Top Circuits Page 46
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Asynchronous counter shown, this circuit no clock synchronization signal can be used in a random counter or independent unit circuit. ..
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CC4017 count/distributor consisting of a circuit diagram of the delay: ..
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Circuit order is triggered by the positive edge. The anode of the triac switches are turned on, the cathode of the switches are closed. Male - female IN4009 positive transient ..
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Have you ever been using the modem or fax and someone else picks up the phone, breaking the connection? Well, this simple circuit should put an end to that. It signals that the phone is in use by lighting a red LED. When the phone is not in use, a green LED....
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The telephone ring generator shown below generates the needed high voltage from a simple switching mode power supply (SMPS) which employs a CMOS Schmitt Trigger square wave oscillator, 10 mH inductor, high voltage switching transistor (TIP47 or other high....
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Sometimes caller might want to preserve his privacy so that his/her number is not send to the called person. Legistlation say that caller must have some way to disable sending of the called ID information when he/she wants to. This can be done by dialling s....
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CallID Unit based on Motorola MC68HC11A1P & MC145447P chips compatible with the standard protocols. if you got a multimeter and a phone you can start testing. Check the voltage across the pair, should be 48VDC in US, 60VDC in Europe. Place a 600 ohm....
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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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The circuit in Figure 1 adapts a small key-chain voice recorder to the Tip and Ring lines of a phone line that has been disconnected from the central office. The purpose is to play a prerecorded message into any phone on the line when its receiver goes....
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I have used this type of circuits for quick testing of telephone equipment. This is a quick hack that does not exactly resemble the characteristics of the real telephone network, but is enough for this kind if applications. If you want better simulation,....
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For this scheme to have satisfactory signal-to-noise and frequency-response parameters, the clip, connecting cable, and amplifier must m be attached parallel to the signal wire and must be as long as is conveniently possiblean inch or moreand preferably....
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This circuit enables automatic switching-on of the tape recorder when the handset is lifted. The tape recorder gets switched off when the handset is replaced. The signals are suitably attenuated to a level at which they can be recorded using the MIC-IN....
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This self-build project can simulate a telephone call / connection between any two local telephone devices. This for a fraction of the outlay of some commercial units, many with cost-increasing features that usually are not required. The circuit is centred....
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This circuit will allow you to connect any tape recorder that has a mic and remote input to a phone line and automatically record both sides of a conversation when ever the phone is in use. You will need to take a couple of voltage readings before connecting....
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The circuit in Figure 1 shows a method of meeting this challenge with 100% margin. In other words, it presents approximately 10-M leakage resistance across the line. The basic relaxation oscillator has the LED of an optoisolator in the discharge path of the....
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With this circuit mounted in or near every phone in the house, it will allow users to know if the phone is being used and not to pick up the phone. When a phone is taken off hook, the voltage across the tip and ring terminals drops to 10 volts or less. This....
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This project displays telephone numbers decoded from tones. A microphone picks up the tones, a preamplifier boosts the signals, an SSI-202 DTMF chip decodes the tones, a Basic Stamp acts as an interface to an LCD display and also provides "RS-232" serial....
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This interface is needed to connect the phone to a PC, because the PC`s serial port works with voltage levels between -12 and 12V (RS232 protocol) and the phone operates between 0 and 5V (TTL protocol). Don`t even think in conecting your phone directly to....
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There`s not much to this circuit. The two RJ-11 jacks are set up to feed the telephone circuit through from the wall to the phone. The active signal for a single phone is on the red and green wires. Yellow and black are usually used for a second phone line.....
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It uses old pulse dial handsets and replaces the AC bell set with a 9 volt DC buzzer. The whole circuit runs from a 12 volt regulated DC supply and is suitable for short term battery operation (eg: Gel Cell). The Link is designed to enable one call at a time....
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The design also overcomes the shortcomings of modem interference protectors. The design eliminates mutual interference between phones and modems, is compatible with the line-usage indicators on multiline phones, can search for an idle phone line in multiline....
