Diagram Plus guide

Most of you asked about a Battery Charger Indicator Circuit.This circuit indicates weather battery is charged or not.This circuit avoid the over charge of batteries purple LED will indicate the battery is charging.After charging purple LED is off.

This is a tracking transmitter.Normally we use these thing to track animals,Rc planes etc.The power of this one is about 3.7mA.This circuit can be operated by using 1.5V button cell.The operating frequency is FM 100Mhz .But if you want to use it between 108Mhz to 88Mhz you have to use Just spread the windings of the coil just a bit About 1/2 a millimeter .This is wonderful project. Have fun with this.




Note

#This is not long range one but you can get the maximum advantage
#supply 1.5 v
#Attach 12 inch antenna

This is a circuit which can be used to monitor batteries or other electric equipments current problems.Here that current will be indicated through the sound and through the LED.So you all can check your low volt equipments easily.

Parts:

U1 LM339 Voltage comparator IC
D1 1N5233B Zener Diode
D2 LED
R1, R3 1K 1/4W Resistor
R2 5K Pot
BZ1 Piezo Buzzer
MISC Board, wire, socket for IC

Note

# This circuit can be operated with 9v to 12v

This jet engine sound generator circuit is based on the sound generator IC HT2844P from Holtek Semiconductors. This particular IC can make four sounds namely low speed sound of jet engine, high speed sound of jet engine, missile sound and machine gun sound. Each of these sounds can be activated by connecting the pins 12, 13, 14and 15 to ground by using the respective push button switches. Resistor R3 can be used for manually increasing or decreasing the speed.LED D1 gives a visible indication of the sound

An low power FM Transmitter using an op-amp as the audio preamp and a single transistor as the RF amplifier.