P1 is of experimental value. Start with 220 Ohms or so and modify to suit your needs. The transistor is a general purpose kind and is not critical, almost any pnp type will work. L1 is a bell-transformer which is usually already present in the house. If you wish, you could use a battery instead of the bell transformer. Just hookup a 9-volt battery to points “A” and “B” (A=+) the diode (D1) is to protect the circuit from accidental polarity reversal and is optional, but required for use with the bell transformer.

T1 is a General Purpose PNP transistor and probably anything will work. L2 comes out of an old am transistor radio. They look like miniature transformers and are usually colored red or green. You have to fiddle with different transformers as the sound can vary depending on the value. The loudspeaker is a 8 Ohm type and must be larger than 200milli-Watt. I used a 2 Watt type, but anything over 0.2 Watt will do. It really sounds like a bird and when you release the doorbell button the sound slowly fades away. I have used this circuit in my house for over 20 years and even build the “Birdie” for others. Although
an old circuit, the experimentation and the final results still give a punch. Having fun..!

Train Horn Parts List

R1 = 330K
R2 = 390K
R3,R6 = 68K
R4,R5 = 33K
C1 = 4.7μF/16volt, electrolytic
C2 = 2.2μF/16volt, electrolytic
C3 = 100nF, ceramic
C4 = 100μF/16volt, electrolytic
C5 = 47nF, ceramic
S1 = on/off switch
Re = Reed Relay (glass tube)
IC1 = NE556 (or use two 555’s) (I used a 2″/2W type)
D1,D2 = 1N4001
LS = 8 Ohm, 0.25-2watt. Others may work too.

Train Horn Circuit Description

Circuit is build up arround the LM or NE556 dual timer. Each timer producing a high or a low tone. The 556 contains two seperate 555 timers so feel free to use the 555’s. If you don’t want to fiddle with the reed relay that is fine too. Just put a push on-off switch between negative and pin 6 of IC1. If you go with the reed relay, mount a strong magnet underneath the locomotive and mount the reed relay somewhere between the tracks on a place where you want the horn to be sound. Make sure the reed relay is positioned in such a way that the magnet is able to close the contacts. Make sure reed relay contacts are facing upwards. The sound is very realistic.

C1 & C2 determine the duration (length) of the tones, C1 & C3 determine the frequencies. My original circuit was used
and modified for use with a R/C boat, I modified the caps in such a way it gave very low tones with a small 2″ speaker. Good luck…!

Here is the simple and low cost mosquito repellent circuit design. The circuit serves to keep the mosquitoes out of the room or the location where the device is installed. According to certain publications, the frequency emitted by the male mosquitoes is said to be around 20??”25 kHz, and so within the realm of ultrasound. But according to others, it is in the region of 5??”7 kHz instead; frequencies that a human ear, even an elderly one, can still hear very well. Rather than spending lots of money buying such a device, which moreover generally have a fixed frequency, weâ€re suggesting building one yourself , especially since the circuit proposed is very simple and cheap to build.

Mosquito Repellent Works

The low cost mosquito repellent circuit uses just a single IC, a CMOS type 4047. This very multi-purpose IC can be wired in very many operating modes, including that of the multivibrator or astable used here. The operating frequency is set by the external components C1, R1, and P1. The latter makes it possible to slightly adjust the frequency, given the uncertainty that exists over the most efective value. To best reproduce the high frequencies produced by the generator, the output transducer used is a simple tweeter, but it must be a piezo one. Such a tweeter behaves in fact much like a capacitor, and so doesnâ€t overload the CMOS IC outputs that are incapable of supplying a substantial current.

To obtain an output signal of sufficient amplitude while being powered from a single 9 V battery. The tweeter is connected between the 4047â€s Q and Q outputs. With this condition, it possible to apply complementary (antiphase) signals to the tweeter so it ‘sees†an alternating voltage of double the supply voltage. In purely theoretical terms, this quadruples the output power available. In practice, itâ€s better to regard it as tripling it, but the beneft achieved by doing it this way is nonetheless very real. All that remains is for you to place the project in the middle of the patio table or beside your lounger in order to get a taste of the calm of a summerâ€s evening without mosquitoes bothering you acoustically or worse, biting. At any rate, thatâ€s what we wish for you.

Source: eeweb

This is the electronic bicycle directional lights circuit that use inexpensive components and is a good substitute to many commercially available versions in the marketplace. This circuit works in an extremely different manner and is convenient to operate.

The bicycle direction indicators circuit works off a 9V PP3 (alkaline-type) battery and is basically a set of two independent free-running oscillators (astable multivibrators) built around four low-power transistors and a few passive components. Both the square-wave oscillators (one built around T1 and T2 and the other built around T3 and T4) drive four red LEDs (LED1 and LED2, and LED5 and LED6, respectively), which blink to indicate the direction of turn. Additional steady-glow LEDs (LED3 and LED4) are incorporated to indicate the working status.