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This version of the familiar current loop offers a simplified and somewhat novel implementation in which optocouplers serve triple duty as level converters, isolation/protection devices, and bus interfaces. Galvanic isolation avoids ground loops, increases....
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This circuit differs from similar circuits in view of its simplicity and a totally different concept of generating the control signals. Usually remote control circuits make use of infrared light to transmit control signals. Their use is thus limited to a....
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This is the lowest cost dialing alarm on the market and shows what can be done with an 8-pin microcontroller. The complete circuit is shown below. You cannot see all the features of this project by looking at the circuit - most of them are contained in the....
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With this circuit can determine whether any of the phones of the same line is busy (it's up the handset), with the help of a LED.To circuit has no measurable effect on the telephone, so that there are problems with phone line company . The circuit is....
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This circuit allows you to record audio from a telephone line into a tape recorder or computer soundcard. Most of the parts for this circuit can be scrounged from an old modem, with some work, it is possible to rewire the modem circuitry and use the old....
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A while ago I got an email asking for the schematic of a circuit to detect cut phone lines. It didn`t take me long to find this circuit in Electronics Now. When the circuit detects that a phone line has been cut, it activates a MOSFET which can be used to....
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This project is really a mixture of ideas, some simple, and others even simpler. The system I have installed in my biamp unit is fan cooling. Once a preset temperature is reached, the fans start, and remain on until the amp is turned off again. This is....
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This is the basis of electronics telephone sets. You can use it to replace the talking circuit of an old telephone set with new design, better noise rejection and reliability one. Also you can use it to build a telephone set without dial circuit to answer a....
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This really isn't much an electronics project as it is a telephone wiring project. Take note that this proejct involves connections to telephone lines. This may be frowned upon by your telephone service provider, AKA The Telephone Company. Always use proper....
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The phone company provides 3 levels of power. With no devices 'off hook' the line rests at 48 volts DC. If you draw any more than a fraction of a milliamp or so, you get the phone company's attention and a dial tone. When the line rings, you get about 100....
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The PIC16F870 chosen for this project has seval analog channels. One of these is used to capture the DTMF tones and decode the digits. The actual phone connections are made using a 'hacked' 5 line expandor from Radio Shack. This device connects between....
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This circuit is used to give "1" signal when the phone is ringing. As you can see the ct. is directly connected to the phone line. The 4.7 uF blocks the DC loading on the phone line. This means that there is voltage on the 10K resistance only when the phone....
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his circuit will allow you to connect any tape recorder that has a mic and remote input to a phone line and automatically record both sides of a conversation when ever the phone is in use. You will need to take a couple of voltage readings before connecting....
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With this circuit mounted in or near every phone in the house, it will allow users to know if the phone is being used and not to pick up the phone. When a phone is taken off hook, the voltage across the tip and ring terminals drops to 10 volts or less. This....
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This circuit will allow you to place a phone call on hold and if you wish to have them listen to music while they are on hold. The circuit operates as follows: The RED wire from the phone jack is typically positive and the GREEN wire is negative or ground.....
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This unit is an upgrade of the previous phone call interceptor. Instead of using an answering machine to provide the outgoing message and recording functions, it uses the ISD4004 (from Windbond Electronics). The ISD4004 records up to 8 minutes of audio. I....
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Creating projects that connect to the phone line can be a real chore without some device like this. It generates the 48 volts DC for the on-hook condition, the 100 volts AC for the ring signal, and the 20 milliamperes DC for the off-hook condition. To use....
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If we have a lot of parallel telephones on a telephone line, we needed a unit that will have the possibility of showing if somebody of the telephone has raised the earphone. Our this possibility give the circuit. The circuit is connected at parallel with the....
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A very simple circuit, that will find application in the case where you have a lot of telephones installed on a telephone line and would want to know if somebody of them is open. Thus you will not be off any discussion. Simultaneously it can cut the certain....
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The UNIVERSAL HOLD circuit detects the dual tone, multi frequency (DTMF) tone that is
generated when the # key is pressed and then activates a circuit that partially loads the telephone line
so that the central office thinks a phone is still off hook even....
