12V DC Flourescent Lamp Driver

Here it is,it uses a normal 120 to 6v stepdown transformer in reverse to step 12v to about 350v to drive a lamp without the need to warm the fiolaments.

Electromagnetic Levitator Circuit

This circuit creates a stunning display of the "magic" of magnetism by suspending a small metal object in mid air. Using an electromagnet, photo sensor and closed loop control, small and light metal objects can be floated just underneath the magnet, enclosed in a decorative arch. "No strings" are easily demonstrated by the ability to pick the metal object out of the air and place it back under the magnet at will. With the object floating about 1/4" under the magnet (exact distance will depend on the weight of the object), an LED and photo transistor arrangement let a feedback circuit know it's position. The circuit controls current to an electromagnet to maintain an equilibrium between the force of the magnet and gravity. Thus, the object floats. Impart a bit of a spin to the object and momentum will carry it for quite a long time as the only friction working against it is between the object and the air.

Electronic Dice Circuit

An electronic dice is a classic first project for those getting interested in electronics. A timer, counter and a few LEDs makes a circuit that can also add a new twist to some old boring board games. When the switch is pressed, a 555 timer in astable mode pulses a BCD counter which lights up a series of LEDs wired to mimic a dice. Two AND gates are used to reset the count back to one whenever the BCD output is seven. Thus, the circuit is not truly random but the natural bounce present in a pushbutton and the normal human ability to operate much slower then the oscillator make the output of the circuit seem random.

Wireless Auto Tachometer

Anyone performing their own automobile tune-ups knows how important it is to know your engines speed. With this tachometer, you can measure your engines speed without any connections or annoying timing lights.
Schematic:

AC Motor Speed Controller

This AC motor speed controller can handle most universal type (brushed) AC motors and other loads up to about 250W. It works in much the same was a light dimmer circuit; by chopping part of the AC waveform off to effectively control voltage. Because of this functionality, the circuit will work for a wide variety of loads including incandescent light bulbs, heating elements, brushed AC motors and some transformers. The circuit tries to maintain a constant motor speed regardless of load so it is also ideal for power tools. Note that the circuit can only control brushed AC motors. Inductive motors require a variable frequency control.

7 Segment LED Counter

This simple counter can be used to count pulses, as the basis for a customer counter (like you see at the doors of some stores), or for anything else that may be counted. The circuit accepts any TTL compatible logic signal, and can be expanded easily (see Notes).

Rangkaian Pendetesi Hujan

This circuit uses a sensor made of a small piece of etched PC board and a simple SCR circuit to detect rain and sound a buzzer. The SCR could also be used to activate a relay, turn on a lamp, or send a signal to a security system.

Alarm tegangan rendah

This low voltage circuit can be used to monitor batteries and other volatile sources of current for problems. The circuit sounds an alarm and lights an LED, but can be interfaced to any number of other circuits for many different uses.

Pendeteksi Aliran Udara

This simple circuit uses an incandescent lamp to detect airflow. With the filament exposed to air, a constant current source is used to slightly heat the filament. As it is heated, the resistance increases. As air flows over the filament it cools down, thus lowering it's resistance. A comparator is used to detect this difference and light an LED. With a few changes, the circuit can be connected to a meter or ADC to provide an estimation on the amount of air flow.

Kunci Kombinasi Tombol Digital

This simple circuit is the electronic version of the combination lock. Using the special purpose LS7220 digital lock IC, the circuit allows a 4 digit combination of your choice to activate a relay for a set period of time. This relay can then be used to trigger a lock solenoid, enable a starter button, open a motorized door, or many other tasks that require a momentary signal.

Merakit power supply

Berikut ini merupakan beberapa rangkaian power supply / catu daya yang sudah umum untuk berbagai keperluan seperti untuk radio / tape, speaker / amplifier, lampu, dsb, sbb:
Power supply standar simple
Power supply ini dikatakan simple, karena hanya menggunakan 1 buah dioda 1 ampere, dan 1 buah elco (elektrolit condensator) dan pastinya dengan komponen utama berupa travo dan dikenal dengan istilah ’penyearah gelombang penuh’, karena menggunakan 1 dioda maka daya yang dihasilkan setengah menghantar, ex: pada travo 12 volt , maka tegangan yang dihasilkan 12 / 2 = 6 volt.
Rangkaiannya adalah sbb:

