Posts Tagged ‘led flashlights’

Smooth Flasher Circuit Diagram

Ordinary LED flashers turn the LED on and off abruptly, which can get a little irritating after a while. The circuit shown here is more gentle on the eyes: the light intensity changes very slowly and sinusoidally, helping to generate a relaxed mood. The circuit shows a phase-shift oscillator with an adjustable current source at its output. The circuit is capable of driving two LEDs in series without affecting the current.

The frequency is set by three RC networks, each of which consists of a 100 µF capacitor and a 22 kO resistor. Operation is largely independent of supply voltage, and the average LED current is set at about 10 mA. The circuit adjusts the voltage across the emitter resistor so that it matches the base voltage of the first transistor (around 0.6 V). The phase shifting network gives rise to the oscillation around this average value. In the prototype of this circuit we used an ultra-bright red LED.

Burkhard Kainka
Elektor Electronics 2008

Two-Led Pilot Light

220vAC mains operated, Very simple circuitry

This circuit is designed on request and can be useful to those whishing to have, say, a red LED illuminated when an appliance is on and a green LED illuminated when the same appliance is off. Any mains operated appliance can be monitored by this circuit provided a suitable mains switch, capable of withstanding the full load current, is used for SW1.When SW1 is closed, the load and D4 are energized, Q1 is saturated and shorts D3, thus preventing its illumination.

Parts:
R1 = 27K-1W
R2 = 27K-1W
R3 = 6.8K
D1 = 1N4007
D2 = 1N4007
D3 = Green
D4 = Red Led
Q1 = BC337
SW1 = SPST Mains Switch

Notes:
* Change R1 and R2 to 15K 1W for 115Vac mains operation.
* SW1 must be capable of withstanding the appliance’s full load current and voltage.

Source : www.redcircuits.com

Flashing Eyes by BC557

Two-LED-eyes follow the rhythm of music or speech, 3V Battery-operated device suitable for pins or badges
This circuit was purposely designed as a funny Halloween gadget. It should be placed to the rear of a badge or pin bearing a typical Halloween character image, e.g. a pumpkin, skull, black cat, witch, ghost etc. Two LEDs are fixed in place of the eyes of the character and will shine more or less brightly following the rhythm of the music or speech picked-up from surroundings by a small microphone. Two transistors provide the necessary amplification and drive the LEDs.

Parts:
R1 = 10K
R2 = 1M
R3 = 1K
C1 = 4.7uF-25V
C2 = 47uF-25V
D1 = 2mm LED
D2 = 2mm LED
Q1 = BC547
Q2 = BC557
B1 = 3V Battery
SW1 = SPST Switch
MIC1 = Electret Mic

Notes:
* Any general purpose, small signal transistor can be used for Q1 and Q2, but please note that R3 could require adjustment, depending on the gain of Q1. For medium gain transistors, the suggested value should do the job. High gain transistors will require a lower value for R3, i.e. about 390 – 470 Ohm. You can substitute R3 with a 1K Trimmer in order to set precisely the threshold of the circuit.
* Any LED type and color can be used, but small, 2mm diameter, high efficiency LEDs will produce a better effect.
* No limiting resistors are required for D1 and D2 even if this could seem incorrect.
* Stand-by current consumption of the circuit is about 1.5mA.
* Depending on dimensions of your badge, you can choose from a wide variety of battery types:
* 2 x 1.5 V batteries type: AA, AAA, AAAA, button clock-type, photo-camera type & others.
* 2 x 1.4 V mercury batteries, button clock-type.

Source : www.redcircuits.com