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The above diagram is a standard low-pass telephone line filter (L1,C1,L3,C2). L2 and L4 are needed since we're dealing with the 'Tip' and 'Ring' of a phone line which may carry up to 90VAC. I used a similar circuit on 3 phone-lines back in the early 80's....
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This project has two features. It will let you know when a single phone is using the line and also when two phones are on the line!
The green LED indicates the first phone and the red LED indicates the second phone! There are many times when you need to....
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R1 and R2 form a voltage divider, insuring that the phone line sees a high impedance load and that high voltages (such as the ring voltage) are easily dissipated by the protective diodes (CR1 and CR2). Also (obviously) they serve to divide all incoming....
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This add-on device for telephones can be connected in parallel to the telephone instrument.
The circuit provides audio-visual indication of on-hook, off-hook, and ringing modes. It can also be used to connect the telephone to a cid (caller identification....
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Here is a teleremote circuit which enables switching on and off of appliances through telephone lines. It can be used to switch appliances from any distance, overcoming the limited range of infrared and radio remote controls.
The circuit described here can....
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Normally the base of a cordless phone has an adaptor and the handset has Ni-Cd cells for its operation. The base unit becomes inoperative in case of power failure. In such conditions, it is better to provide a backup using Ni-Cd cells externally. Here is a....
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The given circuit, when connected in parallel to a telephone, dis- plays the number dialled from the telephone set using the DTMF mode. This circuit can also show the number dialled from the phone of the called party. This is particularly helpful for....
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A compact, inexpensive and low component count telecom head- set can be constructed using two readily available transistors and a few other electronic components. This circuit is very useful for hands-free operation of EPABX and pager communication. Since....
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Here is a telephone line vigilant circuit to guard against mis- use of your telephone lines. It monitors telephone lines round the clock and provides visual as well as an audio warning (when someone is using your telephone lines) which can be heard anywhere....
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H ere is a circuit of an off-line telephone tester which does not require any telephone line for testing a telephone instrument. The circuit is so simple that it can be easily assembled even by a novice having very little knowledge of electronics. A....
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Very often when enjoying music or watching TV at high audio level, we may not be able to hear a telephone ring and thus miss an important incoming phone call. To overcome this situation, the circuit presented here can be used. The circuit would....
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Often a need arises for connection of two telephone instruments in parallel to one line. But it creates quite a few problems in their proper performance, such as overloading and overhearing of the conversation by an undesired person. In order to eliminate....
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The following text describes construction, testing and use of an electronic telephone line simulator of my own design. This self-build project can simulate a telephone call / connection between any two local telephone devices. This for a fraction of the....
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A simple phone automatically shows the recording circuit. In this circuit, after the call Ming sound start switch K is turned on by the sound of automatic message HFC5209D. ..
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Chaolitong Phone Travel Charger for Motorola to 308,328,338 and 368 series mobile phone battery. The charger has a nickel-cadmium, nickel hydrogen, lithium-ion battery switch, ..
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I have received several emails 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...
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It is a relatively simple circuit, with which we can have optical and sound clue, when we have telephone ring in the line of telephone. The calls in the line, are changed in pulses of frequency 400 HZ from the IC2, in exit 3. Then via the IC4, after they are....
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The circuit consists of 6 building blocks and the first is the inverter between pins 1 and 2. This forms a low frequency oscillator with a 1u and 1M + 2M2 resistor. It governs the overall timing of the ring by creating an ON and OFF time. When the output is....
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Many a times one needs an extra telephone ringer in an ad joining room to know if there is an incoming call. For example, if the telephone is installed in the drawing room you may need an extra ringer in the bedroom. All that needs to be done is to connect....
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Using modulated rectangular waves of different time periods, The circuit presented here produces ringing tones similar to those produced by a telephone.
The circuit requires four astable multivibrators for its working. Therefore two 556 ICs are used here.....
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The circuit shown here is used to switch on a lamp when the tele- phone rings, if the ambient light is insufficient. The circuit uses only two ICs and it can be implemented very easily. A light dependent resistance (LDR), with about 5 kilo-ohms resistance in....
