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usb kits presents
dark detector V2

                                                                         

functionality

This is a useful dark or light detector switch based on a ldr variable resistor
and an op-amp TL081 as a comparator!

When the light or dark drops down on the ldr sensor the resistance of it changes and makes the voltage on the inverting input of the opamp change too.

When the voltage on the inverting input goes higher than the non inverting,
the output of the opamp goes high.

You can set the voltage on the non inverting input via a trimmer to select the brightness threshold you desire.

The opamp drives a relay through a npn transistor and you can then select the output you want (N.O. or N.C.).

You can set the brightness or darkness threshold through a trimmer and you can choose the dark or light operation by swapping the ldr with a resistor!

You can select the dark or light functionality at any time via the relay output too, because you have the opportunity to select both the N.O. and N.C. outputs of the relay via a 3pin terminal block.


Dark detector as a laser alarm

How to

You can use the dark detector kit as a laser alarm also.
Just point with a laser direct on the ldr and use the n.c contact in series with a zone in your alarm panel.
You can add in series many radars or magnetic switches.

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Idea!!!

Try to direct the laser path with mirrors and you will have a matrix of laser.
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After your feedback from the first version we made some improvements

please leave your feedback for the kit or your suggestions for more improvements in the future

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V2 release improvements

1) Reverse polarity protection
2) Redusing the noise in the nets with better pcb wirrings and adding capacitors above the chips.
3) Bigger pads for easier constructions
4) Better placing of the components for easier constructions
5) The on off switch now is extended from the pcb so you can mount it in your project box
6) More leds per channel for more intensity and better placing for better optical results.
7) Ability to place the led on the bottom side so you can hide the rest of the structure.
8) The trimmers are now extended from the pcb board so you can mount them in your project box.
9) Bigger heat sink power plates for better heat consumption.
10) A bigger amplification of the bass indicators.

the circuit schematic

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Dark detector schematic

part list

Ref.            Type                                            Value
C1              Ceramic Capacitor            330nF
C2              Ceramic Capacitor            100nF
C3              Electrolytic Capacitor     1000u
C4              Electrolytic Capacitor     2.2u
C5              Electrolytic Capacitor     22u
C6              Smd 0603 Capacitor        100nF
D1              Rectifier diode                     1N4001
D2               3mm Diffused Led            Red
D3               3mm Diffused Led            Green
D4              Diode                                        1N4148
D5              Diode                                        1N4148
D6              Rectifier diode                    1N4001
FU1            Fuse  Glass 20mm            300ma
J1                Usb jack                                  Type B
J2                Terminal Block                    2 pin  Dc input
J3                Terminal Block                    3 pin  Output contacts
SW1          jst 2pin cable                        ON/OFF Switch
U1               Voltage Regulator            7805
Q1               NPN Transistor                  2n3904
R1-R3        Resistor 1/4 watt             10k
R4                Resistor 1/4 watt             1k
R5                Resistor 1/4 watt             470
R6                Resistor 1/4 watt             100k
R7                Resistor 1/4 watt             470
R8                Resistor 1/4 watt             470
U2               Operational Amplifier   TL081
LDR1        Light Dep. Resistors        Variable
RL1            Relay double contacts    5V coil
RV1           jst 3pin cable                        Trimmer 50k

construction help guide

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resistor color code definition
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2n3904
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Standard 5mm pitch terminal blocks
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1n4148
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1n4001
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lm7805
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led
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TL081
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555
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jst 2 pin female pcb mount
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jst 2 pin male cable
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jst 3pin 2.5 pitch for trimmers
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click for soldering and prototyping assistant


downloads

dark_detector_v2_datasheet.pdf
File Size: 136 kb
File Type: pdf
Download File

dark_detector_v2__merged.pdf
File Size: 771 kb
File Type: pdf
Download File


Set the dark or light threshold to operate the switch via the trimmer

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