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Cl is charged to logic 031 through R3 from the high output of NL If the touch con- tacts are now bridged by a finger, the logic high on Cl will be applied to the inputs of Nl through R1 and the skin resistance. For example, in a 5 V 2 A supply for TTL about 3,5 V would be dropped across the series transistor and 7 W would elekttor dissipated in it at full load current. Also, short single pulses will be missed comple- tely. C is related to the distance between the elsktor of the capacitor by the equation d where k is a constant.
This should be adjusted so that the circuit operates on any stereo signal which is sufficiently strong for noise-free stereo listening. The complete circuit figure 2 combines these two functions. To measure frequency one does not eleitor have to ‘go digital 1. This photo shows the output pulse obtained for an Input pulse duration of 1 ms. The triac must also be able to withstand the peak mains voltage i. A transformer with a slightly higher secondary voltage can be used, provided that R1 is uprated to limit the current through this resistor to mA.
The circuit diagram of the servo polarity changer. These consist of an exposed wire el- ement wound on a ceramic former, and are pro- vided with contact dips that may be fixed any- where along the length of the element, 1 kW electric fire heating elements which have a re- sistance of around 60 Q may also be used. Too low a signal level, and the triangle amplitude will be below the diode threshold voltage, so that it will pass without alteration; too high a signal level, and the peaks and troughs will be clipped severely, eleotor not giving a good sine wave.
It can easily be proved that this works! The relative values of C2, C3 and R4 determine the elekfor fre- quency at which the circuit will function. The circuit diagram of the voltage comparator. The negative supply functions in a similar manner. The non-inverting input of A4 receives a positive bias slightly higher elekgor half 3011 voltage from the junction of RJ and Dl. A constant current of – thus flows through R2. However, instruments, and particu- larly complex ones such as oscilloscopes, tend to drift with age, and if more than a year or so old can be highly inaccurate.
The stereo -mono crossover frequency can be in- is As far as component values are concerned, care should be taken to ensure that the maximum cur- rent taken by the triac is at least twice; She rnaxi- mum current drawn by the lamp La. The output signal of the tuner is fed to the input of Al via sensitivity control PI and C3.
In this circuit the quiescent current through II U This is fed through the rectifier A3 to appear on capacitor C6 and hence at the inverting input of comparator A4. An additional bonus is that the alarm will also sound in the event of a lamp filament failure.
The zener voltage can elektod be measured by connecting a multimeter across it as shown. 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. An input signal of sufficient amplitude to over- Figure 1.
In order that the circuit should be kept simple the temperature sensing element is a negative temperature coefficient thermistor NTCThis has the advantage that the temperature coef- ficient of resistance is 3301 large, but unfortu- nately it has the disadvantage that the tempera- ture coefficient is not constant and the tempera- ture-voltage output of the circuit is thus non- linear.
In a nutshell something to please everybody. If the trans- mission is mono then elwktor signal will elekktor fed through the selective amplifier and the compara- tor output will remain high, switching off the stereo decoder. When the car is unoccupied and the ignition is ellektor off R 1 1 holds the inputs of N5 low, so the output is high. When constructing the circuit par- ticular care should be taken to ensure that the 0 V rail is of low resistance heavy gauge wire or wide p.
With S3 in its centre position a signal can be taken from the source to the record inputs of both tape re- corders.
P2 is therefore adjusted so that D3 is lit for input voltages above There seems to be something soothing in watching the flames flicker and play about the coals. Firstly, care must elemtor taken not to exceed the common-mode input rating of the op-amp used, especially with a single-ended asymmetric sup- ply.
Car ammeter A surfeit of circuits has already been published for solid-state car battery voltage monitors. In fact the supply voltage to the series transistor need be no more than 0,5 V above the regulated output voltage, to allow for its saturation volt- age, The solution is to use eleektor separate 8,5 V supply for the and a lower voltage supply for the exter- nal transistor.
It is advisable to use 1 resistors, and PI and P2 should preferably by high-quality preset poten- tiometers. 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.
Elektor – 301 Circuits
If the oscillator which generates the clock pulses is set 96 j so that a pulse is produced say, every 20 ms, then the reaction time of the players can be calculated quite simply by observing which LED remains lit, A new game can be started after pressing the re- set button. The commercial radio stations have, of course, followed this practice for some time. The circuit will then count down until zero is reached, when the carry output will again clock FF1 and so on.
In most cases a value of 1 k should eelktor sufficient. Photos, The three output waveforms pro- duced by the function generator. The circuit can be extended for use as a light or- gan.
Elektor – – [PDF Document]
Normally RI is given the same value as R2. 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 and the cycle repeats.
This is rich ekektor harmonics and, due to the extremely small duty- cycle of the waveform, the power consumed by the output stage, T2, is fairly small. The time from the start of one burst of 66 Resistors: 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.
Sound ele,tor waves deflect the diaphragm, and hence the coil, which cuts the magnetic flux lines and generates an output current and voltage that is an electrical analogue of the acoustic signal. This is done by decreasing the value of R7.