Showing posts with label a. Show all posts
Showing posts with label a. Show all posts
Monday, December 23, 2013
Build a 5 Zone alarm Circuit Diagram
This is a complete alarm system with 5 independent zonessuitable for a small office or home environment. It uses just 3CM IC`s and features a timed entry / exit zone, 4 immediatezones and a panic button. There are indicators for each zone a“system armed” indicator. The schematic is as follows:
5 Zone alarm Circuit Diagram
Circuit Notes:
Each zone uses a normally closed contact. These can be microswitches or standard alarm contacts (usually reed switches).Suitable switches can be bought from alarm shops and concealed indoor frames, or window ledges.Zone 1 is a timed zone which must be used as the entry andexit point of the building. Zones 2 – 5 are immediate zones,which will trigger the alarm with no delay. Some RF immunity isprovided for long wiring runs by the input capacitors, C1-C5. C7and R14 also form a transient suppresser. The key switch acts asthe Set/Unset and Reset switch. For good security thisshould be the metal type with a key.
Operation:
At switch on, C6 will charge via R11, this acts as the exitdelay and is set to around 30 seconds. This can be altered byvarying either C6 or R11. Once the timing period has elapsed,LED6 will light, meaning the system is armed. LED6 may be mountedexternally (at the bell box for example) and providesvisual indication that the system has set. Once set any contactthat opens will trigger the alarm, including Zone 1. To preventtriggering the alarm on entry to the building, the concealedre-entry switch must be operated. This will discharge C6 andstart the entry timer. The re-entry switch could be a concealedreed switch, located anywhere in a door frame, but invisibleto the eye. The panic switch, when pressed, will trigger thealarm when set. Relay contacts RLA1 provide the latch, RLA2operate the siren or buzzer.
Friday, December 20, 2013
Build a 13KV High voltage Power supply Circuit Diagram
This 13KV High voltage Power supply Circuit Diagram has an inverter around Q1 that supplies 150-V pulses to the converter of SCR1 and C2. The output of ?2 is a 4.5-kV pulse that is multiplied by the voltage-tripler network (right) to produce 13.5 kV. R1 is a 3k to 500K CT transistor audio transforfiler, L2 is a flash tube trigger transformer with a 6-kV secondary.
13KV High voltage Power supply Circuit Diagram
Sunday, March 31, 2013
How to Make a Simple 12 Volt LED Lantern Circuit
We have discussed white LEDs comprehensively through many of my earlier articles and have learned how efficient these lights are with power consumption.
In this article we will study a very simple configuration for making a LED lamp or a LED lantern.
New electronic enthusiasts often get confused with the wiring intricacies while configuring many LEDs in groups.
Here we’ll see how we can connect as many as 64 LEDs for making the proposed unit.
The circuit diagram details may be understood from the following points:
White LEDs typically have a forward voltage drop of about 3 volts.
When operated at the above voltage level, the device is able to produce lights at optimum levels and the spec also maintains better life expectancy.
The minimum current required at the above voltage level is around 20 mA, which again is an optimal magnitude and is ideally suited for a white LED.
That means for driving a single white LED in the most straightforward way we would require 3 * 0.02 = 0.06 watts, that’s pretty negligible compared to the relative illumination received from it.
The best thing is that as long as the above voltage and current spec is observed, the device continues to consume 0.06 watts irrespective of the number of LEDs connected.
In the present circuit, the maximum voltage available is 12, dividing 12 by 3 = 4, meaning 4 numbers of LEDs can be accommodated at this voltage and yet we are able to limit the power to 0.06 watts.
However the above calculation would make the circuit quite vulnerable to voltage drops and if the voltage dropped even by a single volt would make the LED too dim or might just shut them OFF, we don’t want this to happen.
Therefore though the efficiency may drop a bit, we opt for a configuration which would enable the circuit to work even at lower voltages. We include only two LEDs in the series @ o.06 watts.
Now it’s all about connecting the desired number of strings of two LEDs each in parallel until all the 64 bulbs are included in the circuit.
However connecting in parallel would mean multiplying current. Since we have 32 parallel connections means the total consumption will now become 32 * 0.06 = 1.92 watts, still pretty much reasonable.
The connection details can be easily traced from the given schematic.
Your simple LED lantern is ready and may be taken anywhere outdoors with you, probably during night time explorations.
Pats List
All resistors are = 470 Ohms, 1.4 watts,
All LEDs are = white, 5mm, hi-efficiency
Diode = 1N4007
Wednesday, March 27, 2013
zBot 10 A Power Stage for DC Motor
If you look at the chassis of the zBot vehicle1, you’ll find two parts requiring intelligent control: the steering servo and the DC motor. The so called H-bridge is the normal circuit for electronic control of revolution speed and direction. The DC motor of a Tamiya car is powerful enough to propel zBot at up to 20 miles per hour.
The motor then consumes more than 10 A, so we choose high-current power MOSFETs for the driver stage. There are lots of different devices to choose from. The MOSFET we require has to supply the maximum motor current and, importantly, it has to be switched with gate voltages of about 5 V. In this case, the microcontroller switches the power stage (‘low side’) directly. For high side driving level shifters are necessary. The schematic of the H-bridge power stage shows a few inverters, NAND gates and two tri-stateable drivers. These logic functions are very important as the easier way, i.e.., directly controlling all four MOSFET has a fatal disadvantage.
In case of a software crash it could happen that two ore more MOSFETs are switched on incor-rectly for exam-ple, T4 and T7. In that case, the current through the transistors is limited by the internal resistors of the MOSFETs (about 10 mO) only. Such a fatal error would destroy the MOSFETs. The logic functions configured here effectively avoid illegal states.To control the DC motor, three signals are needed: DIR, PWM and STOP. DIR controls the direction of the motor revolution, PWM the speed, and STOP brakes the motor.
The software module for the DC motor is called dcm.c.(070172-I) The complete document called Zbot the Robot Experimental Platform is available for free downloading from the Elektor Electronics website. The file number is 070172-11.zip (July/August 2007).
Author: Jens Altenburg Copyright: Elektor
Monday, March 25, 2013
A Simple Fog Lamp Sensor
For several years now, a rear fog lamp has been mandatory for trailers and caravans in order to improve visibility under foggy conditions. When this fog lamp is switched on, the fog lamp of the pulling vehicle must be switched of to avoid irritating reflections. For this purpose, a mechanical switch is now built into the 13-way female connector in order to switch of the fog lamp of the pulling vehicle and switch on the fog lamp of the trailer or caravan. For anyone who uses a 7-way connector, this switching can also be implemented electronically with the aid of the circuit illustrated here.
Circuit diagram:
Fog Lamp Sensor Circuit Diagram
Here a type P521 optocoupler detects whether the fog lamp of the caravan or trailer is connected. If the fog lamp is switched on in the car, a current flows through the caravan fog lamp via diodes D1 and D2. This causes the LED in the optocoupler to light up, with the result that the photo-transistor conducts and energies the relay via transistor T1. The relay switches of the fog lamp of the car. For anyone who’s not all thumbs, this small circuit can easily be built on a small piece of perforated circuit board and then fitted somewhere close to the rear lamp fitting of the pulling vehicle.
Author :Harrie Dogge Copyright :Elektor Electronics 2008
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