Description

Stereo per channel
VCC=9V;RL=4?/3W
VCC=9V;RL=8?/2W

Bridge Application
VCC=9V;RL=8?/5W
VCC=9V;RL=4?/8W

Supply Voltage min = DC3v @ 500mA
Supply Voltage max = DC12v @ 500mA
Supply Voltage recommended = DC9v @500mA

DESCRIPTION
Above circuits are based on TEA2025 is a monolithic integrated audio amplifier in a 16-pin plastic dual in line package manufactured by UTC .Circuit has an Internal Thermal Protector. It is designed for portable cassette players and radios. You can also use it as your PC Audio Amplifier. A few external components required to build this circuit. Use 9v transformer to play the circuit. But not more than DC12v. Because it can damage the amplifier IC. So build n Enjoy.

author: YMYA electronics – IZHAR FAREED

9V Battery powered – Very low current drawing

Design description:

The target of this project was the design of a small portable mixer supplied by a 9V PP3 battery, keeping high quality performance.
The mixer is formed assembling three main modules that can be varied in number and/or disposition to suit everyone needs.
The three main modules are:

Input Amplifier Module: a low noise circuit equipped with a variable voltage-gain (10 – 100) pre-set, primarily intended as high quality microphone input, also suitable for low-level line input.

Tone Control Module: a three-band (Bass, Middle, Treble) tone control circuit providing unity-gain when its controls are set to flat frequency response. It can be inserted after one or more Input Amplifier Modules and/or after the Main Mixer Amplifiers.

Main Mixer Amplifier Module: a stereo circuit incorporating two virtual-earth mixers and showing the connection of one Main Fader and one Pan-Pot.

The image below shows a Block diagram of the entire mixer featuring four Input Amplifier Modules followed by four in-out switchable Tone Control Modules, one stereo Line input, four mono Main Faders, one stereo dual-ganged Main Fader, four Pan-Pots, a stereo Main Mixer Amplifier Module and two further Tone Control Modules switchable in and out for each channel, inserted before the main Left and Right outputs.
Obviously this layout can be rearranged at everyone wish.
An astonishing feature of this design lies in the fact that a complete stereo mixer as shown below in the Block diagram draws less than 6mA current!

Block diagram:

Input Amplifier Module

Parts:

R1,R2,R7_______22K   1/4W Resistors
R3,R4,R5_______47K   1/4W Resistors
R6______________4K7  1/4W Resistor
R8,R13________220R   1/4W Resistors
R9______________2K   1/2W Trimmer Cermet (See Notes)
R10___________470K   1/4W Resistor
R11___________560R   1/4W Resistor
R12___________100K   1/4W Resistor

C1____________470nF   63V Polyester Capacitor
C2,C8_________100΅F   25V Electrolytic Capacitors
C3,C4,C5________2΅2   63V Electrolytic Capacitors
C6_____________47pF   63V Ceramic Capacitor
C7______________4΅7   63V Electrolytic Capacitor

Q1____________BC560C  45V 100mA Low noise High gain PNP Transistor
Q2____________BC550C  45V 100mA Low noise High gain NPN Transistor

IC1___________TL061   Low current BIFET Op-Amp

Circuit description:

The basic arrangement of this circuit is derived from the old Quad magnetic pick-up cartridge module.
The circuit was rearranged to cope with microphone input and a single-rail low voltage supply.
This low-noise, fully symmetrical, two-transistor head amplifier layout, allows the use of a normal FET input Op-Amp as the second gain stage, even for very sensitive microphone inputs.
The voltage-gain of this amplifier can be varied by means of R9 from 10 to 100, i.e. 20 to 40dB.

Notes:

• R9 can be a trimmer, a linear potentiometer or a fixed-value resistor at will.

• When voltage-gain is set to 10, the amplifier can cope with 800mV peak-to-peak maximum Line levels.

• Current drawing for one Input Amplifier Module is 600΅A.

• Frequency response is 20Hz to 20KHz – 0.5dB.

• Total Harmonic Distortion measured with voltage-gain set to 100: 2V RMS output = < 0.02% @ 1KHz; < 0.04% @ 10KHz.

• Total Harmonic Distortion measured with voltage-gain set to 10 & 33: 2V RMS output = < 0.02% @ 1KHz & 10KHz.

