Birdie Doorbell Ringer

Audio light modulator

Modulator Easy

AM Modulator

Alternating ON-OFF Switc

R1 = 10K
R2 = 100K
R3 = 10K
R4 = 220 Ohm (optional)
C1 = 0.1µF, Ceramic (100nF)
C2 = 1µF/16V, Electrolytic
D1 = 1N4001
Led1 = Led, 3mm, red (optional)
Q1 = 2N4401 (see text) IC1 = 4069, CMOS, Hex Inverter (MC14069UB), or equivalent
S1 = Momentary on-switch
Ry1 = Relay )

Air Flow Detector

R1 100 Ohm 1/4W Resistor
R2 470 Ohm 1/4W Resistor
R3 10k 1/4W Resistor
R4 100K 1/4W Resistor
R5 1K 1/4W Resistor
C1 47uF Electrolytic Capacitor
U1 78L05 Voltage Regulator
U2 LM339 Op Amp
L1 #47 Incandescent lamp with glass removed (See "Notes")
D1 LED

Notes:
1. The glass will have to be removed from L1 without breaking the filament. Wrap the glass in masking tape and it in a vise. Slowly crank down until the glass breaks, then remove the bulb and carefully peel back the tape. If the filament has broken, you will need another lamp.

AGC Sound

Adjusrable60 Hz filter

Active Power Zener

Stereo Decoder2

Stereo Decoder

Zener Oscillator

These two circuits are interesting from an academic point of view. Their practical implementation is rather critical and it is not easy to get steady operation. Circuit (a) requires a "cooked" zener: connect it first to a constant current generator, then increase the current until the voltage across the zener starts to decrease. Reduce the supply current and wait a few minutes until it really warms up. The zener is now ready for the circuit: increase the voltage slowly until it oscillates (1KHz in the circuit shown). You may need to decrease the voltage once oscillation takes place. With suitable circuit components it will oscillate up to 20MHz. Circuit (b) will oscillate at a very low frequency, normally 2-5Hz, provided the voltage is increased very slowly, loading is critical and you may find that a slightly different lamp will work better. Higher voltage zeners work better than low voltage zeners and the circuits operate only with the specified types. The reasons for the oscillations are unknown, although, for circuit (b) it is felt that some kind of reversible thermal breakdown is at work.

Wireless Auto Tachometer

1 1 0.47uF Capacitor
C2 47uF Electrolytic Capacitor
D1 8V 1W Zener Diode
D2, D3, D4 1N914 Diode
M1 200uA Meter
Q1, Q2 2N3391A Transistor
R1, R2, R9 1K 1/2 W Resistor
R3 47K 1/2 W Resistor
R4 10K 1/2 W Resistor
R5, R6 25K Trim Pot
R7 10K Trim Pot
R8 200 Ohm 2 W Resistor
R1 15K 1/2 W Resistor
R1 2.2K 1/2 W Resistor
S1 SPST Togglae Switch
S2 Three Position Single Pole Rotary Switch



Notes:
1. Calibrate the unit as folows:

a. Set up this circuit:

b. Turn on the Tach and allow a few minutes for temperature stabilization.

c. Set S2 to 4 cylinders and adjust R5 for a meter indication of 180 (1800 rpm).

d. Set S2 to 6 cylinders and adjust R6 for a meter indication of 120 (1200 rpm).

e. Set S2 to 8 cylinders and adjust R7 for a meter indication of 90 (900 rpm).

2. To use the Tach, turn it on and let it sit for one minute to allow for temperature stabilization. Extend the antenna, select the right number of cylinders and hold the unit over the engine. If the reading is erratic or the needle jumps around, move the antenna closer to the ignition coil or spark plug wires.

