low power consumption. The circuit is an...
Category: LED-Circuits
Simple Mains Voltage monitor
This Circuit helps in the monitoring of mains supply voltage. It does not use a isolation step down transformer. This has to be constructed only by skilled people with knowledge of safety requirements. C1...
InfraRed LED Flasher for Optical Switch
This circuit is used to detect objects by reflected infrared light. It can be built into a cylindrical enclosure just like an inductive proximity switch. Part of – InfraRed Detector for Proximity Switch This...
LED Voltage Level Indicator
This circuit is derived from a Siemens Application Note 1974. This circuit uses common components of today. The circuit is here as it is of high educational value. I have not tested it. You...
Constant Current Source for LED
This article will explain the way a simple transistor based current source is designed, this will give an idea on how some components can be used in a practical way to make the circuit...
Mains Voltage Indicator with a LED
This is a mains 230V AC voltage indicator and is a LIVE CIRCUIT, so take care. The Resistor has to be a fusible ceramic wire wound and the capacitor 630V AC or higher capacity....
Mains Current Indicator with a LED
This is a mains 230V AC load current indicator and is a LIVE CIRCUIT, so take care. The Resistors have to be a fusible ceramic wire wound. More at Mains Voltage and Power Circuits...
LM3914 meter for 25 V DC
“I wish to assemble a bargraph display to indicate approximately 25volts dc.How many LM3914 I should cascade? How to calculate resistor value which is grounded from the junction of Pin 6 & 7 (Rhi...
