Monday, February 26, 2024

Simple Touch-Free Automatic Handwash / Sanitiser Dispensing Machine

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We are passing through a critical time and the life of everyone has been impacted due to the wake of COVID-19 pandemic.

Corona virus disease 2019 (COVID-19) is a respiratory disease caused by the SARS CoV-2 virus which is highly infectious in nature. Originated from China, it has spread in more than 212 countries and killed more than 2 lakh people all over the globe. Our country is also fighting this war against this invisible enemy and more than 9,500 people have already died out of confirmed 3,33,000 plus corona patient for this corona/COVID-19 disease as on mid of June 2020. Though the affected countries have declared lockdown and stopped everything except basic activities still the COVID-19 virus is spreading for its tremendous capability of transmission from one person to another. Touching of object contaminated by COVID-19 virus affected person is one of the easiest ways of spreading corona virus. A person may get COVID-19 by touching a surface or object that has SARS-CoV-2 on it and then touching their own mouth, nose, or possibly their eyes. 

As per WHO guidelines, our hands are to washed frequently at intervals using soap/ liquid hand wash, as soap kills the corona virus dissolving it’s outer lipid (fatty) bilayer. But if the liquid soap/ hand wash bottle itself get contaminated by the COVID-19 infected person while taking the soap / hand wash from it, there is potential hazard of corona infection for next users. It is more applicable in office, hospital, canteens, shop floors etc. where hand washing facility is availed by many people. To overcome this challenge and his sincere effort to contribute something in the nation’s fight against corona, presented here one simple & innovative TOUCH-FREE AUTOMATIC HANDWASH DISPENSING Machine. Alcohol based sanitizer also kills the Corona virus and it’s bottle also get contaminated where many people use the same bottle. This machine can be used for liquid hand wash as well as alcohol based sanitizer provided the material should be thin enough to pump. Jell type thick sanitizer or hand wash cannot be used for this machine. 

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Using discarded and waste house hold materials like wooden drawers of broken table, plastic bottle, pet jar, fruit juice packets, plastic pipe used in aquarium etc. and some electronic components, this useful gadget has been made which is an effective tool to fight against spreading of corona virus. It has a container to store the liquid HANDWASH, a submersible pump, a DISPENSING pipe, Infra-Red proximity sensor based pump control circuit, power supply & indicator LEDs. When hand is placed below the DISPENSING pipe opening, the pump is actuated by the proximity sensor and liquid soap/HANDWASH is dispensed on hand automatically without touching anything. Thus avoiding direct contact with the DISPENSING Machine, spread of infectious corona virus is prevented. Cost of this machine is quite low but the utility is very high especially in present crisis of corona pandemic.

Author has made various models (few shown below) of this unit depending upon the availability of resources and has donated these Touch Free Sanitizer / Hand wash Dispensers to some Government Hospitals & Offices for the use of people visiting hospital/office and frontline warriors of corona war i.e. doctors, nurses & health crews etc. of Hospitals.

Fig.1: Author’s Prototype

Components Required

  1. IR Proximity Sensor module
  2. 220 volt AC to 5 volt, 1A DC power supply module
  3. 6 volt DC mini submersible pump 
  4. 10 mm dia plastic flexible pipe
  5. Plastic container for storing the liquid soap/ liquid sanitizer
  6. Outer Casing (wood/ card board)
  7. BC 547 / BC 549 (NPN/ PNP) Transistor
  8. 5 mm Green LED
  9. 100 Ohm Resistors
  10. 5v Relay
  11. 1N4007 Diode
  12. Wires
  13. Level showing LED / strip (optional)
  14. Piezo buzzer (optional)
Fig.2: Type-1 IR Proximity Sensor (local made)
Fig.3: Type-2 IR Proximity Sensor
Fig.4: 220v ac to 5v dc 1A Power Supply module
Fig.5:  Mini submersible pump

