Top Circuits Page 271
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The UBA is limited to discharging up to 2. 5A per channel. This discharge rate is adequate for testing 99% of the batteries on the market. It is not sufficient to properly test batteries that are rapidly discharged in normal use (for example, some medical....
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If a page name is not selected by pressing the button, the previously selected page name continues to be used. The value is stored in EEPROM and may be changed at any time. When the unit is first powered on, and any time the Position page is displayed, the....
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PIC C Compilers are used to compile my source code. Liberal use is made of the many built-in functions provided by these compilers. One statement in C can generate pages of PIC ® RISC instructions. instructions you don`t have to write by hand! CCS still only....
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The modulator and the demodulator (pdf < 10 kb). For the easier tuning of the modem it could have been built with potentiometers, but it was easier to reach a smaller size this way (I didn`t want to use SMD potentiometers). Unfortunately, even like this, the....
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The type C system was first installed about 1925 and has been very extensively used. It incorporates the most desirable features of the systems just considered. Like the type A system, the carrier is suppressed, and hence the effect of line attenuation is....
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In the Hartley circuit (Fig. 14 B), the amplified energy of the plate circuit is fed back to the grid circuit by means of fluctuating magnetic fields. They are both of the so-called magnetic feedback type. The Hartley circuit uses only one coil, part of....
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A simple oscillator which may be used for code practice. In order to have sufficient inductance to produce an audio frequency, an iron core transformer such as used in audio transformer-coupled amplifiers is hooked up as shown...
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One of the outstanding problems in the design of vacuum-tube oscillators is that of keeping the frequency constant despite mechanical vibrations, temperature changes, voltage variations in the supply lines, and changes in the amount of power taken out of the....
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The use of a quarter-wave parallel-wire line as a tuning unit has been discussed in the chapter on Short-Lines, where it was pointed out that these " circuits " have comparatively high Q even at the higher frequencies. Their great length ( »/4) prevents....
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Wave-filter principles are applied in many circuits other than filters. An example is the design of modulation transformers for high-level amplitude-modulated radio transmitters. Some of these transformers are large. In plate-modulated power amplifiers, the....
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Transformer OCL and capacitor C1 form a tank circuit, to which are coupled sufficient turns to drive the grid in the lower left-hand winding. The output circuit is coupled by a separate winding. For good wave shape in such an oscillator, triodes and class B....
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If a strip of conductive metal is stretched, it will become skinnier and longer, both changes resulting in an increase of electrical resistance end-to-end. Conversely, if a strip of conductive metal is placed under compressive force (without buckling), it....
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If possible, try to obtain TIP41 and TIP42 transistors, which are closely matched NPN and PNP power transistors with dissipation ratings of 65 watts each. If you cannot get a TIP41 NPN transistor, the TIP3055 (available from Radio Shack) is a good....
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This experiment may be built using only one 8-position DIP switch, but the concept is easier to understand if two switch assemblies are used. The idea is, one switch acts to hold the correct code for unlocking the lock, while the other switch serves as a....
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This is one of the most basic 555 circuits. This circuit is part of this chips datasheet, complete with the math needed to design to specification, and is one of the reasons a 555 is referred to as a timer. The green LED shown on the illustration lights when....
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High frequencies are here defined as those above 50, 000 cycles per second. For industrial power supply the Golpitts circuit, Fig. 28-1, or the coupled-grid self-excited oscillator circuit, Fig. 28-2, is most commonly used. In either circuit, the alternating....
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Vacuum-tube or electronic voltmeters make use of some of the unique characteristics of electron tubes, and so are available in many types. They are available for measuring direct, rms, average or peak voltages. Of the many types available, only the simplest....
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Any vacuum-tube oscillator configuration has an equivalent transistor circuit. For example, consider the vacuum-tube oscillator, illustrated in Fig. 6-1 (A), which represents one form of Hartley oscillator. Positive feedback is accomplished by arranging the....
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The DSC Sine and DRC Random vibration controller cards have current sources on the two inputs available for powering integrated accelerometers without requiring external power supplies. These current sources have an 18 VDC open circuit voltage and output 4....
