Introduction: DIY Automatic Hand Sanitizer Dispenser
In this project I will show you how to build an automatic hand sanitizer dispenser. Since the use of hand sanitizers has increased enormously with the Covid 19 outbreak, I thought it would be a good idea to make a decent non-contact dispenser that also looks presentable.
There are already several designs available on the internet. The difference from these designs is that with this design there is no contact between the alcohol and the pump. The air pump puts pressure on the bottle so that the liquid comes out through the other tube. In addition, it naturally also differs in appearance. The dispenser does not have its own reservoir but can be placed on the bottle of hand sanitizer. When the bottle is empty, the dispenser can be put on a new bottle.
The challenges were controlling the air pump and limiting the liquid flow. The air pump can be controlled with an Arduino, this would make the costs much too high. That is why I opted for a proximity sensor and a simple circuit with a PNP transistor and a resistor to control the pump. Limiting the liquid flow is achieved by the use of thin tubes and a small nozzle.
Parts & Materials:
Step 1: Making the Housing
I made the top and bottom of the housing using a self-made template.
The housing is made of thin plastic that I cut from an old plastic storage box. Copy the shape from the template onto the plastic plate. This can be done by tracing the shape with a marker or by sticking the template with adhesive tape. Cut the shape out of plastic twice.
Step 2: Install the Cap
Stick a cap to the bottom plate using a glue gun. For this you can use the cap of the bottle of disinfection or another cap of the same size.
Many bottles of disinfectant liquid have a DIN 28 cap, this format is used on many bottles (for example soft drinks) and is the most universal. You can also use a different size.
Step 3: Drill Holes for Tubing
Drill 2 holes slightly thicker than the tubing through the cap and bottom plate.
Step 4: Mount the Air Pump
Mount the air motor with some hot glue on the bottom plate. It is important that the 2 holes from step 3 remain free so that the tubing can still pass through.
Step 5: Mounting the Proximity Sensor
A small hole has to be made through the bottom plate for the sensor to see through. Hold the sensor where it should be and mark the hole. Cut out the hole with a Stanley knife. Now place the sensor and mount it with some hot glue.
Step 6: Mounting the Transistor
Mount the transistor with a little bit of hot glue on the bottom plate.
Step 7: Connecting the Resistor and Electrical Wiring
For the connection of the electrical part I have made a simple diagram that you can follow. Below are the connections written out again:
- Connect Resistor between Proximity sensor OUT and Transistor B
- Connect Proximity sensor VCC with Transistor E using red wire
- Connect Transistor C with DC Air Pump + using red wire
- Connect Proximity sensor GND with DC Air Pump – using black wire
The USB connections are described in the next step.
Step 8: The USB Connection
For this project I used a USB connection. The components used operate at voltages under 6 volts, so the USB connection (5 volts) was an obvious choice. Because the USB connection can be powered by a charger or by a power bank, it is also universal.
Use the male USB plug. Cut and strip the cable on the other side. Connect USB cable to the Proximity sensor:
- Connect Red wire with Proximity sensor VCC
- Connect Black wire with Proximity sensor GND
Step 9: Test and Calibrate
Connect the USB cable to a power supply. If the connections are good, the "power LED" (left) should now light up. The "Object detection LED" (right) lights up when the sensor detects something. By turning the tuning knob (trimmer resistor) you can set the range of the sensor. Set it to respond to a few centimetres away. After setting, disconnect the USB cable from the power supply.
Step 10: The Nozzle
Twist off the front of a ballpoint pen. This will be used as a nozzle.
Drill a hole through the bottom plate through which the screw thread of the nozzle fits, the nozzle should not be able to go all the way through. Place the nozzle in the bottom plate. Mount it with a little bit of hot glue.
Step 11: Assemble the Tubing
Connect a tube to the air pump outlet. Place the tube to the cap and put it in a little bit.
Put another tube in the nozzle and also pull it through the cap. This tube must have enough length to reach the bottom of the bottle. Secure all tubes securely with some hot glue.
Step 12: Assembling the Bottle
Hold the dispenser next to the bottle and determine how long the tube should be. Cut it to the correct length. Now place the dispenser on the bottle and tighten it.
Step 13: Finishing the Housing
Take the second plastic plate from step 1. Determine how high the enclosure should be so that all components fit inside. Cut a strip to this width and long enough to go around the entire top plate. Mount the strip all around to the top plate with hot glue. Make a recess at the back for the USB cable. Then mount the cap with a few drops of hot glue on the dispenser.
For the look I chose to spray paint the housing. Some hot glue was showing in some places and I had made a few scratches on it.
Step 14: Ready!
The automatic hand sanitizer dispenser is ready to use!
Tip: If the dispenser continues to drip for too long, this can be solved by making a (SMALL) vent hole through the cap.
I hope you enjoyed the project!
Stay healthy and see you soon!