Circuit and Working

Block diagram of working principle of the Touch free automatic Sanitizer/ hand wash dispenser is shown in Fig.6: 

Block Diagram

Fig.6: Block diagram of working principle of the Touch free automatic Sanitiser / hand wash dispenser 

Whenever power is ON, the IR LED of IR Proximity Sensor continuously glows. In case of any obstruction to it like by placing hands in front of it, IR ray is reflected and falls on IR Diode. Falling of IR on IR diode causes changing of output status from either low to high or high to low depending on the type of IR Sensor. Author has used 2 types of sensors in different models. For type-1 sensor shown in Fig .2, LM358 based OPAMP comparator output changes from Low to High during any obstruction infront of IR LED & Photo Diode pair. This High signal is fed to the Base of NPN Transistor BC 547/548 via a 100 Ohm Resistor and a 5 mm Green LED. Thus the Transistor is switched On and 5v Relay is picked up whose coil is connected between +5v & Collector of Transistor. Emitter of the Transistor is kept grounded. When the Relay picks up, the Green LED glows and gives indication for operation of the relay and pump. Pump is connected to 5 volt DC supply via the NO contact of the Relay (Fig.7 Circuit Diagram). As soon as the Relay picks up, the mini submersible pump works and delivers liquid soap or sanitizer on hand through the plastic delivery pipe.

Fig.7: Circuit diagram with type-1 IR sensor

For type2 IR Proximity Sensor, shown in Fig.3, the output of the Comparator / Sensor remains On all the time. In case of obstruction i.e. placing of hand infront of it, the output changes from High to Low. This Low output signal is used to switch On the PNP Transistor BC 557/558 feeding to its base via 100 ohm Resistor and 5 mm Green LED. But here LED is connected in opposite direction. In this case, the relay coil is connected between Collector and ground and Emitter of Transistor is connected to +5v (Fig.8 Circuit Diagram). 

Fig.8: Circuit diagram with type-1 IR sensor

In both the circuits, One LED and 9v small buzzer can be connected parallel to Pump for audio Visual Indication of operation of Pump. Moreover for visibility of liquid level in the liquid container, one White LED or a 4 V LED strip may be connected directly to 5 volt supply. But in case of LED strip, a separate power supply is to be used otherwise Pump will not run as the capacity of our power supply module (shown in Fig.4) used for the operation of the circuit is low (around 1A).   

In both the cases a diode (1N4007 is to be used in reverse bias across the relay coil. It works as free wheel diode and bypasses the surge voltage during chopping of inductive load of relay coil and saves the transistor from damage.  

In case the readymade IR Proximity Sensor is not available, it can be made easily around Dual Comparator IR LM358. Circuit of IR Proximity Sensor has been shown in Fig.9. Here only one OPAMP of the IC LM358 has been used as comparator. IR LED glows continuously. In case of obstruction and thereby falling of reflected IR ray, causes flow of charges in photo diode, which in turn causes disturbance in balance between Inverting & Non Inverting Terminals and changes the Comparator output status from Low to High. That signal is used to switch the NPN transistor BC 547/548 and the Pump as described earlier.

Fig.9: Circuit of IR Proximity Sensor

Construction

In case the readymade IR Proximity sensor is not available, the circuit of the IR sensor can be built on zero PCB. For readymade sensor no PCB is required for connecting Power supply and Relays. All may be connected using wires and can be kept hidden inside the Outer shell of the dispenser.  

Above mentioned Pump based circuits will work for liquid soap and liquid sanitizer only. This mini submersible Pump is not that much powerful to pump thick Jell type sanitizer or hand wash soap. For using thick jell of Sanitiser or Hand wash, another model of Touch free Automatic Sanitiser / hand wash dispenser may be made using same IR Proximity Sensor. In that case a gear motor and cam system is be used to press the hand pump of the sanitizer/ hand wash bottle instead of actuating the submersible pump. Author’s prototype has been shown in Fig.1.

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