Showing posts with label cheap. Show all posts
Showing posts with label cheap. Show all posts
Sunday, April 7, 2013
Surge Protected Cheap Transformerless Hi Watt LED Driver Circuit
This circuit is just a proof of concept just to show that the good old 555 timer can still be
used for a modern and quite demanding application. It is by no means an optimized circuit
that can be readily used for mass production. It appears relatively big by today's standard
because I used only through hole components. You may shrink it to 50 % of its original
size if you use modern SMD parts. You may also be able to increase the efficiency of this
circuit. Unfortunately I didnt't have time to do extensive measurements with all sorts of
inductors. There may be some room for optimizations.
Parts list
R1 2.2 kΩ / 0.1 W
R2 10 kΩ / 0.1 W
R3 100 kΩ / 0.1 W
R4 470 Ω / 0.1 W
R5 1 kΩ / 0.1 W
R6 2 Ω / 0.25W
C1 220 pF NPO ceramic disc capacitor
C2 10 µF / 16 V electrolytic
C3, C4 470 µF / 6.3 V, low ESR
L1 custom made transformer, see text
L2 47 µH / 2 A (TDK SLF 12575 / Fastron PIS4728 series)
D1 1N4148
D2 SB240 (SB360, MBRS240, MBRD650)
D3 BZX55C 4V7, 4.7 V Zener Diode
D4 1 W High Power LED
T1 BC 337-40 (2N2222A)
T2 BC547B (2N3904)
T3 2SK2869 (IRLR2905, IRLZ 34N)
IC1 ICM7555 (TLC555, HA17555)
Monday, March 11, 2013
Cheap Emergency Light Circuit Diagram Using a Flashlight Bulb
Though its the world LEDs today, an ordinary flashlight bulb can also be considered a useful light emitting candidate especially because its much to configure than an LED.
The shown circuit diagram is quite simple to understand, a PNP transistor is used as the primary switching device.
A straight forward power supply provides the power to the circuit when mains is available.
As long as power is present, the transistor T1 remains positively biased and therefore remains switched OFF.
This inhibits battery power from entering the bulb and keeps it switched OFF.
The mains power is also utilized for charging the involved battery via the diode D2 and the current limiting resistor R1.
However, the moment AC mains fails, T1 is instantly forward biased, it conducts and allows the battery power to pass through it, which ultimately turns ON the bulb and the emergency light.
The entire unit may be adjusted inside a standard AC/DC adapter box and plugged IN directly in to an existing socket.
The bulb should be kept protruding outside the box so that the illumination reaches the external surrounding amply.
The moment AC mains fails,
Cheap Emergency Light Using a Flashlight Bulb Circuit Diagram
The shown circuit diagram is quite simple to understand, a PNP transistor is used as the primary switching device.
A straight forward power supply provides the power to the circuit when mains is available.
As long as power is present, the transistor T1 remains positively biased and therefore remains switched OFF.
This inhibits battery power from entering the bulb and keeps it switched OFF.
The mains power is also utilized for charging the involved battery via the diode D2 and the current limiting resistor R1.
However, the moment AC mains fails, T1 is instantly forward biased, it conducts and allows the battery power to pass through it, which ultimately turns ON the bulb and the emergency light.
The entire unit may be adjusted inside a standard AC/DC adapter box and plugged IN directly in to an existing socket.
The bulb should be kept protruding outside the box so that the illumination reaches the external surrounding amply.
The moment AC mains fails,
Cheap Emergency Light Using a Flashlight Bulb Circuit Diagram
Parts List
R1 = 470 Ohms,
R2 = 1K,
C2 = 100uF/25V,
Bulb = Small Flashlight Bulb,
Battery = 6V, Rechargeable Type,
Transformer = 0-9V, 500 mA
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