How the Bicycle Directional Signal Lights Works

When switch S1 is flipped to “on” position, DC supply from the battery is extended to the oscillator circuit formed by transistors T1 and T2. Now the left-side oscillator starts oscillating and the visual indicators at the front left (FL) and rear left (RL) start blinking at a rate determined by timing capacitors C1 and C2. Resistors R2 and R3 limit the operating current of LEDs (LED1 and LED2). At the same time, the green LED (LED3) starts glowing to indicate the present direction status.

Similar action happens in the next oscillator circuit built around transistors T3 and T4 when switch S2 is flipped to “on” position. Indicators at the front right (FR) and rear right (RR) start blinking, and at the same time the green LED (LED4) glows to indicate the direction status.

Switch S3 is used for emergency indication. When it is flipped to “on” position, both the oscillators get power supply through diodes D1 and D2. As a result, LED1 through LED6 start working simultaneously. In this condition, all the LEDs blink, except LED3 and LED4, which glow steadily.

Bicycle Directional Lights Assembly

After assembling the circuit on a general purpose PCB, enclose it in a suitable cabinet as shown the following image and mount on the handle bar of the bicycle, preferably at the mechanical centre point.

Connect switch S1 at the left-hand side, S2 at the right-hand side and emergency switch S3 in the middle of the master unit. Now place this master unit at the top of the handle bar and do the essential interconnections using flexible wires. Connect the front indicators (LED1 and LED5) to the left and right side of the handle and similarly rear indicators (LED2 and LED6) can be mounted in the carrier frame of the bicycle.

For the direction indicator, you can use the direction symbol and place it at the centre of the handle, look at above image for reference.

R1 = 100Kohms
R2 = 47Kohms
R3 = 100Kohms
R4 ….. 10 = 2.2Kohms
R11 ….. 17 = 10Kohms
R18 ….. 24-25-26 = 220 ohmios
R25-26 = 1.2Kohms

C1 = 2200uF 25V
C2 = 100uF 25V
C3 = 18nF 100V
C4-5 = 10nF

D1 = 1N4148
Q1 a Q7 = BC550
Q8 a Q13 = BC560

IC1 = MM5314N ( Discontinue, National Semiconductor)

GR1 = 4X1N4002
T1 = 220V AC/12V 1A
DS1 a DS7 = Display Common Anodo

Datasheet document for digital clock IC MM5314N can be accessed here:
http://www.datasheetspdf.com/PDF/MM5314N/514207/1

This is the electronic circuit diagram of metronome sound generator. The circuit featured adjustable volume and beats/minute with potentiometers. LED used to be a beat indication. The circuit powered with 9V DC voltage, a 9V battery can be used to operate this metronome circuit. This circuit designed by Velleman.

A metronome is any device that produces regular, metrical ticks (beats, clicks) ? settable in beats per minute. These ticks represent a fixed, regular aural pulse.

The metronome is used by musicians to help keep a steady tempo as they play, or to work on issues of irregular timing, or to help internalize a clear sense of timing and tempo. The metronome is also often used by composers as a standard tempo reference, to indicate the intended tempo for the piece.

The manual kit for this metronome sound generator circuit can be view/download from below link:

Metronome Circuit Manual mk106

Metronome Kit Preview:

This is the circuit diagram of electronic quiz button table. This circuit is simple, easy to built and of course it is not expensive. This quiz circuit used for four game participants. It determines the contestant who first presses the switch (S1 through S4) to answer a question and locks out the remaining three entries so the others contestant’s buttons won’t work. Simultaneously, the respective audio alarm sounds and the bulb glows. The quiz table can be used for more number of contestants simply by adding buzzers, bulbs, MOSFETs and diodes.

This electronic quiz circuit provides an option for varying the time for which an individual buzzer and the corresponding bulb should be “on” after a particular competitor has pressed the push button. These timings can be set by presets VR1 through VR4 as required.

The circuit works off 12V, 1.5A power supply. The current rating of the power supply should be according to the load (wattage of bulbs). For higher-wattage bulbs, use power supply of a higher current rating. LEDs can be an alternative for low current power supply (battery).

This is the figure of how to setup the electronic quiz button on the quiz table:

If participant A presses switch S1, MOSFET T1 is triggered and the corresponding bulb BL1 (connected between drain of the MOSFET and 12V supply) glows and simultaneously piezobuzzer PZ1 connected in parallel to bulb BL1 sounds for the preset time. At the same time, capacitor C1 charges up to 12V, which then discharges through preset VR1. The discharging time of capacitor C1 is decided by preset VR1. For example, if preset VR1 s set for a resistance of 4.7k, it will give a delay of approximately 4 seconds, meaning that buzzer PZ1 and bulb BL1 will be “on” for 4 seconds. It also indicates that participant A is the first to press his switch. Even if any other participant, say, participant B, presses switch S2 after participant A has already pressed switch S1, buzzer PZ2 and bulb BL2 will not function since MOSFET T2 has no gate voltage to trigger because it is grounded through R2 and D1. The same principle applies for other contestants as well.