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Many a times one needs an ex- tra telephone ringer in an ad- joining room to know if there is an incoming call. For example, if the telephone is installed in the drawing room you may need an extra ringer in the bedroom. All that needs to be done is to....
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As shown for the 20Hz signal generator, may be applied to the telephone ringing system, the signal source can also be used for alarm systems and other electronic Used. The circuit is actually a transformer T and a transistor VTl, VT2 composition..
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The call is made using language chip ISD1016 voice instead of using the phone ringing message controller schematic circuit. The controller can store messages, music, song, or other sounds, as an alternative to monotonous ringing...
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As shown in FIG later, RTD temperature collected in the field, which was converted into a voltage by the XTR105 voltage is converted into 4 ~ 20mA current output, and then the ..
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As shown in FIG, RTD using Pt100 type thermocouple. When the temperature is 100 ~ 600oC when, XTR105 output current 4 ~ 20mA, RCV420 output voltage of 0 ~ 5V. The figure for th..
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As shown, collected at the scene RTD temperature, it is converted into a voltage by the XTR112/114 voltage is converted into 4 ~ 20mA current output, and then the twisted pair ..
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Check loop circuit for automatic telephone answering or tone generator for use reverse automatic repair. ..
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Here is a simple transmitter that when connected to a phone line, will transmit anything on that line (execpt the dial tone) to any FM radio. The frequency can be tuned from 88 to about 94Mhz and the range is about 200 feet. It is extremely easy to build and....
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My FM Wireless Microphone has been a very popular project with beginners and experienced constructors alike. It has been used inside guitars and as the basis of a remote control system. I do however, receive many requests for a higher powered circuit and....
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One of the nicest features of the 8-bit KX8 microcontroller (manufactured by Freescale Semiconductor) is that it includes an internal clock generator (ICG). This allows the chip to run without the trouble and expense of an external crystal or canned....
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Bugdozer is an autonomous mini-Sumo robot. Her main board consists of a MC68HC908GP32 microcontroller along with input/output support chips, a voltage regulator, a crystal oscillator, and the usual assortment of resistors, capacitors, and switches. All chips....
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The microcontroller is able to make about 7000 complete line-following decisions per second, which is almost 7 decisions per millimeter when the robot is going full speed. By upping the clock, unrolling loops, and removing my wireless debugging and....
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The project consists of 35 LEDs arranged as a 5x7 matrix. This may not seem very impressive but you can display all sorts of effects and treat it like a "window on a large video screen." The project comes with a series of test programs to test the operation....
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This was my first sucessful project with a PIC chip. I used a 16F84 with a 10MHz resonator with built in caps. Click here to view the source code to this project. The code is written in Hi-Tech C. Click here to download the source code to this project. File....
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This LCD terminal provide two modes of operation by selecting jumper J1. When J1 is open the terminal operate as a normal ascii display terminal, when J1 is closed the terminal displays the input serial data in hexadecimal format. This mode is useful for....
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The JavaBot1 is a small line following robot designed to follow a black line drawn on a dry erase board. It is designed to follow very tight curves. The software still has lot`s of room for improvement but works well as is. The JavaBot1 uses 2 Cirrus CS-70....
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The F84 MRTC was my second design of a miniature real-time controller. This version uses PIC16F84 running with a low power X-tal 32,768Hz. The scheduler for 6-channel output was saved in EEPROM. No terminal for serial downloading of the scheduler. It`s....
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I finally found a very nice universal window based software designed to work with any serial programmers for PIC16F84, i.e., WPicProg16 V1.20, written by Nigel Goodwin. Build this programmer before started experimenting the forthcoming many interesting F84....
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PicCon is a PIC microcontroller based radio controller designed for hidden transmitter hunting. When combined with a radio transmitter, it will produce tone sequences and Morse code messages at user-programmed times. It is completely field programmable via....
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This is a beta release of the PIXpand project. The PIXpand which is a device that connects to a TI calculator and enable it to store and retreive data to and from Playstation Memory cards. I am making this beta release as I do not have the time to continue....
