Touch Free Hand sanitizer dispenser using LDR
Touch-free hand sanitizer dispenser that automatically dispenses sanitizer utilizing LDR sensors and MOSFETs to switch the motor we designed this to be in accordance with COVID 19 coronav…
Know the mission before touching a wire.
Understand what you are making, prepare the right tools, and make the workbench safe.
Project details
Touch Free Hand sanitizer dispenser using LDR is a arduino project. Touch-free hand sanitizer dispenser that automatically dispenses sanitizer utilizing LDR sensors and MOSFETs to switch the motor we designed this to be in accordance with COVID 19 coronav…
- Source pages
- 640-643
- Named parts
- 11
- Build goal
- Working, tested prototype
Tools you need
- Digital multimeter
- Wire stripper and side cutters
- Soldering iron with a fine tip
- Current-limited bench supply
- Computer with a data-capable USB cable
Use eye protection, good lighting, and a clean insulated surface throughout the build.
Safety precautions
- Disconnect every power source before changing a connection.
- Check component polarity, pinout, and supply voltage twice.
- Use a current limit for the first power-up.
- This project may involve hazardous voltage. Work only with qualified supervision and proper isolation.
Gather, identify, and understand every part.
Use the standardized inventory, then open What's this? to learn each part's role, advantages, limitations, handling, and specifications.
What's this?Image, role, pros, cons, handling & specifications
Arduino UNO & Genuine UNO
A programmable controller that reads inputs, makes decisions, and drives the project's outputs.
What it does hereIt is the control centre and must use the documented board, pin map, supply, and logic level.
Buy / compare this part ↗Advantages
- Reprogrammable and reusable
- Large learning ecosystem
- Complex behaviour remains changeable
Limitations
- GPIO voltage and current are limited
- Some pins affect boot or communication
- Loads normally need a driver
Handling
- Disconnect power before rewiring
- Avoid static discharge
- Never power motors, relays, or pumps directly from GPIO
Specifications to verify
- Use the exact model, value, package, and rating listed for Arduino UNO & Genuine UNO; similar-looking parts are not always interchangeable.
- Confirm operating voltage, logic level, pinout, memory, USB interface, and maximum GPIO current.
What's this?Image, role, pros, cons, handling & specifications
Fairchild semiconductor
A named project component whose exact role is defined by the source circuit and build guide.
What it does hereIt performs a documented electrical, control, interface, or construction function in this project.
Buy / compare this part ↗Advantages
- Selected for this project
- Can be checked independently
- Supports modular troubleshooting
Limitations
- Substitutes may differ
- Generic names can hide variants
- Pinouts and ratings vary
Handling
- Compare the received part with the source
- Keep it labelled
- Do not force connectors or adjusters
Specifications to verify
- Use the exact model, value, package, and rating listed for Fairchild semiconductor; similar-looking parts are not always interchangeable.
- Confirm dimensions, ratings, connection method, polarity, and environmental limits.
What's this?Image, role, pros, cons, handling & specifications
Power MOSFET N-Channel
A semiconductor stage performs switching, amplification, regulation, rectification, or logic.
What it does hereIt controls current or signal flow at a defined point in the circuit.
Buy / compare this part ↗Advantages
- Fast and efficient
- Compact
- Can control larger loads from smaller signals
Limitations
- Pin order varies
- Sensitive to overvoltage and reverse polarity
- May need cooling or bias components
Handling
- Verify the datasheet pinout
- Avoid static and soldering heat
- Check notch, stripe, or flat-face orientation
Specifications to verify
- Use the exact model, value, package, and rating listed for Power MOSFET N-Channel; similar-looking parts are not always interchangeable.
- Confirm pinout, maximum voltage/current, dissipation, gain or forward voltage, and package.
What's this?Image, role, pros, cons, handling & specifications
MODULE LEARNING VIEWLDR, 5 Mohm
A sensor converts a physical condition into an electrical signal the circuit can measure.
What it does hereIt provides project input as an analogue, digital, resistive, frequency, or calibrated signal.
Buy / compare this part ↗Advantages
- Adds real-world awareness
- Can usually be tested independently
- Often supports calibration
Limitations
- Readings can drift
- Placement affects results
- Some sensors need warm-up or calibration
Handling
- Protect the sensing surface
- Observe supply voltage and polarity
- Keep signal leads away from noisy power wiring
Specifications to verify
- Use the exact model, value, package, and rating listed for LDR, 5 Mohm; similar-looking parts are not always interchangeable.
- Confirm supply range, output type, measurement range, accuracy, response time, and pin order.
What's this?Image, role, pros, cons, handling & specifications
N4007 - High Voltage, High Current Rated Diode
A passive component sets current, voltage, timing, filtering, or signal behaviour without adding gain.
What it does hereIts exact value and tolerance determine how the surrounding stage behaves.