• THD is much lower @ 1V RMS output.

• Maximum undistorted output voltage: 2.8V RMS.

Tone Control Module

Parts:

P1,P2_________100K   Linear Potentiometers
P3____________470K   Linear Potentiometer

R1,R2,R3_______12K   1/4W Resistors
R4,R5___________3K9  1/4W Resistors
R6,R7___________1K8  1/4W Resistors
R8,R9__________22K   1/4W Resistors
R10___________560R   1/4W Resistor
R11___________100K   1/4W Resistor
R12___________220R   1/4W Resistor

C1______________1΅F   63V Polyester Capacitor
C2_____________47nF   63V Polyester Capacitor
C3,C5___________4n7   63V Polyester Capacitors
C4_____________22nF   63V Polyester Capacitor
C6,C8_________100΅F   25V Electrolytic Capacitors
C7______________4΅7   63V Electrolytic Capacitor

IC1___________TL061   Low current BIFET Op-Amp

Circuit description:

This is a straightforward design using the Baxandall-type active circuitry slightly modified to obtain a three-band control. Total voltage gain of this module is 1 when controls are set in their center position.

Notes:

• Current drawing for one Tone Control Module is 400΅A.

• Frequency response is 20Hz to 20KHz – 0.5dB, controls flat.

• Tone control frequency range: ± 15dB @ 30Hz; ± 19dB @ 1KHz; ± 16dB @ 10KHz.

• Total Harmonic Distortion measured @ 2V RMS output = < 0.012% @ 1KHz; < 0.03% @ 10KHz.

• THD is below 0.01% @ 1V RMS output.

• Maximum undistorted output voltage: 2.5V RMS.

Main Mixer Amplifier Module

Parts:

P1,___________100K   Linear Potentiometer
P2_____________10K   Linear Potentiometer

R1,R2,_________15K   1/4W Resistors
R3,R4,R11,R12_100K   1/4W Resistors
R5,R6__________22K   1/4W Resistors
R7,R8_________390K   1/4W Resistors
R9,R10________560R   1/4W Resistors
R13___________220R   1/4W Resistor

C1,C2_________330nF   63V Polyester Capacitors
C3,C8_________100΅F   25V Electrolytic Capacitors
C4,C5__________10pF   63V Ceramic Capacitors
C6,C7___________4΅7   63V Electrolytic Capacitors

IC1___________TL062   Low current BIFET Dual Op-Amp

Circuit description:

The schematic of this circuit is drawn as a stereo unit to better show the input Main Fader and Pan-Pot connections. The TL062 chip contains two TL061 in the same 8 pin case and is wired as two virtual-earth mixer amplifiers having a voltage gain of about 4, to compensate for losses introduced in the passive Pan-Pot circuitry. Therefore, total voltage-gain is 1.
Each channel added to the mixer must include the following additional parts:
P1, P2, R1, R2, R3, R4, C1 and C2.
These parts must be wired as shown in the above circuit diagram, connecting R3 and R4 to pin #2 and pin #6 of IC1 for Right and Left channel respectively. These IC1 pins are the “virtual-earth mixing points” and can sum together a great number of channels.

Notes:

• Current drawing for one stereo Main Mixer Amplifier Module is 800΅A.

• Frequency response is 20Hz to 20KHz – 0.5dB.

• Total Harmonic Distortion measured @ 2V RMS output = < 0.008% @ 1KHz; < 0.017% @ 10KHz.

• THD is 0.005% @ 1V RMS output.

• Maximum undistorted output voltage: 2.8V RMS.

