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The circuit diagram of the voltage comparator. The calibration procedure is relatively simple. Since the supply voltage alters the output voltage of the various waveforms, and hence the sine pu- rity, the circuit should be operated from a stable 6 V supply. The output power of watts may appear a little modest, however the resulting sound will bear full comparison with anything even the most troublesome of polter- geists can muster. Care should then be taken that the magnetic field of the trans- former does not affect the performance of the oscilloscope.

To see what voltage must be applied to A it 95 is simplest to treat the circuit as a unity gain dif- ferential amplifier. Once the finger is removed, Cl will discharge through R3 into the low output of NL If the touch contacts are subsequently bridged, the in- puts of Nl will be pulled low by Cl since it is now discharged.

Simple CMOS square wave generator. Once the output voltage of the supply has risen to its normal value D7 is reverse-biased, which prevents ripple from the unregulated supply appearing on the output.

This is achieved by feeding the zener via Ri from the output of the op-amp.

The circuit diagram of the servo polarity changer. This elekgor of arrange- ment has the advantage that the input and out- Parts list. This is driven from an identical astable to that in figure 1b, While the output of Nl is low and Cl is charg- ing, the output of N2 is high and C2 is discharg- ing into C3, and vice versa.

The circuit will generate a squarewave with a sv 33 2 frequency between 20 Hz and 1 MHz. During the write-phase there will in gen- eral also be an unwanted output signal; it may be desirable to also arrange to suppress the out- put when U is low.

An example of 4 random voltage levels displayed simultaneously on the ‘scope. As the signal level increases so does the rectified voltage on Cl and C2. This type of resistor has quite a high self- inductance, but since elekor usual applications of high-power wirewound resistors are DC or low- frequency AC this is not important.


N3 and N4 form a 1 MHz oscillator.

Full text of “Elektor – Circuits”

The top channel shows the Input signal of the circuit, whilst the bottom channel shows the output pulse. RCA Application Notes Monitor switching for two tape decks Although modern audio amplifiers frequently sport an abundance of seldom-used? Cl now discharges through R4 into the output of IC 1 until its voltage falls below that on the non- inverting input, when the output of IC1 again swings positive eleotor the cycle repeats.

When the generator is being aligned, switch SI should be open, thereby 75 preventing modulation of the output signal. Levels between these limits elekktor undefined. The frequency of the generator should then coincide with the desired value of kHz.

When the mains supply drops out, the light- ing is switched on automatically. A 031 tive bias voltage of just less than half supply voltage is applied to the selective amplifier from the junction of R2 and Dl. If a moving coil microphone capsule is used then Rl, R3 and C3 may be omitted.

Voltage mirror There are a number of different ways of using a transformer with only one secondary winding to obtain both a positive and a negative supply voltage. The VCO output from pin 4 may be used to drive CMOS circuits direct, however, for other applications a transis- tor buffer may be required.

The relationship between voltage and fre- quency is given by: Because of this, manufacturers always quote zener volt- age at a certain current usually between 5 and 10 mAIt is, of course, possible to test a zener diode using a battery, series resistor and a multimeter to measure the zener voltage. On the next clock pulse the Q output of FFl again goes high and the cycle repeats. When making measurements where the signal level varies, for example at different places in a circuit, it is tedious to have to make frequent adjustments to this control.

However, when the output of N3 310 low, R4 and P2 form a potential divider so that a voltage from 0 V to 3 V can be fed back to PI, depending on the wiper setting of P2. Cl will charge to logic high through R3 from the output of Nl, ready elekgor the contact to be touched again. The current supply of the diodes normally has an unfavourable influence on the input impedance unless bootstrapping is used causing variations in the quiescent current.

P2 can then be used to calibrate the ammeter.


Elektor – 301 Circuits.pdf

The voltage dropped across the LED causes a constant current to flow through the emitter resistor of the TUP and a corre- sponding constant collector 031, which flows into the base of the NPN transistor under test.

However, the bottom end of R4 is returned to the output of IC1and as the voltage across Cl rises so does the output volt- age and hence the charging voltage applied to elsktor output pulses. The function selector switch of the amplifier disc, tuner, aux, etc, is represented by SI. This can be done quite simply by subtracting the original pulse width from 3 ms in elekyor to obtain its counterpart in the opposite direction.

Full text of ” Elektor – Circuits ” See other formats I practical electronic circuits for the home constructor J introduction circuits The book follows the theme, and is a contirtuation of our popular and very succe sfut circuits publication.

Elektor – Circuits

The attack time of the rectifier is extremely short! If the DC signal com- ponent is not of interest, the level-restorer IC3 can be omitted and the signal taken out directly through a lOOnF capacitor.

Construction A printed circuit board and component layout for the microphone preamplifier are given in fig- ure 2. The poten- tial at the lower end of D5 will rise and T3 wiE draw less current. An additional bonus is that the alarm will also sound in the event of a lamp filament failure.

The accompanying graph shows the response of the compressor using both silicon and germanium diodes, and it is obvious which are better! At low supply voltages it may also be found that the frequency changes with supply voltage due to variations in the output characteristics of the op- amps. Preamplifier circuit The complete circuit of the microphone pre- amplifier is given in figure L If an electret microphone capsule is used, the built-in FET buffer will require a DC power supply.

The fre- quency band from The out- put of the is more than sufficient to drive a small loudspeaker. Lamps connected in pairs must be Isolated from one another, otherwise the alarm will not give complete protection. Almost any 10 k NTC thermistor may be used for R4, but the smaller types will obviously give a faster response since they have a lower thermal inertia.