3. The unit draws power from the car battery. If it is connected backwards, it will not work, but it won't be damaged.

Wire Loop Alarm

R1 100K 1/2W 1% Resistor
R2, R4 10K 1/2W 1% Resistor
R3 1 Meg 1/2W 1% Resistor
C1, C3 0.1uF Ceramic Disc Capacitor
C2 0.01uF Ceramic Disc Capacitor
IC1 4001UBE Quad 2-i/p NOR Gate
Q1 MPSA14 Low Power NPN Transistor
SIREN Micro piezo siren 12V DC 150mA, 110dB @ 1M
LOOP See "Notes"
The loop can be any type of hookup wire, with a maximum resistance of about 90K. Using very thin wire (40AWG, for example) will make a very sensitive trip wire, but will shorten the distance it can be strung due to the high resistance.
The siren can be replaced with a relay to drive external loads.

Video Activated Relay

R1, R2 10K 1/4 W Resistor
R3 1K 1/4 W Resistor
R4 33K 1/4 W Resistor
C1 1uF Electrolytic Capacitor
Q1, Q2, Q3 2N2222 NPN Transistor 2N3904 NPN Transistor
D1, D2, D3 1N4148 Diode
K1 9V Relay
J1 RCA Jack

Notes:
1. Since you may be using this circuit to switch mains voltage, it should be enclosed in a case.

2. The circuit will also work with most line level audio, although you may have to adjust the value of R1

Ultra Low Frequency Receiver

The frequency covered is from 0.1Hz to 10Hz and useful signals are received up to 16Hz. The first Op-Amp, properly shielded, must be installed close to the antenna (1-3m long) and connected to the rest of the circuit with a 5-core shielded cable. Adjust the 100k trimmer so that the DC setting at the output of the OPA124 does not change when turning the 220k sensitivity pot. A low pass filter followed by a notch filter take care of the mains induced noise. The values in brackets are good for a 60Hz mains. 1% components should be used for the 3 resistors and 3 capacitors of the notch filter. A voltage controlled oscillator gives an audible frequency that follows the input signal and it is very handy if the unit is made portable although I found that just walking around is enough to bury the signal being received. The output signal goes first to a meter and then is available for the connection to a data logger, which is an almost essential part of the receiver. Sensitivity is quite adequate: any TV set switching on in the area will be detected. There are also a host of other mysterious signals of unknown origin. The input protection diodes are special low leakage type and should not be replaced by standard diodes. These diodes can be dispensed with if the antenna is installed with care and away from strong electric fields. The diodes connected to the meter are Schottky diodes and will provide a bias against very small signals (mostly noise) which will not go through to the data logger. Pin connection for OPA124: 1 and 5: DC set, 2 and 3: inverting and non-inverting, 6: output, 8: substrate. Pin connection for LF412: 2 and 3: inverting and non-inverting, 1: output, 6 and 5: inverting and non-inverting, 7: output

Time Domain Reflectometer(TDR)

Switch Debuncer

Subcarrier(SCA ) Adapter From FM

step-up converter (MC34063A)

The step up converter is the power unit to make the output voltage which is higher than the input voltage. The converter which was made this time can make stable output voltage with the input voltage of +12V. The stable output voltage can be controlled in the range of +13V to +32V. Because it makes the limitation value of the input electric current about 1.3A, the maximum with the input electric power is about 16W.

Square Wave Generator (100Hz)

Sound Triggered Flash

If you wish to take a picture of a fleeting event which generates a sound, you can do it with this sound activated trigger. It does not require any power supply: it feeds on the high voltage available on the flash trigger terminal. Any economic ceramic microphone is suitable for the purpose. The 68nF capacitor introduces a small delay in the operation of the flash and may help in getting the picture in exactly the right moment although you should expect to take several shots for best results. With this circuit you will be able to catch a cork leaving the champagne bottle or the moment a balloon is punctured. The whole circuit could be assembled in the mike housing making a very compact device.

Seismic Detector

SCR Invertor

The only drawback with this circuit is that it might latch in the conducting state if the load is too heavy or if there is a short at the output, this requires some kind of protection, on the input line, in the form of a fuse or similar. The transformer used is a 10W mains type with 6V+6V windings on the SCR side and a 110V+110V windings, in series, at the output. Efficiency is 50% and the ideal load is equivalent to a 22k resistor, 5W. The output waveform is vaguely sinusoidal at a frequency of 400Hz.