Further Parts:

To parts listed above should be added: one Main on-off SPST switch, a LED used as pilot-light with its dropping 2K2 1/4W series-resistor, DPDT switches to enable or omit Tone Control Modules as shown in the Block diagram, input and output connectors of the type preferred, one stereo dual-gang 100K potentiometer to fade the Stereo Line Input as shown in the Block diagram, battery clip, PP3 9V battery, knobs etc.

source: RED Free Circuit Designs

Parts:

R1____________10K   1/4W Resistor
R2,R3_________22K   1/4W Resistors
R4___________100K   1/4W Resistor
R5,R9,R10_____56K   1/4W Resistors
R6_____________5K6  1/4W Resistor
R7___________560R   1/4W Resistor
R8_____________2K2  1/4W Resistor
R11____________1K   1/4W Resistor
R12___________33K   1/4W Resistor
R13__________330R   1/4W Resistor

C1___________100nF  63V Polyester Capacitor
C2____________10΅F  25V Electrolytic Capacitor
C3___________470΅F  25V Electrolytic Capacitor
C4____________47΅F  25V Electrolytic Capacitor

D1_____________5mm. Red LED

IC1__________LM358  Low Power Dual Op-amp

Q1___________BC327  45V 800mA PNP Transistor

MIC1_________Miniature electret microphone

SW1__________2 poles 4 ways rotary switch

B1___________9V PP3 Battery

Clip for PP3 Battery

Device purpose:

This circuit is intended to signal through a flashing LED, the exceeding of a fixed threshold in room noise, chosen from three fixed levels, namely 50, 70 & 85 dB. Two Op-amps provide the necessary circuit gain for sounds picked-up by a miniature electret microphone to drive a LED. With SW1 in the first position the circuit is off. Second, third and fourth positions power the circuit and set the input sensitivity threshold to 85, 70 & 50 dB respectively.
Current drawing is <1mA with LED off and 12-15mA when the LED is steady on.

Use:

• Place the small box containing the circuit in the room you intend to measure ambient noise.

• The 50 dB setting is provided to monitor the noise in the bedroom at night. If the LED is steady on, or flashes bright often, then your bedroom is inadequate and too noisy for sleep.

• The 70 dB setting is for living-rooms. If this level is often exceeded during the day, your apartment is rather uncomfortable.

• If noise level is constantly over 85 dB, 8 hours a day, then you live in a dangerous environment.

source: RED Free Circuit Designs

By: George Peirson

Whether you are just starting a web design project, looking at revamping an existing site, or just wanting to double check the usability of your current web site you should consider these 7 Basics of Good Web Design.

These Basics are aimed at new visitors/customers, your repeat customers will be judging your web site on different values. Just like wearing the appropriate clothes for a job interview, these basics will help you pick out the “look” of your web site so that you make a good first impression.

1. Fast Loading Web Site – Any way you look at it, a fast loading page should be your number 1 concern. The web is all about speed, fast searches, fast purchases, fast information. You can’t have any of that with a slow loading page. Ask yourself this question, have you ever been on Google doing a search for something important and a link you clicked on didn’t open up immediately? What did you do? Patiently wait for the page to open or move onto the next link on the list? My favorite sites open almost immediately.

So, a few suggestions: Make sure that your images are properly optimized. Don’t use very many large images, save those for a different page. Keep any auto-running multimedia to a minimum, offer links to run media instead. Check your code for anything else that could affect your page loading times. Since text loads almost instantly go ahead and use all the text you want, just keep everything else under control.

2. No Meaningless Splash Page – Do you appreciate a fancy animation page that doesn’t tell you anything and you have to wait for before the web site will open? Neither do I. The last thing I want once I find an interesting site is to wait through some animation before getting to the first page. This doesn’t mean that I don’t want multimedia on a site, I do. I just don’t want an animation before the first page that forces me to wait for it to finish before getting onto the site. Its like having to wait for a salesperson to finish their memorized speech before you can ask them a question. No thanks! I like animation, just in the right place and at the right time. Plus if I am a returning customer I will have already seen that animation and don’t need to see it again.

My recommendation is to use a smaller animation contained in your main landing page which also includes your main message and links to the rest of your site. It will make for a faster loading page (smaller file) and your visitors can go ahead with accessing your site without having to wait for the animation to finish.

One final note, never, ever put your logo as the only content on your landing page with a link that says “Enter Site”. This just screams Unprofessional and will drive away potential visitors in droves. The last thing I want to do is to click on another link just to get into the site. This is a total waste of my time. I usually will skip a site if I see this.

3. No Annoying Web Gimmicks – Now that you have your visitor on your site quickly the one thing you don’t want to do is to drive them away just as quickly. So, don’t put anything annoying on that first page. No loud background music that makes them quickly hit the volume control or the back button on their browser. No flashing animations while they are trying to read your content. No popup, flyout, expanding ads that cover your home page. Basically leave the gimmicks alone until you are sure that your visitor will stay on your site. Most casual visitors will leave your site in just a few seconds, no sense on driving them away more quickly.

