Rongge

Generated millions of times every day by our telephone keypads, the eight DTMF frequencies were chosen so that the harmonics and intermodulation do not generate significant in-band signal levels. The signal is encoded as a pair of sine waves, ensuring that no frequency is a multiple of the other and the sum and difference between two frequencies does not match any single tone and that’s why DTMF sounds so ugly!T he DTMF encoder circuit show n here is based on the HT9200B tone generator device produced by Holtek and distributed by Futurlec  among others. The encoder is complemented by a decoder elsew her e in this publication. 8-Channel DTMF : Encoder Schematic The HT2900B is supplied as a nice old fashioned 14-pin device. It can be instructed by a microcontroller to generate 16 dual tones and (in serial mode only) 8 single tones from the DTMF pin output . It s 8 - pin ‘ younger brother’ the HT9200A provides a serial mode only whereas the HT9200B contains a select-able serial/parall...

This is the Simple Auto Tachometer Circuit Diagram. Anyone performing their own automobile tune-ups knows how important it is to know your engines speed. With this tachometer, you can measure your engines speed without any connections or annoying timing lights.   Simple Auto Tachometer Circuit Diagram  PC board layout and parts placement Notes Calibrate the unit as folows: a.    Set up this circuit:    Turn on the Tach and allow a few minutes for temperature stabilization. Set S2 to 4 cylinders and adjust R5 for a meter indication of 180 (1800 rpm). Set S2 to 6 cylinders and adjust R6 for a meter indication of 120 (1200 rpm). Set S2 to 8 cylinders and adjust R7 for a meter indication of 90 (900 rpm). To use the Tach, turn it on and let it sit for one minute to allow for temperature stabilization. Extend the antenna, select the right number of cylinders and hold the unit over the engine. If the reading is erratic or the needle jumps around, move th...

SIMPLE RADIO FREQUENCY REMOTE SWITCHING CIRCUIT RF TRANSMITTER SECTION Today we are going to discuss about the simple RF (Radio Frequency) Transmitter and Receiver circuit. RF(Radio Frequency) is a High Frequency signal commonly used for communication applications, due to its high frequency we can transmit signal to a sufficient distance (about 300 Foots) without attenuation. Here, the simple RF switching circuit is used to turn ON and turn OFF an LED (For Demonstration) you can replace the LED with a switching RELAY and control any appliances. Read More.....

This project flashes eight LEDs in an apparently random manner. It uses a 4060 combined counter and display driver IC which is designed for driving 7-segment LED displays.  Circuit diagram : Simple 8 Random Flashing LEDs The sequence is not really random because seven of the LEDs would normally be the display segments, the eighth LED is driven by an output that is normally used for driving further counters. The table below shows the sequence for the LEDs. You can use less than eight LEDs if you wish and the table may help you decide which ones to use for your purpose.

This is a Simple Analog-to-Digital Converter with LT1018. An analog-to-digital converter (abbreviated ADC, A/D or A to D) is a device that converts a continuous physical quantity (usually voltage) to a digital number that represents the quantity's amplitude.The converter has a 60-ms conversion consumes 460 pA of 1's. 5 V power supply and maintains an accuracy of 10 bits on a 15 ° C in the temperature range of 35 ° C.   Simple Analog-to-Digital Converter with LT1018 Circuit Diagram A pulse applied to convert the command line causes Q3, operating in reverse mode, the discharge path through the diode 10 kO, forcing its collector low. Q3 results of reverse mode switching in a capacitor discharge to 1 mV of ground. During the time of the ramp value is less than the input voltage, output of the CIA is low.  This allows pulses ClB stabilized quartz oscillator, modulating Q4. The output data appears at the collector of Q4. When the ramp crosses the starting value of the output ...

his is the Simple 12V To 24V DC-DC Converter Circuit Diagram. This simple DC-DC converter can provide up to 24V from a 12V source. It can be used to run radios, small lights, relays, horns and other 24V accessories from a 12V vehicle with a maximum draw of about 800mA.   Simple 12V To 24V DC-DC Converter Circuit Diagram It can be used to charge one 12V battery from another, or step up the voltage just enough to provide necessary overhead for a 12V linear regulator. Using one op-amp as a squarewave oscillator to ring an inductor and another op-amp in a feedback loop, it won't drift around under varying loads, providing a stable 24V source for many applications. With a wide adjustment in output this circuit has many uses. 

