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Everything You Need to Know About Touch Sensor Circuits

What happens when one of your five senses fails to act properly? You won’t be able to taste your favorite food and smell your favorite flowers! In physics, sensors do the same job. Electronics need sensors so that they can detect what’s happening around them. Willem Von Simens invented the first-ever temperature sensor in the 80s. After this invention, other physicists brainstormed some new versions of sensors.

Later, the IR sensors came into being in the early 90s. Since technology has been advancing at a rapid pace, we all know that new inventions are more important than ever to stabilize the economy of countries. Today, critical domains rely on different types of sensors that detect humidity, smoke, and motion. Two broad categories of sensors are analog and digital. However, due to time constraints, we won’t be able to inform you about all types of sensors. So we have picked touch sensors to discuss in this post. 

What is a Touch Sensor Circuit?

Touch Sensors are incredible devices. We say this because you can use such sensors when you want to sense touch through your devices. Pretty obvious, no? They mainly work as regular switches when you touch them to turn them ON and OFF. These are important for their interface, which is intuitive. You can also call touch sensors tactile sensors. 

Features of Touch Sensor Circuit

  • They are easy to construct
  • They are affordable to produce
  • They can be produced in bulk
  • They are reliable to be used in the place of switches


Types of Touch Sensor Circuit

  • Capacitive sensors: These are for determining the capacitance of your devices and are mainly useful for small and portable devices. These are heavy-duty and endure abrasive damage to a large extent.
  • Resistive sensors: These sensors do not need any magical electrical characteristics for fine performance. Their job is to detect the pressure on any surface under observation. 

Principle of Touch Sensor Circuit

Touch sensors have a special working principle that they follow for natural performance. Their working principle is not different than that of a switch. When you will touch them, or they will detect some pressure, it will trigger the sensor, and it will perform just as a closed switch does. When you remove the pressure from the sensor, it will behave like an open switch. 

Working of Capacitive Touch Sensor Circuits

If we talk about capacitive touch sensors, they consist of a pair of parallel conductors. There is an insulator placed between these conductors. The conductor is actually our capacitor in this case. When you touch the sensor, the plates also interact with your touch. It will boost the capacitance value since our fingers are a conductive entity for the sensor. The default value of the capacitor is C0 which means it will change as there will be some change in the capacitance. 

Working of Resistive Touch Sensor Circuit

Now let’s discuss resistive touch sensors. In this case, their job is to detect the pressure, right? So, they will determine the amount of pressure on a particular surface so that they can sense the touch at the same time. There are also two conductors present in resistive touch sensors, like capacitive sensors. The plates have a layer of indium tin oxide that serves as an excellent conductor. However, there has to be a little space between these plates. There is also voltage present between these plates. When you apply the pressure on the surface, it will be sensed till the bottom of the plates. It reduces the voltage, and the sensor detects it impressively. This is how it uses pressure to detect the touch in general cases. 

Applications of Touch Sensor Circuit

If you still don’t know how touch sensors contribute to making our daily lives easier, we are going to discuss their applications in this section. Let’s see them below:

  • Mobile phones use touch sensors.
  • Consumer electronics and home appliances also work with touch sensors.
  • Touch sensors can be used to determine distance and pressure in the construction of devices.
  • Resistive touch sensors are useful for detecting little pressure and touch and have applications like touchpads and keypads. 

Demerits of Touch Sensor Circuit

Sometimes touch sensors can undergo glitches which can make them produce false results like false alarms. Due to this, it is important to understand their maintenance and use reliable and industrial-grade touch sensors every time. 

Best Touch Sensor Circuits


·       4017 IC 

There are some standard touch sensors that most producers rely on. One of them is the 4017 IC. We are going to see how it performs and what makes it so special to be a producer’s first choice!

  • There are normally 5-10 outputs in most of the ICs.
  • The output begins from pin3 and ends at pin11; however, this can be different as per the type of the IC.
  • This range contains all the outputs that play their role in transferring higher logic throughout the pins whenever a single pin detects a positive pulse.
  • The sequence does not necessarily have to end at the last pin, which is pin11. You can stop it whenever you want at any pin.
  • You need an extra pin15 so that when the sequence reaches this particular pin, the cycle must stop. The new cycle will be the same, and the sequence will follow the same order as well. 


One thing that induces the cycle is when you touch the plates. It creates a positive pulse that shows up at pin14 when you will touch it. Now, imagine you have turned ON the switch, and the higher logic is present at pin3. You have not connected the pin to anything yet. At the same time, you have connected the pin2 with the relay.

Right now, the relay is OFF. When you touch the plate, the positive pulse of pin14 will generate the output sequence that goes from pin3 to pin2 and turns ON the switch. It is fixed and does not change with the relay and the load. When you touch the plate for the second time, the order of the sequence will be pin2-pin4 which means it will persuade the IC to change the logic at pin3. It will turn OFF the relay and the load. 




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