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Using this circuit you will connect to a single parallel port electronic circuits requiring up to 96 digital output, optically insulated lines, 3 to 15V powered. The CD4094B consists of an 8-bit shift register and a 8-bit latch. Data is shifted serially....
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I currently own 3 metal case PETs, a working 8032 that I restored about a year ago (was working, just needed physical TLC, and still needs a tube), another 8032 that has never worked, and a 4016 that has never worked. I finally got the bug to start working....
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Many later radios use four 7-pin valves and require a 90V HT supply at typically 12mA and a 1. 5V LT supply at 125mA or 250mA depending on the valves used. The original batteries are sadly no longer made. One possibility is to make up a 90V battery using ten....
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The high voltage electrolytic capacitors in valve equipment tend to deteriorate if the equipment is not used for an extended period. This deterioration takes the form of reduced capacitance and greatly increased leakage current. In some cases, the capacitor....
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This unit is designed for monitoring the audio output level across a loudspeaker when carrying out alignment of radios. As no great precision is required, a simple passive circuit arrangement has been used. The circuit is a voltage-doubling rectifier driving....
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This signal generator is intended for realignment of radio receivers. The unit is cheap and fairly basic, but perfectly adequate for its intended purpose. However, the output is not a pure sine wave, so the unit may not be suited for more exacting electronic....
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The driver stage works in the same manner as the class A output stage described previously. However it is only working at a couple of milliamps, so efficiency is not an issue here. The biasing arrangement should be familiar by now. Some sets, including the....
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The DZ-2 was built by RCA, Camden NJ, for the U. S. Navy for use in naval aircraft as a Radio Direction Finder. With a contract date of June 30 1939, the receiver is an interesting example of pre-war design. The receiver was powered by the aircraft`s 24v DC....
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The Model LM-13 Crystal Calibrated Frequency Indicating Equipment has been specially designed to provide a simple, accurate and reliable frequency indicating equipment of the crystal calibrated type for use in the (U. S. ) Naval radio service. It is....
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The unit is based on a PHILIPS FM880 link transceiver which was originally supplied to a Telecom Australia specification for telephone applications in remote areas of Australia. The FM880 in turn is part of the family of equipment including the PHILIPS....
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The most popular is MED-NET, which covers all the mediterranean sea with its observation points. The shown map shows the observation points in the mediterranean sea. For further information about this net being part of the Italian Geophysical National....
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So there is a chance to use them in combination with a condenser microphone amplifier for a VLF Receiver. Bingo. The first tests as a Monopole gave good results. I live in a small town located at J041VG with approximately 7500 inhabitants. The height above....
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It took sometime to develop this interface for Echolink. It uses PIC16F84A and accepts external DTMF from Radio. My Latest Version Foxecho-k7 provides total isolation between Rig And PC and has AGC on received audio. Delay on this project was in part of....
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This diagram will give you a simplistic idea of how it all works, as you can see the only time left and right come together from the indicator switch is from the stalk to the hazard switch, so get the steering column off too and go all the way from the....
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A Video Switcher which can be controlled using the computer`s parallel port. Unfortunately, fewer PCs are fitted with parallel pors these days and, for a laptop, it`s not really an option so the need to control the Switcher through a USB port became....
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Taking the wiring going to the external amp, in the 15 pin connector you will want pins 8 and 9. I believe they are brown/white and dark green/white looking at the thread in the link you posted. Circuits 367 and 368. Then I clipped and stripped the....
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Gently work a small screw driver around the mic element rubber boot, and slowly work it out from the mic front casing. Be gentle and take your time. I found that there was a spot near the top of the mic housing where I could work the screwdriver in to get....
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WB5LUA described GaAsFET preamps for several microwave bands which included an active bias circuit for the GaAsFET. Many devices have come along since then which offer better performance, but require a bias point with different current and voltages. It isn`t....
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The logical first choice was to start out with simple regenerative circuits. Just one or two transistors and maybe a simple audio amplifier using one integrated circuit. I already have a few simple tube radios that I bought at flea markets, so I will defer....
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Building a solid-state linear amplifier. I have an old Heathkit SB 221 that after a major overhaul and redesign is now working great on 80, 40, 20, and 15; but not 17, 12 and 10. With this in mind I got on the internet at the motel we were staying in and....