Power supply 2 dioda

Power supply atau catu daya ini menggunakan 2 diode 1 amper dengan menggunakan travo CT (Center Tap) / travo tegangan terbelah.dan beberapa komponen pendukung, rangkaiannya sbb:

 Power supply jembatan (4 dioda)
Dibuat dengan 4 buah dioda 1 ampere dengan travo biasa (tidak membutuhkan travo CT) dan beberapa komponen pendukung, rangkaiannya sbb:

 Power supply regulator
Power supply regulator Power supply ini merupakan power supply yang tegangannya stabil oleh karena adanya tambahan komponen aktif dengan IC regulator, rangkaiannya sbb: 

>> Lakukan pengukuran tegangan dengan multitester (AVO meter) atau Volt meter sebelum
dihubungkan ke kit lain n pastiin tegangan sesuai dengan voltage yang diinginkan (ga
terlewat terlalu jauh sesuai hasil pengukuran).
>> Hati – hati terhadap bagian primer travo (high voltage) jangan sampai menyentuh bagian
tubuh.

Police Siren

Remote control using VHF modules

Rangkaian intercome

Intercome circuit can be used as a communication tool with a considerable distance,this circuit using a wave flowing through the wire.so that the longer the wire is used the more distant the distance the other person.

Components used :

• Tr1: Transistor PNP type AF 116
• Tr2: Transistor PNP type OC 126
• Tr3: Transistor PNP type OC 126
• R1 :  Resistor 4K7ohm
  
• R2 :  Resistor 270 ohm
  
• R3 :  Resistor 1K5 ohm
• R4 :  Resistor 150 ohm
• R5 :  Resistor 680 ohm
• R6 :  Resistor 330 ohm
• R7 :  Resistor 27K ohm
• R8 :  Resistor 10K ohm
• C1 :  Ceramic Condenser 4700pF
  
• C2 :  elektrolit condenser 100 uF
  
• C3 :  Elco 100 uF
  
• C4 :  Elco 0,1 uF
• C5 :  Elco 10 uF
• C6 :  Elco 32 uF
• C7 :  Elco 0,1 uF
• Sp :  Switch
  
• S   :  Switch on/off
  
• Ls :  Loudspeaker
  
• M  :  Microphone
  
• K  :  Wire
  
• B  :  Voltage 6 Volt

 How to use it is to press the switch on / off, then pressing the SP (switch the conversation).when pressing the switch SP all the components that connect the microphone to work, while the components connected to the speakers not working 
When finished talking, the switch SP is returned its original position.

Radio pemancar empat transistor

The series follows below can be used as a transmitter to transmit power switch 5km. This circuit can radiate in a circular wave 5 km.

Transmission distance are excluded from this series because there are four types of PNP transistors and megaphones.To extend the transmission distance of more than 5km we can use the antenna as high as 20m.

In order to obtain satisfactory results of transmission, it must be careful in installing components and adjusted to the symbols.specifically for the transistors should be attached with a metal material so as not to burn.

Information:

• R1   :  Fixed restan 3K ohm
• R2   :  Fixed restan 500 Ohm 
• R3   :  Fixed restan 100 Ohm 
• Tr1  :  Transistor PNP Type 2SA 70
• Tr2  :  Transistor PNP Type 2SA 70
• Tr3  :  Transistor PNP Type OC70 
• Tr4  :  Transistor PNP Type OC71
• C1   :  Ceramic condenser 0,001 pF
• C2   :  Elektrolit Condenser 0,01 upF
• C3   ;  Trimer Condenser  200 pF
• C4   :  Variable condenser
• C5   :  Ceramic condenser 0,001 pF
• C6  :   Ceramic condenser 0,01 pF
• C7   :  Ceramic condenser 0,01 pF
• S     :  Switch
• B    :   Voltage 12V
• C    :   Spull oscilator
• T1   :  OT with 70 winding transformer with kokr 3cm, thickness 0.3mm wire
• M    :   Speaker

 After the series finished, prepare a radio receiver.

Disco lamp

Disco lamp circuit serves to adjust the lights automatically follow the rhythm of the music. When the music will ring out the lights burning brightly, when the music soft lights dimmed, and the lights will go out when the music stopped .

The circuit is using a condensor mic to detect strains of the music, so just brought near to the source of the sound / music, lights will turn on, dim, and dies to the music

Good luck!!!