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Accessories inside the ekektor, such as radios and cassette players, may also be protected by con- necting a wire from one of the alarm epektor to the earthed case of leektor equipment. If a seven decade counter Is used that gives a reading of 1. Since the resultant voltage is DC-isolated from the transformer, to which the other rectifier D When a squarewave is fed to the dock input the circuit will count up until the counter reacheswhen the carry output will go low and clock FF1.
The values of R1 and R2 de- pend on the secondary voltage: This produces a train of short pulses from the squarewave input signal and these are fed to an audio amplifier comprising T1 and T2. Automotive voltmeter Although vital for satisfactory operation of the vehicle, the car battery is often taken for granted and rarely receives adequate maintenance.
While the cell is being charged D1 is lit. Fine frequency control is pro- vided by PI which varies the charge and dis- charge current of Cl or C2 and hence the rate at which the integrator ramps up and down. Elekhor complete the unit, a clock generator is inclu- ded NI The diodes prevent excessive drive voltages e,ektor reaching the input of the comparator IC1.
This is sufficiently long for the indication to be seen.
Any one oF the three waveforms may then be selected by a three-position switch and fed to an output buffer amplifier. The output of the calibrator can be brought out to a socket on the front panel of the oscilloscope elektot that the calibration can easily be checked by inserting a probe into the socket.
CMOS function generator Using only one inexpensive CMOS IC and a handful of discrete components, it is possible to build a versatile function generator that will pro- vide a choice of three waveforms over the entire audio spectrum and beyond. A portion of the output signal from AI is rectified by D1 and the resulting peak positive voltage is stored on C4. There surely cannot be many meters with a sensitivity lower than that, if one has a separate moving coil milliameter avail- able, it can be fitted with a series resistor that makes its internal resistance up to the value re- quired of a voltmeter giving elektod.
Should the authentic poltergeist then fail to put in an ap- pearance, the ambitions ghost-hunter can ensure success by virtue of his electronic stand-in. When the contact is not touched the signal from the output of N4 is fed via C2 and C3 to the input of Nl, which causes the output of N1 to go high and low at a 1 MHz rate. A lowpass filter built around IC1 removes any clock frequency components from the output.
It is so compact that it can be built into virtually any oscilloscope, making regular calibration a simple procedure. The Filters remove the har- monic content of the squarewave leaving only the sinusoidal fundamental. If one of the lamps fails, then the current through the operating coil falls to about half, causing the relay to drop out and the LED on the dashboard to be extinguished. Although a circuit that draws 25 mA is not too well suited to battery supply, one may need or wish to do this.
D1 and D2 are included to stabilise the reference voltage.
Photos, The three output waveforms pro- duced by the function generator. This arrangement is necess- ary to facilitate demodulation of the FSK signal.
The revised graph of frequency against R and C is shown in the accompanying nomogram. If the reference voltage is exactly 2.
Elektor – 301 Circuits.pdf
The use of a total of elejtor op- ellektor in the circuit may seem rather excessive, but as eight of these are LM quad op-amps the total package count is only four ICs. The values of zener voltage obtained for differ- ent zener currents may be plotted on a graph of zener voltage versus zener current, as shown in figure 3.
The reference voltage obtained from the op-amp output can supply currents of up to 15 mA. On the other hand, coal fires are difficult to light, slow in producing heat, and also extremely messy to dean out. The exact formula is given in the diagram. An ideal basis for constructional projects and a comprehensive source of ideas for anyone interested in elec- tronics. The ac- companying diagram represents the basic univer- sal design for such a generator. The circuit consists simply of a timer con- nected as a 1 kHz astable multivibrator.
Full text of “Elektor – Circuits”
This in turn results in a gradual change in the triggering angle of the triac, caus- ing the lamp La to flicker. Supply failure indicator — S 12V When the supply is interrupted all voltages, of course, fall to zero. Figure 3, In order to set the servo In the neu- tral position a pulse duration of 1. An example of 4 random voltage levels displayed simultaneously on the ‘scope. With modern transis- tor oscilloscopes this should be no problem, the supply can probably be derived from one of the low-voltage supplies in the oscilloscope either- direct or via a simple zener stabilizer.
Elektor – 301 Circuits
HF current gain tester. By terminating the input and out- put with a 1 elektro resistor in parallel with an IS p trimmer capacitor, passband ripple can be tuned down to 2 dB. To charge a number of cells the portion of the circuit enclosed in the dotted box must be dupli- cated. Printed circuit board and com- ponent layout for the calibrator.
The input voltage Vi is applied to the inverting input of IC2, which functions as an integrating comparator. The will now deliver a DC output voltage corresponding to the frequency of the input sig- nal. A higher supply voltage is permissible, if it is easier 52 2 to obtain 4.
The circuit of the zener tester, which contains only nine components, is given in figure 2, T1 and T2 function as a voltage regulator. P2 is therefore adjusted so that D3 is lit for input voltages above