TTP 223 module is a popular capacitive touch-sensitive circuit, this module comes in an almost complete package i.e. IC TTP 223 and few other necessary components are mounted on a double-sided Printed circuit board, we just need to provide power supply and have to touch the capacitive touch area on the board and this will cause a change in output of the module.
This output can be used in various ways depending upon, for what we are using this module, let’s see some examples=
) we can drive a relay from the output of this module in such a way that one touch will activate the relay and another touch will deactivate the relay, and this relay can be used as a switch for any electrical device or appliance such as AC lamp, Fan, Cooler e.t.c.
) we can connect the output of this module to one of the inputs of Arduino or any similar microcontroller and this module will act as a touch-sensitive input for Arduino or microcontroller.
Using TTP 223 module
Using TTP 223 module is simple
Step 1 – Select the mode ( we will discuss it later )
Step 2 – Connect Vcc and Gnd to the Power supply
Step 3 – Use output as per your requirement
We will see this with an example:-
In the above image, we are using TTP 223 module to turn ON and turn OFF an AC Lamp. In this circuit, one touch will turn ON the connected AC Lamp and another touch will turn it OFF.
let’s see what we have done here, we have connected Vcc to +Ve of power supply and GND to the -Ve of Power supply, here we are using 5v dc power supply for this module.
Vcc and Gnd pin( or point) on module are used to provide power supply to the module.
we have connected base of the transistor to the output of the module and yes, there’s a resistor between base and output ..
we can also see a relay switch which is acting as an ON/OFF switch for the connected AC Lamp
Ok, now let’s see what’s going on how things are working
This module is designed to detect the change in capacitance of the touch-area.
When we touch the ‘touch area’ a noticeable change in capacitance is detected by TTP 223 and this IC TTP223 takes it as a command and in response to this command it changes its output state from ‘0 to 1’ or ‘1 to 0’ or we can say that, initially if the output is at LOW( 0 ) then a single touch will make it HIGH(1) and if it is at HIGH(1) then a single touch will make it LOW(0).
Ok, what are these 0 and 1 or HIGH and LOW here??
….. Here when we say HIGH or 1 that means there will be some amount of voltage present at OUTPUT this will be around 3.3v and when we say LOW or 0 then there will be 0v or a negligible amount of voltage present at the OUTPUT of module.
When Output is in High state, the voltage at this pin(output) is around 3.3v but the maximum current that this pin can deliver is very low, with this little current we cant drive a relay even if we are using a 3V relay. so we will take help of a transistor, for this we will use the transistor as a switch. -” A small amount of base current can turn this transistor ON” which means that when we apply a small amount of current to the base of transistor It allows a large amount of current to flow in the direction of Collector to Base.
Now look at the circuit..
On a single touch output will go HIGH which will turn ON transistor. so, relay will also get activated ,,,”” why?? how?? ……,, In the circuit, look at coil pins of the relay, one pin is directly connected to VCC i.e. +ve of Power supply and another pin goes to the Collector of Transistor.. When transistor is in OFF state It does not allow current to pass from Collector to Base and when transistor is in ON state current can flow from Collector to Emitter. So, when Output is HIGH, one of the pin of Relay is connected to Vcc and another gets connected to Gnd via transistor resulting relay gets turn ON.
In this circuit, we are using this Relay to turn ON and OFF the connected AC Lamp, So when relay gets activated the connected AC Lamp also gets ON.
TOGGLE MODES IN TTP223 MODULE
We can see two rectangular boxes marked as A and B on Module and inside each of these rectangles there are two solder pads, these solder pads inside the rectangle can be soldered together to get a different kind of output i.e. A and B on Module can be used to configure the different mode of the module.
Mode 1- When A and B both are not welded.
Output- Output will go high when we touch the touch area and it will be Low if we are not touching the touch area. Suppose if we place a finger over the touch plate then the output will become High and it will remail High until our finger is over the touch plate and on removing the finger the Output will become Low.
Mode 2- When solder-pads on A are not welded and solder-pads on B are welded together.
Output- In this mode, it will work like a touch ON Off Switch, one single touch will make Output High and another single touch will make it LOW.
In the above circuit( touch ON/OFF switch for AC Lamp) we are using TTP223 Module in this mode.
In this mode Initially, the output will be in low state i.e. when we give power to the module the output will be in LOW state.
Mode 3- When solder pads on A are welded together and solder pads on B are not welded.
Output- This mode is just opposite of Mode 1. In this mode, output will be Ideally HIGH and on touching the touch area it will become LOW and on removing the finger from the touch area it will again become High.
Mode 4- When solder pads on A and B both are welded.
Output- In this mode also module act as OFF/ON switch, one touch will make the output LOW and next touch will make it HIGH. This mode is similar to Mode 2 only difference is that, Initially Output will be High in this mode i.e. when we give power to the module the output will be in HIGH state.
If you are interested, here’s the circuit,
when we weld A, pin 4 of IC gets connected to pin 5 and when B is welded, pin 6 gets connected to pin 5.
Touch Plate for TTP 223
A small area for touch is provided on one of the sides of module, but we can connect an extra touch plate.
Look at below image
The size of touch-area on module board is very small, just size of a fingernail. In practical use, most of the time this tiny touch area may not be sufficient, to overcome this we can add an extra touch plate as shown in above image. A small to medium size metal plate can be used as this extra touch plate and should be connected to the point shown in the image using a small piece of wire.
For best result cut a piece of thin metal plate in circular form i.e. use a thin circular metal plate [The sensitivity will be maximum at the center]
When using TTP223 module without an external touch plate, sensitivity can feel balanced; not too high not too low. but after connecting the external touch plate the sensitivity can go much higher, It will depend on size of the touch plate.
To reduce this sensitivity we will have to add a capacitor between GND and Pin 3 of IC TTP223.
The value of this capacitor can be anything between 0 to 50pf. Higher the value of capacitor lesser will be the sensitivity of touch Plate and It will be most sensitive if no capacitor is used.
[some of the commonly available capacitors in this range are 10pf (100), 15pf (150), 22pf (220). 33pf (330), 47pf (470). numbers inside the bracket are code for the respective capacitor, sometimes capacitor code is written on capacitor in place of capacitor value]
Where to place touch Plate/ how to use it
It is a capacitive touch sensor so it is not necessary to directly touch it, we can place touch-plate under a non-conductive material such as Glass or Plastic and it will work when we touch over this extra layer of material. It is similar to touch used in our smartphones when we apply a protective film or glass on the screen, touch works over it.
Power Supply/ Voltage
TTP 223 works in a voltage range of 2.5v to 5.5v , any Power supply between this voltage range can be used.