Top Circuits Page 222
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Do you long for a beach holiday on a tropical island, but you don t have the necessary wherewithal? We ve got just the answer: build the i-TRIXX surf simulator, put on your headphones, and dream yourself away from this dreary realm. Let the rhythmic rush of....
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This simple circuit will energize and de-energize a relay at the push of a button. Pushing the button once - will energize the relay. And pushing it a second time - will de-energize the relay. The accompanying Circuit offers a good introduction to the....
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This is a circuit for alternative sources selection. It combines mechanical selection using a rotating switch S1, the electronic drive of the relays RL 1-10 and also the optical indication of the selection by the Display DSP1....
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It is useful where the load needs to be switched on from one location and switched off from another. Any number of momentary (N/O) switches or push buttons can be connected in parallel....
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This 555 timer circuit toggles a relay when a button is pressed. Pins 2 and 6, the threshold and trigger inputs, are held at 1/2 the supply voltage by the two 10K resistors. When the output is high, the capacitor charges through the 100K resistor, and....
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This toggle circuit operates by using a couple 555 timers wired as inverters. Pins 2 and 6 are the threshold and trigger inputs to the first timer and pin 5 is the output. The output at pin 5 will always be the inverse of the input at pins 2 and 6. Likewise,....
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The circuit requires a double pole, double throw relay in conjunction with a single transistor to allow toggling the relay with a momentary push button. One set of relay contacts is used to control the load, while the other is used to provide feedback to....
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The IR photo transistor Q1 (Radio Shack 276-145A) or similar is connected to the set input (pin 6). The photo transistor should be shielded from direct light so that the voltage at the set input (pin 6) is less than 1 volt under ambient conditions and moves....
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A simple and convenient way to interface 2 relays for switching application in your project. This relay driver boosts the input impedance with a regular BC547 NPN transistor (or equivalent). Very common driver. It can drive a variety of relays, including a....
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This is a great intercom circuit that can be used in many ways. It uses 22V to operate and maybe it will work at a lower voltage (you can try it). For input/output it uses a loundspeaker (20-45 Ohm) on each side....
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This nifty little circuit lets you record your phone conversations automatically. The device connects to the phone line, your tape recorder`s microphone input, and the recorder`s remote control jack. It senses the voltage in the phone line and begins....
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You are asking how to connect up some lights so that when the phone rings, they flash. This is very useful in a situation were there is lots of noise and it is impossable to hear the phone, such as a workshop. Here is such a device. The ring detect part of....
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This circuit was designed to detect when a call is incoming in a cellular phone (even when the calling tone of the device is switched-off) by means of a flashing LED. The device must be placed a few centimeters from the cellular phone, so its sensor coil L1....
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This timer will provide a sequence of up to ten separate events. The length of each event is set independently. And the sequence will run a fixed number of times - or repeat continuosly. The individual events within the sequence - can be made to repeat....
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A pair of multi-range timers offering periods of up to 24 hours and beyond. Both are essentially the same. The main difference is, that when the time runs out, Version 1 energizes the relay and Version 2 de-energizes it. The first uses less power while the....
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This circuit has an adjustable output timer that will re-trigger at regular intervals. The output period can be anything from a fraction of a second to half-an-hour or more - and it can be made to recur at regular intervals of anything from seconds to days....
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This is a simpler repeating timer circuit. It uses just one Cmos IC - wired as an asymmetric oscillator. The length of time the relay remains energized - and the length of time it remains de-energized - are set independently....
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This circuit is the opposite of Repeating Timer No.3. Its operation can be limited to the hours of darkness. Again - the variable resistor (preset) lets you choose the level of darkness at which the timer will begin to function....
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This timer circuit will only run when the temperature rises above a preset level. There`s an alternative version - Repeating Timer No. 6 - that only works while the temperature is below the preset level. R7 lets you set the temperature. The value of the....
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This circuit is the opposite of Repeating Timer No.5. It will only begin to operate if the temperature falls below the preset level. Again - the variable resistor (preset) lets you choose the temperature below which the timer will function....
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Time is set by potentiometer R2 which provides a range or 1 sec. To 100 seconds with timing capacitor C1 of 100uF. The output at pin 3 is normally low and the relay is held off....
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This circuit has an adjustable output timer that will re-trigger at regular intervals. The output period can be anything from a fraction of a second to half-an-hour or more - and it can be made to recur at regular intervals of anything from seconds to days....
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A 100 second delayed turn ON relay RL1 switch, if plug power +12V in circuit. In Fig. 2 see a two range 6-60 second and 1-10 minute auto turn off relay timer circuit, with 555...
