Hobby Electronics Circuits

Timer with 2 Digit 7 Segment Display

2008-10-27T01:04:00.000-07:00

Below is the schematic for a 2 digit 7 segment display using an microcontroller to drive them. This can be used also for large 5 inch LEDs.

This program/hex file for this circuit can can be downloaded here.

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Vibration / Sound Activated Switch

2008-04-13T23:03:00.000-07:00

Someone asked me for a circuit for vibration or sound activated switched in a forum. I had drawn this quickly by hand.

The sound is detected by the electret microphone then is amplified by the PN2222 NPN transistor. Then the amplified signal is DC converted by the 2 1n4148 diodes.

A comparator is then used to detect the right voltage set by the potentiometer at the inverting input. A small hysteresis is added. The last NPN transistor is the one to drive a relay and with another 1n4148 diode to protect it from the reverse EMF generated by the relay coil when the transistor goes off.

3V Input to 5V/TTL Converter

2008-03-11T17:08:00.000-07:00

This circuit converts 3V input to be connect to 5V or TTL device. This is a very simple common-base configuration circuit and uses 4 components only. R1 and R3 are used to pull-up voltage to 3V and 5V respectively if no 3V input is present. While R2 is used to limit the base current of Q1 when its start to conduct when the input becomes low.

Telephone Ring Indicator Using LED Lamp

2008-03-10T23:13:00.000-07:00

This is the circuit for Telephone Ring Indicator Using LED Lamp. The telephone ring is typically 90VAC RMS so is more than enough to light a single LED. C1 is used for DC blocking thus no OFF-HOOK condition at standby state. R1 is to dissipate excess voltage, while D1 and C2 rectifies it to positive DC voltage. D2 regulates the voltage to 9VDC with R2 again limits the current of the LED during ringing.

220V Line Powered LED Lamp

2008-03-04T20:55:00.000-08:00

To connect a single LED lamp to the 220V AC line, the minimum need are a series a high voltage capacitor and a resistor. A diode also in parallel with the LED in reverse polarity connection.

The diode prevents reverse voltage breakdown of the LED. The resistor is needed to prevent in-rush (surge) current to the capacitor if from OFF (discharged). An additional resistor in parallel to the capacitor to bleed the charged voltage when the circuit is OFF to prevent electric shock.

Computing for values:
I(led) = 0.02
Xc = V/I(led) = (220-3)/.02 = 10850
Cmin = 1/(2*pi*Xc) = 1/(2 *pi * 60 * 10850) = 0.24uF = 0.22uF nearest value

Very Simple 2 Transistor LED Flasher Circuit

2008-02-22T23:31:00.000-08:00

This is a very simple 2 transistor circuit. It is very easy to construct. The parts can even be soldered without using a PCB.

This can be a your first circuit to construct for learning and introduction to electronics.

My New Blog

2007-12-27T15:22:00.000-08:00

I have create a new electronics and programming blog. Here I will post electronic projects, circuits and codes. Please visit this site.

Stanford's nanowire battery holds 10 times the charge of existing ones

2007-12-19T19:30:00.000-08:00

BY DAN STOBER

Courtesy Nature Nanotechnology silicon nanowires

Photos taken by a scanning electron microscope of silicon nanowires before (left) and after (right) absorbing lithium. Both photos were taken at the same magnification.

Stanford researchers have found a way to use silicon nanowires to reinvent the rechargeable lithium-ion batteries that power laptops, iPods, video cameras, cell phones, and countless other devices.

The new version, developed through research led by Yi Cui, assistant professor of materials science and engineering, produces 10 times the amount of electricity of existing lithium-ion, known as Li-ion, batteries. A laptop that now runs on battery for two hours could operate for 20 hours, a boon to ocean-hopping business travelers.

"It's not a small improvement," Cui said. "It's a revolutionary development."

The breakthrough is described in a paper, "High-performance lithium battery anodes using silicon nanowires," published online Dec. 16 in Nature Nanotechnology, written by Cui, his graduate chemistry student Candace Chan and five others.

