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Category Archives: Circuits

Circuits and Schematics, pdf, png.

Simple WorkBench Dual Power Supply

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I will just explain part of this circuit. D9 and D10 provide a low cost -1.4 from -5 V. This is needed to reach near 0.00 for LM317 Min. setting. An LED also can be used with proper bias. Note that there is a Temperature Coefficient in ppm,  but it may not matter upto 8 bits accuracy.

TIP2955, TIP3055 (NPN), TIP2955 (PNP) Complementary Silicon Power Transistors. It is a Darlington, that means good current gain. When current in R1 10E goes more than 50mA a voltage of 50mA X 10E = 500mV is applied across Emmiter-Base junction. So lower than 500mV no bias the tap is turned off, 500mV-700mV the tap starts turning on depending on type of transistor.

Power Supplies Section

The transistor is like a water Tap. So TIP2955 carries the major current burden thru the load allowing LM317 to do the decision making when to turn-on or off. It is analog control, it is not On-Off but linear-proportional. The LM317 is very cool as the burden is passed off to TIP2955 who will need a heatsink to keep going and deliver the power you want.

WorkBench Dual Power Supply

Put the filter caps appropriately. The Hum-Noise will be filtered. The cap after the regulator should be a small guy. The main filter cap after the Bridge can be as big as your cabinet or budget.

Mains Voltage Power Transformers

If you build it and wire it without designing a PCB, then make all wiring and connection very sound. The test of this ability you can know easily, If your project stops working after the last screw of the cabinet is tightened, Then we need to improve.

eCircuit Center – Spice Schematics

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“The goal is a site where the learning of electronics is hands-on and fun. And the SPICE circuit simulator is a great software tool to achieve that goal. It hit me the first time I used SPICE – simulating is fun! And because it’s easy to use, I’ve spent a lot of time building and exploring circuits.” – Rick

eCircuit Center – Spice Schematics

SPICE is capable of performing both AC (frequency) Analysis and Transient (time) Analysis. SPICE also performs a number of other analyses like DC, Sensitivity, Noise and Distortion.

SPICE Basics, SPICE Commands, Circuit Collection

eCircuit Center - Spice Schematics

“At the core of the function generator is a triangle wave generator. How do you generate a triangle wave? The most common way is to get a capacitor and then alternate charging it and discharging it. But how to you get a nice linear ramp across the capacitor?”

Triangle and Square-Wave Generator

Simulation Circuit Examples –

  • Programmable Gain Amplifier (PGA) Op Amp
  • Single-Supply AC Inverting Amplifier
  • Instrumentation Amp (3 Op Amp)
  • Sensor Bridge with Current Bias
  • The PID Controller
  • Pulse Width Modulation
  • Precision Half-Wave Rectifier

PWM Control Circuit – TL494

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The TL494 incorporates all the functions required in the construction of a pulse-width-modulation (PWM) control circuit on a single chip. Designed primarily for power-supply control, this device offers the flexibility to tailor the power-supply control circuitry to a specific application.

PWM Control Circuit – TL494

  • Complete PWM Power-Control Circuitry
  • Uncommitted Outputs for 200-mA Sink or Source Current
  • Output Control Selects Single-Ended or Push-Pull Operation
  • Internal Circuitry Prohibits Double Pulse at Either Output
  • Variable Dead Time Provides Control Over Total Range
  • Internal Regulator Provides a Stable 5-V Reference Supply With 5% Tolerance
  • Circuit Architecture Allows Easy Synchronization

PWM Control Circuit - TL494

The TL494 contains two error amplifiers, an on-chip adjustable oscillator, a dead-time control (DTC) comparator, a pulse-steering control flip-flop, a 5-V, 5%-precision regulator, and output-control circuits.

TL494 Related Links

Open Circuits – Open Source Electronics

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Open Circuits is a wiki for sharing open source electronics knowledge, schematics, board layouts, ports and parts libraries. This include open hardware Music Players, atomic microscopes, PC, PDA and mobile phones, and batteries. Please help us to build this resource by submitting your component descriptions, projects, techniques, and PCB footprints.

Open Circuits – Open Source Electronics

Some Projects that look Interesting are

  • Multi-purpose Embedded System
  • dsPIC33 Development Board
  • ADuC832 Development Board
  • N8VEM Home Brew Computing Project

The Open Source Movement, typically covers Open Hardware, Open Firmware, and Open Software. The Open Firmware movement provides firmware which you may also know as soft-IP or FPGA coding see Open Cores for more details.

Excellent examples of Open Hardware projects range from projects at OpenCircuits to Tiny Embedded Ethernet Devices and Advanced & Intelligent Camera Designs which provide solid-state camera and FPGA assisted hardware designs. A solid overview of projects can also be found at Open Innovation Projects.

Interface ICL7135 Voltmeter to Atmel 89C52 or PC

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This circuit is an interface between 89C52 of Atmel with 7135 of Intersil. With This circuit you can read analog data of both polarities you can change the range scale with extra circuits, you can store data on a EEPROM or send them to PC thru RS232 or Comm port.

ICL7135 to Printer port Interface

The four Digit Drive outputs and four BCD outputs of the Multiplexed Display Driver of 7135, along with A-D status output which is also four, are routed to four input pins on printer port via three 74HCT373 Digital Switches. This is because we have less Input pins on Port and 4 are shared by making one 74HCT373 transparent and others High Impedance when PC takes a reading. So the three sets of four outputs of 7135 can be read sequentially.

74HCT139 U9A which is controlled by the PC program can select U3, U4 or U5 for sending data to 4 pins on printer port. Data sent on the eight output pins of printer port can be latched by U10B into U6. This eight outputs of U6 can drive relays or lamps.

See also – Milli Volt Source for Printer Port.

Serial Interface a 80C31 to ICL7135

uC Input and Output I/O is Keyboard and LCD when you build a Calculator or a Text/Morse Communicator. When you control a motor it is Drive/Speed and Direction for Motor and Tacho or Opto Counters for Feedback. In both cases you have Input and Output which is Logic or Analog which has to reach the CPU.

Getting the analog into the uC is done here with ICL7135, with a simple two wire serial interface. Here a Pair of CD4538 MMV is used to shape the pulse just right for uC data transfer,…

AT89C52 Parallel Interface to ICL7135

This circuit is an interface between 89C52 of Atmel with 7135 of Intersil. With This circuit you can read analog data of both polarities you can change the range scale with extra circuits, you can store data on a EEPROM or send them to PC thru RS232 or Comm port.

TechLib – Electronic Experimenter Records

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TechLib – Electronic Experimenter Records

A technical library for the hobbyist and experimenter. – Charles Wenzel

  • World’s Smallest Geiger Counter
  • Karen’s Mic. Input Telemetry Device
  • Temperature Controlled Ovens
  • Two-Transistor Atomic Frequency Standard
  • Super-Sensitive Ionization Chamber
  • Cockcroft-Walton Diode Voltage Multipliers

SWTPC Computer Documentation Repository

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SWTPC Computer Documentation Repository Radio Electronics June 1949, Guitar Preamp

This site’s purpose is to address the lack of technical information for some of the rarer vintage computers and related peripherals, with a strong focus on SWTPC.

More than 600 pages of assembly instructions, schematics, program listings, catalogs, photos and much, much more!

  • Bill’s Knowledge Base
  • Popular Electronics
  • Radio-Electronics
  • Hands-on Electronics