Friday, May 31, 2013
Wiring Regulationssetting Standards Electrical Installations
City And Guilds Exam Success Iee Wiring Regulations Paperback By.
Guide To The Wiring Regulations 2008 Iee Wiring Regulations Bs 7671.
17th Edition Iee Wiring Regulations.
Iee Wiring Regulations Bs 7671 2008 And Part P Of Building.
Bs 7671 Iee Wiring Regulations 17th Edition.
Iee Wiring Regulations Design And Verification Of Electrical.
Work Updated To Iee Wiring Regulations 17th Edition Bs 7671 2008.
Iee Wiring Regulations Setting Standards In Electrical Installations.
Bathroom Lighting Zones.
Guide To The 15th Edition Of The Iee Wiring Regulations E Book Zella.
Monday, May 13, 2013
Personal Alarm
This circuit, enclosed in a small plastic box, can be placed into a bag or handbag. A small magnet is placed close to the reed switch and connected to the hand or the clothes of the person carrying the bag by means of a tiny cord.
If the bag is snatched abruptly, the magnet looses its contact with the reed switch, SW1 opens, the circuit starts oscillating and the loudspeaker emits a loud alarm sound.
The device can be reverse connected, i.e. the box can be placed in a pocket and the cord connected to the bag.
This device can be very useful in signalling the opening of a door or window: place the box on the frame and the magnet on the movable part in a way that magnet and reed switch are very close when the door or window is closed.
Sunday, May 5, 2013
Brightness Control for small Lamps
This device was designed on request, to control the light intensity of four filament lamps (i.e. a ring illuminator) for close-up pictures with a digital camera, powered by two AA or AAA batteries. Obviously it can be used in other ways, at anyones will.
IC1 generates a 150Hz squarewave having a variable duty-cycle. When the cursor of P1 is fully rotated towards D1, the output positive pulses appearing at pin 3 of IC1 are very narrow. Lamp LP1, driven by Q1, is off as the voltage across its leads is too low. When the cursor of P1 is rotated towards R2, the output pulses increase in width, reaching their maximum amplitude when the potentiometer is rotated fully clockwise. In this way the lamp reaches its full brightness.
LP1 could be one or more 1.5V bulbs wired in parallel. Maximum total output current allowed is about 1A.
R2 limits the output voltage, measured across LP1 leads, to 1.5V. Its actual value is dependent on the total current drawn by the bulb(s) and should be set at full load in order to obtain about 1.5V across the bulb(s) leads when P1 is rotated fully clockwise.
Parts:
P1 470K Linear Potentiometer
R1 10K 1/4W Resistor
R2 47K 1/4W Resistor (See Notes)
R3 1K5 1/4W Resistor
C1 22nF 63V Polyester Capacitor
C2 100µF 25V Electrolytic Capacitor
D1,D2 1N4148 75V 150mA Diodes
IC1 7555 or TS555CN CMos Timer IC
Q1 BD681 100V 4A NPN Darlington Transistor
LP1 1.5V 200mA Bulb (See Notes)
SW1 SPST Switch
B1 3V (Two 1.5V AA or AAA cells in series, etc.)
ReadMore....
IC1 generates a 150Hz squarewave having a variable duty-cycle. When the cursor of P1 is fully rotated towards D1, the output positive pulses appearing at pin 3 of IC1 are very narrow. Lamp LP1, driven by Q1, is off as the voltage across its leads is too low. When the cursor of P1 is rotated towards R2, the output pulses increase in width, reaching their maximum amplitude when the potentiometer is rotated fully clockwise. In this way the lamp reaches its full brightness.
LP1 could be one or more 1.5V bulbs wired in parallel. Maximum total output current allowed is about 1A.
R2 limits the output voltage, measured across LP1 leads, to 1.5V. Its actual value is dependent on the total current drawn by the bulb(s) and should be set at full load in order to obtain about 1.5V across the bulb(s) leads when P1 is rotated fully clockwise.
Parts:
P1 470K Linear Potentiometer
R1 10K 1/4W Resistor
R2 47K 1/4W Resistor (See Notes)
R3 1K5 1/4W Resistor
C1 22nF 63V Polyester Capacitor
C2 100µF 25V Electrolytic Capacitor
D1,D2 1N4148 75V 150mA Diodes
IC1 7555 or TS555CN CMos Timer IC
Q1 BD681 100V 4A NPN Darlington Transistor
LP1 1.5V 200mA Bulb (See Notes)
SW1 SPST Switch
B1 3V (Two 1.5V AA or AAA cells in series, etc.)
Wednesday, May 1, 2013
9V Battery Replacement Power Supply
This circuit was originally designed to power a motorcycle intercom from the vehicle supply system. This type of intercom, which is used for communication between driver and passenger, generally requires quite a bit of power. In order to improve intelligibility there is often elaborate filtering and a compander is sometimes used as well. The disadvantage is that a battery doesn’t last very long. You could use rechargeable batteries, of course, but that is often rather laborious. It seems much more obvious to use the motorcycle power supply instead. A 9-V converter for such an application has to meet a few special requirements.
For one, it has to prevent interference from, for example, the ignition system reaching the attached circuit. It is also preferable that the entire circuit fits in the 9-V battery compartment. This circuit meets these requirements quite successfully and the design has nonetheless remained fairly simple. In the schematic we can recognize a filter, followed by a voltage regulator and a voltage indicator. D1, which protects the circuit against reverse polarity, is followed by an LC and an RC filter (C3/L1/L2/C1/R1/C2). This filter excludes various disturbances from the motorcycle power system.
Moreover, the design with the 78L08 and D3 ensures that the voltage regulator is operating in the linear region. The nominal system voltage of 14 V can sometimes sag to about 12 V when heavy loads such as the lights are switched on. Although the circuit is obviously suitable for all kinds of applications, we would like to mention that it has been extensively tested on a Yamaha TRX850. These tests show that the converter functions very well and that the interference suppression is excellent.
Moreover, the design with the 78L08 and D3 ensures that the voltage regulator is operating in the linear region. The nominal system voltage of 14 V can sometimes sag to about 12 V when heavy loads such as the lights are switched on. Although the circuit is obviously suitable for all kinds of applications, we would like to mention that it has been extensively tested on a Yamaha TRX850. These tests show that the converter functions very well and that the interference suppression is excellent.
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