Introduction: Entry Counter

Do you or any of your relative or friend own a shop or store. You you want to help them to grow their business. Then this project will surely help them to grow their business. By counting number of peoples entering in your store and through statistics you can calculate the average profit and profit earned on one person. Some major brands uses this tactic to grow their business and increase their profit. You can also use it in your house to count the number of people entering your house. So coming on the project. To count the number of people, it uses a laser trigger. A beam of laser falls on the photocell attached to linkit one. When any person enter your house, he or she obstruct the beam of light and the voltage output in linkit one decreases. This decrease in voltage indicates the linkit one to increase the count of number of people and the count is then displayed on a 16X2 LCD. You can see how many people passed from that point through a 16X2 LCD. This project will be a fun making a will help your businessman friend to grow in his or her business.

Step 1: Gather Parts

Here is the part list. Instead of laser module, you can use a normal laser pointer and for a photocell module, a normal photocell would also work. Here is the list:

  • Linkit one
  • laser module
  • photocell module
  • A 16X2 LCD
  • A box
  • A 3V supply if your laser module works on 3V
  • A 9V battery and a 5V voltage regulator if your laser module work on 5V
  • Jump cables
  • 10K potensiometer
  • Female header
  • and PCB
  • A battery for linkit one

Step 2: Hook Up the Battery

This is the first and the most basic step. Your linkit one board already comes with a 3.7V 1050mah li-ion battery. Just pick up that battery and insert the plug of the battery into the plug present on your linkit one board in left side. It will go inside only one way. To check your battery status or power level of your battery go in examples folder of your arduino ide and upload "LBattery" code to your board and open the serial monitor. Your battery level would be displayed there.

Step 3: Choosing a Enclosure

This time I thought of choosing the enclosure before making the project. This would surely help you to make your project properly. This will help you to choose a correct place for your component in the box. First stick your linkit one to your box. I placed my LCD and photocell outside the box so as to save spaceinside the box for other things like battery potensiometer. Stick your linkit one inside your box using tape and drill two holes in it. One for jump cables of photocell and one for wires of LCD.

Step 4: Connecting the Lcd

The LCD which I though would be most apporiate for me was a 16X2 LCD. The reason was that I was easy to use and handle. I connection was also not very though and the size and working of this LCD was best for this project. The code which I developed is based on 16X2 LCD. With a little change in it you can make it work for any different LCD. Here this LCD is used to display the number of persons passed from the gate. Solder you LCD on a perfboard. Don't forget to use a female header. Here are the connections of LCD:

  • pin 1-----gnd
  • pin 2-----5V
  • pin 3-----10K potensiometer middle pin
  • pin 4-----digital pin 12
  • pin 5-----gnd
  • pin 6-----digital pin 11
  • pin 11-----digital pin 5
  • pin 12-----digital pin 4
  • pin 13-----digital pin 3
  • pin 14-----digital pin 2
  • pin 15-----5V
  • pin 16-----gnd
  • potensiometer 1st pin-----5V
  • potensiometer 3rd pin-----gnd

Step 5: Attaching the Photocell

A photocell is used to receive the beam of laser. The pointer of laser light is kept in such a way that it falls on photocell. The photocell send command to linkit one that laser pointer is falling on it. When there is some obstruction in the laser beam, the photocell tells to linkit one that there is a obstruction a count of number of people is increased. If you do not have a photocell module, you can make one with a LDR. Here are its connections:

  • vcc to Linkit one 5V
  • gnd to Linkit one gnd
  • Vout to linkit one analog pin A0

Step 6: Making a Laser Module

I am using a laser module for a laser beam. If you do not have a laser module, you can use a laser pointer. There are some laser module which work on 3V and some work on 5V so make sure that you choose the correct power supply for your module otherwise you will damage it. I have a 5V laser module so I built a power supply for it using 5V voltage regulator and a 9V battery. The laser module should not be powered with Linkit one because it will be difficult for you to take care of the wire with would always be under the steps of various people. Make the module and stick it to your 9V battery using tape. Now your laser module is ready.

Step 7: Code to Check Your Photocell Value

When the laser beam falls on your photocell, it send a voltage output to linkit one.From that voltage output, we measure that when laser light is falling on it and when not. The laser light will not fall on it if it is obstructed by something. Here is the code to find what value does photocell send to linkit one when laser light fall on it. You can see it on serial monitor. You have to change your value from "512" in the main code:

int photocell=A0;

void setup()




void loop()


int value=analogRead(photocell);




Step 8: Upload the Code

This is the code which you should upload to your board to make this project work. Don't forget to change your photocell value" 512" value. Here is the code:


LiquidCrystal lcd(12, 11, 5, 4, 3, 2);

int photocell=A0;

int count=0;

void setup()




void loop()


int value=analogRead(photocell);





lcd.print("Count of people");






Step 9: Test

Now your project is ready and you surely want to test it. Go to your doorstep and turn on the laser module as well as your linkit one. On one side of the door, place the laser module and on other side place your counter i.e linkit one. Arrange the laser module in such a way that its beam falls on the photocell. Now walk in or out from your door and the count of people in your LCD will increase by one. If your count does not increase, check your connection with LCD and photocell.

Step 10: The End

Install this entry counter at the doorstep of your house or shop and count how many people entered your shop or home. This is the end of this instructable. Hope you liked it and enjoyed it and it was a fun making this project. For any problem or issue regarding the project comment below and I will try to solve it. THANK YOU

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