You can also use a group of LEDs to replace the bulb lamp, so you may create the better decoration for the looks of the lamp.

The game is simple. As stated above, it is a scoring game and the competitor who scores 100 points rapidly (in short steps) is the winner. For scoring, one has the option of pressing either switch S2 or S3. Switch S2, when pressed, makes the counter count in the forward direction, while switch S3 helps to count downwards.

Before starting a fresh game, and for that matter even a fresh move, you must press switch S1 to reset the ci cuit. Thereafter, press any of the two switches, i.e. S2 or S3.

On pressing switch S2 or S3, the counter”s BCD outputs change very rapidly and when you release the switch, the last number remains latched at the output of IC2. The latched BCD number is input to BCD to 7-segment decoder/driver IC3 which drives a common anode display DIS1. However, you can read this number only when you press switch S4.

The sequence of operations for playing the game between, say two players “X” and “Y”, is summarised below:

1. Player “X” starts by momentary pressing of reset switch S1 followed by pressing and releasing of either switch S2 or S3. Thereafter he presses switch S4 to read the display (score) and notes down this number (say X1) manually.
2. Player “Y” also starts by momentary pressing of switch S1 followed by pressing of switch S2 or S3 and then notes down his score (say Y1), after pressing switch S4, exactly in the same fashion as done by the first player.
3. Player “X” again presses switch S1 and repeats the steps shown in step 1 above and notes down his new score (say, X2). He adds up this score to his previous score. The same procedure is repeated by player “Y” in his turn.
4. The game carries on until the score attained by one of the two players totals up to or exceeds 100, to be declared as the winner.

Several players can participate in this game, with each getting a chance to score during his own turn.

Construct the circuit using a multipurpose PCB. Fix the display (LEDs and 7-segment display) on top of the cabinet along with the three switches. The supply voltage for the? circuit is 5V. You may use three batteries with series connection to operate this game scoring display circuit.

This is the circuit diagram of Clap On / Off Switch. The circuit allows you to operate your lighting or any circuit device which use 24V / 3A maximum supply, simply by clapping your hands.?It has a relay output that can be used to turn external devices on/off.? This circuit is good and ideal for disabled or elderly people.

Circuit Features:

• good immunity against surrounding noises
• ‘1-clap’ or ‘2-clap’-mode selection
• ‘2-clap’-mode features built-in safety turn-off timer (approx. 5h)
• output relay ‘pulse’ or ‘toggle’ selection
• microprocessor-controlled
• output relay with LED indicator

Circuit Specifications:

• Supply 12Vdc / 150mA i.e. mains adapter (Order Code 660.446UK)
• Outputs 1 x SPDT Relays
• Output Load 3 Amps @ 24V max.

Notes:

• This circuit available in kit, you can order the kit at quasarelectronics.co.uk, the circuit copyright belongs to them.
• To switch 220V AC, you may try to find suitable relay meet your requirement.

This is the traffic baton circuit which available in two versions that are traffic baton with LED flasher and traffic baton with bulb flasher. Both the circuits powered with a 6V, 4.5Ah rechargeable battery, which is clipped to the operator”s waistband. This circuit which come from EFY mag, will help the police or someone to regulate the traffic with hand signals at night or in dark condition. Since their hand signals may not be visible at night, it is necessary to have some illuminated direction indicator.

The image #1 displays the circuit of traffic baton with LED flasher. It uses an astable multivibrator to flash the LED, it similar to flipflof circuit. The “on” time of the LED cluster is about 108 milli seconds and “off” time is around 105 milliseconds. The frequency is around 5 Hz. A diode is wired in series with the base of BD140 to increase the forward voltage in order to ensure that when BD139 conducts, BD140 is cut-off. Select the LED which consumes low current (20 mA or so) but flashes bright.

The image #2 displays the circuit of the trafic baton with bulb flasher. Similar with LED flasher version, the timer NE555 is wired as an astable multivibrator. The “on” period of flashing bulb is around 344 milliseconds and “off” period is around 329 milliseconds. The frequency is around 1.5 Hz. Bulb-driver transistors 2N3053/ BD139 and 2N2905/BD140 are used to light up the lamp. Two diodes are used in series with the base of 2N2905 to increase the forward voltage in order Bto ensure that when BD139 is conducting, BD140 is cut-off. Slide switch S2 is used to change the colour status of the flashing bulb.

Build the LED flasher and bulb flasher circuits on separate general- purpose PCBs. Place the LED flasher in a transparent acrylic pipe as displayed in above images. The bulb flasher circuit can be enclosed in another transparent acrylic pipe. Slide switches and red and green acrylic sheets are used for appropriate colour emissions.

Good luck.