Multimedia is great on a web site, just don’t bombard your visitor with it first thing. If you want audio then put in a nice picture with a link, like a picture of yourself with text saying something like “Let me tell you how to make $50,000 this month!” If they are interested they will click on the link and listen to your message, if they are not interested in audio then you should be using a different pitch anyway.

Also, monitor what advertisers are putting on your site if you sell ad space. I am sure you have seen those ads with the animated dancing figure, cute the first time you see it. But after seeing it 10,000 times with every imaginable character I have added the company to a list I keep of companies I will never do business with. So their animation has gone from “look at me” to “you annoy me” in my mind. Ads like these will impact your visitor’s experience. So even if your site is perfectly designed, one misplaced ad can ruin all of your hard work.

4. Have a Clear Message – Too many web sites are a mish-mash of content. This is especially true of blog pages. Certain types of sites lend themselves to stream of consciousness content, but most don’t. Make it easy for your viewer to understand what your web site is about, don’t make them guess. Have a clear topic headline, followed by clear and concise text. This is also where a picture is worth a thousand words, but only if the picture directly pertains to your message.

You want your visitor to be able to quickly understand what your message is. If they like your message they will take the time to read the rest of your page and look around your web site. If they don’t like your page, then it won’t do you any good having them stay on your site anyway. So, don’t make your visitors guess, let them know what you are about quickly and cleanly and you will have happy visitors. And when thinking about a sales page, a happy customer is a buying customer.

5. Coordinated Design – This one should be self evident, but it is surprising how many sites change their design for every page. You want your visitor to be comfortable in your site and one way to achieve that is by having a coordinated web design. Having a consistent logo, using a consistent color scheme, keeping your navigation in the same place. All of these help to create a coordinated design. This does not mean that you can’t change colors or the “Look” on different segments of your site, but if you do, the changes should not be so drastic that it feels like you have moved on to a different site.

If you select one place for your logo, one place for your navigation, one look for your buttons or other common graphic elements and stick with those then you will be well on your way to a coordinated design. If you change colors for a different section, but keep the same logo location, the same navigation location, the same button shape then your visitors will not become lost as they move from page to page.

6. Easy Navigation – Once you have grabbed your visitors attention you want them to be able to easily move around the different areas of your web site. This is done with easy to use navigation. There are three standard, accepted locations for navigation elements on a web page: along the top, on the left side, and at the bottom. I will usually put my main navigation either along the top or along the left side. I will then put text based navigation at the bottom of the page, this text based navigation is more for the search engines than anything else, but it also makes it easy for your visitors to move to the next page when they have reached the bottom of the current page.

Most people start reading a page from the top left and then read towards the bottom right. So navigation at the left or top will be seen as soon as someone enters your page. Also navigation at the left or top will not move or change position if the browser window is adjusted in size. The worst thing you can do is to put your main navigation on the right side of the page and have your page set for a large screen size. Let’s say that your page is set for 1024 across with the navigation on the right, and someone views your page at 800 across, they will not see your navigation at all. The left side of your page will show perfectly, but the right side will be hidden outside of their viewing area. Of course by using floating or popup menus you can overcome some of these design limitations and keep your navigation visible at all times.

Unless you know that your audience will enjoy it, don’t use Mystery Navigation. This is where your navigation is hidden within images, or spaced around the web page in some mysterious random order. This can be fun on gaming sites, or social networking sites, but in most cases the navigation should be easy to see and easy to use. If you do want to use Mystery Navigation I would recommend keeping the text based navigation at the bottom of the page, just in case.

7. Have a “Complete” web site – And finally, no one wants to go to a web site only to find that the site is “Under Construction” and the content they are looking for is not there. These are words that you should never use. If a section of your web site is not ready for prime time yet, then simply don’t show it yet. It is better to have your site look complete and professional, then to have it look like a work in progress that should not be up on the web yet.

