Forum Diagram

DCF77 Preamplifier Circuit Diagram A popular project among microcontroller aficionados is to build a radio-controlled clock. Tiny receiver boards are available, with a pre-adjusted ferrite antenna, that receive and demodulate the DCF77 time signal broadcast from Mainf lingen in Germany.

DCF77 has a range of about 1,000 miles. All the microcontroller need do is decode the signal and output the results on a display. The reception quality achieved by these ready-made boards tends to be proportional to their price. In areas of marginal reception a higher quality receiver is needed, and a small selective preamplifier stage will usually improve the situation further. 

The original ferrite antenna is desoldered from the receiver module and connected to the input of the preamplifier. This input consists of a source follower (T1) which has very little damping effect on the resonant circuit. A bipolar transistor (T2) provides a gain of around 5 dB. The output signal is coupled to the antenna input of the DCF77 module via a transformer. 

DCF77 Preamplifier Circuit Diagram The secondary of the transformer, in conjunction with capacitors C4 and C5, forms a resonant circuit which must be adjusted so that it is centered on the carrier frequency. An oscilloscope is needed for this adjustment, and a signal generator, set to generate a 77.5 kHz sine wave, is also very useful. This signal is fed, at an amplitude of a few milli-volts, into the antenna input. With the oscilloscope connected across C4 and C5 to monitor the signal on the output resonant circuit, trimmer C5 is adjusted until maximum amplitude is observed.

It is essential that the transformer used is suitable for constructing a resonant circuit at the carrier frequency. Our proto-type used a FT50-77 core from Amidon on which we made two 57-turn windings. It is also possible to trim the resonant frequency of the circuit by using a transformer whose core can be adjusted in and out. In this case, of course, the trimmer capacitor can be dispensed with. Rainer Reusch Elektor Electronics 2008

SAFELY DISCHARGE X CAPACITORS ELECTRONIC DIAGRAM

BURGLAR ALARM USING IC TIMER 555/556 ELECTRONIC DIAGRAM

AUDIO LEVEL METER ELECTRONIC DIAGRAM

4x25W CAR AMPLIFIER TDA7381 ELECTRONIC DIAGRAM

Usb series player is an electronic device or electronic circuit that functions as an MP3 player that is stored on a storage device such as USB flash.In this usb circuit using an IC as a modifier of digital voice data into analog so that it can be applied to a headphone, or again through the power amlplifier strengthened so that it can be heard through the speakers. IC used in this circuit using IC PCM2902 as a modifier of a digital data into analog data storage.

Huawei C2601 Circuit Diagram

Baseband, Power Management, RF, RF Parameters, Assembling Description, C2601 Explosion Diagram, Assembling Description, Troubleshooting, No Vibration, No Display of LCD, “Check UIM” is displayed afterwards the buzz is powered on, No Ringtone, No complete is heard afterwards the alarm is set up, Outgoing Alarm Cannot be Initiated, No Charging, The buzz cannot be powered on, Key Failure, No Signal, Weak Signal, Appendix, Unused Pad of the BGA, Networks to the Test Point, Acronyms and Abbreviations, PCB

This circuit converts an input signal into one that is composed of a number of discrete steps but which re- mains otherwise identical to the input signal.
Because the steps are of equal height, the harmonic con- tent of the output signal will be dependent upon the amplitude of the input signal. This chararacteristic is extremely useful in the making of electronic music. The circuit uses quantitised pulse- width modulation for the adding of the step—shaped input signal. Pulse-width modulation is obtained by comparing a triangular voltage with the analogue input signal by means of a comparator; the quantitising, that is the adding of the steps, takes place by replacing the triangular voltage with a stepped l voltage.

The stepped-voltage generator con- l sists of three gates, N1 . . . N3 and transistor Tl. N1 operates as an astable multivibrator, that oscillates at a frequency depending on the value of Cl and Rl. Transistor stage T1 fu nctions as a charger circuit: each time the output of N1 is logic l, the transistor transfers the charge on C2 to capacitor C4. During the next half cycle C2 is recharged via Dl. ln this way the voltage across C4 increases in discrete steps, the height of the steps being deter- mined by the ratio C2:C4. When the voltage across C4 rises above a certain value, N2 switches transistor T2 on via gate N3 and discharges capacitor C4. When the capacitor is completely discharged, N2 switches off T2 and C4 continues to charge again in discrete steps The stepped voltage is set to the inverting input of lC2 which is connected as a comparator.

 Low- pass filter R4/C7 in the output of lC2 converts the pulse-width modu- lated signal back to an analogue one. The d.c. voltage level at the non- inverting input is set by potentiometer P2 to half the magnitude of the stepped voltage. The setting of P1 is dependent upon the input signal which must be attenuated such that the maximum value at the slider of P1 is always smaller than the maximum value ofthe stepped voltage. The number of steps can be selected by varying the value of C4. lt is possible to use a varicap in place of C4 with the varicap voltage being controlled by the music program or the input signal. Interesting and individual effects can be obtained in this way.

Automatic Water Tank Filler Circuit Diagram



Automatic Water Tank Filler Schematic Circuit Diagram

The schema described has been used to maintain the level of water in the header tank within prescribed limits. It controls a 3HP submersible bore pump which has a high starting current, necessitating a solid-state relay sufficient to take the starting load. Two Darlington transistors, Q1 & Q3, in conjunction with Q2 & Q4, are connected to the upper and lower water sensors in the tank. Q2 & Q4 have a common 5.6kO load resistor and function as a NOR gate. The output of the NOR gate drives Q5 which activates relay RLY1.

 Initially, when the water level is low, both sensors will be open-schema, the NOR gate output will be high and the relay will be turned on. This causes the normally closed (NC) contacts of the relay to open and disconnect the lower sensor. However, the upper sensor will still be open schema and the NOR gate output will be high, keeping the relay closed. The normally open (NO) contact of the relay will be closed to operate the solid-state relay RLY2 to run the pump.

This state continues until the water reaches the top sensor which will then drop the output from the NOR gate to 0V. The disables relay RLY1 and the pump is stopped. In practice the upper level sensor is just below the overflow from the tank and the lower sensor about half way up the tank. The sensor contacts are simply two stainless steel screws about 25mm apart and screwed through the poly tank walls. The wiring junctions on the side of the tank are protected by neutral-cure silicone sealant.