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Perhaps you might want to provide a little ALC feedback to your driver, or use signals from a directional coupler to drive power monitors or SWR lockout circuits. I use this modest little circuit to do these things; the basic idea is to use a microwave diode....
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Here is the single- 813 crystal oscillator transmitter, designed by RCA and exhibited in their advertisement on the back page of a "QST" magazine in 1938, and published by RCA in their HamTips bulletin, vol. 1, no. 4, dated December 1938. This transmitter`s....
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This is a variation of the the Electron Coupled Oscillator circuit, pioneered by Dow in 1931. Dow`s ECO has the screen "grounded" for RF. In this circuit, because I am using filament-type tubes instead of heater-cathode types, and because I didn`t want to....
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The Johnson 275 watt and Kilowatt Matchboxes are both unnecessarily exaggerated and unnecessarily maligned. They are not exceptional tuners, and are not poor designs. The primary drawbacks are the fixed coupling link, and the fact they are balanced VOLTAGE....
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Floating the grid above ground is bad for RF, and bad for arc protection. The control grid ground is also the single most critical connection for stability. The grid connection to ground should always be as wide and short as possible, and use as many pins as....
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Grid driven tetrodes like 6146, 807, or 4CX250`s have high power gain. High gain systems require very little feedback to become unstable, so they are generally neutralized. The also often require some form of grid loading resistor to reduce or stabilize....
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The intelligent discussion of VHF systems requires a feel for VHF systems, and how VHF energy moves through a system. At VHF, wavelength is very short. Wavelength in feet is F/983. 6, a typical 150 MHz system would have a quarter wavelength of 19. 8 inches.....
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The 1956 Regency ATC-1 converter heralded the dawn of a new era for amateur radio. The little converter had only two transistors - one PNP, one NPN, both germanium, both now long obsolete - but they were the start of a revolution. Amateurs responding to the....
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The original f-m transmitters manufactured by the General Electric Company were the direct f-m type employing the regular electronic automatic frequency control system similar to that discussed in connection with the CBS transmitter. The f-m multiplication....
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The 2009 Robot Rally spotlighted all the flaws that result from a quick 3 week engineering and building project. Time saving shortcuts in code and hardware bit my butt several times. Failed edge detectors - Ouch! Failed beacon tracker. chomp! Ow! Line....
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They are op-amp based filters and are most useful in the audio frequency range. These parts calculators are based on formulas and tables from the book " Electronic Filter Design Handbook " by Arthur B. Williams. Bandpass filters pass a contiguous range of....
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If you`ve ever wondered how electronic devices like computers can count, this article gives a simple introduction to binary and logic and shows how they are tied together with electronics to make both simple and complex computers. Please note: There are a....
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This project implements a composite USB device supporting two USB 2. 0 full-speed gameport HID interfaces. The physical joystick ports are wired in accordance to the `Atari standard` allowing connection of most Commodore 64 and Amiga joysticks as well as....
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Use the Microchip C18 compiler to be based around my latest USB framework libraries for both the PIC and Windows. This should provide a smoother path from this basic tutorial to more complex projects. As always I welcome your feedback and suggestions over in....
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The aim of this project was to create a front-end for Commodore 64 emulation using VICE. One of the primary problems with emulators (especially for machines from the `80s) is that there was no standard keyboard arrangement. In this project I took a broken....
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This project shows how to build a simple LED light string display using seven 24V LED light strings. I built this project for Christmas 2009 in order to decorate my balcony with lights. The light strings used are very common and (at least in Sweden) can be....
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Nearly all the existing designs I found used direct switching of the lights (with no software control in between) and contained manual potentiometers for light sensitivity and overall gain setting. Furthermore, I couldn`t find many references to the....
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This project shows how to create an MB Electronics Simon game clone using an 8-pin PIC12F683 microcontroller. The game includes a full emulation of the original Simon `game 1` and the ability to select from 4 skill levels which control the number of colours....
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If you`ve dabbled with PIC18F microcontrollers and the USB Generic HID standard before (perhaps you`ve even tried my Building a PIC18F USB device project) then you will have noticed that there is a lot of complexity in supporting USB on both the PIC18F and....