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A small circuit that can find a lot applications of measurement time. She has the possibility us inform with sound signal from the BZ1. At the same time, exist the possibility drive a external circuit via the optocoupler IC2, after we connect the applicable....
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This is a programmable clock timer circuit that uses individual LEDs to indicate hours and minutes. 12 LEDs can be arranged in a circle to represent the 12 hours of a clock face and an additional 12 LEDs can be arranged in an outer circle to indicate 5....
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In the circuit, 60 individual LEDs are used to indicate the minutes of a clock and 12 LEDs indicate hours. The power supply and time base circuitry is the same as described in the 28 LED clock circuit above. The minutes section of the clock is comprised of....
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This is a combination digital clock timer and solar panel charge controller used to maintain a deep cycle battery from a solar panel. The timer output is used to control a 12 volt load for a 32 minute time interval each day. Start time is set using 9 dip....
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This circuit provides a visual 9 second delay using 10 LEDs before closing a 12 volt relay. When the reset switch is closed, the 4017 decade counter will be reset to the 0 count which illuminates the LED driven from pin 3. The 555 timer output at pin 3 will....
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In this circuit a LM339 quad voltage comparator is used to generate a time delay and control a high current output at low voltage. Approximatey 5 amps of current can be obtained using a couple fresh alkaline D batteries. Three of the comparators are wired in....
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The two circuits illustrate using the 555 timer to close a relay for a predetermined amount of time by pressing a momentary N/O push button. The circuit on the left can be used for long time periods where the push button can be pressed and released before....
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The circuit below illustrates generating a single positive pulse which is delayed relative to the trigger input time. The circuit is similar to the one above but employs two stages so that both the pulse width and delay can be controlled. When the button is....
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Here`s a power-on time delay relay circuit that takes advantage of the emitter/base breakdown voltage of an ordinary bi-polar transistor. The reverse connected emitter/base junction of a 2N3904 transistor is used as an 8 volt zener diode which creates a....
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The two circuits illustrate opening a relay contact a short time after the ignition or ligh switch is turned off. The capacitor is charged and the relay is closed when the voltage at the diode anode rises to +12 volts....
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Most thefts happen after midnight hours when people enter the second phase of sleep called ˜paradoxical sleep. Here is an energy-saving circuit that causes the thieves to abort the theft attempt by lighting up the possible sites of intrusion (such as kitchen....
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The purpose of this circuit is to power a lamp or other appliance for a given time (30 minutes in this case), and then to turn it off. It is useful when reading at bed by night, turning off the bedside lamp automatically in case the reader falls asleep After....
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This timer was designed for people wanting to get tanned but at the same time wishing to avoid an excessive exposure to sunlight. A Rotary Switch sets the timer according to six classified Photo-types (see table). A Photo resistor extends the preset time....
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This circuit is intended for alerting purposes after a certain time is elapsed. It is suitable for table games requiring a fixed time to answer a question, or to move a piece etc. In this view it is a modern substitute for the old sandglass. Useful also for....
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This circuit turns-off an amplifier or any other device when a low level audio signal fed to its input is absent for 15 minutes at least. Pushing P1 the device is switched-on feeding any appliance connected to SK1. Input audio signal is boosted and squared....
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This timer was designed mainly to switch off a portable radio after some time: in this way, one can fall asleep on the sand or on a hammock, resting assured that the receiver will switch off automatically after some time, saving battery costs. R1 and C1....
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This simple circuit tests speakers, microphones, transformers and voltage. It`s basically a very low frequency oscillator that produces extremely short `fruity` pulses. The type of sound produced is very easy to hear and to determine the precise direction it....
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A milliamp meter can be used as a volt meter by adding a series resistance. The resistance needed is the full scale voltage reading divided by the full scale current of the meter movement. So, if you have a 1 milliamp meter and you want to read 0-10 volts....
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The ICL7107 is a 3 1/2 digit LED A/D convertor. It contains an internal voltage reference, high isolation analog switches, sequential control logic, and the display drivers....
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This circuit is intended for precision centigrade temperature measurement, with a transmitter section converting to frequency the sensor`s output voltage, which is proportional to the measured temperature. The output frequency bursts are conveyed into the....
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Class D audio power amplifier schematic diagram with TDA7480, capable of 10W output power at a load of 8w/4w and a total harmonic distorsion of 10%. Requires a split-supply (max. ±20V)....
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The combination of the LM4651 driver IC and the LM4652 power MOSFET Class D power amplifier IC provides a high efficiency amplifier solution, suitable for self-powered speakers, subwoofers and quality car boosters. The LM 4651 is a fully integrated....
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Most sound card microphone inputs require a minimum signal level of at least 10 millivolts, but some older 8-bit cards need as much as 100 millivolts. The typical impedance of the PC soundcard microphone input is in order of 1 to 20 kohms (can vary from card....
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The LM1830 fluid level detector circuit is a device intended to signal the presence or absence of aqueous solutions, featuring low external parts count, wide supply operating range, internally regulated supply and AC or DC output. In a typical application....
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7W Mono Audio Amplifier Kit - This small amplifier is constructed around the TDA2003 IC, capable of delivering 7 watts music power into 4 ohms....
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This kit was designed to control the speed of AC motors with carbon brushes, anything from drills to saws to vacuum cleaners. Unlike other circuits such as normal dimmers the kit performs a phase cut only once per period. The moment of cutting determines the....
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All LEDs require some form of current limiting. Connecting an LED directly to the power supply will burn it out in a heartbeat. Overdriving, even briefly, will significantly reduce it`s life and light output. Fortunately, driving a single or a string of low....
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The MT-2 Metal Zone ™ is one the most popular guitar pedals, providing over-the-top, insane distortion tones with huge mids and lows and an ultra-saturated sound. It has a unique dual-gain circuitry, providing long sustain and heavy mids and lows like a....
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The DD-2 is one of the best digital delay pedals and actually sounds very analog! The pedal was sold from 1983 and it did officially go out of sale 1986 but it was relaunched without changes as the DD-3 (later versions of the DD-3 use a different design).....
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There are at least 3 different versions of this circuit. The first DM-2 version was using the MN3005 BBD and the MN3101 Clock Driver IC (PCB marking: ET5214-510). Later they changed the clock driver to MN3102 and the BBD to the low current version of the....
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The Boss GE-7 Equalizer pedal adjusts the harmonic contents of an instrument in 7 separate bands ranging from 100Hz to 6. 4kHz, with a boost/cut 15dB per band. The additional Level control knob helps you to set a different volume for normal and effect sound....
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The original coil that came with the Heathkit project was preassembled at the factory. It had a diameter of around 15cm (6 inch). A larger (30cm, 12inch) coil can be made using the following data:..
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The Pearl CH-02 Chorus is a long discontinued pedal with a superb sound. It has 4 knobs: DEPTH, SPEED, TONE and MIX BALANCE. The TONE knob only adjusts the tone of the effect sound and The MIX BALANCE adjusts the mix ratio between the direct and effect....
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The Boss SD-1 Super OverDrive is a pedal with a simple design, using only one dual operational amplifier (uPC4558C) and 6 transistors, with an asymmetric overdrive circuitry for a classic, natural tube amp growl. It generates the warm distortion of an....
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If TIP32C (Q2) gets excessively hot, use an IRF9640 MOSFET instead. Experiment with different values for R6 to find the optimal value (I use a 390 ohm resistor). Temporarily substitute R6 for a trim potentiometer (470 or 1k) to find the optimal dumping....
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The White`s Classic I was a very simple, easy to use machine, ideal for the entry-level detectorist to pick-up-and-go. It was a simple detector with no bells or whistles, only an on/off switch and a turn knob for a discriminator. It did not have much depth....
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TDA2003 has improved performance with the same pin configuration as the TDA 2002. The features of TDA 2002 - very low number of external components, ease of assembly, space and cost saving - are maintained. The device provides a high output current....
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The Tda2005 IC has a high output power: PO=10W+10W @ RL=2ohm, d=10% (stereo) and PO=20W @ RL=4ohm, d=1% (bridge) for Vs=14. 4V. The high reliability of the IC comes from the various protections against: output DC and AC short circuit to ground, overrating....
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This wireless FM microphone is simple to build and it has a useful transmitting range (over 300 meters in the open air). Despite its small component count and a 3V operating voltage it will easily penetrate over three floors of an apartment building. It may....
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24v DC is a very popular voltage used in industrial settings. The circuit below was designed to accept four different 24v DC alarm input signals, which are then used to drive a single low power beeper. The beeper is a magnetic type with its own....
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Here you can find plans for a simple ground plane antenna that works well in the FM Band (88-108MHz). It`s built of a small plastic disk 6 x 6 Loop Antenna - This new loop antenna by Graham Maynard is his best design yet and I am proud to be the first to....
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The mixer circuit below has 3 line inputs and 3 mic inputs. The mic inputs are suitable for low impedance 200-1000R dynamic microphones. An ECM or condenser mic can also be used, but must have bias applied via a series resistor. Circuit to Connect Telephone....
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The circuit below uses a CMOS dual D flip flop (CD4013) to toggle a relay or other load with a momentary push button. Several push buttons can be wired in parallel to control the relay from multiple locations. A high level from the push button is coupled to....