The greatly expanded storage capacity could make Li-ion batteries attractive to electric car manufacturers. Cui suggested that they could also be used in homes or offices to store electricity generated by rooftop solar panels.

"Given the mature infrastructure behind silicon, this new technology can be pushed to real life quickly," Cui said.

The electrical storage capacity of a Li-ion battery is limited by how much lithium can be held in the battery's anode, which is typically made of carbon. Silicon has a much higher capacity than carbon, but also has a drawback.

Silicon placed in a battery swells as it absorbs positively charged lithium atoms during charging, then shrinks during use (i.e., when playing your iPod) as the lithium is drawn out of the silicon. This expand/shrink cycle typically causes the silicon (often in the form of particles or a thin film) to pulverize, degrading the performance of the battery.

Cui's battery gets around this problem with nanotechnology. The lithium is stored in a forest of tiny silicon nanowires, each with a diameter one-thousandth the thickness of a sheet of paper. The nanowires inflate four times their normal size as they soak up lithium. But, unlike other silicon shapes, they do not fracture.

Research on silicon in batteries began three decades ago. Chan explained: "The people kind of gave up on it because the capacity wasn't high enough and the cycle life wasn't good enough. And it was just because of the shape they were using. It was just too big, and they couldn't undergo the volume changes."

Then, along came silicon nanowires. "We just kind of put them together," Chan said.

For their experiments, Chan grew the nanowires on a stainless steel substrate, providing an excellent electrical connection. "It was a fantastic moment when Candace told me it was working," Cui said.

Cui said that a patent application has been filed. He is considering formation of a company or an agreement with a battery manufacturer. Manufacturing the nanowire batteries would require "one or two different steps, but the process can certainly be scaled up," he added. "It's a well understood process."

Also contributing to the paper in Nature Nanotechnology were Halin Peng and Robert A. Huggins of Materials Science and Engineering at Stanford, Gao Liu of Lawrence Berkeley National Laboratory, and Kevin McIlwrath and Xiao Feng Zhang of the electron microscope division of Hitachi High Technologies in Pleasanton, Calif.

RS232 to TTL Conversion Using Bipolar Transistors

2007-12-19T01:10:00.000-08:00

There is a simple trick to transform R232 levels to TTL levels by just using 2 bipolar transistors.
See the attached schematic.

This is useful for micro-controller boards when using serial communication with the PC.

For PIC micro-controller serial communication routines are here.

Etching In House

2006-09-12T21:47:00.000-07:00

How to use a very expensive etching setup to make nice PCBs
Intro

For a certain number of projects, including first-prototype, surface mount 'breadboarding', layout experimentation, rapid multiple-revisions, and 1-hour deadlines doing your own PCB etching can be quick, clean, and very very inexpensive. The method set up in the Media Lab basement is somewhat-similar to that of large pcb manufacture shops, except in scale and automation. There is no system for through-hole plating, automated drilling/routing or multilayer design. However, you can make precisely aligned doublesided boards with simple registration techniques.

Added 2/7/04: The etching setup is now in the Holography darkroom, in the LL across from the shops. To get access/training please email or visit me (ladyada@ml in office 020D)

Added 2/7/05: Ha! I graduated. Bug someone else in the Computing Culture group...

When To Use

A tool is only good towards the application it was designed for. Using the etcher for something other than what its good for will frustrate you and waste time.

When using the spray etcher is a good idea:

You need the boards quickly
The substrate is 1/16" with 1oz or 2oz copper either FR4 or paper phenolic (preferred)
The design is single sided
There are many surface mount parts
The design is double sided, with no hidden vias (vias underneath surfacemount parts) or through-hole part vias (vias that also serve as through-hole component holes) that you cannot solder on both sides
You can visually scan for shorts
The design follows a 12/12 mil rule (this is probably not true, I'm sure 10/10 or even 8/8 is fine, but yield will drop) That is, 12mil minimum trace width, and 12mil minimum trace distance.
You only need a few boards, or are willing to live with a yield as low as 50%
Drill hole locations can be imprecise (up to 10 mils off!)