Buy / compare this part ↗Advantages
- Simple and dependable
- Low cost
- Easy to measure before installation
Limitations
- A wrong value can stop or damage the circuit
- Ratings must not be exceeded
- Polarized parts require correct orientation
Handling
- Measure unclear values
- Observe capacitor polarity
- Avoid overheating leads while soldering
Specifications to verify
- Use the exact model, value, package, and rating listed for N4007 - High Voltage, High Current Rated Diode; similar-looking parts are not always interchangeable.
- Confirm value, tolerance, power or voltage rating, polarity, and package size.
What's this?Image, role, pros, cons, handling & specifications
LED (generic)
An output component turns an electrical control signal into light, sound, motion, switching, or displayed information.
What it does hereIt presents the circuit result or acts on the physical world.
Buy / compare this part ↗Advantages
- Makes system state visible
- Can be tested separately
- Supports clear troubleshooting
Limitations
- Loads may exceed controller current
- Polarity or driver direction can matter
- Inductive loads create voltage spikes
Handling
- Use the documented driver stage
- Check polarity and load current
- Add flyback protection for inductive loads
Specifications to verify
- Use the exact model, value, package, and rating listed for LED (generic); similar-looking parts are not always interchangeable.
- Confirm voltage, current, polarity, interface, driver requirements, and duty cycle.
What's this?Image, role, pros, cons, handling & specifications
PASSIVE LEARNING VIEWResistor 220 ohm
A passive component sets current, voltage, timing, filtering, or signal behaviour without adding gain.
What it does hereIts exact value and tolerance determine how the surrounding stage behaves.
Buy / compare this part ↗Advantages
- Simple and dependable
- Low cost
- Easy to measure before installation
Limitations
- A wrong value can stop or damage the circuit
- Ratings must not be exceeded
- Polarized parts require correct orientation
Handling
- Measure unclear values
- Observe capacitor polarity
- Avoid overheating leads while soldering
Specifications to verify
- Use the exact model, value, package, and rating listed for Resistor 220 ohm; similar-looking parts are not always interchangeable.
- Confirm value, tolerance, power or voltage rating, polarity, and package size.
What's this?Image, role, pros, cons, handling & specifications
Keystone 233 image 75px
A named project component whose exact role is defined by the source circuit and build guide.
What it does hereIt performs a documented electrical, control, interface, or construction function in this project.
Buy / compare this part ↗Advantages
- Selected for this project
- Can be checked independently
- Supports modular troubleshooting
Limitations
- Substitutes may differ
- Generic names can hide variants
- Pinouts and ratings vary
Handling
- Compare the received part with the source
- Keep it labelled
- Do not force connectors or adjusters
Specifications to verify
- Use the exact model, value, package, and rating listed for Keystone 233 image 75px; similar-looking parts are not always interchangeable.
- Confirm dimensions, ratings, connection method, polarity, and environmental limits.
What's this?Image, role, pros, cons, handling & specifications
V Battery Clip
A power component supplies, converts, stores, or regulates energy for the project.
What it does hereIt must provide the documented voltage, polarity, isolation, and sufficient current safely.
Buy / compare this part ↗Advantages
- Stable power improves reliability
- Current limiting protects first tests
- Regulation reduces resets and noise
Limitations
- Wrong polarity can cause immediate damage
- Underrated parts overheat
- Mains circuits require qualified supervision
Handling
- Measure output before connection
- Use a fuse or current limit
- Insulate exposed conductors
Specifications to verify
- Use the exact model, value, package, and rating listed for V Battery Clip; similar-looking parts are not always interchangeable.
- Confirm input/output voltage, current, polarity, connector, isolation, and thermal rating.
What's this?Image, role, pros, cons, handling & specifications
1N4004 - diode
A passive component sets current, voltage, timing, filtering, or signal behaviour without adding gain.
What it does hereIts exact value and tolerance determine how the surrounding stage behaves.
Buy / compare this part ↗Advantages
- Simple and dependable
- Low cost
- Easy to measure before installation
Limitations
- A wrong value can stop or damage the circuit
- Ratings must not be exceeded
- Polarized parts require correct orientation
Handling
- Measure unclear values
- Observe capacitor polarity
- Avoid overheating leads while soldering
Specifications to verify
- Use the exact model, value, package, and rating listed for 1N4004 - diode; similar-looking parts are not always interchangeable.
- Confirm value, tolerance, power or voltage rating, polarity, and package size.
What's this?Image, role, pros, cons, handling & specifications
PASSIVE LEARNING VIEW1N4007 - diode
A passive component sets current, voltage, timing, filtering, or signal behaviour without adding gain.
What it does hereIts exact value and tolerance determine how the surrounding stage behaves.
Buy / compare this part ↗Advantages
- Simple and dependable
- Low cost
- Easy to measure before installation
Limitations
- A wrong value can stop or damage the circuit
- Ratings must not be exceeded
- Polarized parts require correct orientation
Handling
- Measure unclear values
- Observe capacitor polarity
- Avoid overheating leads while soldering
Specifications to verify
- Use the exact model, value, package, and rating listed for 1N4007 - diode; similar-looking parts are not always interchangeable.
- Confirm value, tolerance, power or voltage rating, polarity, and package size.
Connect one verified path at a time.
Explore the named components and standardized signal flow, then use Source Check to verify exact physical pins, values, and topology before applying power.
Trace this circuit.
Touch Free Hand sanitizer dispenser using LDR: interactive parts, standardized terminals, responsive anchored wires, student explanations, and the original circuit reference in one shared system.
Trace before wiring
Follow power, ground, inputs, processing, and outputs in that order. Never guess a pin from package shape alone.
Connect with power off
Make short, labelled connections and share a common ground only where the schematic requires it.
Inspect every joint
Check continuity, polarity, adjacent shorts, and loose connections before the first power-up.
Open all source diagrams and build views 4 visuals
Confirm the hardware-only control path.
This project does not include firmware in the source. The circuit itself provides the required behaviour.
How to connect
- Match every controller label to the circuit view and source pin map.
- Join grounds before signal wires when separate low-voltage supplies are used.
- Keep motors, relays, pumps, and other loads on a suitable driver and external supply.
Common mistakes
Reversed VCC/GND, board-label versus GPIO-number confusion, missing common ground, and charge-only USB cables.
Troubleshoot
Disconnect loads, continuity-test one path at a time, then test with a current limit.
Software preparation
No IDE, board package, library, or firmware upload is required for this project.
If you add a programmable controller as an extension, document its pin map separately.
How to upload code
The original design is implemented entirely in hardware, so proceed after verifying the circuit and supply.
Assemble, deploy, test, and troubleshoot.
Use the complete source notes in build order, then pass the final checks before calling the project finished.
Build in functional stages
- Power and regulation
- Controller or processing stage
- Inputs and sensors
- Outputs and loads
- Enclosure and strain relief
Power up safely
- Inspect unpowered continuity first
- Apply the lowest safe current limit
- Measure supply rails before signals
- Add one load at a time
- Record expected and actual results
Work from simple to complex
- Confirm power, ground, polarity, and orientation
- Compare each pin with the source
- Test inputs separately from outputs
- Replace only one variable at a time
- Power off before every correction
Follow the documented instructions.
These notes come from this project's source and remain in their original order.
Project overview
Project build noteTouch-free hand sanitizer dispenser that automatically dispenses sanitizer utilizing LDR sensors and MOSFETs to switch the motor we designed this to be in accordance with COVID 19 coronavirus. Coronavirus (COVID-19) is spreading across the world. Nearly every country is experiencing the devastating effects of the Coronavirus. A Pandemic disease has been declared by WHO and many cities are in lockdown situations. Many people's lifestyles have been changed drastically. Globally, the WHO is advising disease control officials to maintain Healthy Hand washing and Sanitation Habits, but our problem mainly involves our physical contact when we do this. The virus can be spread by touching infected bottles of alcohol or sanitizers with infected hands. We will make an automated hand sanitizer dispenser by using infrared sensors to detect a hand, and an automatic pump will pour the liquid on the hand.
Many Arduinos automated liquid dispensers are floating around the web. Nevertheless, my aim is to keep it straightforward and inexpensive, so anyone can produce it. A simple transistor or MOSFET with an IR proximity sensor would probably be the easiest solution for this purpose, and it would drastically reduce the costs as well. Because no microcontroller is present, spills are unlikely to be controlled, but the use of a smaller nozzle may reduce the flow of liquid.
Components Required
Project build noteArduino UNO & Genuine UNO Fairchild semiconductor Power MOSFET N-Channel LDR, 5 Mohm
Fairchild semiconductor 1n4004. 1N4007 - High Voltage, High Current Rated Diode Fairchild semiconductor 1n4004. 1N4007 - High Voltage, High Current Rated Diode 09590 01 LED (generic) Resistor 220 ohm Keystone 233 image 75px 9V Battery Clip
Circuit Diagram
Project build noteA basic working principle of579 the automatic sanitizer dispenser is that when the distance sensor detects an obstruction within its line-of-sight, it will trigger the servo to turn on the sanitizer tap. When the person's hand gets in the way of the sensor and obstructs the line of sight, the Arduino board detects the low distance and instructs the servo motor to activate the sanitizer. Here is the Circuit Diagram of a sanitizer or alcohol dispenser based on IR sensor. No microcontroller is required. Automatic Dispenser
You built Touch Free Hand sanitizer dispenser using LDR.
You followed the full workflow from understanding the mission to testing the finished project. That is a real engineering achievement - well done.
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