12 Volt Lamp Dimmer with ic 555

Here is a 12 volt / 2 amp lamp dimmer that can be used to dim a standard 25 watt automobile brake or backup bulb by controlling the duty cycle of a astable 555 timer oscillator. When the wiper of the potentiometer is at the uppermost position, the capacitor will charge quickly through both 1K resistors and the diode, producing a short positive interval and long negative interval which dims the lamp to near darkness. When the potentiometer wiper is at the lowermost position, the capacitor will charge through both 1K resistors and the 50K potentiometer and discharge through the lower 1K resistor, producing a long positive interval and short negative interval which brightens the lamp to near full intensity. The duty cycle of the 200 Hz square wave can be varied from approximately 5% to 95%. The two circuits below illustrate connecting the lamp to either the positive or negative side of the supply.


 
tags: Timer ,  555 Timer Circuit ,  lamp

LED Torch

A common problem with small torches is the short life-span both of the batteries and the bulb. The average incandescent torch, for instance, consumes around 2 Watts. The LED Torch in Fig. 1 consumes just 24 mW, giving it more than 80 times longer service from 4 AA alkaline batteries (that is, up to one month's continuous service). Although the torchs light output is modest, it is nonetheless quite sufficient to illuminate a pathway for walking.
The LED Torch is based on a 7555 timer running in astable mode (do not use an ordinary 555). A white LED (Maplin order code NR73) produces 400 mcd light output, which, when focussed, can illuminate objects at 30 metres. Try Conrad Electronic for what appears to be a stronger white LED (order code 15 37 45-11).
A convex lens with short focal length is placed in front of the LED to focus the beam. If banding occurs at the beams perimeter, use another very short focal length lens directly in front of the LED to smooth the beam.
If a different supply voltage is preferred, the value of resistor R3 is modified as follows:
9V - 470 Ohm
12V - 560 Ohm

2 Transistor LED Flasher

This is a classic 2 transistor astable multivibrator. Many other NPN small signal or switching transistors can be used, including 2N4401, PN2222 or 2N2222 using the circuit on the left. The circuit can also be inverted using PNP transistors such as 2N3906, 2N4403, PN2907, or 2N2907 as shown to the right.

The 470 ohm resistors determine the LED brightness. Lower resistance means higher current, and more light. LEDs that require more current or have a higher operating voltage (such as green and yellow) may work better with 300 ohms.
The RC time constant of the 39K ohms resistor and the 10uF capacitor determines the on time for each side. (The two sides do not need to match - vary the RC time constant for one side to get a lower or a higher duty cycle). With the values shown, the flash rate is about 1 cycle per second at 50% duty cycle.

100W Mosfet J162 + K1058

Power Amplifier OCL 100W Mosfet J162 + K1058

This is circuit MOSFET power amplifier OCL, Output 100w , use mosfet k134+j49 or Mosfet J162 + K1058 Output 112W at Speaker 8 OHM. Power Supply +56V/-56V 4A /Ch.

Power Supply 6 to 12 V DC

Here the another variable power supply which have adjustabled output voltage from 6-12 DC volt.
Parts List:
T1 = 115[220]/8 VAC transformer.
Q1 = 2N1613, NTE128, or substitute. Use heatsink!
BR1 = 40V, 4A. (Check max current of your mini-drill and add 2A)
R1 = 470 ohm, 5%
R2 = 1K, 5%
P1 = potentiometer, 10K
C1 = 1000uF, 25V

Notes:

• C1 filters the noise and spikes off the AC. If you find the circuit output too noisy add another electrolytic capacitor over the output terminals. Value can be between 10 and 100uF/25V.
• The output voltage is variable with the 10K-potentiometer.
• The transformer input voltage refer to your home power source.

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1A Power Supply with 0 to 15 Volts

1A Power Supply with 0 to 15 Volts Adjustable Output

Circuit Project Description

The objective of the circuit is to create a power supply that would produce an output of 0 V to 15 V at 1 A current.

Terminology

2N3055 – a complementary Silicon Epitaxial-Base planar NPN transistor mounted in Jedec TO-3 metal case for use as power transistorBridge Diode – also known as bridge rectifier which has four diodes arranged in a bridge configuration where the output voltage has the same polarity with either polarity of the input voltage Circuit Explanation

The construction of this power supply circuit is very simple in such a way that the components used are easy to be located while the cost is very cheap. With the biggest provided current at 1 A, the output voltage is adjusted for minimal ripple effect and stabilized in the range of 0 V to 15 V DC. This is made possible by the standard transformer output of 1.5 A with a primary winding voltage of 220 V and secondary voltage of 18 V. The current is being limited by the Zener diode D1 with a rating of 18 V and 1.5 W. The linear potentiometer R2 is responsible for the regulation of current.

The power transistor Q1 is a classic type that would require to be placed in a suitable heatsink to suppress the high heat dissipation during the operation of the circuit. The heat dissipation will be continuous during the presence of the highest current. The bridge diode GR1 will provide full wave rectification from the AC input which will also convert the incoming alternating current (AC) input into direct current (DC) output. One good feature of the bridge diode is maintaining the same polarity of the output regardless of the polarity of the input.

Part List R1= 56ohm 2W
R2= 330ohm Lin. pot.
C1= 2200uF 35V
C2= 100uF 35V
C3= 10uF 25V
C4= 220uF 25V
C5= 100nF 100V
GR1= 4 X 1N4007
Q1= 2N3055
T1=220V@18V 1.5A
D1= 18V 1.5W zener
Application

The 15V/1 A power supply may be used to handle home automation control system which can be powered by 12 Vdc. They can be made into power adapter models to support a wide variety of applications such as TFT monitors, broadcasting, laptops, digital cameras, telecommunications, PSP’s, routers, notebooks, guitar effects pedals, KVM extenders, iPod’s, scanners, CCTV’s, printers, cassette players, radios, and other portable applications.

2x20 Watt Stereo Amplifier

Description

This circuit is a small stereo amplifier for all suitable applications like amplifying small speakers, boxing, etc. It is also suitable for car use but before, the power supply must be choked with at least 150mH and it must give up to approximately 6 to 7 amps during the upstream performance.

schematic

PCB

layout

Technical data:
Performance of TDA2005M: (for this circuit); At 14.4 V supply voltage: 2 x 20 watts (stereo) into 4 Ohms.
Distortion: Approx. 0.2% at 4 Watts into 4 ohm load.
Frequency Range: Approx. 20 Hz to 22 KHz.
Input Sensitivity: Approx. maximum 150 mV rms. .
Power supply: + 8 to 18 volts, approx. maximum 3.5 Amps per channel.

Appropriate heatsink for the amplifier is SK08 with a height of 50 mm (approx. 2.5 K per watt). You should drill the cooler after soldering the board to center it properly. TheTDA2005 also needs not be isolated from the heat sink, since the metal mounting part of the IC is grounded. You should use thermal paste to improve the heat dissipation. After the assembly , case construction is left to the builder. 100K potentiometers are used for adjusting the input volume. The potentiometers are absent in the layout. The 100K resistors need only be installed if the 100 K potentiometers are not used as shown in the layout.

You should use a well designed quality transformer to get less noise. It will be another good way to use a sufficient battery to power the circuit. Keep the supply wires as short as possible. Input source should be isolated from the external noises too. It is recommended to use coaxial cable to connect the input audio.

Click here to download schematic, PCB and layout files.

source : www.circuit-projects.com