Conversely, when using the spray etcher is a bad idea:

You dislike wet chemistry/cleaning
Are using exotic substrates
There are many vias, or throughhole parts, and you dont want to drill holes/solder vias.
You want the boards to be perfect without checking for shorts or opens
You need printed overlays, multiple layers, through hole plating or solder masks.
You want many parts. Remember that for $200 you can just about get as many boards as your heart desires, and from a reputable PCB manufacturer.

Getting the Layout Ready

In this step you will prepare your layout for etching. For this step you will need: a quality laser printer, a sheet of transluscent paper.

The photoresist method we use in PCB etching is a positive process, which means that when UV light hits the resist, it softens, and then is washed away. What remains is a positive of the PCB design. What this boils down to is that you will want a positive printout of your PCB design (black where there will be copper). Preferably mirrored. Most all PCB design tools let you print out your layout mirrored. Or you can mirror your entire design in the software. Whichever. Also, if possible, have it print white holes where you will drill, these will be your drill guides. Because the drill holes will not be precise, make your annular rings (the copper around a drill hole) larger than normal. Since you will lose as many as half of the design to exposure/development/etching flaws, tile 2-3 times layouts as many as you want.

In Eagle: After your design is ready, go to the CAM Processor, and open the "layout2.cam" job. As output select PS. Change the extention to ".ps" as well. Be sure that Mirror is selected but that Fill Pads is not. Then open the ps with any free postscript viewer and print it. (Also you could print it to "Gerber274x" and use a gerber viewer, or any other format you can print.)

After you have verified the above, print your design to a high quality (600dpi at least) laser printer, in monochrome mode, onto a white piece of paper. Double check that it is as you want it, in the correct orientation, enough tiling, mirrored, dark ink, slightly smaller than the PCB you have, etc. Now print it onto translucent paper, there is a box of it in the cabinet underneath the etcher, in a thin cardboard sleeve.

Left, plain paper test. Right, translucent paper. Both are mirrored.

In this picture, I have two layouts I want to etch. I tiled one three times and one twice. The one I tiled three times has a very fine pitch IC (TSSOP-16) so it is less likely to come out. On the left is opaque laser print. On the right, translucent paper. Note that the design (noticably the text) is mirrored.

Exposing the Board

This step transfers your layout design to a positive-resist PCB by exposing UV light to the sensitized PCB with the printout as a mask. For this step you will need: a presensitized positive photoresist copper clad board, scissors, tape, a UV bulb and thin plate glass or exposure unit. This step takes 5-10 minutes.

First cut out the layout leaving a few millimeters of space on the edges. If you are going to perform the exposing and etching in the same session, go ahead and turn the etching machine on now, since it takes 10 minutes to warm up.

Cut the translucent paper, leaving at least a few mm boarder

Next, locate an unused PCB. There is a bag of them in the cabinet underneath the etcher. You may need to cut a larger board down using a metal shear. Using a larger PCB than necessary is wasteful, and exhausts the chemicals faster than a board that is well-fit. You can also purchase your own stash of PCB material in many different substrates, thicknesses, etc. and, of course, that is encouraged. (See "Where to Purchase Supplies, at bottom")

The best PCBs are those that have a plastic sticky sheet protecting them (some are just sold in a plastic bag) so that they can be handled, drilled and sheared without excess UV exposure. The plastic is easy to peel off:

The underlying substrate should be a greenish colour

Place your design on top of the exposed resist, ink-side down, so that it appears not-mirrored when you look through the paper at the board. Placing the ink closest to the resist means less light can leak around and cut into thin traces. Next, tape down the design on two edges, so that the tape does not overlap any of the layout, but holds the paper flat...

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STARTING OUT IN BASIC ELECTRONICS

2006-07-11T21:38:00.000-07:00

Where do I start in basic electronics?

I have provided a whole section devoted to basic electronics covering every topic I can imagine with more being added a time goes by. However I kept getting email asking "where do I start in basic electronics?". This page is the result of those enquiries.