You can easily tell your visitors that you will be having more content in the future without looking like your site is unfinished. Just use phrases like “Content Updated Weekly” or “New Products Added Monthly”. Both of these will tell your visitors that it would be worth their time to come back and visit at later, but neither one will make your site look unfinished. So no matter how small your web site is, give the impression that you have taken the time to complete the site before putting it up on the internet, this makes for a more professional presentation and a better visitor experience.

In Closing – By following these simple 7 Basics of Good Web Design you will be well on your way to having an easy to use and successful web presence. Just keep in mind what you look for when you first land on a web page after doing a web search in Google or Yahoo, or other search engine. If you want fast loading pages, make sure your pages load fast. If you want to be able to find what you are looking for quickly and easily then make sure you have easy navigation. Just keep your first time visitor in mind, put yourself in their web shoes and make your web site an enjoyable place to visit and success should follow.

Open connection to local MySQL database using MySQL ODBC 3.51 Driver
“Provider=MSDASQL; DRIVER={MySQL ODBC 3.51Driver}; SERVER= localhost; DATABASE=Your_MySQL_Database; UID= Your_Username; PASSWORD=Your_Password; OPTION=3″

MySQL OLE DB & OleDbConnection (.NET framework) connection strings

Open connection to MySQL database:
“Provider=MySQLProv;Data Source=Your_MySQL_Database;User Id=Your_Username; Password=Your_Password;”

Optimizing your website is not really that difficult, there are many search engine optimization techniques, or SEO techniques, that can be employed even by a novice webmaster with limited html skills and the will to learn new things.

This article will deal with the on page search engine optimization techniques, or seo techniques that you employ on your website to make it more search engine friendly. While off page search engine optimization, or SEO that is performed through the use of other websites, such as with link building; is vitally important. Proper optimization of on page elements of your website should be considered the foundation which you build all other search engine marketing (SEM) methods on.

Page title optimization

Of all of the seo techniques that you can employ on your website, the title tag is largely undisputed as being the most important element of on page optimization. The title tag should be different for every page of your website and it should be keyword focused with the most important keywords at the beginning of the title.

It’s somewhat disputed amongst professional SEO’s whether there should be multiple keyword phrases within the title or only the two or three that directly relate to the page that the title represents; as of this moment in time there seems to be proof that either of these methods can be beneficial.

Use of headings

Using the headings tags are considered an important aspect of your website’s optimization. These start out at <h1> and continue down in order of importance to the <h6> tag. While the content contained within headings tags are not weighted as heavily as the title tag, headings still have considerable power for keyword focusing of your content in the eyes of many search engines.

Headings tags should be keyword focused, and as with the page title, important keywords should be kept towards the beginning of the heading tag. Your most important headings should be used with the <h1> tag and the less important headings can be used with the <h2> tag, the <h3> tag and so on. An important note, however: your page title and headings should not be identical. Mixing and matching of keyword phrases is the recommended practice when employing our search engine optimization techniques with the title and the headings.

Content is king – website content optimization

Maybe the phrase “content is king” is slightly overdone, and often times it’s used out of context, however, creating keyword focused and optimized content is one of the more important search engine optimization techniques that you can employ for your website.

Keyword focusing is a big factor when optimizing your website content. For instance, this article is about search engine optimization techniques. If you’ll look back and read though this article you’ll notice the phrase search engine optimization techniques purposely being placed throughout the article’s body. This is the keyword focusing aspect of creating optimized website content.

Search engines are pretty smart, and they’re getting smarter every day. What this means for website content optimization is that keyword focusing isn’t enough anymore. In order to help improve the relevancy of your website’s content for certain keywords and phrases, you should also work to incorporate related keyword phrases as well into the content. Taking our example of this articles keyword phrase focus search engine optimization techniques, you’ll notice that phrase as well as SEO techniques and SEO being used in lieu of search engine optimization. Basically, when you’re looking to optimize your website content, you’ll want to use natural substitutions of your main keywords and phrases that you might find on other websites about the same topic.

Use of sitemaps / link directory

Last, but not least on our list of search engine optimization techniques is the use of a website sitemap. There are actually two types of sitemaps that you can use for your website, and we’ll touch on both of them here.

