New dark detector v2 kit pcb layouts.
Download it from our site.

-->Watch it here<--

This is our new improved version of dark detector.
You can find the datasheet here in the site.

-->Dark detector datasheet<--

These devices are low cost, high speed, dual JFET input
operational amplifiers with an internally trimmed input offset voltage .
They require low supply current yet maintain a large gain bandwidth product and fast slew rate.
In addition, well matched high voltage JFET input
devices provide very low input bias and offset currents.

For a Light Emitting Diode to emit any form of light it needs a current to flow through it, as it is a current dependant device. As the LED is to be connected in a forward bias condition across a power supply it should be current limited using a series resistor to protect it from excessive current flow. From the graph above we can see that each LED has its own forward voltage drop across the PN-junction and this parameter, which is determined by the semiconductor material used, is the forward voltage drop for a given amount of forward conduction current.

The LM3914 is a monolithic integrated circuit that senses analog voltage levels and drives 10 LEDs, providing a
linear analog display. A single pin changes the display from a moving dot to a bar graph. Current drive to the
LEDs is regulated and programmable, eliminating the need for resistors. This feature is one that allows operation
of the whole system from less than 3V.
datasheet here

0-5v led volt meter lm3914

This is a delay off circuit based on the 555 timer. You can adjust the output time via the 10k trimmer.
When you push the button and release it timer counts backwords and keep high its output until timer go zero.

The counters are advanced one count on the negative transition of each clock pulse.
The counters are reset to the zero state
by a logical ``1'' at the reset input independent of clock.