Be careful going through these. Often students will want to roll through the tutorials as fast as possible. Most of the time that leads to what I have written becoming confused in your mind. Your brain needs time to digest all of this. If I might make a suggestion, don't do more than two tutorials a day. Therefore if you haven't already done so.......

Long teaching experience has taught me that students say they have read an entire chapter of a book on basic electronics, yet cannot remember what they have read.

That's because getting to the end was the goal, not getting the most out of the reading.

Speed kills. Give your brain time. Here's an example. You have read all of this, right? Well, without looking up the page... tell me what was the common email question.

You rolled before you crawled, before you walked, before you ran. Give your brain time to roll around these easy tutorials. Above all be systematic in your approach. I certainly recommend you read each electronics tutorial and then print it out for future reference.

This is your main starting point in basic electronics tutorials. You start with electron theory and atoms then move along to the basic units and topics of current, resistance, ohms law, voltage, reactance and resonance. After that you move to the more difficult topics.

As with the basics of anything you must master them before proceeding any further. Indeed you will find a need to return and refresh both your mind and understanding. Remember without mastering the basics you can't dribble a basketball, throw a curve in baseball, bowl a cricket ball or flick pass the ball in football. Every human endeavour requires you to master the basics. If you hadn't mastered the basics of the alphabet as a child you couldn't read this page...

Read More...

Tiny Threads - Tiny Multitasking Threads for Microcontrollers

2006-06-29T22:14:00.000-07:00

by: Regulus Berdin

Idea based on http://www.chiark.greenend.org.uk/~sgtatham/coroutines.html.
Only 1 byte RAM needed per thread.
Very small overhead context switching.

Limitations:

Maximum 254 lines per thread.
Thread context switching will not work within a switch block.

Usage example:

     TT_DEF(1)
   {
      TT_BEGIN(1);
    while (1)
      {
         ...
         TT_SWITCH(1);
         ...
         ...
         TT_WAIT_UNTIL(1,keypress);
      }
      TT_END(1);
   }
 
   TT_DEF(LED_TASK)
   {
       TT_BEGIN(LED_TASK);
       while (1)
       {
           LedOn();
           delay=DELAY_1_SECOND;
           TT_WAIT_UNTIL(LED_TASK,delay==0);
           LedOff();
           delay=DELAY_1_SECOND;
           TT_WAIT_UNTIL(LED_TASK,delay==0);
       }
       TT_END(LED_TASK);
   }
  
   void main(void)
   {
       ...
       ...
       while(1)
       {
           TT_SCHED(1);
           TT_SCHED(LED_TASK);
       }
   }


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LED Circuits

2006-06-28T22:19:00.000-07:00

LOW BATTERY VOLTAGE FLASHER (9) (undervol)
This circuit is designed to monitor two alkaline cells (3v) that from the battery often used in portable electronic equipment. It use an inexpensive IC from Panasonic that is connected to an efficient LED flashing circuit. When the battery voltage drops below a certain point the circuit flashes the LED. In the off state the circuit draws only 1uA, while in the active flashing state it draws 20uA. Published in EDN, Jan 2, 1997

FLASHING LED POWER INDICATOR DRAWS LOW CURRENT (18) (3vledfs1)
This circuit flashes a power indicator LED to keep the average current low.

1.5V LED FLASHER VERSION A (23) (ac14fls)
Many published circuits that flash LEDs need 3 volts or more. This circuit uses only a single inexpensive C-MOS IC and flashes the LED for a full year on a single 1.5 volt AA alkaline battery cell. The circuit uses a charge pump technique to provide the LED the needed voltage.

1.5V LED FLASHER VERSION B (24) (1vled3)
To squeeze even more energy from a alkaline battery cell, this circuit adds two transistors to a circuit similar to the above design to boost the efficiency. A small 1.5 volt alkaline N cell should flash the LED for a full year. It too uses a "charge pump" technique to provide a LED the needed voltage.