Sitemaps for search engines

Sitemaps built for search engines, such is the case with Google sitemaps, help search engines to easily find all of the pages of your website so that your pages can be indexed. While the use of Google sitemaps is pretty popular amongst a certain sub-culture in the webmaster world, the need for this type of sitemap really isn’t needed. In fact, you can get the same results or even better results from using a different type of sitemap.

Sitemaps for people and search engines

Let’s say you have a fairly large website; some 30 pages, maybe more. It’s generally recommended that every page on your website is no more than two clicks from your homepage. Maintaining a link to every page of your website on your homepage simply isn’t an option when you have a large website for cosmetic reasons, let alone overall user friendliness. In order to achieve the “two clicks” recommendation, you absolutely need a sitemap.

Not only will a sitemap help users find the less popular pages on your website, in terms of search engine optimization techniques, the use of a static sitemap is just a good idea. You also have the ability to work on keyword focusing for the anchor text used to link to your internal pages, another one of the many search engine optimization techniques that will help you improve your website for SEO.

While the search engine optimization techniques listed on this page are not exhaustive, the seo techniques listed here will give you a much needed advantage in improving the overall search engine friendliness of your website. All things considered, using the techniques outlined here will give you a solid foundation for any off page search engine optimization methods that you choose to employ.

So you have a huge site with multiple PHP Scripts and you get a load of traffic all of a sudden, when you built the site you didn’t figured 0.01 second load time was fine right? Well, say you get 5,000 visitors daily; that 0.01 can turn into 50 seconds!!!

Don’t know how to benchmark your script? It’s easy:

Now, lets turn that frown of yours upside-down.

Echo is faster than Print (marginally, but it all adds up)

Unset variables and arrays (especially); this will only help load speeds if your servers ram is full and strangling it, though it is still a good practice to unset variables and arrays when you no longer need them.

Use full paths in Include and Requires, this allows the server to be a zombie; and not have to resolve the filepath constantly.

Don’t limit yourself to just Logic statements, use select() for statements that would better suit it, don’t just assume that if/then/else will cover it all, because it might; but it can become slow if you have a huge list of redundancies.

Suppressing errors with the @ sign can be extremely slow. Instead use error_reporting(0)

Close DB connections when you no-longer need them, this is along the same lines as unsetting variables; but will give your database some breathing room.

Calling arrays with single quotes is much faster than no quotes ($array['1'] is faster than $array[1])

Globals are marginally slower than variables (only noticeable in duplicate applications).

Use single quotes for strings instead of double quotes (if you use double quotes, PHP searches for strings inside the string)

Use static HTML where possible, PHP can be up to TWENTY times slower than HTML. This is due to the fact that PHP compiles the script every time you call it, go learn how to cache the files. If you run a dedicated or VPS server, you will want to ask your host about ZendOptimizer for your PHP Installation. You can check to see if you already have it: php_info your server and CTRL+F for “Zend” and it should bring up it’s own block of info. If it’s installed, you should have at least basic caching setup.

$add++ is slower than ++$add

Don’t make everything in OOP, as this will end up just adding overhead, use OOP for things that should be in OOP, and nothing more.

Use the default PHP functions where possible, no sense in making your own function that does the same thing as a pre-defined default function.

For those of you that have servers buckling under the stress of traffic, you may consider taking all PHP out of your site’s pages and making different scripts that are run once nightly by a cronjob that will then build the HTML files for your site. This keeps the site dynamic, but also keeps the server from dropping to it’s knees every time a page is loaded by a visitor.

Also: If you believe my benchmark’s are skewed because I ran them at the same time, you will be happy to know that I ran the slower methods before running the faster methods. I’ve also put (omit) next to each of the results that seem to have hit extreme peaks or dips in performance.

The circuit of Fig.1 takes the guesswork out of proximity detection by inducing eddy currents in a living being, whether animal or human. Five turns of enamelled copper wire (say 30 s.w.g.) are wound around the area within which detection is to take place (4m x 4m in tests), and an audio signal of about ¼ Watt is pulsed through this, the Tx, coil. A smaller Rx coil (say 100 turns of 30 s.w.g. enamelled copper wire wound on a 150mm dia. former) is used as a pick-up coil. The circuit is adjusted by means of tune and fine-tune controls VR1 and VR2, so that it is deactivated when one stands back from the Rx coil.

