Powerful Pest Repeller Circuit

Most of the electronic pest repeller circuits have a major drawback of low power output hence their effectiveness suffers. The ultrasonic pest repeller circuit described here generates powerful ultrasonic signals therefore efficient to repel pests like mosquitoes. In addition to the ultrasonic frequency oscillator, we use a  separate push-pull power amplifier and transformer  to boost ultrasonic signals.

Car Reverse Horn With Flasher

This is a circuit of car reversing horn with normal auto lamp flasher that uses timer ICs NE556 and NE555. When the car is in reverse gear, the switch S1 which is the reverse gear switch of the car get shorted and the monostable timer give a high output. So the diode D1 and D2 goes for high for a time period R4C4. 

Touch Sensitive Musical Bell With Timer

This circuit diagram is a UM66 based touch sensitive musical bell. The circuit is built around CMOS IC CD4011 and popular melody generator IC UM66. The circuit contains a pair of touch plates. When these are bridged by hand for a moment, the um66 starts making music. Moreover this circuit has a timer which stops the music automatically after a few seconds. This makes the circuit, an automatic music bell.

Electronic Harmonium Using 555

Here's the circuit diagram of a simple electronic harmonium that can produce all the seven notes. As timer IC 555 based design, the circuit is very simple to assemble and use. It only requires single 555 IC, one or two capacitors and some resistors.

Rain Sound Generator Using NE555

The circuit diagram shows a timer 555 based rain sound generator. The circuit requires a 9V dc power supply and can be fed from a 9V battery.  The loud speaker for producing sound is of 0.5W 8ohm speaker.The circuit will readily generate a rain like sound whenever the circuit fed by a 9V supply.

Simple Music Bell Circuit Diagram

Here is a circuit which can be assembled easily with very few components. This DIY music bell can be used as door bell, cycle bell , car reverse horn and it only requires 3V battery. The core of this circuit is a 3 terminal IC chip which can produce music when properly biased. This IC may looks like a transistor but cant drive a loudspeaker by itself.

Calling Bell Circuit

Apart from the normal musical calling bell circuits, this special electronic calling bell has been created to identify the sound even if there is noisy atmosphere. This bell circuit is not a typical Ding-Dong bell but has the capability of producing different sound that is very useful in noisy surroundings. By pressing a far away switch can trigger this circuit to work as a bell.

Door Bell Circuit Using BEL 188

Here is a low cost one touch door bell circuit using Bel 188 transistor. I think this may be the most cheap bell circuit that can be made. The core of this circuit is a output transformer of push-pull amplifier that often used in transistor radios and a Bel 188 PNP transistor.

Automatic School Bell Circuit

Here is automatic school  bell electronic circuit that works on the basis of the following criteria

Consider that a school has a total of eight periods with a lunch break after the fourth period. Each period is 45 minutes long, while the duration of the lunch break is 30 minutes. The bell will be ringed to start the class, end of each period, extension at lunch break etc.

Musical Car Reverse Horn Circuit

Want to make some stuff that fits your car or motor cycle? Then here is a simple musical horn circuit that can be connected to the 12V battery of any car or motorcycle. This circuit commonly used as reverse musical horn. Here we use a commercially very low cost musical IC UM66. But this Ic can only handle supply voltage below 4V. So we used a 7805 regulator ic for adjusting the voltage to 5V and its further reduced to 3.8 volt by connecting two diodes D1 and D2 then it will supplied to musical horn producer UM66.