Laser and infrared operated digital object counter

This is a basic digital object counter for electronics beginners. Previously, I was selling this as a do-it-yourself kit. Now, it is sold as a fully assembled kit because several customers complained that it takes a lot of time to build and some customers could not make it.


If school teachers want to buy a do-it-yourself(DIY) version of the kit, they can contact me.


The kit is based on the CD4026 decade counter. The counter module counts from 000 to 999 and it only counts up.


The infrared transmitter module is directed towards the infrared sensor (on the counter module) and when the infrared ray falling on the sensor is obstructed, the counter module gets triggered and increases the count. In the same way, the laser light module is directed towards the photoresistor on the counter module and when the light is obstructed, the counter increases the count.


The infrared sensor is sensitive to tube light, CFL light, and sunlight and any other sources light that generates infrared. However, if the device is placed anywhere avoiding any unwanted infrared interference, it gives 100% accurate results.

There is no false triggering or false counting. It always counts accurately provided that there is no infrared interference.


The kit has been designed to allow the users to use either infrared or photoresistor. There is the possibility of using both sensors at the same time also. The 3 pin female header allows the users to remove the infrared sensor if the user wants to use photoresistor only.


The counter module comes with a micro USB connector module so that the users can power it up with a 5V DC adapter, for example, using a mobile phone charger or by connecting it to a computer.


The laser module also has a micro USB connector module which also works with DC 5V.

The infrared transmitter module has to be powered with a 9V battery.


How does the digital object counter work ?


The counter module has a NE555 timer-based monostable circuit that gets triggered whenever the infrared light (falling on the infrared sensor) or the laser light (falling on the photoresistor) is interrupted. The output pin 3 of the NE555 is connected to one of the CD4026 chips (via PC817 optocoupler) and the other two CD4026 chips are further connected together. Whenever the timer gets triggered, it sends a pulse to the CD4026 decade counter, which in response to the trigger, starts counting. The NE555 timer on the infrared transmitter module is configured in astable mode giving 38Khz infrared signal to the sensor.


The kit is available at BuildCircuit Store