2 LINE TELEPHONE LINE STATUS INDICATOR (46) (2phostat)
Many home businesses use multiple phone lines. This circuit gives you a visual indication when a line is in operation. The two AA battery cells should provide enough power for about one year of operation. The circuit is line polarity insensitive...

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Bowden's Hobby Circuits

2006-06-26T22:09:00.000-07:00

A small collection of electronic circuits for the hobbyist or student. Site includes over 100 circuit diagrams, links to related sites, commercial kits and projects, newsgroups and educational areas. Most of the circuits can be built with common components available from Radio Shack or salvaged from scrap electronic equipment. Most all of the circuits have been built and tested and believed to perform as described, however possible mistakes may be found.

Digital/Computer

16 Bit PC Serial Port Receiver (CMOS)
24 bit ISA card Installs into your computer. Parts, plans, schematics and programmng available. Also may be purchased as a kit.
32 Bit Serial Receiver (57.6 K Baud TTL & CMOS)
Parallel Port Relay Interface Circuit
Reading Data From The Parallel Port
1 Second Time Base From Crystal Osc.
32.768 KHz Oscillator Using A Common Watch Crystal
Digital Electronic Lock
Telephone Circuits
Use Old Telephones as Intercom
Telephone In-Use LED Indicator
...

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Magnetic Levitation Schematic

2006-06-25T22:07:00.000-07:00

Why Build a Magnetic Levitation Device?

Wacko Sales Pitch

Want to amaze and impress your friends?

Can something be held in mid-air with nothing touching it?

Do flying saucers use electrogravitics?

How does a maglev vehicle work?

Need a super accurate force/weight measurement?

Want to measure small changes in gravity?

Who says gravity cannot be beaten?

Want to see a simple coil levitate a steel ball in a magnetic field?

As long as you're building a coilgun, and have: magnet wire, power supply, breadboard, voltmeter, resistors and capacitors, switches, hookup wire, and other miscellaneous parts, why not?!

Maglev for Science Fair

I started this project with my 2nd grade son for a science project. The science fair was on March 16th, 1999, at an elementary school in Washington state. This was a fair, not a competition, where the emphasis is on having fun. Most sane parents would not design a closed-loop feedback control system with a second-grader, but as it turned out we didn't enter the project in the fair after all. It didn't work quite well enough, and the coil would overheat after a few minutes.

The benefits of doing this project were many, but not where I expected. I somehow expected to relate some ideas about electronic design. In reality the benefits were probably of more lasting effect. I worked together with my 7-year old and we had a great time. This was a chance for him to cut boards with a saw, drill holes, handle a screwdriver, measure and mark with a square, cut wires, and plug in chips and resistors. We handled parts, learned their names and looked at their symbols in schematics.

Some other things we accomplished were:
- To play with a cool gadget that we made ourselves.
- To experiment with magnetism, and see and feel how it works.
- To be challenged by designing a closed-loop control system.
- To use what I learned from my first coilgun, and learn more that might help with my next one.
- To refresh my knowledge of op-amps and analog circuits.
- To use up part of a mile of 24ga magnet wire.
- To buy new tools, in this case a dual-tracking 30v 5a lab bench power supply bought cheap at an auction.
- To learn how IR emitters and phototransistors work.
- To help fill my garage with electromagnet toys...

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Circuit Schematic Symbols

2006-06-25T21:35:00.000-07:00

The schematics symbols for most major electrical components can be found in this table. However, each component may have numerous possible representations. In cases where there is more than one common symbol we have tried to give an alternate representation.

COMPONENT	SYMBOL	ALTERNATE
Ammeter
And Gate
Antenna, Balanced
Antenna, General
Antenna, Loop, Shielded
Antenna, Loop, Unshielded
Antenna, Unbalanced
Attenuator, Fixed
Attenuator, Variable ...

