120 and 240Vac LED Voltage Indicator Circuit

Useful for power lines control Simple, transformerless circuitry

This circuit, designed on request, has proven to be useful to indicate when the voltage in a power supply line is changing from 120V to 240Vac. It can be used in different circumstances and circuits, mainly when an increase in ac or dc supply voltage needs to be detected. D3 illuminates when the line voltage is approaching 120V and will remain in the on state also at 240V supply. On the other hand, D6 will illuminate only when the line voltage is about 240V and will stay on because the latching action of Q1, Q2 and related components. C1, D1 and D2 provide a low dc voltage in the 4.5V - 6V range in order to allow proper operation of latch circuit and LEDs.

Circuit diagram :

 120 and 240Vac LED Voltage Indicator Circuit diagram

Parts :

R1_____________470R  1/2W Resistor
R2_____________220K  1/4W Resistor
R3,R7__________470R  1/4W Resistors
R4_______________1K  1/4W Resistor
R5_______________2K2 1/4W Resistor
R6_____________330R  1/4W Resistor

C1_____________330nF 630V Polyester Capacitor
C2______________10µF  25V Electrolytic Capacitor

D1,D2________1N4007   1000V  1A Diode
D3,D6___________LEDs  (Color and shape at will)
D4_________BZX79C10   10V 500mW Zener Diode (See Notes)
D5___________1N4148   75V 150mA Diode

Q1____________BC547   45V 100mA NPN Transistor
Q2____________BC557   45V 100mA PNP Transistor

Notes:

• D4 value could require some adjustment in order to allow precise switching of the circuit at the chosen voltage. If the case, please try values in the 8.2V - 15V range.
  
• Warning! The circuit is connected to 240Vac mains, then some parts in the circuit board are subjected to lethal potential! Avoid touching the circuit when plugged and enclose it in a plastic box.

Source : www.redcircuits.com

Fine Control Super Bright LED Pulser

Four timing controls - 12V supply, Suitable for Halloween or Christmas props

This circuit, designed on request for a Halloween prop, allows fine control of a pulsing Super Bright white LED. The four potentiometers or trimmers will set precisely: on, off, ramp up and ramp down time-delays respectively. Ramp up and ramp down time-delays can be set roughly in the 1 - 15 seconds range, whereas on and off time-delays can range from a few seconds to about one minute. A 12V battery or regulated power supply is required, provided it is reasonably stable. Total current drawing is about 25 - 30mA when the LED reaches maximum brightness.

Parts:

R1,R5,R12,R13___10K 1/4W Resistors
R2,R5___________10K 1/2W Trimmers or Lin. Potentiometers
R3______________47K 1/4W Resistor
R4______________22K 1/4W Resistor
R6_______________1K 1/4W Resistor
R7,R8,R9,R14___100K 1/4W Resistors
R10,R11__________2M2 1/2W Trimmers or Lin. Potentiometers
R15____________220R 1/4W Resistor
C1,C2__________100nF 63V Polyester or ceramic Capacitors
C3,C4___________22µF 25V Electrolytic Capacitors
C5_____________220µF 25V Electrolytic Capacitor
D1,D2________1N4148 75V 150mA Diodes
D3______________LED Super Bright white (e.g. RL5-UV2030)
Q1____________BC337 45V 800mA NPN Transistor
IC1___________LM324 Low Power Quad Op-amp IC
IC2____________4093 Quad 2 input Schmitt NAND Gate IC

Notes:

• Wanting to use two white LEDs, the second device must be wired across the Emitter of the transistor and negative ground with its own limiting resistor wired in series, like R15 and D3 in the circuit diagram.
• If common red, yellow or green LEDs are required, please wire two of them in series, in order to present roughly the same voltage drop of one white or blue LED.
• Please note that the unused sections in both ICs must have their inputs tied to negative ground whereas the outputs must be left open, as shown at the bottom of the diagram.
• All time-delays can be increased by changing the value of C3 and C4 to 47µF 25V or even higher. Please vary the value of these capacitors only, as the values of the resistors wired to the four control pots are rather critical and should not be changed.