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TTP223 from the ground up!

A project log for Wheelchair EZ-Motion

Hacking wheelchairs / mobility scooters to make them more accessible to folks with more than 1 disability

criptastichackerCriptasticHacker 04/19/2023 at 04:340 Comments

Spent the past 2x days creating new PCB designs... Took a while because I decided to tweak all my FPC libraries for improved accuracy and also had to create the TTP223 footprint from scratch for Eagle (really? yes, I was surprised this common part isn't available).  At least the package is a common SOT-23-6L.

It's worth noting that this smaller package for the TTP223 (there's a much larger one in SSOP-16 package) loses some features.  It does not support:

1) Power on reset

2) Open drain output (a.k.a. hi-Z)

3) The press time is fixed at ~1.6ms

4) Doesn't have maximum on time (100 sec)

None of these are a significant loss though, so I think we're still in good shape.

we have here a 3D mockup of my 5X TTP223 touch PCB - specifically designed as a solder mount for my new slider PCB.  
I think this slider design should work well, but just to be safe I made a 3X version as well for shorter finger travel distances.

Disregard the silk and vias outside the board perimeter - these are edge castellations, but KiCAD 3D modeling doesn't know how to interpret them.


I also went ahead and designed a standalone version, since the cheapo models around the internet usually don't have:

1) Mounting holes

2) FFC connectors

3) Proper isolation of the projective capacitance pin

4) A footprint to tweak the projective capacitance (0-50pf variable cap is in the TTP223 datasheet).


Alright, I think I'm all set for capcitive touch stuff!  Next is onto breakout PCBs and magnet stuff :)

[more coming soon...]

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