Monthly Archives: August 2014

Adafruit 2.8″ Capacitive Touch Screen

I received my Adafruit 2.8″ capacitive touch screen a little while ago and have been messing around with it. I followed the Adafruit guide found here and was able to get it working. I also find some instructions here to get the Pi to boot directly to the screen. The instructions essentially boil down to the following:

Install xserver-xorg-video-fbdev (My Raspbian image already had it installed)
sudo apt-get install xserver-xorg-video-fbdev

Create a config file with following contents in /usr/share/X11/xorg.conf.d/99-fbdev.conf containing the following:
Section "Device"
Identifier "myfb"
Driver "fbdev"
Option "fbdev" "/dev/fb1"
EndSection

After doing the above, my Pi boots to the piTFT screen. I then went about and set TightVNCserver to autostart.

My next steps include getting my basic Python TKinter app to load on boot and fill the screen. Once I have the screen functioning the way I want it for the Thermostat project, I’ll verify powering from the 24V AC line still works OK.

TQ2SA-L2-5V Relays

I verified the relays I purchased work as “expected”. I hadn’t realized I ordered latching relays but I did. No big deal, they’ll work but non latching would have been simpler as I will now need to utilize 2 GPIO ports per relay. I also did a little more research into wiring of my particular AC unit and believe I’m getting a better grasp on how it operates. More to come on this as I continue testing. On a side note, Adafruit got the touch screen in stock I wanted so I ordered that along with a but buttons and a case that may work for what I want with a few tweaks.

HIMS Thermostat Relays

Didn’t get too much done tonight but I soldered some leads off of one of the surface mount relays I purchased from Jameco. Hopefully I’ll be able to do some minimal testing with it in the next few days to verify it works as I think it should.

HIMS – Thermostat

Well, the first part of my thermostat project is coming together. I’ve validated that I can power the Raspberry pi from a 24V AC source with what I’d consider minimal additional components. I’m still waiting for Adafruit to get the capacitive touch screen in stock but I believe this setup will be capable of powering the entire system. I created a forum thread for a brief “how to” on this topic. You can find it here. The next thing I will be testing are some relays that just arrived from Jameco which I’ll use to signal the HVAC unit to come on or shut off.

 Here is a schematic and my bench top setup:24VAC_to_5VDC_Schematic24AC_TO_DC