Hello Freinds ! Here designed SIMPLE BAR DISPLAY WITH ALARM FLASHER . Schematic: Return to Display Circuits. By using two switching transistors and two LEDs, this circuit can distinguish low-level ac and dc signals. If the red LED illuminates, the signal is positive dc. If the yellow LED lights, the signal is negative dc. If the signal is ac, both LEDs will light. Bar Display With Alarm Flasher Circuit Schematic

The whole project was developed on a friend's request. Its purpose was to remotely monitor the water-level in a metal tank located in the attic by means of a very simple control unit placed in the kitchen, some floors below. Mains requirements were: No separate supply for the remote circuit Main and remote units connected by a thin two-wire cable Simple LED display for the main unit Battery operation to avoid problems related to mains supply and water proximity As the circuit was battery operated a low current consumption was obviously welcomed The very small remote unit is placed near the tank and measures the water level in three ranges by means of two steel rods. Each range will cover one third of the tank capacity: Almost empty - signaled by means of a red LED (D3) in the control unit display About half-level - signaled by means of a yellow LED (D2) in the control unit display Almost full - signaled by means of a green LED (D1) in the control unit display Simple Water Level...

This is a Simple Directional Signals Monitor Circuit Diagram . A unijunction transistor audio oscillator drives a small speaker. The oscillator`s frequency is determined by resistor R2 and capacitor C2. The ope rating voltage is supplied from the car`s turn-signal circuit(s) through Dl and D2. The diodes conduct current from the blinker circuit that is energized, and prevent stray current flow to the other blinker circuit. Simple Directional Signals Monitor Circuit Diagram

This is a compact three transistor, regenerative receiver with fixed feedback. It is similar in principle to the ZN414 radio IC which is now no longer available. The design is simple and sensitivity and selectivity of the receiver are good. Notes: All general purpose transistors should work in this circuit, I used three BC109C transistors in my prototype.The tuned circuit is designed for medium wave. I used a ferrite rod and tuning capacitor from an old radio which tuned from approximately 550 - 1600kHz. Q1 and Q2 form a compund transistor pair featuring high gain and very high input impedance. This is necessary so as not to unduly load the tank circuit. The 120k resistor provides regenerative feedback,between Q2 output and the tank circuit input and its value affects the overall performance of the whole circuit. Too much feedback and the circuit will become unstable producing a "howling sound". Insufficient feedback and the receiver becomes "deaf". If the circuit o...

LM 35 temperature sensor IC is a IC chip production Natioanal Semiconductor which serves to determine the temperature of an object or space in the form of electric scale, or can also be defined as an electronic component that is used to change the temperature changes are accepted in the electrical wholesale changes. LM35 temperature sensor IC temperature change can change a change in voltage at the output. LM35 temperature sensor IC requires +5 volts DC source voltage and DC current consumption of 60 mA in operation. Physical form LM 35 temperature sensor is an IC chip with packaging that varies, in general packaging LM35 temperature sensor is packaged TO-92 as shown in the figure below. From the picture above it can be seen that the temperature sensor IC LM35 basically have 3 pin that serves as a source of supply voltage of +5 volts DC, as a result of sensing the output pin in the form of a change in the DC voltage and Vout pin to Ground. IC LM35 temperature sensor characteristics are...

This is the schematic design of HiFi Expandor Circuit with De-emphasis . The circuit is based NE570. The NE570 can be used to construct a high performance compandor suitable for use with music. This type of system can be used for noise reduction in tape recorders, transmission systems, bucket brigade delay lines, and digital audio systems. The circuits to be described contain features which improve performance, but are not required for all applications.  HiFi Expandor Circuit  Diagram  The expandor to complement the compressor is shown in the above circuit. Here an external op amp is used for high slew rate. Both the compressor and expandor have unity gain levels of 0dB. Trim networks are shown for distortion (THD) and DC shift. The distortion trim should be done first, with an input of 0dB at 10kHz. The DC shift should be adjusted for minimum envelope bounce with tone bursts. When applied to consumer tape recorders, the subjective performance of this system is excellent....

This lamp circuit using ultra-bright white LEDs provides sufficient light for reading purposes while consuming approximately 3 watts of power. In the case of AC mains failure, the battery backup circuit instantly lights up the LEDs. When the power resumes, the battery supply is automatically disconnected and the lamp circuit again works off AC mains. The power supply circuit consists of 0-7.5V, 500mA step-down transformer X1, rectifier diodes D1 through D4 and filter capacitor C1. Regulator IC 7805 (IC1) provides regulated 5V to LEDs, so there is no variation in the intensity of the lamp light even if the mains power supply fluctuates. A total of ten white LEDs (LED1 through LED10) are connected in parrallel across the 5V power supply. Resistors R1 through R10 (each 56 ohms) are connected in series with the white LEDs to limit the current. To increase the intensity of the lamp light, you can add more LEDs in the same manner; a maximum of 15 LEDs can be used for the lamp. LED-Based Read...

