21june.net

This is Electronic Siren circuit diagram. The sound produced imitates the rise and fall of an American police siren. When first switched on the 10u capacitors is discharged and both transistors are off. When the push button switch is pressed to 10u capacitor will charge via the 22k resistor.

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Here the analog flip-flop which built based on 2 transistors work as switch. This is very easy made and very cheap circuit

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Notes
This simple charger uses a single transistor as a constant current source. The voltage across the pair of 1N4148 diodes biases the base of the BD140 medium power transistor. The base-emitter voltage of the transistor and the forward voltage drop across the diodes are relatively stable. The charging current is approximately 15mA or 45mA with the switch closed. This suits most 1.5V and 9V rechargeable batteries. The transformer should have a secondary rating of 12V ac at 0.5amp, the primary should be 220/240volts for Europe or 120volts ac for North America.

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The circuit presented here wakes you up with a loud alarm at the break of the daylight. Once again the 555 timer is used here. It is working as an astable multivibrator at a frequency of about 1kHz. The circuit’s operation can be explained as follows: When no light falls on the LDR, the transistor is pulled high by the variable resistor. Hence the transistor is OFF and the reset pin of the 555 is pulled low. Read the rest of this entry »

This is a police alarm circuit. The two 555 timer ICs used as astable multivibrators. The frequency is controlled by the pin 5 of the IC. Actually, the sound is genereted by combination of sound from both IC 555. One timer generated low frequency and the another generated high frequency. By varying VR1 you can set how fast the siren changes from high freq. to low freq. VR2 sets the siren frequency.

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Bagi semua siswa kelas 8 yang akan melakukan praktek pembuatan rangkaian lampu flip flop adapun bahan dan kompenen yang dibawa :

1. PCB lobang sebanyak 1 buah
2. Resistor sebesar 22K sebanyak 2 buah dan 470 ohm sebanyak 2 buah
3. Kapasitor ELCO dengan kapasitansi 4,7 mikro farad dengan tegangan 16 volt sebanyak 2 buah
4. Dioda LED sebanyak 2 buah (warna berbas)
5. Transistor 9014 sebanyak 2 buah
6. Kabel 1 meter
7. Batubaterai dengan teganga 9 volt

Bagi siswa yang todak dapat membeli kompenen eletronika diatas silahkan hubungi guru pembimbing atau telpon di 08123669300