Eliminating LED Pop/Click Noise Circuit

Posted by Micro System

on Monday, September 27, 2010

This is a simple circuit for LED pop noise circuit. Typical LED indicator consist of resistor (R2) and LED, connected in series with a switch.  When the switch is closing or opening, a glitch noise may occur at the supply line. To avoid this noise, R2 and C1 are added to the indicator circuit and value of R1 is adjusted. This is the figure of the circuit;

Very slightly delay is provided by the R2-C1 circuit which is used to prevents the pop sound, but the LED still lights up fast enough that the eye cannot see the delay. The question is, why not just add the C1 capacitor and not have R1 in the circuit? The current in the LED is limited by the 390 ohm resistor when C1 dumps its charge as the switch is toggled. These spikes can cause the life of the LED become shorter even cause it to burn out. To give the proper brightness with the LED that is being used, the value of R2 should first be selected. You can increase the value of C1 to 22uF or even 47uF as needed if the LED indicator circuit is still causing a pop in the audio.

LED Torch Circuit Using 7555 IPA IC’s

Posted by Micro System

on Tuesday, August 17, 2010

This is a circuit for LED torch circuit that is consumes just 24 mW, giving it more than 80 times longer service from 4 AA alkaline batteries (that is, up to one month's continuous service). Although the torchs light output is modest, it is nonetheless quite sufficient to illuminate a pathway for walking. This is the figure of the circuit;

The LED Torch is based on a 7555 timer running in astable mode (do not use an ordinary 555). A white LED (Maplin order code NR73) produces 400 mcd light output, which, when focused, can illuminate objects at 30 meters. Try Conrad Electronic for what appears to be a stronger white LED (order code 15 37 45-11). A convex lens with short focal length is placed in front of the LED to focus the beam. If banding occurs at the beams perimeter, use another very short focal length lens directly in front of the LED to smooth the beam. [Circuit schematic source: zen22142.zen.co.uk]

12V 6-12 Watt Fluorescent Tube (Neon) Lamp Inverter Circuit

Posted by Micro System

on

This is a circuit for a 40 watt fluorescent tube lamp or two 20-watt tubes in series will be driven by this circuit but this circuit will produce less brightness than usual, since this circuit only deliver 6-12 Watts. This circuit draws 0.9-1.2 Amps for 2 x 20 watt tubes, or 0.45-0.9A for 1 x 20 watt tube, depending on the potentiometer setting. This is the figure of the circuit;

The transformer is wound on a ferrite rod 10mm diameter and 8cm long. The diameter of the wire is fairly critical but has been successfully implemented using 0.28mm wire for all the windings in the prototype. When the circuit is operating, do not remove the tube as the spikes produced by the transformer will damage the transistor. The brightness varies with the current consumption adjusted by the pot. Heat-sink must be greater than 40sq cm. Use heat-sink compound.

White LED Mains Night Light Circuit

Posted by Micro System

on Thursday, August 5, 2010

This is a circuit for LED main night lights. This circuit is very sensitive. This is the figure of the circuit;


Don’t touch the circuit when plugged to the mains supply, this will cause a lethal electrical shock since it’s not isolated from the mains supply. A column of 10 white LEDs is illuminated by this circuit. The flicker is prevented by 10u capacitor and reduced by 100R resistor.