What is this I2C PWM breakout board?

In one of my project, I needed more PWM output for servo control, but the board I'm using only have 2 PWM output, which mean I have two choice, either use a software base PWM (slow) or external PWM chip, I decided to go with external chip.

And the most common DIY I2C PWM chip is PCA9685 or TKC5940, and because PCA9685 is have free running feature (does not require constants update from micro microcontroller or CPU), we are going with this chip. 

You can buy prebuilt board such as Adafruit 16-Channel 12-bit PWM/Servo Driver.  But it cost over $15USD and mail to Malaysia will added few more dollar.  And because I such a cheapskate, I wanted to see how can I do to reduce the cost and also not spending a lot of time building my own PCB. 

First is to check if I can buy this chip locally, and Farnell/Element14 does carry them, and it about 9.42RM/2.49USD. Which I think is very reasonably price.

Second thing I do is to see if there is a TSSOP to DIP conversion board, if I can convert the pins to DIP, it make everything simpler, since I can build my own breadboard.  And ebay is your friend, I found 5 pieces TSSOP to DIP28 for $1.66 and free shipping.  Also got myself 50pin Gold plated male pin for $0.25USD.

For cost of $3.33, I have all the needed part, yes, it not as nice as the Adafruit I2C PWM board, but for 1/5 of the cost, I can live with that.

One of the main concern is how the hell are we going to solder TSSOP tiny pins? it so small, the fact is, it really easy to solder them, the trick is to solder all the pins at once and then clean it up later.

Here is the step:

• Hold down the part to be solder, I used glue.

• Next is to align the pins, you need a magnifier glass for this.

• Add solder to the pins, short is ok, will clean up later.

• Try to remove the excess solder by using your soldering iron as much as possible then use multicore wire and with a lot of solder flux to remove any remaining solder. Just put the multicore wire on top of the shorted area and hold down the soldering iron to transfer the solder to the wire.

• Once you removed all the solder, you will have a clean and short free board.

From the picture, you can see that you can get really good connection using this simple method.  And it save a lot of money too.

Very importance to visually check the pins to see if there is any shorts, I'm using a 3X magnify glass from Daiso, it only $5RM/$1.5USD.

The whole process only take 20min, and it reduce the cost by 5X!!  It really a wonderful learning. I hope you will try this out too...

Here is some useful information that you can get from datasheet.  Here is the pin information:

   Also here is the application example, I notice that Adafruit board have 220ohm as output protection.  So in  diagram below, you can replace the transistor, led and resistor to single 220ohm, will build the breadboard in my next update: