e017033.PDF

(516 KB) Pobierz

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">

033

EMD-immune Electronic Doorbell

P. Lay

Whenever an antediluvian electric door-

bell is used in an apartment building, the

rain of sparks that is generated when the

Wagnerian hammer pounds against the

‘sounding body’ infests the bell network

with interference pulses. These can sig-

nificantly disturb electronic doorbells, or

even cause them to give up the ghost. If

you cannot convince your neighbour to

convert to something more modern, or at

least to build in a noise suppression net-

work, you can use the electronic doorbell described here,

since it is immune to EMD.

This circuit is based on a simple multivibrator stage to

which a loudspeaker is connected. Capacitor C4 provides

dc isolation between the multivibrator and the loudspeaker

(8

S2

S1

R1

R2

R3

R4

D2

Tr1

D6

D3

1N4004

C4

R5

680 Ω

C2

C3

4x

R6

1N4004

33n

33n

1µ

25V

LS1

D 1

T1

T2

D5

D4

D9

D8

D7

C1

rot

rood

red

rouge

1N4004

1N4004

2200µ

25V

18V

1W

8 Ω

BC547

BC547

250mW

014005 - 11

bell transformer. For this purpose, the ac voltage must be

rectified by D3-D6, and Zener diode D7 prevents the volt-

age from rising above approximately 18 V. EMD immunity

is provided by the lowpass network R5/C1. The bell can

also be silenced using switch S2. In this case, the only thing

that happens when someone presses on the bell button is

that D1 lights up.

, 0.25 W). The frequency is determined by the RC net-

works R2/C2 and R3/C3; it lies at around 0.7 RC = 2 kHz.

The multivibrator stage receives its supply voltage from the

(014005-1)

66

Elektor Electronics

7-8/2001

855735931.051.png

855735931.057.png

855735931.058.png

855735931.059.png

855735931.001.png

855735931.002.png

855735931.003.png

855735931.004.png

855735931.005.png

855735931.006.png

855735931.007.png

855735931.008.png

855735931.009.png

855735931.010.png

855735931.011.png

855735931.012.png

855735931.013.png

855735931.014.png

855735931.015.png

855735931.016.png

855735931.017.png

855735931.018.png

855735931.019.png

855735931.020.png

855735931.021.png

855735931.022.png

855735931.023.png

855735931.024.png

855735931.025.png

855735931.026.png

855735931.027.png

855735931.028.png

855735931.029.png

855735931.030.png

855735931.031.png

855735931.032.png

855735931.033.png

855735931.034.png

855735931.035.png

855735931.036.png

855735931.037.png

855735931.038.png

855735931.039.png

855735931.040.png

855735931.041.png

855735931.042.png

855735931.043.png

855735931.044.png

855735931.045.png

855735931.046.png

855735931.047.png

855735931.048.png

855735931.049.png

855735931.050.png

855735931.052.png

855735931.053.png

855735931.054.png

855735931.055.png

855735931.056.png

Plik z chomika:

Inne pliki z tego folderu:

bge.jpg (26 KB)
detail1.htm (5 KB)
detail2.htm (4 KB)
detail3.htm (4 KB)
detail4.htm (6 KB)

Inne foldery tego chomika:

Zgłoś jeśli naruszono regulamin