Category: Bluetooth

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Connecting Touch sensor to Bluetooth Amplifier

TTP223 Touch sensor

First of all, I would like to wish everyone a Happy New year of 2019, this will be my first post of 2019. I hope you had a great start of the year.

I had discovered a capacitive touch sensor TTP223 which simulate a switch function by “touch”, it is using the capacitive of your hand or any other organic matter to allow the switch function. It can be configured to as “Toggle” or “On/Off”.

I recently post a review about various Bluetooth Amplifier that I had been testing. And the CSR8635 Dual 5W Bluetooth Amplifier had a particular interesting feature where you can “Skip” tracks, “Vol+” Vol-“, “Play/Pause” which also double up as “Pick up” call function. The problem with this is the Switch needs to connect each function to the “common” connection. So I am trying to experiment whether this will work using the touch sensor above.

Touch Sensor and Bluetooth Amplifier

The picture on the left shows how the functionality of the touch sensor. When the touch area is being touch, it will connect the I/O pin to the Vcc. While the Bluetooth Amplifier switch needs to connect the “Next” pin to the “common” pin. After some research the common pin is connected to Vcc. So I wonder whether I can connect the I/O pin straight away to the “Next” pin. So I had experimented using the circuit below, and it seems to work ok.

Connecting the Touch Sensor to Bluetooth Amplifier control pins

So I had connected a 10K ohm resistor to limit the current that flow from Vcc of the touch sensor to the Bluetooth amplifier. It seems to be working ok at this stage. I had connected 2 pin, the “Next” pin and “Play/pause” pin. Both seems to work ok.

You can see the final connection in the following picture.

Touch sensors connected to Bluetooth Amplifier controls

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Bluetooth Amplifier Review

Finally all my Bluetooth Amplifier arrived. So naturally I started to tinker with them. Started with the following

“Bluetooth 4.0 Digital 2.1 Class D HIFI Power Amplifier”

Bluetooth 4.0 Digital 2.1 Class D HIFI Power AmplifierThis is so far supposed to be the loudest amplifier boasting the following feature:

  • 100W subwoofer
  • Left and Right channel of 50W each.

I am rummaging through my junk box trying to find a power supply that can supply recommended 24V with 5A rating. I had none, I probably had one in the garage, so I opted using my trusted modified PC power supply which can only supply up to 11V. Bluetooth module works ok, I can connect using my iPhone, but trying to connect one of the speaker using my 8 ohm speaker doesn’t produce any sound. Well I will need to figure that out later.

Over the weekend I get my speaker out, it is a Mordaunt speaker which is capable of handling up to 100W. Once I connect everything, there is no sound coming out of the speaker, only after a few seconds later the sound came out. It seems that the circuit had some sort of protection for the speaker. The sound is quite clear and crisp. I will need to make the video recording in youtube and posted later.

Second one on the list is “TDA7492P Bluetooth 4.0 Digital amplifier”

TDA7492P 50W+50W Bluetooth
TDA7492P 50W+50W Bluetooth

This is boasting to be capable of output 50W+50W. So I connected this to 9V battery. The Bluetooth connect seamlessly and the “Play”, “Pause”, “Next” and “Previous” button works seamlessly with Music app in iPhone and Spotify. I connect my 8 Ohm speaker to one of the output, and it produce a sound and then it stopped. I am not sure what is going on, so after looking at the speaker, one of the wire came off, so I had to solder it back, but still no luck with the speaker sound. The next test is to plug in the headphones, this works brilliantly, so I can test the “vol +” and “Vol -” button, this seems to work ok too.

When I try to connect my Mordaunt speaker to it second time around, the bluetooth light doesn’t came up any more, so I can’t connect the iPhone and play any music. It might had been damaged, so I am contacting the seller at the moment, and I will post back later with the result.

The third one in the list is “CSR8635 Dual 5W Bluetooth 4.0”

CSR8635 Dual 5W BluetoothThis board is small but quite powerful, it had all the bells and whistle of the second board (TDA7492P). It also have the microphone connector which the second board doesn’t have. The board have the connection for “Play”, “Next”, “Prev”, “Vol+”, “Vol-“, “Mute” buttons. Given the size you will have to connect all the buttons yourself depends on what sort of speaker you are trying to build. You don’t have to necessary connect all the buttons.

I connected one of the speaker output to my Sony surround sound speaker. I connect it to the middle speaker. The connect the power supply to +5V. The red bluetooth light light up to allow connection. Again I use the Spotify app on my iPhone, and it connect seamlessly. The sound is quite crisp and clear.