This project was created as a response to the UNDP challenge to provide low cost solutions in the fight against COVID-19. It works by simply detecting human presence and triggering a sanitizer to come on and sanitize the full body.FULL EXPLANATION OF WORKING
When steps into the device, it detects the person by means of an ultrasonic sensor. it then beeps and displays and LED light signifying stop. after 3 seconds, a stepper motor begins to rotate pulling up a sanitizer which has been depressed by a servo triggered at the time the stepper motor begins to rotate. when the motor reaches the top, another beep is heard and the stepper motor begins to rotate in the opposite direction after signalling the individual to turn the other side. after that, the last LED turns on telling the individual to leave the stand.HOW ITS MADE
Firstly, the frame where the on which the components will be mounted should be constructed. This can be constructed using wood or any other suitable structure. preferably the height should be 7 feet, width 3 feet and thickness 0.5 feet. the picture of a suitable frame
isometric view showing frame with location of components
next is to place the components as seen on the isometric view. Use what is best and suitable for the frame such as, gum, nails.
After placing the components on the frame and fastening the them, start to connect them together. we start with the stepper motor driver. you must make sure that the stepper motor and the breadboard are placed together on the top right as shown on the isometric drawing for easier connection. also make sure you have wire extensions for your jumper wires. the best way to do this is to cut the jumper wire in half and add a long wire in between.
Now we start to wire up.
For the stepper motor, we place the ULN 2803 ic on the breadbooard and wire up as shown on the screen shot. in the fritzing screenshot, you may notice I used a ULN2003 ic. it is for lack of the 2803, but they are basically the same.
then you must connect the stepper motor as shown below to the IC and then to the arduino. Unipolar stepper motor wirings vary in colour, so it is best to look up your own wiring and connect them accordingly. this would help greatly https://www.arduino.cc/en/tutorial/stepperSpeedControl replace the IC with your own IC, as they are both darlington arrays.
As you would notice from the fritzing picture, there is a 12v output that powers the circuit.
The next thing is that you prepare the sanitizer by placing the servo together with it and holding it by use of a gum. you must make sure that at position zero, the servo handle just rests on the aerosol sanitizer button. in my pictures, you may notice that there are rubber bands on the aerosol can, this is because my servo was not powerful enough to depress the can, so I added rubber bands to add force on the button, I recommend a stronger servo to eliminate the problem.
the next thing is to tie a rope from the rear end of the can and connect to the stepper motor rotating spindle. you need to find a spindle suitable for holding the rope. by now the stepper motor must already be mounted on the frame.
There are additional wiring not yet discussed that are shown here
Then next we connect the servo and buzzer, they both should have already been mounted at their specific spots on the frame
Notice that the buzzer location is overhead
Then build a suitable frame for holding the four LEDs in view of the person in the machine.
Connect the LEDs as shown the the fritzing screenshot below. Use a 100ohm resistor not 220 ohms to ground the LEDs. (You may notice that two to three of my LEDs are on at the same time, this is because I used two dual colour LEDs at the middle, so instead of turning of, they change colour)
Lastly wire up the servo with the arduino, make sure that your wire is long enough to accommodate the servo moving up and down with the aerosol can.
Lastly make a Loose ring of round the frame and the side of the aerosol and gum the aerosol to it. This will prevent the can from swinging around.
You can connect the 12 v supply of the stepper motor and the arduino together. that means you will use an extra 12v jack and connect them in parallel to the 12v supply. but you will have to connect a 4700uf capacitor across on the side of the arduino and diode to prevent the capacitor from sending current the other way. this help help maintain enough current to the arduino while the stepper motor is running.
If the device is to be operated outside, a 12v solar panel can be used and regulated using the battery regulator seen on the on the bill of materials.