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Games and fun stuff (schematics)

2006-06-22T22:14:00.000-07:00

Visor cradle serial interface

Electronic coin tosser

Electronic craps game

First response monitor

VCR ping pong game

Video ping pong game

MBC5/CPLD for the GameBoy

GameBoy Camera Parallel Port Interface

PSX controler to PC MIDI converter

Dreamcast PC serial adapter

GameBoy Cart Programmer

Memory game

32 Kb x 8 emulator for the GameBoy

Project: NES to Atari 2600 controller interface

Battery Meter for Pinball Machines

SRX1 (Stephane's Robotic eXperiment 1)

Pine Racecar Victory Judge

Interfacing Sony control stick to Empeg

Electronic Nicad glow plug driver

GameBoy LCD schematic

GameBoy Power & Cartridge schematic

GameBoy ROM+RAM+MBC1 Cart Schematic

GameBoy MBC1 circuit equivalent

Super GameBoy schematic

Bingo!!! (on your tv)

Slot car TV cronograph

Furby reverse-engineered circuit

Sanyo 20EZ monitor Arcade Game (300k ZIP)

Burger Time Arcade Game (500k ZIP)

Dig Dug Arcade Game (800k ZIP)

Frogger Arcade Game (500k ZIP)

Galaga Arcade Game (542k ZIP)

Gyrus Arcade Game (800k ZIP)

Junior Pacman Arcade Game (400k)

Ladybug Arcade Game (335k ZIP)

Mappy Arcade Game (470k ZIP)

Moon Cresta Arcade Game (300k ZIP)

Mr.Do Arcade Game (554k ZIP)

PacLand Arcade Game (316k ZIP)

Pengo Arcade Game (313k ZIP)

Q*Bert Arcade Game (600k ZIP)

Qix Arcade Game (476k ZIP)

Scramble Arcade Game (600k ZIP)

Time Pilot'84 Arcade Game (870k ZIP)

Xevious Arcade Game (450k ZIP)

Magic Wand Conjuring Trick

Quiz game circuit

E.S.P. Conjuring Trick

DIT shutterglasses controller

Tic-tac-toe game using PIC16F628

Archery timer

PIC micro Tetris game

Magic lamp, IR remote control jammer and other fun circuits (PDF)

Lego Mindstorms Double Rotation Sensor

Source

Discover Circuits

2006-06-20T22:29:00.000-07:00

Discover Circuits, with its 23,000+ electronic circuits or electronic schematics cross-referenced into 500+ categories, is a vital resource for engineers, hobbyists, inventors & consultants. The site's collection of links will help you find quick solutions for electronic design problems. Bad links are removed and new circuits or schematics are added frequently.

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Telephone Circuits

2006-06-20T21:25:00.000-07:00

Telephone Ring Generator Using Switching Supply

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 voltage, 1 amp transistor) and a driver ...

Telephone Ring Generator Using Small Power Transformer

This ring generator will ring a telephone once every 10 seconds. The interval between rings can be lengthened or shortened by varying the value of ...

Telephone In-Use Indicator

Telephone In-Use Relay Controller

Circuit to close a relay when any phone extension is off-hook. Voltage at the gate of the MOSFET should be ...

Telephone Audio Interface

Audio from a telephone line can be obtained using a transformer and capacitor to isolate the line from external equipment. A non-polarized capacitor is placed in series with the transformer line connection to prevent DC current from flowing in the transformer winding which may prevent the line from returning to the on-hook state. The capacitor should have a voltage rating above the peak ring voltage of 90 volts plus the on-hook voltage of...

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Microsoft Rolls Out Robotics Dev Kit

2006-06-20T20:36:00.000-07:00

By Lance Ulanoff

Robotics has captured the minds and imagination of those inside and outside the technology market, but as a market unto itself, robotics can barely get its act together. Microsoft today announced during Robo Trend Inc.'s RoboBusiness Conference...

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New Blog

2006-06-20T19:10:00.000-07:00

Welcome to my new blog!

This site will contain new circuits and microcontroller programs for hobby use. Please check out this site from time to time for new updates.

For RSS feeds point your feedreader to http://hobbycircuits.blogspot.com/atom.xml.