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Model railway lighting Generally speaking, the internal lighting for model railway carriages is powered direct from the voltage on the rails. D2 will extinguish and D3 will light due to cur- rent flowing through it from the output of IC2 to the output of IC1.
Full text of “Elektor – Circuits”
The result is that the chip, and hence the refer- ence voltage, is held at a virtually constant tem- perature. Sawtooth-CCO 6 15V This sawtooth waveform generator which is built round a current controlled oscillator is dis- tinguished by its large sweep range.
The clock frequency, and hence the speed of the running light, can be altered by means of PL R This design is a contribution towards such a the discussion. The tem- perature coefficients of D3 and D4 could intro- duce errors by varying the charge and discharge times of Clso these are compensated by includ- ing identical diodes in series with R3 to produce a similar variation in the reference voltage at the non-inverting input oflCL P2 is included to null the offset voltage of 1C2 which would otherwise cause a zero error.
As was the case in the above circuit, there is a 031 permissible value for R fj. The complete output waveform, shown in figure 2comprises a burst of pulses approx. A TTL-compatible pulse output is epektor A for simple frequency counters etc.
Using the in a low-voltage high-current supply, with an external series transistor oper- ating from the same supply rail as the circuuits, in- variably results in excessive dissipation in the series transistor. The ac- companying diagram represents the basic univer- sal design for such a generator.
This will supply Tl with more base current, turning it on harder so that the output voltage of the regulator will rise. It will be noticed that the LEDs do not light and extinguish at exactly the same voltage. It is then possible to dis- pense with the on-off switch by making a short- ing link in the connector plug, as shown in circuuts ure 3. If a seven decade counter Is used that gives a reading of 1.
Kaul Common-base virtual-earth mixer The most usual form of virtual-earth mixer wlektor sists of an inverting amplifier with the inputs to be mixed or more accurately summed being fed via resistors to the virtual-earth point at the in- verting input.
Elektor – Circuits : Free Download, Borrow, and Streaming : Internet Archive
The direct and phase-shifted signals are summed by IC2d. However, with supply voltages greater than 10 V this should not be a problem. 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 flektor by the lamp La. To measure frequency one does not immediately have to ‘go digital 1. This is driven from an identical astable to that in figure 1b, While the output of Nl is low and Cl is charg- ing, the output of N2 is high and C2 is discharg- ing into C3, and vice versa.
The use of a total of ten op- amps in the circuit may seem rather excessive, but as eight of these are LM quad op-amps the circjits package count is only four ICs. A red LED should be used for D7. For a nor- mal sized fire a 4 A type should prove sufficient.
Elektor – 301 Circuits
If cur- rent is passed through any one of these resistors, a corresponding voltage drop will appear across this resistor. The output from the tempera- ture sensor can be monitored with a mV-meter, and P2 is then set so that the relay drops out when this voltage reaches 20 mV, corresponding to 4Q0 D C.
Circjits upon the logic level of the input signal, one of the above frequencies is fed to the output. P3 should be adjusted so that the audio gener- ator just fails to oscillate under quiescent con- ditions.
The negative -going edge of the waveform is independent of the amplitude of the input signal and occurs always at the zero- crossing point. Once Cl has again reached the trigger voltage of the diac, the entire cycle repeats itself. There is no doubt that most people find the sight of an open fire pleasing. If this output is high the clock fre- quency is cirucits and vice versa.
With PI in its mid- position both signals have approximately the same amplitude whilst at the two extremes one signal is completely blocked whilst the other is passed continuously.
When the contacts are released the input of N1 is held low by the output via Rl, so the output remains low indefinitely. A portion of the signal is fed to an envelope follower, which rectifies and filters It to produce a positive voltage that follows the amplitude en- velope of the input signal. The input voltage Vi is applied to the inverting input of IC2, which functions as an integrating comparator.