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When the upper pair of contacts is bridged the input of N1 is taken high, so the output goes high. At this level the maximum permissible current of 10 mA flows into Nl and 1. 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.
At a certain point, as the 55 iron heats up, the output from the temperature sensor will exceed the reference voltage causing the opamp output to swing negative, turning off XL R6 introduces hysteresis to avoid relay ‘chatter’. Most have only a single tape socket, with facili- ties for making a recording onto one tape deck and monitoring that recording, and have no pro- vision for a second tape deck.
It is advisable to use 1 resistors, and PI and P2 should preferably by high-quality preset poten- tiometers. Seek The Netherlands Price Rs.
N1 and N2 are Schmitt triggers connected to form a monostab ie multivibrator with a period of about 15 ms. HF current gain tester. The triac must also be able to withstand the peak mains voltage i. The maximum zener voltage that can be measured is thus about 22 V P The circuit may be modified to test higher voltage zeners by using a higher voltage transistor for Tl, but care will have to be taken not to exceed the dissi- pation of TJ or the zener epektor the elektot current ranges.
The circuit is based on the wellknown 1C regulator. Analogue frequency meter A true ‘universal meter’ should be able to read not only voltage, current and resistance – but also other quantities. When the receiver, which is hidden somewhere in the same room, picks up the ultrasonic signals from the transmitter an audio generator is activated. Now slightly re- adjust PI to achieve symmetrical clipping of an excessive signal.
Elektor – Circuits : Free Download, Borrow, and Streaming : Internet Archive
Pseudo random running lamp V If a number of the outputs of a shift register are fed back in a certain fashion via an EXQR gate to the data input, then the Q outputs of the regis- ter will run through the maximum possible num- ber of mutually different logic states.
If this is not required, C2 and D5 can be omitted and R14 and R15 are replaced by a single 1 k resistor, J. Nl, N2 and N3 form an astabie multivibrator with a virtually symmetrical square wave output and a frequency of approximately kHz.
The circuit is provided with the possibility of AM and FM modulation. 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. 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.
The circuit shown in the accompanying diagram is for a filter with a – 6 dB bandwidth of roughly 2,2 kHz. It can easily be proved that this works! For this reason a start button SI is included which, when pressed, takes the input of Nl low. However, since the IC is fairly expensive it is recommended that a permanent buffer stage be connected to the out- put.
The output of Nl will thus go high and the output of N2 low, which will hold the inputs of Nl low even after the finger has been removed. It is not sufficient for these appli- cations to gate the output of a free-running oscil- lator, since the ‘enable’ signal is not normally synchronised to the oscillator.
When power is applied, the relay will pull in.
A suitable value for the main reservoir capacitor C2 is between and M F per amp of output current. 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. By summing only the high-frequency com- ponents of the signal it is possible to eliminate the annoying high-frequency noise without de- stroying the stereo image since channel separ- ation is still maintained at middle and low fre- quencies.
In addition, transcription from either tape re- corder to the other is possible, while at the same time a totally different source disc, tuner, etc.
Elektor –
An obvious example is in that infamous dark cupboard under the stairs, so that, should a fuse blow, a replacement can be epektor found and fitted. The exact posi- tive- and negative-going output swing achieved depends on the type of opamp used.

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. Super-simple touch switch Although there is a plethora of designs for touch switches, it is always a challenge to come up with a design that is simpler than previous versions.
The disadvantage is that bat- teries of ceils cannot be charged. Block diagram The principle of the automatic mono-stereo switch is illustrated in the block diagram of fig- ure 1. The switching circuit is shown in figure 1.
Elektor – 301 Circuits
The power dissipated in these transistors causes the chip temperature to rise. Any change elektir the input voltage at C will produce the same change at the output, but of opposite This circuit presents an interesting alternative method of constructing a low-distortion buffer or output stage for use at low output powers.
The logic levels for CMOS are not defined as absolute voltages but as percentages of supply voltage. The cir- cuit described here is intended to remedy that de- fect. However, if the emitter voltage 16 2 3 should try to rise above the 0,6 V base emitter knee voltage of T2, then T2 will draw elekttor cur- elfktor, pulling down the base voltage of T1 and thus reducing the emitter voltage. Two points must be noted when using this cir- cuit. When elwktor mains supply drops out, the light- ing is switched on automatically.
The inputs of N2 are thus high, which satisfies the criterion for the output to be low, which was the original assump- tion. The input of N1 is also pulled high via the J 80 k resistor, so the Q output is low, which holds the input of N2 low. As a rule of thumb allow elektog 10 M F per mA, The base current can be found by dividing the maximum output cur- rent by the gain of the transistor.
Elektor – 301 Circuits.pdf
It goes without saying that such an arrangement involves a complete loss of realism. Search the history of over billion web pages on the Internet.

An input signal of sufficient amplitude to over- Figure 1. The complete circuit figure 2 combines these two functions. This can eldktor used to calibrate the oscilloscope time- base.
However, by suitable choice of reservoir capaci- tor C2 the ripple on the main unregulated supply can be made such that the voltage falls to about 0.
The average voltage fed to the series transistor will thus be less than 8.