A simple clock generator (IC1a-IC1b) and power MOSFET (TR1) are used for the transmitter, and a 7555 timer (IC2) is wired as a sine-square convertor for the receiver. IC2′s inputs are biased through VR1, VR2 and R4. IC2 in turn switches NAND gates IC1c and IC1d, to drive relay RLA. Capacitor C5 switches the relay for about two seconds, and its value may be increased or decreased to give different timing periods. D2 is critical to prevent back-e.m.f. from re-triggering the circuit. Supply decoupling capacitors C1 and C4 are also critical, and should be located close to IC1 and IC2 respectively.

When a living being – animal or human – comes within tens of centimetres of the Rx coil, the circuit is triggered. This coil may be placed in the threshold of a door, under a carpet, or around a hatch, at the base of a tree, and so on. A number of such coils may also be wired in series.

Coils may be wound with a larger or smaller diameter, with more or less turns, and the power of the transmitter may be varied, as well as the sensitivity of the receiver. Note that a.m. radio reception may be affected at close proximity to the Tx coil.

author: Thomas Scarborough

Circuit diagram

Here is a simple triangle/squarewave generator using a common 1458 dual op-amp that can be used from very low frequencies to about 10 Khz. The time interval for one half cycle is about R*C and the outputs will supply about 10 milliamps of current. Triangle amplitude can be altered by adjusting the 47K resistor, and waveform offset can be removed by adding a capacitor in series with the output.
author: Bill Bowden
e-mail:
web site: http://www.geocities.com/
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30 minutes operation
Blinking LED signals 6 last minutes before turn-off

Circuit diagram

Parts:
R1 1K 1/4W Resistor
R2 4K7 1/4W Resistor
R3 10M 1/4W Resistor
R4 1M 1/4W Resistor
R5 10K 1/4W Resistor
C1 470µF 25V Electrolytic Capacitor
C2-C4 100nF 63V Polyester Capacitors
D1-D4 1N4002 100V 1A Diodes
D5 5mm. Red LED
IC1 4012 Dual 4 input NAND gate IC
IC2 4060 14 stage ripple counter and oscillator IC
Q1 BC328 25V 800mA PNP Transistor
Q2 BC238 25V 100mA NPN Transistor
P1,P2 SPST Pushbuttons
T1 220V Primary, 9 + 9V Secondary 1VA Mains transformer
RL1 10.5V 470 Ohm Relay with SPDT 2A 220V switch
PL1 Male Mains plug
SK1 Female Mains socket

Device purpose:
The purpose of this circuit is that of power a lamp or other apparatus for a given time (30 minutes in this case), and then to turn it off. It’s useful when reading at bed by night, turning off the bedside lamp automatically in case the reader falls asleep… After turn-on by P1 pushbutton, an LED lights for c25 minutes, but 6 minutes before the turn-off, start blinking for two minutes, then stop blinking for other two minutes and finally blinks for other two minutes, thus signaling that the on-time is ending. If the user want to prolong the reading, can earn another half-hour of light by pushing on P1. Turning-off the lamp at user’s ease is obtained pushing on P2.

Circuit operation:
Q1 and Q2 forms an ALL-ON ALL-OFF circuit that in the off state draw no significant current. P1 starts the circuit, the relay is turned on and the two ICs are powered. The lamp is powered by the relay switch, and IC2 is reset with a positive voltage at pin 12. IC2 start oscillating at a frequency settled by R4 and C4. With the values shown pin 3 goes high after c30 minutes, turning off the circuit via C3. During the c6 minutes preceding turn-off, the LED does a blinking action by connections of IC1 to pins 1,2 & 15 of IC2. Blinking frequency is provided by IC2 oscillator at pin 9. The two gates of IC1 are in parallel to source an higher current. If needed, a piezo sounder can be connected at pins 1 & 14 of IC1. Changing IC2 brand name, varies the oscillation frequency. In particular Motorola’s ICs run faster. Obviously, time can be varied changing C4 and R4 values.

This circuit was awarded with publication in ELECTRONICS WORLD “Circuit Ideas”, October 1999 issue, page 819.
author: RED Free Circuit Designs
e-mail:
web site: http://www.redcircuits.com/
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