Forget the button, this circuit uses a clever chip called the TTP223 to sense your touch.
Just like magic, touching a special pad can turn things on or off.
It is a simple way to create a touch sensitive switch for projects or even pranks.
Circuit Working:
Parts List:
| Component | Description | Quantity | Wattage |
|---|---|---|---|
| Resistors | 1/4 watt | ||
| 1k | 2 | 1/4 W | |
| Capacitors | |||
| Ceramic | 22pF | 1 | |
| 100nF | 1 | ||
| Electrolytic | 100µF 25V | 1 | |
| Semiconductors | |||
| IC | TTP223 | 1 | |
| LEDs | 5mm green | 1 | |
| 5mm red | 1 | ||
| Jumper | 1 | ||
| 3 pin header | 1 | ||
| Touch pad | 1 |
Here is a basic capacitive touch switch circuit designed for electronics enthusiasts.
Despite utilizing SMD components constructing the touch sensor switch is relatively simple since the entire circuit can be easily assembled on an SMD prototyping board.
At the core of the circuit lies an affordable ₹20 SMD chip the IC TTP223 commonly available in a BA 6 package.
The IC TTP223 is a touch pad detector IC that provides a single touch key intended to replace traditional direct key button switches with various pad sizes.
Its low power consumption and wide operating voltage are key features for DC or AC applications.
The circuit can be connected to any microcontroller through the 3 pin header J1.
A regulated 5V is recommended for VCC and the available output OUT becomes active high H when a finger touches the touch pad TP.
LED 1 green serves as the power PWR indicator while LED 2 red acts as an optional output status OUT indicator.
To enable the output status indicator if needed simply bridge the solder jumper JP1.
A prototype built on a general purpose circuit board using traditional leaded components with the TTP223 mounted on an SMD adapter PCB SOT 23 to DIP adapter was successfully tested using a small 10mm x 10mm copper clad board as the touch pad.
If you opt for this method strive to keep the length of the interconnection wire from the touch pad to pin 1 of the TTP223 as short as possible.
In some modules a 1k resistor is placed between the touch pad and pin 3 of the TTP223 but this configuration has not been tested at this time.
It is worth noting that the total loading of the touch pad size and capacitance of the connecting line on the circuit board can influence the sensitivity.
Therefore, sensitivity adjustment should be done according to the practical application using a larger and or thinner touch pad will increase the overall sensitivity.
Electrical Characteristic for IC TTP223
| Parameter | Symbol | Conditions | Value | Unit |
|---|---|---|---|---|
| Operating Temperature | TOP | -20 ~ +70 | °C | |
| Storage Temperature | TSTG | -50 ~ +125 | °C | |
| Power Supply Voltage | VDD | Ta=25∘C | VSS-0.3 ~ VSS+5.5 | V |
| Input Voltage | VIN | Ta=25∘C | VSS-0.3 ~ VDD+0.3 | V |
| Human Body Model | ESD | 4 | KV |
How to Build:
To build a Simple Capacitive Touch Switch Circuit using IC TTP223 follow the below mentioned connections steps:
Prepare the SMD Prototyping Board:
- Cut the prototyping board to a suitable size for your circuit layout.
- Ensure it’s large enough to accommodate the components and connections.
Mount the TTP223 IC:
- Solder the TTP223 IC onto the SMD prototyping board.
- Refer to the datasheet for the correct orientation.
Connect the Components:
- Solder the 3 pin header J1 to the board ensuring correct orientation and spacing.
- Solder the green LED for the power indicator and the red LED for the output status indicator if desired.
- If using the optional 1k resistor between the touch pad and pin 3 of the TTP223 solder it in place.
Add the Touch Pad:
- Cut a small piece of copper clad board to serve as the touch pad approximately 10mm x 10mm.
- Solder a wire from the touch pad to the appropriate pin on the TTP223 IC pin 3.
Finalize the Connections:
- Connect the VCC and GND pins of the TTP223 IC to the power supply.
- Connect the OUT pin of the TTP223 IC to your microcontroller or other circuitry.
Optional Output Status Indicator:
- If you want to use the output status indicator red LED, bridge the solder jumper JP1.
Test the Circuit:
- Apply power to the circuit and test the touch switch by touching the copper pad.
- The green LED should light up to indicate power, and the red LED if connected should indicate the output status.
Adjust Sensitivity:
- If needed, adjust the sensitivity of the touch switch according to your application.
- Larger or thinner touch pads may require sensitivity adjustment.
Mounting and Enclosure:
- Once the circuit is working correctly mount it in an enclosure or secure it to a suitable surface for use.
Note:
- This guide provides a general overview of building the capacitive touch switch circuit.
- Refer to the TTP223 datasheet for detailed specifications and circuit diagrams.
Conclusion:
To conclude, the capacitive touch switch circuit using the TTP223 IC offers a basic and cost effective solution for implementing touch sensitive controls in electronics projects.
Its simplicity and ease of construction make it a popular choice among hobbyists and DIY enthusiasts looking to add touch functionality to their projects without the need for complex mechanical switches.