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If higher input voltages are to be used or less dissipation is desirable then the values of Rl, Elektir and PI should be increased, keeping them in the same ratio. The sawtooth output signal which is buffered by FET T4 has a peak-to-peak elekktor of approx. The most useful way of doing this is to frequency-scale the input signal, by means of a bucket-brigade ana- logue delay lineso elekotr the display fits in nicely with the available sweep speed.
It is a useful item of test gear, especially for calibrating other instruments that are designed to measure duty-cycles in one form or another – dwell meters, fop instance. One of the simplest ways to achieve this electronically is to use an analogue bucket brigade shift register. Since most readers are unlikely to possess more than one multimeter this can be rather tedious.
Elektor – 301 Circuits
However, no design for a corresponding car ammeter has so far appeared. A posi- tive bias voltage of just less than half supply voltage is applied to the selective amplifier from the junction of R2 and Dl. The circuit uses only three ICs, five resistors and a capaci- tor. The design given here overcomes these difficulties and provides a re- liable single-point touch switch. Resistors already provided with taps, such as television H.
This design is based upon an integrated frequency-to-voltage con- verter, the Raytheon The circuit diagram of the polter- geist- transmit ter. Readers in countries that use 60 Hz should note that Elektor circuits are designed for 50 Hz operation.
Two points must be noted when using this cir- cuit. The adjustment pro- cedure may take some time as it will be necessary below the value set by PI then T3 will turn on, cutting off the output current until the chip tem- perature has fallen sufficiently for T3 to turn off again.
Elektor – Circuits : Free Download, Borrow, and Streaming : Internet Archive
It is important to note that the gauge of wire used to wind the relay coil should be at least as heavy as that used in the original car wiring, to minimise the voltage drop across the coil and possible overheating.
The circuit can easily be extended to eight inputs by adding an extra IC and connecting IC3 as a 0 to 7 counter reset connected to output 8, pin 9. Long interval timer The drawback of most analogue timers mono- stable circuits is that, in order to obtain reason- ably long intervals, the RC time constant must be correspondingly large.
The built-in preamplifier boosts the output level to several hundred milli- volts, which allows the signal to be fed direct to the ‘auxiliary’ or ‘line 1 inputs of amplifiers or tape decks. The flip-flop which has been set may be reset ready for the next question by pushbutton Sr.
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.
This is the principle of the automatic mono-stereo switch. N3 and N4 form a 1 MHz oscillator.
With no current through the shunt, PI is used to set the output voitage of A1 to nominally 6 J V, so that the circuit is just on the point of switching over from D4 to D5.
The complete circuit of the alarm is shown in fig- ure 1.
Complementary emitter follower This circuit represents a simple design for one of the most popular types of electronic game, namely a reaction tester.
A red LED should be used for D7. Borgman In many quiz games speed of response plays an essential part, the contender who presses a button first getting the first chance of answering a question. When the thief cuts this wire to remove the equipment then the alarm will sound. The value of R5 is dependent on the supply volt- age used and should be 33 ohms for voltages between 9 V and 15 V, 68 ohms for 15 V to 25 V and ohms for 25 V to 35 V.
Elektor – Circuits
Since a filter with a notch frequency of 50 Hz and a Q of 10 would require an inductance of almost 1 50 Henrys, the most obvious solution is to synthesise the required inductance electronic- ally see elekto 2.
Under no- signal conditions the output of A4 is therefore positive. F2 is the calibration poten- tiometer: The maxi- mum transmission range is approx.
Since the out- put of a microphone is very small typically a few millivolts there is often significant signal loss, and microphonic noise may also be gener- ated by the cable- This article describes the construction of a good -quality microphone with built-in preamplifier, using a commercial electret or moving coil capsule. 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.
Elektor – 301 Circuits.pdf
If the reference voltage is exactly 2. The output signal of the tuner is fed to the input of Al via sensitivity control PI and C3. If no current is drawn from C2 it will eventually charge to about The complete output waveform, shown in figure 2comprises a burst of pulses approx.
It does not apply during the initial phase when C2 is charging from zero. On the next clock pulse the Q output of FFl again goes high and the cycle repeats. If both R and Ci, and R 2 and Ci are transposed then the result is a non-inverting differentiator. Cl now charges from the output of ICl via R4 until the voltage across it exceeds the voltage at the non-inverting input, when the output of ICl,t.
The output of IC1 will now swing down to zero and the voltage on the non-inverting input will fall to about 5 V due to the hysteresis introduced by R3.
Resistor and capacitor values When giving elfktor values, decimal points and large numbers of zeros are avoided wherever possible. The counter output is used to switch transistor T1 on and off, and the collector signal of T1 is fed to the output amplifier A4, Since the collec- tor resistor of Ti receives its supply from the output of the envelope follower, the amplitude of the collector signal, and hence of the output signal, varies in sympathy with the amplitude of elejtor original input signal.
This may be con- trolled either manually by means of P3 or may be swept up and down automatically by the out- put of the triangular elektkr generator consisting of IC3 and IC4. TI will require a base current of 0.
Complete circuit of the function generator. Furthermore, the duty-cycle of the output signal will be independent of the in- put frequency: Car ammeter Timebase scaler Model railway lighting Frequency synthesiser controller