DIY Automatic Sensor Hand Sanitizer
Automatic Hand Sanitizer Based on Distance Sensor (No Arduino Required)
Detailed description
During the epidemic, frequent hand washing is a very important protection work. Today we will introduce a very simple structure of automatic induction hand sanitizer, very practical!
Materials are also easy to obtain, if you have enough materials on hand, you can try this project. It can be used as a simple disinfecting tool when entering and leaving. It is really convenient to have such an automatic sensor hand sanitizer at home.
I’ve found that most similar products are built on Arduino. But for this simple project only transistors or MOSFETs are needed and the cost will be lower.
Although this project does not use a microcontroller to control the part that spills the liquid, I use a smaller nozzle so that the flow of liquid can be limited to some extent. There is a two transistor RC circuit in the project to solve the overflow problem.
tutorial
Component list
- Distance sensor × 1
- DC water pump × 1
- TIP32C PNP transistor × 2
- 1N4007 Diode × 1
- Thin water pipe × 1
- old glass jar × 1
- Ballpoint pen × 1
- Hand Sanitizer/Alcohol × 1
Bill of Materials
- Distance sensor x 1
- DC water pump x 1
- TIP32C PNP transistor x 2
- 1N4007 diode x 1
- thin water tube x 1
- old glass jar x 1
- ballpoint pen x 1
- hand sanitizer/alcohol x 1
main structure
1. Preparing
the jar Find a suitable glass jar or container.
2. Connect the tube to the motor
Use pliers to connect the end of the tube to the motor, the tube is the outlet of the liquid, heat it with a lighter to reinforce it, and finally use a snap-on cable tie to fully secure it.
3. Drilling
Drill two holes on the cover, which are the wire hole and the pipe hole.
4. Cut off the excess tube
as shown in the picture, use scissors to cut off the excess tube.
5. Insert the bent copper wire
In order to prevent the tube from sagging, insert the copper wire into the tube, so that the tube can maintain a certain arc. If you have a better way to replace it.
6. Making the Nozzle
Nozzle is made with the nib part of a ballpoint pen, you can also try other methods.
7. Attaching the sensor
You can use nuts and bolts to hold the sensor in place or directly use hot melt glue to mount it in place.
8. The circuit of the fixed transistor (no PCB board required)
project is very simple, using the transistor as a simple switching device. No need to use a breadboard or PCB. The TIP32C is powerful enough to handle a DC pump without heating up. Use glue to mount the transistor in place.
Schematic
This is how the components are wired as shown.
Why not just connect the pump directly to the digital output of the sensor?
For one thing, connecting the pump directly to the IR sensor could damage the LM393 op amp chip because the sensor’s digital output can only handle a few milliamps of current.
On the other hand, when no object is detected, the default digital output of the sensor is a high value, and when an object is detected, the default digital output of the sensor is a low value.
Therefore a logic inverter is required to make the distributor work properly. Use PNP transistors to solve both problems.
Modifications to the schematic
MOSFETs
were originally planned to use logic level MOSFETs instead of BJTs. MOSFET As a switching device, MOSFET can also handle more current. BJTs are typically used in active regions rather than saturated regions.
In the end, BJTs were chosen because BJTs are more common than MOSFETs.
A flyback diode
motor acts as an inductive load. A flyback diode is a diode connected across an inductor. It is used to eliminate flyback when the inductive load has a sudden rise in voltage spikes when the current of the inductive load is suddenly reduced or interrupted.
You can add common rectifier diodes such as 1N4007 or Schottky diodes to speed up the reaction. A quick measurement and observation revealed that the motor of a particular DC pump emits only a very small amount of back EMF due to the size of the motor and the inability of the shaft to stop immediately. Regarding the switch, a common approach is to add flyback diodes to electronic equipment. Although I didn’t have a problem with the lack of a flyback diode in this project, it’s a good idea to add one if you have one on hand.
Circuits and Components
1.
The connection of the circuit circuit is very simple. Solder the wires and components together as shown.
2. The installation of the USB male socket
project is to operate at a voltage below 6V. A USB power supply is the most common power supply and can provide 5V. Any USB cable will do, cut the other end of the wire and use wire strippers to strip the wire for later use.
3. Reinforce the electronic equipment
After the USB wire is soldered, you need to test whether the project is feasible. If there are no problems, its electronics can be reinforced with hot melt adhesive, which not only prevents accidental electric shock but also waterproofs.
4. Select the power adapter
as the project runs on USB power. You can use an AC USB charger or power bank to power the hand sanitizer. According to the capacity calculation, the power bank will continue to operate for several weeks. Using a power bank hand sanitizer will be lighter!
5. The distance threshold sensor for the calibration sensor has
a tuning knob (trim resistor). You can use a flat-blade screwdriver to make adjustments. The tuning knob limits the detection threshold range. Turn it to make the adjustment sensor more sensitive or dull, just adjust it to the right position.
Add hand sanitizer/alcohol
Now, you can add whatever sanitizer you need in it, and it can also be used as an automatic dishwasher. The specific use is up to you.
Finish
So far, the project has been completed, you can test and use it!
