TTP223 Self latching touch sensor switch problem

I purchased one of these from eBay:

It does not stay on when I press and let go. Doing some research, it looks like I have to solder together the two dots in "B" block to make it self latching. Problem is, my solder is not sticking to the board. Is it because my iron may be too hot?

Has anyone on here had any experience with these modules, making them self latching?

Can you melt solder on your soldering iron tip?

Tom.... :slight_smile:

:confused: Yes, but when I lift the iron away from the board, all the solder pulls off the board remaining in the solder tip.

“Problem is, my solder is not sticking to the board”
Usually caused by oxide on the pads preventing metal to metal contact. Wipe the pads clean with a little alcohol, then rub the pads with a clean pencil eraser. When they are bright put a small dab of soldering flux on the pads and the solder should adhere. Also, make sure the iron tip is clean and bright with just a touch of solder on it when you apply it to the pads. If you feel the iron is too hot unplug it and let it cool down for a minute, then clean the tip and apply a little solder to it and touch the pads.

What is your solder, what diameter, how long do you hold the tip on the pads before adding solder?

Tom... :slight_smile:

60/40 .032" roughly about half a second

But this is also swaying away from my original question. Or maybe not made too clear. By soldering the two dots together on the "B" pad on this board. Is this going to make it Latching?

By looking up the data sheet for the chip, it looks like tying pins 5 & 6 of the 6 pin chip together will place the output in Toggle mode, which I assume to be the "latching" operation you are inquiring about.

From this link, here's my interpretation of the operating modes:

Mode            I/O      B      A

Momentary High  __/‾\__  open   open

Latch High      ___/‾‾‾  short  open

Momentary Low   ‾‾\_/‾‾  open   short

Latch Low       ‾‾‾\___  short  short


60/40 .032" roughly about half a second

Not long enough, try 1 second, don't be scared to keep the iron there to get the pads up to temperature.

What is your soldering iron rated at and tip size?

Tom.... :slight_smile:

If you put solder onto the iron, and then touch it to the workpiece, you'll never solder anything (without adding flux). Solder on rolls is typically "rosin core" - that has flux inside the solder - but the flux burns off almost immediately. What you want to do is put the iron right next to or on the work piece, then add the solder.

Adding flux can be useful (any "no clean" gel flux is fine, it comes in syringes), but you don't normally need it if you are using the solder correctly. For common tasks I usually add more solder and remove the excess instead of using solder - that gets you the flux you need, and the rosin flux is less messy than the "no clean" gel flux, and you don't need to get out another tool.

Be sure to use a temperature controlled soldering iron - I use one set to 700F - much more than that, and the pads tend to lift off the board. A non-temperature controlled soldering iron is not suitable for electronics work, especially by someone who is not experienced with soldering (I had to use one in a pinch recently, and I had a horrible, horrible time and made a godawful mess of the board). I'm convinced that the majority of the "what am I doing wrong when I try to solder" posts are from using a non-temp controlled iron - I routinely see people post pictures of boards that look like they reworked them with a firebreathing dragon.