SCR oscillations

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.

RF Sinal Generator

RC Notch Filter (Twin T)

The twin T notch filter can be used block an unwanted frequency or if placed around an op-amp as a bandpass filter. The notch frequency occurs where the capacitive reactance equals the resistance (Xc=R) and if the values are close, the attenuation can be very high and the notch frequency virtually eliminated. The insertion loss of the filter will depend on the load that is connected to the output, so the resistors should be of much lower value than the load for minimal loss. At audio frequencies, the filter could function as a bass and treble boost circuit by attenuating the mid range frequencies. Using 1.5K resistors and 0.1uF capacitors, the band stop at -10dB is about 500 Hz to 2Khz. The depth and width of the response can be adjusted somewhat with the 0.5R value and by adding some resistance across the C values. If the circuit is used around an op-amp as a bandpass filter, the response may need to be dampened to avoid oscillation.

Proximity Alarm

Power-On

Here's a power-on time delay relay circuit that takes advantage of the emitter/base breakdown voltage of an ordinary bi-polar transistor. The reverse connected emitter/base junction of a 2N3904 transistor is used as an 8 volt zener diode which creates a higher turn-on voltage for the Darlington connected transistor pair. Most any bi-polar transistor may be used, but the zener voltage will vary from about 6 to 9 volts depending on the particular transistor used. Time delay is roughly 7 seconds using a 47K resistor and 100uF capacitor and can be reduced by reducing the R or C values. Longer delays can be obtained with a larger capacitor, the timing resistor probably shouldn't be increased past 47K. The circuit should work with most any 12 volt DC relay that has a coil resistance of 75 ohms or more. The 10K resistor connected across the supply provides a discharge path for the capacitor when power is turned off and is not needed if the power supply already has a bleeder resistor.

Power-Off หน่วงเวลารีเลย์

The two circuits below illustrate opening a relay contact a short time after the ignition or ligh switch is turned off. The capacitor is charged and the relay is closed when the voltage at the diode anode rises to +12 volts. The circuit on the left is a common collector or emitter follower and has the advantage of one less part since a resistor is not needed in series with the transistor base. However the voltage across the relay coil will be two diode drops less than the supply voltage, or about 11 volts for a 12.5 volt input. The common emitter configuration on the right offers the advantage of the full supply voltage across the load for most of the delay time, which makes the relay pull-in and drop-out voltages less of a concern but requires an extra resistor in series with transistor base. The common emitter (circuit on the right) is the better circuit since the series base resistor can be selected to obtain the desired delay time whereas the capacitor must be selected for the common collector (or an additional resistor used in parallel with the capacitor). The time delay for the common emitter will be approximately 3 time constants or 3*R*C. The capacitor/resistor values can be worked out from the relay coil current and transistor gain. For example a 120 ohm relay coil will draw 100 mA at 12 volts and assumming a transistor gain of 30, the base current will be 100/30 = 3 mA. The voltage across the resistor will be the supply voltage minus two diode drops or 12-1.4 = 10.6. The resistor value will be the voltage/current = 10.6/0.003 = 3533 or about 3.6K. The capacitor value for a 15 second delay will be 15/3R = 1327 uF. We can use a standard 1000 uF capacitor and increase the resistor proportionally to get 15 seconds.

Power Flasher

There is no need to resort to complex circuitry if what you are looking for is a simple power flasher. The light will flash at around 1Hz with a 100W bulb at a duty cycle of 50%. The max. load that can be driven with this circuit is 200W and if you wish to have a different frequency you have to change the value of the capacitor. Operation at 110VAC has not been tested although I expect it to work provided the resistors are set at about half the stated value. The SCR is manufactured by Siemens but any other equivalent semiconductor, with standard gate sensitivity, should work fine. WARNING! - This circuit is directly connected to the mains and proper safety precautions should be taken. A more modern design would use a sensitive gate SCR, other low power resistors, an additional resistor between gate and cathode, and a 10mF, 250V electrolytic capacitor

Pluse Timer

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)

PLL synthesizing oscillator 3