Designing various electronic circuit system (synthesizer, modem, decoder, data converter, etc) of ten need a frequency modulator subsystem. An FM modulator is very easy to build with TC9400 since the it has very good linearity as V/F converter. While Vin determines the amount of modulation (FM deviation) around the center frequency, the potentiometer determines the center frequency. Vin can be negative as well as positive. Superlinear FM Circuit Diagram

Here is simple electronic circuit Project of phase-controlled dimmer circuit. A phase-controlled dimmer delays the triac turn-on to a selected point in each successive ac half cycle. Phase-Controlled Dimmer Circuit Diagram:   Use this circuit only for incandescent lamps, heaters, soldering irons,or universal motors that have brushes.

Because I’m old school, I wanted to build a Garage Door Closing circuit without relying on integrated configurations (555 timer etc) to keep it simplistic. The circuit closes the garage door after two minutes with C3 and four minutes with the addition of C2. The timer relay is surprisingly accurate (+/- five seconds). Another feature is to ensure that the garage door actually did close, such as if it’s stopped mid-operation by the user. S3 (magnetic N.C.) is located at the garage door and activates the circuit when the garage door opens. RL1 is the reset timer. It’s maintained in the “on” position for two minutes by C3 while the trigger capacitor, C4, is charged. RL2 is the conduit, directing C4 to either RL3 or R1 to ground when off. Purpose of R1 is to prevent arching across contacts and a fast discharge. RL3’s contacts are connected to the Garage Door’s Momentary Switch and is sustained “on”  for a half second by C5. When C3 discharges to the cutoff voltage of RL1, it turns off ...

This is the Simple Overtone oscillator with crystal switching Circuit Diagram. The large inductive phase shift of LI is compensated for by Cl Overtone crystals have very narrow bandwidth;, the re fore, the trimmer has a smaller effect than for fundamental-mode operation.  Simple Overtone oscillator with crystal switching Circuit Diagram

A very simple fluid lever sensor can be designed using this circuit diagram . This fluid level sensor electronic circuit project is very simple and can be used to control water pump or to activate /stop some devices when the sensor detects presence of water. Simple Fluid Level Sensor Circuit diagram This fluid level sensor circuit uses an ac sensing signal to eliminate electrolytic corrosion on the probes .The ac signal rectified is used to drive T1 transistor that drives a 12 volt relay , that can activate or stop some device . R2 resistor is used to modify the sensor sensitivity and can be replaced with a small variable resistor . MC104093B is a p channel quad 2 input NAND schmitt trigger and is pin to pin compatible with the CD4093 . The unused inputs must be tied to an appropriate voltage level , either ground or +12 volts (8,9,12 and 13) and the unused outputs must be left open (10 and 11) . The circuit can be powered with an input voltage between 3 and 18 volts dc , but in our ca...

This is the Simple UPS Power Supply Circuit Diagram. This circuit is a simple form of the commercial UPS, the circuit provides a constant regulated 5 Volt output and an unregulated 12 Volt supply. In the event of electrical supply line failure the battery takes over, with no spikes on the regulated supply. Notes: This circuit can be adapted for other regulated and unregulated voltages by using different regulators and batteries. For a 15 Volt regulated supply use two 12 Volt batteries in series and a 7815 regulator. There is a lot of flexibility in this circuit. TR1 has a primary matched to the local electrical supply which is 240 Volts in the UK. The secondary winding should be rated at least 12 Volts at 2 amp, but can be higher, for example 15 Volts. FS1 is a slow blow type and protects against short circuits on the output, or indeed a faulty cell in a rechargeable battery. LED 1 will light ONLY when the electricity supply is present, with a power failure the LED will go out and outp...

Build a 3 volt to 9 volt with LMC555 Circuit Diagram. This is a Build a 3 volt to 9 volt with LMC555 Circuit Diagram. This dc converter is built with the CMOS version of 555 timer. You can get 12V too if you change the zener diode to a 12V version. 3 volt to 9 volt with LMC555 Circuit Diagram