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It is sometimes necessary to retrieve data at power-up in the same way that they were at the last power-down, so that the product wakes up in the state it had before shutdown or to retrieve some measurement. One approach is to save critical variables into....
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You can use a low-cost PC sound card as an analog-function generator by controlling the PC with the program "SoundArb." [To obtain SoundArb, download di2409setup.exe, a 1.06-Mbyte self-extracting installation program.] The program generates standard....
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Many security-alarm systems require the use of a random number. A computer program uses this random number to create a sequence of random numbers to prevent unwanted visitors from gaining entry into a protected facility. You can use a "rolling-code....
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The 16F84 has 13 outputs. All 13 can serve as inputs, but only 12 are normal outputs, one is an open-drain. An open-drain output has no active pull up- you have to provide an external (passive) pull up. Since the `F84 is CMOS based, this leaves us 12 outputs....
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Sequence detection is a common operation in many communication and security systems. Some good examples are HDLC-flag identification and signature analysis. As the complexity of the system increases, designing circuitry for sequence detection becomes tedious....
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The example program included with the PG2051 evaluation kit is a basic serial to parallel converter written in 8051 assembler. This is probably a good example of the uses to which an AT89C2051 can be put - it would be hard to get a serial to parallel....
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A simple logic-analyzer design is compatible with all versions of Windows and pushes the PIC 18C252 chip to its speed limit to achieve a 1-MHz sampling rate (Figure 1). The circuit can examine three channels of relatively low-speed logic signals that have....
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A recent Design Idea prompted me to offer the simpler solution that I used in a recent project (Reference 1). We needed a momentary power switch with processor supervision. This supervision would allow the processor to delay a power-down request from a press....
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The Infineon C16x Series of µCs use an internal 16-bit-register architecture. The architecture can also process byte-wide functions. The µC uses byte moves to implement library functions such as memset() or memcopy(). This process makes the library code....
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Many of today`s designs use low-cost microcontrollers from Freescale and Microchip, but during the last decade, device packages have resorted to ever-smaller footprints featuring as few as eight or even six pins. Although these packages minimize pc-board....
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Wine doesn`t like subzero temperatures, and during wintertime, my "winecellar" got pretty cold. There was an electric heating element, but the thermostat was broken, so it was either full burn or nothing. That`s how the temperature monitor/controller came to....
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Most of the ideas in this chapter can be found on the pages of this website, but just in case you want to go over the capabilities of the `508A, we have brought them together. Quite often when you are programming, the first thing you will run out of is....
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The Pocket Programmer is a stand alone serial programmer that can program most of the PICmicro®MCU range of microprocessors. (12C6xx, 16Cxxx, 16Fxxx, 18Cxxx) It works from a single 18VDC supply or with 2 X 9 volt batteries. Combine this with 64K of on board....
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You can use Microchip`s low-cost PIC16F818 microprocessor and a pair of gates to construct a digital PLL that can clean noisy digital signals over a range of 4 to 40 kHz. Featuring programmable lock range, phase differential, and loop gain, the digital-PLL....
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The 8051 series µCs offer idle and power-down modes, both of which you invoke by setting appropriate control bits from the code. For instance, a 5V, 12-MHz Atmel AT89C2051 consumes approximately 9 mA in active mode, 1.8 mA in idle mode, and only 12 µA in....
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The 4- to 20-mA current loop is ubiquitous in the world of controls in manufacturing plants. Discrete logic, microprocessors, and microcontrollers easily cover the digital portions of control schemes, such as limit switches, pushbuttons, and signal lights.....
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The watchdog circuit in Figure 1 uses a single NAND Schmitt-trigger IC. The circuit is more cost-effective than dedicated, commercially available watchdog ICs. The circuit generates an active-high reset signal upon power-up and remains in a low state as long....
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Wisp628 is designed to be used as an in-circuit programmer only, hence no socket is provided for the target chip. `Why use such a limited design`, you might ask, `an ex-circuit programmer with a ZIF socket can do the same things and more!` You are partially....