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For the first version of my Open Source Framework for USB Generic HID devices based on the PIC18F and Windows I made a quick example of how to use the library using a USB interface for an LCD. Now that I`ve completed the second version of the library I....
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On a continuing mission to build an autonomous sailing robot we needed a way to more rapidly prototype boat designs and wanted to use a standard remote control model control system to save time by using off-the-shelf parts. When controlling servos with....
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This project creates a RGB LED lit love heart which is controlled by a PIC12F683 microcontroller. I designed the project as a gift for my wife on our 15th wedding anniversary (since she puts up with my addiction to electronics I thought she deserved....
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These little devices had a 1. 5 inch 128x128 colour TFT as well as USB, batteries and 16 Mbytes of storage for around 140 pictures. Best of all they were very cheap, so I purchased a few to see if they could be re-purposed into something useful. Looking on....
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The MB Electronics Pocket Simon game has a very simple circuit thanks to the inclusion of a custom MB Electronics processor (the MB4850) which performs nearly all of the functions for the game. The only other significant piece of electronics is a SN75494N....
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This project implements a USB device which provides a real-time clock for the purpose of time-stamping events in an non-networked embedded computer environment. For embedded applications where a periodic time-stamp is required (such as entry-system logs,....
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Simon18F is a project to replace the custom MB4850 processor of the MB Electronics Simon game with a PIC18F2550; initially to emulate the original Simon games and, later, to enhance the existing games and add new ones. The Simon18F processor board is based....
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The USB Performance monitor is a PIC18F2550 based device which shows the performance of your computer using two analogue meters and a RGB LED. The design is based around a stock Hi-Fi VU-meter which is controlled using PWM from the PIC18F microcontroller.....
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This project creates a RGB LED VU Meter which is controlled via USB by a Windows 7 or Vista host machine. The project serves several purposes: Firstly, it demonstrates how to read audio information from the Windows machine and pass this over USB to the....
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The Pulsed Multiple Gas (PMG) laser described in this chapter is very similar in many ways to the Home-Built Pulsed Argon and/or Krypton (Ar/Kr) Ion Laser from Scientific American. However, the developers of the PMG laser have also used it with xenon (Xe)....
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This chapter contains circuit diagrams for several power supplies for pulsed solid state lasers. These include units suitable for driving the popular Hughes ruby and YAG rangefinder laser assemblies as well, one using the flash from a disposable pocket....
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The EPIC Plus Programmer, Serial Programmer, USB Programmer or U2 USB Programmer may be used for in-circuit serial programming of serially programmable PIC Microcontrollers through the 10-pin expansion header J3. Vpp, RB6, RB7 and ground should be connected....
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We added an external piezoelectric element to set on the bench top, making it easier for kids to reach. We simply soldered this external piezo element to the same pads as the Tap-Tempo Metronome`s built-in piezo element. Here`s the large piezo we used. For....
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TX OpAmps TX Mixer (QSE) PTT RX Switching PA/Filters External Connectons Comments Revisions WB5RVZ SDR Home This stage adds the TX Mixer to the board and provides the modulation of the Dividers` output signals by the 4 I and Q signals from the OpAmps. The....
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The current draw should be somewhere between 80 and 100 mA. The exact value is very much dependent upon the Si570, the version (CMOS vs LVDS), the frequency setting, and component variations in the circuit. You can test the SW1 programming of U3 by checking....
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In the "DSP" tab`s "Local Oscillator" section, click on the button marked "Single Band" and type in the desired center frequency (7046000). This sets Rocky`s center frequency at 7. 046 MHz. Set up your transceiver (or other signal source) to transmit a low....
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The mixer stage ("QSD" - Quadrature Sampling Detector) acts like two traditional direct conversion mixers operating in tandem. Each takes in half of the filtered RF from the bandpass filter stage and one of the quadrature center frequency signals, then....
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This stage adds the TX Mixer to the board and provides the modulation of the Dividers` output signals by the 4 I and Q signals from the TX OpAmps (Quadrature Sampling Exciter - QSE). The result is a double sideband RF waveform that will be coupled into the....