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AN79 Linear Technology AN79 modifies methods presented in AN74, permitting verification of 30 nanosecond amplifier settling times to 0. 1% resolution. sampling-based technique used is detailed and results presented. Appendices cover oscilloscope overdrive....
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The schematic above illustrates dividing a crystal oscillator signal by the crystal frequency to obtain an accurate (0. 01%) 1 second time base. Two cascaded 12 stage counters (CD4040) form a 24 stage binary counter and the appropriate bits are gated....
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This circuit can be used to operate an electric strike or an electromagnetic lock on a door. It is not the door being opened/closed, but a small electromagnetic strike which unlocks the door. The opener has the following features currently programmed in....
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The circuits in Figure1 and Figure 2 exhibit certain advantages over the circuit shown in the Design Idea in EDN, "Circuit detects first event, " May 3, 2001, pg 89. The n-player first-event-detection circuit offers several improvements: It has fewer passive....
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Usually when the car door is closed, the dome light just goes OFF. With this circuit, you can have our dome light fade slowly in brightness and finally go OFF. Electronic Transformer Dims halogen Lamp : 05/11/00 EDN-Design Ideas / (several circuits in PDF)....
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When you need to test an audio circuit with broadband noise, this circuit works great. It uses just three inexpensive C-MOS ICs that generate a series of output pulses whose widths vary randomly. Audio noise generator drives earphones or small speaker - This....
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Active amplified transformer isolated signal splitter that enables hum-free connection of1-guitar to more than1-amp as well as having a direct output Transformers for Audio Interfacing: Discussion on using audio transformers in equipment interconnections,....
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This almost trivial circuit may be used to charge a pair of AA or AAA sized cells in the sun. I have used it to keep my Palm Pilot and walkman radio running perpetually. This is an unregulated charger, proper charging is achieved by placing the unit in the....
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Class D amplifiers are much more efficient than other Classical amplifiers, but their high efficiency comes at the expense of increased noise and distortion. You can assess the frequency- and Time-domain characteristics of a Class D amplifier, including the....
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Simple CATV Upstream Fiber Optic Receiver Uses DC Pilot AGC. Upstream fiber links in a community antenna television (CATV) system are usually among the most difficult elements of the network to align properly. Set-top boxes and cable modems employ....
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To avoid the deep discharge that can destroy or shorten the life of a rechargeable battery, you must disconnect its load before the discharge is complete Circuit Protects Against AC Line Disturbances : 07/29/98 EDN-Design Ideas / operates by switching off....
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Converting periodic waveforms to square waves is an integral part of extracting a clock signal from data, creating waveform generators, and making timing-pulse generators. Any square-wave-conversion circuit is more valuable when the square wave`s duty cycle....
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This circuit uses12V DC instead od mains AC. This is very good idea if you don`t want to mess with direct mains voltage connected circuit or you want to run the stroboscope from batteries. Flash Slave Trigger : Flash slaves are used when you need to....
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Many applications require low-frequency signal generators that can deliver high-performance, high-resolution signals. This Design Idea presents a circuit that generates frequencies of 0 to 1 MHz. Sinusoidal, triangular, and square-wave outputs are available.....
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First introduced by the Signetics Corporation as the SE555/NE555 about 1971. Pin connections and functions: (See schematic below for basic circuits) Pin 1 (Ground) - The ground (or common) pin is the most-negative supply potential of the device, which is....
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This circuit is a modified Hartley oscillator with a couple of extra components included. The transformer is a small audio transformer, type LT700. The primary is center tapped with an impedance of 1Kohms at 1KHz. The secondary has an impedance of 8 ohms.....
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It is all very well knowing how to program the PIC in theory, but the real learning comes when you try your code on a PIC and see the results yourself in a circuit. You could build a circuit each time and program the PIC to see if the program works, or you....
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There is one slight drawback to our flashing LED program. Each instruction takes one clock cycle to complete. If we are using a 4MHz crystal, then each instruction will take 1/4MHz, or 1uS to complete. As we are using only 5 instructions, the LED will turn....
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The core infrared theory for getting this tutorial working was already described in the Infrared Receiver tutorial, so I`ll run through an abridged version here. First I`ll describe as an overview what infrared is and how it relates to our lives, then I`ll....
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The IC is a quad 2 input "AND" gate, a CMOS 4081. These gates only produce a HIGH output, when BOTH the inputs are HIGH. When the key wired to `E` is pressed, current through R1 and D1 switches Q5 on. The relay energizes; and Q5 is `latched on` by R8. Thus,....
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