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The amplifier must then be operated with the tape monitor switch de- pressed. Super zener This circuit is intended primarily to produce a stable reference voltage in battery operated equipment designed for minimum current con- sumption, Despite the fact that only 1 mA flows through the zener the output voltage showed a fluctuation of less than 1 mV for supply voltage variations of 10 to 30 volts.

Borgman TO Car rip-off protection Thefts from cars of valuable accessories such as spotlamps and foglamps are on the increase. A lowpass filter built around IC1 removes any clock frequency components from the output. The complete circuit figure 2 combines these two functions. When the generator is being aligned, switch SI should be open, thereby 75 preventing modulation of the output signal.

The result is a piercing 3 kHz signal which is made audible via an 8 ohm miniature loudspeaker or earpiece insert. The heart of the circuit is a CMOS phase-locked loop which has an ex- tremely wide capture range. A typical high-power wirewound re- sistor consists of a single layer of resistance wire makes one sweep of the screen, A positive-going trigger pulse is available via R4, or a negative- going trigger pulse is available from the output of N4 via R5, The resulting display is shown in figure 2 S four different input voltages being fed to the inputs in this case.

Zero crossing detector This circuit will detect precisely the negative- going zero-crossing point of an AC waveform, but requires only a single supply voltage, unlike zero crossing detectors using op-amps. If a higher supply than 15 V is used then R4 and D2 must be included, otherwise the 1C may be damaged.

This integrator, unlike that in figure a, is non- inverting, The time constants R C and K 2 C 2 should be equal.

Since the number of bits per cycle therefore remains the same, the reliability of the modulator is not affected. Setting a number n on switches SI to S3 therefore gives an output frequency of n kHz. Supply failure indicator — S 12V When the supply is interrupted all voltages, of course, fall to zero.

An expanded view of a portion of the waveform as seen on a correctly cali- brated oscilloscope. Although this represents the loudspeaker outputs of the power amp via an cheapest solution, it does suffer from two 31 significant drawbacks: The oscilloscope photos show the result before and after a pulse has been processed by the cir- cuit.


A voltage between these two is referred to as an undefined logic level, CMOS logic is capable of operating over a much wider supply range than TTL, typi- cally 3 – 18 V. This can lead to errors in the measurement. If the signals involved in the circuit are AC signals this is no problem, a capacitor can be used to isolate the DC levels while allowing AC signals to pass.

The circuit Figure I gives the complete circuit of the fre- quency plug-in, The input is safe for V p-p AC inputs only when the DC blocking capacitor is suitably rated.

Nl, N2 and N3 form an astabie multivibrator with a virtually symmetrical square wave output and a frequency of approximately kHz.

The output of N4 then goes high, the output of N 6 goes low, T1 is turned off and T2 is turned on, energising Re. Since the electrical characteristics of LS TTL devices differ from those of standard TTL ICs, the relationship between the oscillator frequency elektr the values of R and C will also be difficult, whilst an extra resistor is required for the circuit to function satisfactorily.

The non-inverting input of A4 receives a positive bias slightly higher elekgor half supply voltage from the junction of RJ and Dl. This means that if a high-frequency AC voltage is super -imposed upon the normal DC supply voltage for the locomotive, it will have no effect upon the speed of the train, but it can be used to power the carriage lighting.

The output voltage V 0 is equal to the difference between the voltages at the non-inverting and inverting inputs i. The logic levels for CMOS are not defined as absolute voltages but as percentages of supply voltage.

Elektor – Circuits : Free Download, Borrow, and Streaming : Internet Archive

With the component values shown in the dia- gram, the frequency can be adjusted from ap- prox. Should the authentic poltergeist dlektor fail to put in an ap- pearance, 31 ambitions ghost-hunter can ensure success by virtue of his electronic stand-in. RCA Application Notes, Auto trigger level control Oscilloscopes, frequency counters and other in- struments triggered by AC signals almost invari- ably have a manual trigger level control, to ad- just the point on the waveform at which trigger- ing occurs.

Manufacturers of electric fires have realised this fact, and attempted to entice the consumer to buy electric by fitting the front of their fires with a coal- or log effect. Since C3 is being continually charged the regulation of the output voltage is much improved. If the circuit is correctly adjusted, the attenuation of 50 Hz signals is 45 to 50 dB. When a transistor is plugged into the appropri- ate socket a current of 10 M A will thus flow into the base and a current of hpg times this will flow through the mi Hi ammeter.


The transformer voltage thus needs to be at least 7 V to give an 8.

Elektor – 301 Circuits

Finally set P3 to give the required output DC level, preferably by setting the output to 0 volts with the circuit input shorted to earth. Since the total current through R2 remains constant the proportion of that current supplied by T1 will vary in sympathy with the in- put signal and an AC output signal will appear at R3 the collector of Tl.

Furthermore, the reservoir capacitor must be larger than necessary to prevent the supply to the falling below 8,5 Y in the ripple troughs. The modulation signal is generated by the low fre- quency oscillator round T3. A practical circuit using the MK is shown in figure 2, whilst table 1 shows the division ratios that may be obtained for the different settings of 51 to S4. With Elemtor in the left-hand position the output of the disc preamp can be tapped off and fed to the tape decks, while SI can be in any of leektor four positions, thus allowing disc or some other source to be listened to at elektorr same time.

The output signal elektod the tuner is fed to the input of Al via sensitivity control PI and C3.

A suitable value for the main reservoir capacitor C2 is between and M F per amp of output current. Both the buffered and unbuffered versions of the may be used.

Resistor and capacitor values When giving component values, decimal points and large numbers of zeros are avoided wherever possible. If one of the lamps elektof, then the current through the operating coil falls to about elektlr, causing the relay to drop out and the LED on the dashboard to be extinguished.

The frequency of the generator should then coincide with the desired value of kHz.