Simple Touchless Hand Sanitizer

Published Jul 25, 2020

GPL-3.0-only

1 hours to build

Beginner

electronics

The circuit is made by 555 timer ic & LM358 op-amp. The Ir-Led and Photodiode is used as a sensor to detect hand.

Components Used
LMV358 Operational Amplifier LMV358 is a dual, low-voltage operational amplifier with rail-to-rail output swing.	X 1
555 Timer 555 Timer	X 1
Photodiode Photodiode	X 1
Diode 1N400x Diode 1N400x	X 2
BC547 TRANSISTORS BC547 TRANSISTORS	X 2
IR LED Infrared Emitters IR LED Infrared Emitters	X 1
BC557 Bipolar Transistors BC557 Bipolar Transistors	X 1
Submersible Water Pump Adafruit Accessories Submersible 3V DC Water Pump with 1 Meter Wire - Horizontal Type	X 1
Resistor 220 Ohms Metal Film Resistors - Through Hole 220 OHM 1/4W 1%	X 2
Resistor 120 kOhms Metal Film Resistors - Through Hole 120K OHM 1/4W 1%	X 1
Capacitor 10 µF Aluminium Electrolytic Capacitors - Radial Leaded 100V 10uF 85C 2k Hour Radial	X 1
Capacitor 10000 pF Multilayer Ceramic Capacitors MLCC - Leaded 250V 0.01uF C0G 5%	X 1
Resistor 1 kOhms Metal Film Resistors - Through Hole 1K ohm 1/4W 1%	X 2
Resistor 10 kOhms Metal Film Resistors - Through Hole 10 kOhms 250 mW 1% 100 PPM / C	X 1
Potentiometer 10Kohms Potentiometers 10Kohms 10% 12.5mm Cermet Element	X 1

Description

Step1:

Connect 220ohm resistor (R1) to +5v & the Ir Led (D1) positive terminal, negative terminal to ground(GND).

Step2:

Next, Connect the negative terminal of photo-diode (D2) to +5v & 10k ohms resistor(R2) to positive of photo-diode and GND.

Step3:

Connect LM358 ic (U1) pin 8 to +5v & pin 4 to GND. Connect a wire to the positive terminal of photo-diode to the non-inverting terminal of the op-amp pin 3

Step 4:

Potentiometer (POT1), connect end terminals to +5v and GND. The remaining terminal is connected to pin 2 of the op-amp which is inverting terminal. This potentiometer uses a set point or reference voltage to the op-amp.

Note: The output will high if the non-inverting terminal is more than the inverting terminal voltage which is set by us in step 4

Step 5:

The output pin 1 of the op-amp connected to the resistor 1k ohm (R4) and another end of the resistor to the base of transistor BC547 (Q1)

Step 6:

The Transistor BC547 (Q1) emitter connected to GND. The collector of the transistor BC547(Q1) to 1k ohm resistor(R5) to the base of the transistor BC557 (Q2)

Step 7:

The emitter of BC557 (Q2) connected to +5v and collector to pin 8 & pin 4 of 555 timer IC (U2).

Step 8:

Connect 10uF capacitor (C1) positive terminal to pin 2 & pin 6, the negative terminal of the capacitor to ground.

Step 9:

Connect 10nF capacitor (C2) positive terminal to pin 5 & the negative terminal of the capacitor to ground.

Step 10:

Connect diode (D3) cathode terminal to pin 7 & anode terminal pin 6, Potentiometer (POT2) connect one end terminal to pin 7 & middle terminal to pin 6.

Note: The Turn off time can change by turning the potentiometer (pot2).