SCR Oscillator

Silicon controlled rectifiers (SCR) can easily oscillate if there is an inductor (a speaker coil in this case) which gives just enough extra voltage to completely switch off the sustain current. In this way a new cycle may start and oscillations set in. It operates over a wide range of supply voltage and components values are not critical at all. Operational frequency in this circuit goes from 100Hz at 11V to 10KHz at 100V.

Pulse Timer

The circuit is a pulse timer. Use timer chip to generate clock pulse.Increase the time period by increase C1 to 100uF and R1 (2 seconds/100K ,3 seconds/220K ,6 seconds/470K ,15 seconds/1M).
Part list :
R1 = 1 Meg, Preset Pot
R2 = 10K
R3,R4 = 1K
C1 = 10uF, 16V
C2 = 0.01uF
T1 = BC547 (Gen Purp NPN)
T2 = 2N2222 (Hi Current NPN)
D1 = 1N4001 (Gen Purp Si)
IC1 = 555 (Lo-Power version)
RLA1 = Relay, 9V (amps of your choice)

AM Tone Transmitter

This circuit uses a 4049 hex inverter to form an AM radio tone transmitter. The RF oscillator in this circuit uses one inverter; its frequency is controlled by a 1 MHz microprocessor crystal. Two more inverters amplify its output. Meanwhile, the two inverters at the top left produce an audio tone, which is modulated onto the RF signal by the last inverter. You can tune this in as an audible whine at 1000 kHz on your AM dial. A few inches of wire attached to the output terminal should suffice as a transmitting antenna. This circuit also has another use. It emits harmonics at all whole-number multiples of 1 MHz (i.e. 2 MHz, 3MHz, etc., up to at least 10 MHz) and you can use it to check the dial calibration of a short-wave radio

45Hz to 90 Hz Hum filter

The circuit filter the signal frequency between 45 Hz and 90 Hz.Adjust frequency from 45 Hz to 90 Hz by using RV1 and adjust band width by using RV2.
Part list :
C = 0.047uF x 3 ,10uF
R = 4.7K ,75K ,620K,2.2K ,100Kx2
RV1 = 20K
RV2 = 100 Ohm

10 MHz to 1 MHz Converter

This converter circuit convert 10 MHz signal frequency to 1 MHz signal frequency.The 10MHz generated by using crystal 10 MHz and convert to 1MHz by using counter chip 1490A.
Part list :
IC1 = 7404
IC2 = 7490A
R = 1 K
R = 3.3 K
C = 39 pF (Trimmer)
C = 4.7 uF 16V (electrolyte)
C = 47 nF 16 V (Mirra)
C = 10 nF 16 V (Mirra)
C = 68 pF 50 V (Ceramic)

6Vdc to 12Vdc Converter

This converter circuit convert a 6 dc voltage to 12 dc voltage and can provide up to 800mA of 12 voltage power.
Part list :
R1, R4 2 .2K 1/4W Resistor
R2, R3 4.7K 1/4W Resistor
R5 1K 1/4W Resistor
R6 1.5K 1/4W Resistor
R7 33K 1/4W Resistor
R8 10K 1/4W Resistor
C1,C2 0.1uF Ceramic Disc Capacitor
C3 470uF 25V Electrolytic Capcitor
D1 1N914 Diode
D2 1N4004 Diode
D3 12V 400mW Zener Diode
Q1, Q2, Q4 BC547 NPN Transistor
Q3 BD679 NPN Transistor
L1 See Notes
Notes
1. L1 is a custom inductor wound with about 80 turns of 0.5mm magnet wire around a toroidal core with a 40mm outside diameter.
2. Different values of D3 can be used to get different output voltages from about 0.6V to around 30V. Note that at higher voltages the circuit might not perform as well and may not produce as much current. You may also need to use a larger C3 for higher voltages and/or higher currents.
3. You can use a larger value for C3 to provide better filtering.
4. The circuit will require about 2A from the 6V supply to provide the full 800mA at 12V.

40 LED Blinking with IC555

The IC555 is used to blink LEDs. Each LED can be on, off, or flashing at duty cycle designed.
Path List :
R1 = 4.7K
R2 = 150K
IC = IC555
C = 1uF ,0.1
Transistor = 2N2905 ,2N3053
R = 100 ,220 , 160 Ohm

Relay Select for 8 Source

Relay select for 8 source.Select each relay by supply 24 DC Voltage to pin 1 -8 of SL2.
Path List :
R1-8=4.7 Kohms T1-8= BD139 (R1-8=15 Kohms if T1-8=BD679)
RL1-8=6V-24V dc Relay D1-8=1N4148

DC Power Supply 5,9,12,15,24 Volt

The power supply that supplies electrical 5,9,12,15,24 DC Voltage. The power supply consisted of a rectifier and a capacitor filter. The rectifier was essentially a conductor.
Part List :
T1 = 115 VAC/24 VAC
LM78XX = LM7805(5VDC) ,LM7808(9VDC) ,LM7809(9VDC) ,LM7812(12VDC) ,LM7815(15VDC) ,LM7824(24VDC)

Transistor Power Amplifier 3W

Here is a little audio amplifier similar to what you might find in a small transistor radio. The input stage is biased so that the supply voltage is divided equally across the two complimentary output transistors which are slightly biased in conduction by the diodes between the bases. A 3.3 ohm resistor is used in series with the emitters of the output transistors to stabilize the bias current so it doesn't change much with temperature or with different transistors and diodes. As the bias current increases, the voltage between the emitter and base decreases, thus reducing the conduction. Input impedance is about 500 ohms and voltage gain is about 5 with an 8 ohm speaker attached. The voltage swing on the speaker is about 2 volts without distorting and power output is in the 50 milliwatt range. A higher supply voltage and the addition of heat sinks to the output transistors would provide more power. Circuit draws about 30 milliamps from a 9 volt supply.

Tube Power Amplifier 3W

Power output 3W/8 ohm - 1KHZ .Input sensitive 600mV for 2W.
Distrotion 3%.Frequency response 22HZ-50KHZ -3dB.s/n 90dB
Part List :
R1= 22Kohm C1-7-9= 100nF 1KV V1= ECC81
R2-3= 1Kohm C2= 220uF 350V V2= 6BX7
R4-5= 1.5Kohm C3= 150nF 400V T1= 220V@2X250V/6.3V/6.3V
R6-7= 470Kohm C4= 100uF 25V T2=Audio transformer
R8-9= 1Kohm 2W C6-8= 2X100?F 350V
RV1= 250Kohm Log. pot. D1-2= 1N4007

Power Amplifier 1W

The semiconductor LM386 is a general purpose power amplifier designed for use in low voltage applications. Gain may be set between 20 and 200.
Part List :
C1 = 100nF
C2 = 47 nF
C3 = 470 uF
C4 = 10uF
C5 = 33 nF
P1 = 10K
R1 = 10K
R2 = 10 Ohm
IC1 = LM386

12Volt to 9Volt DC Converter

Parts List:
R1 = 560 ohm
C1 = 1000uF/40V, Electrolytic
C2 = 10uF/25V, Electrolytic
C3 = 330nF, Ceramic
Z1 = 9.1V, 1watt zener
Q1 = ECG184, NTE184

Notes:
To get a more precise output voltage, replace zener diode Z1 with 10V and R1 with a 1Kilo ohm potentiometer. A Coolrib for Q1 is optional but highly recommended. You can replace Q1 for a more robust type to get more output amps depending on your requirements. Simple circuit to power your 9 volt cassette recorder and other stuff.

From : http://www.uoguelph.ca/~antoon/circ/car912.htm