Low Voltage Alarm Circuit Schematic With explanation

This low voltage circuit can be used to monitor batteries and other volatile sources of current for problems. The circuit sounds an alarm and lights an LED, but can be interfaced to any number of other circuits for many different uses.

Parts

Part Total Qty. Description Substitutions R1, R3 2 1K 1/4W Resistor R2 1 5K Pot U1 1 LM339 Op Amp IC D1 1 1N5233B Zener Diode D2 1 LED BZ1 1 Piezo Buzzer MISC 1 Board, wire, socket for IC

Notes

1. The circuit will operate from 9V to 12V.
2. Adjust R2 until the alarm goes off at the correct voltage.s

Source : aaroncake.net/

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7 Segment LED Counter Circuit With explanation

This simple counter can be used to count pulses, as the basis for a customer counter (like you see at the doors of some stores), or for anything else that may be counted. The circuit accepts any TTL compatible logic signal, and can be expanded easily (see Notes).

Parts

Part	Total Qty.	Description	Substitutions
R1-R7	7	470 Ohm 1/4 Watt Resistor
U1	1	74LS90 TTL BCD Counter IC	7490,74HC90
U2	1	74LS47 TTL Seven Segment Display Driver IC	7447,74HC47
DISP1	1	Common Anode 7 Segment LED Display
MISC	1	Board, Sockets For ICs, Wire

Notes

1. All pulses to be counted are to be TTL compatible. They should not exeed 5V and not fall below ground.
2. You can add more digits by building a second (or third, or fourth, etc...) circuit and connecting the pin 11-6 junction of the 74LS90 and 74LS47 to pin 14 of the 74LS90 in the other circuit. You can keep expanding this way to as many digits as you want.

www.aaroncake.net

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Latest Touch Alarm System circuit schematic with explanation

Touch Alarm circuit is widely used for security, which is installed on the door. The advantages of this alarm is because the cost is cheap and difficult to detect by burglars / intruders. The following is an example of a touch of alarm circuit which is designed by Tony Van Roon.

Components List:

R1 = 100K R2 = 56K R3 = 10M R4 = 220K P1 = 100K D1 = 1N4004

T1 = 2N3904, or equivalent U1 = 555 Timer* C1 = 47μF/16V** C2 = 33μF/16V** Re1 = Relay***

Notes:

*The 555 can be a LM, NE, or MC(cmos) type, they’re all pin-compatible.

**C1/C2′s operating voltage should be elevated to 25V if you decide to go with a 12V energy source. Rule of thumb: the operating voltage of capacitors are at least double the supplied voltage, in other words, if the powersource is 9Volt, your capacitor(s) is a minimum of 18V. Transistor T1 could be any approximate substitute.

*** Use any suitable relay for the project and if you are not tight on area, use any size. I’ve develop this specific circuit to prevent students from fiddling using the security cameras in pc labs in the University I’m employed. I made certain the metal casing was not grounded. But as the schematic shows you can essentially hook it as much as any type of metal surface. I utilized a 12-vdc power adapter. Use any appropriate relay to handle your requirements. A ‘RESET’ switch (Usually Closed) can be added between the constructive and the ‘arrow-with-the-+’. The trigger (touch) wire is connected to pin 2 of the 555 and will trigger the relay, utilizing the body resistance, when touched. It is apparent that the ‘touching’ component has to be clean and can make good get in touch with with the trigger wire. This particular circuit may not be suitable for all applications. Just in case you wonder why pin 5 isn’t listed within the schematic diagram; it isn’t truly required. In certain noisy conditions a little ceramic capacitor is placed in between pin 5 and ground. It does no harm to add one or leave it out.

Extra note: For all those of you who didn’t discover, there is an approximate 5-second delay build-in prior to activation of the relay to avoid false triggering, or a ‘would-be’ thief, etc.

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Tips on Choosing a Right Power Source for 12V LED Lights

If you are looking for how to choose a right power source for 12 volt LED lights, you will come to right place, This video gives you things to think about when choosing between a plug-in 12V adapter and a hardware 12V driver; how to choose the best wiring for a large installation; and about how permanent you want your LED light setup to be.

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Safely Driving With Dual LCD Display Digital Alcohol Breath Tester

If you had a digital alcohol breath tester on hand after you had a few drinks you could have easily and conveniently measured your blood alcohol content to be certain it was safe and legal for you to get behind the wheel. You are really taking a gamble on those occasions when you think youre okay to drive but yoere not certain if youre under the legal blood alcohol content. Here I will show the dual lcd display digital alcohol breath tester with audible alert white.

There is no doubted that this alcohol breath tester is compact enough for you to carry in your pocket all the time. About 13,000 people a year are killed on our roads in drink-drive incidents, so we must continue to be vigilant in our efforts to prevent drunk driving. Breath analysis is the most common method of testing for blood-alcohol content in use today, it can ensure the safety of yourself and others! Nobody wants a DUI conviction or its consequences - you risk a night in jail, thousands of dollars in fines and legal fees, the embarassing publication after a trial. You had better not drive if you are not sure, just play it safe and call a cab - the cheapest alternative.

Features

* Backlight LCD display
* Replaceable sensor module
* Dual LCD screen breathalyzer
* Quick response and resume
* Auto power off
* Temperature display in ℃ or °F
* Digital alcohol Breath Tester with audible alert
* Professional airway design, LCD screen display
* Accumulative test record counting display before tests
* Promptly and conveniently design alcohol breath analyser for measuring BAC
* A simple method to analyse blood alcohol concentration at anytime and anywhere
* Countdown & count-up timer keep the time limit of your parking
* LCD Alcohol Tester Breathalyzer uses 2 x AAA alkaline batteries(batteries not included), clock use 1 x * AG13 button cell (batteries not included)
* This Alcohol Breath Tester with LCD screen and noncontact expiring design is compact and lightweight
* This Digital Alcohol Detector is pretty easy for carrying and convenient for using
* Numbers will be shown on the LCD screen so that you can judge by analyzing the numbers
* And if the alcohol content of tested expiring gas is out of range, this LCD Alcohol Tester Breathalyzer will automatically gives out audible alert
* This personal LCD Alcohol Tester Breathalyzer measures your blood alcohol level via a breath test anytime you need to know if youve crossed the line between safe and not safe
* Pretty useful as it is, such an LCD Alcohol Tester Breathalyzer is a really a good gift for yourself or anyone else you cares
* Lightweight and easy to use, this mini breathalyzer uses illuminating lights to tell you the outcome of your breath test
* Advanced semiconductor sensor with high accuracy and repeatability

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