I've got the TX and RX set up now on my desk. Most parts are soldered onto the PCBs, but I've left a few bits on a supporting breadboard, which I intend to mount into the cases later:
- TX LED - I'm using a common anode 2-colour LED for RF transmission indicator and fan indicator
- 9V power supply - I've rigged up a 7809 linear regulator to use for the RX+ until it's housed in a box with a plug-in switched-mode power supply
I've hard-coded the TX to send 20 degrees C and 50% humidity as not sensor attached. An SHT31 is attached to the RX+.
It all seems to be working pretty well
, but not quite perfectly 
Things I've noticed, and questions which I'd be very grateful if people could give feedback on:
- I realised after (grrr!) I'd put thermal grease on the heatsink and mosfet on the TX that it probably didn't need a heatsink with the fan being switch fully on and off, so heatsink is superfluous. Hmm. I suppose it matches the 7809, but I'm thinking the less metal to interfere with the RF transmission, the better.
- The RX+'s 3.3V linear regulator (IC3) and its metal pad (heatsink I assume?) on the PCB get very hot to the touch, too hot for me to touch for long - is that normal?
- The RX+ makes a bit of ticker-ticketty noise (a bit like a spinning hard drive seek noise) when it responds to an http request over the wifi network to serve up its weather page. It will probably be muffled a bit when the RX+ is in a box, hopefully not enough to be annoying in a quiet room, but again, is this normal?
- Finally, and perhaps most importantly, if I don't touch the system for a while, the "big digit" clock mode kicks in. If I then leave it for longer, a couple of hours, say, or overnight, when I come back, the display is corrupted. The text and drawn boxes etc are reversed and rotated 90 degrees from what they should be. Then, if I touch the screen:
- sometimes it redraws the summary screen and goes back to working fine again
- other times, it draws the new screens also rotated 90 degrees and reversed text. It does still seem to be working ok otherwise, though - I can cycle through the screens and see them being updated to the TFT - it's just all scrambled on the screen.
Had anyone else seen this and can anyone suggest a cause? I'd be grateful if anyone could help.
I'm going to try placing the TX further away, and see if the screen glitch still happens.
As you'll see in the photos, the ribbon cable is about 25cm long, and runs 10cm from the TX unit (could be interfering with the serial connection to the screen?). I've wired the screen up following instructions in Wizza's build thread (thanks!). I didn't make a connection to the SDO (MISO) pin on the LCD, as per Wizza.
- TX LED - I'm using a common anode 2-colour LED for RF transmission indicator and fan indicator
- 9V power supply - I've rigged up a 7809 linear regulator to use for the RX+ until it's housed in a box with a plug-in switched-mode power supply
I've hard-coded the TX to send 20 degrees C and 50% humidity as not sensor attached. An SHT31 is attached to the RX+.
It all seems to be working pretty well
, but not quite perfectly Things I've noticed, and questions which I'd be very grateful if people could give feedback on:
- I realised after (grrr!) I'd put thermal grease on the heatsink and mosfet on the TX that it probably didn't need a heatsink with the fan being switch fully on and off, so heatsink is superfluous. Hmm. I suppose it matches the 7809, but I'm thinking the less metal to interfere with the RF transmission, the better.
- The RX+'s 3.3V linear regulator (IC3) and its metal pad (heatsink I assume?) on the PCB get very hot to the touch, too hot for me to touch for long - is that normal?
- The RX+ makes a bit of ticker-ticketty noise (a bit like a spinning hard drive seek noise) when it responds to an http request over the wifi network to serve up its weather page. It will probably be muffled a bit when the RX+ is in a box, hopefully not enough to be annoying in a quiet room, but again, is this normal?
- Finally, and perhaps most importantly, if I don't touch the system for a while, the "big digit" clock mode kicks in. If I then leave it for longer, a couple of hours, say, or overnight, when I come back, the display is corrupted. The text and drawn boxes etc are reversed and rotated 90 degrees from what they should be. Then, if I touch the screen:
- sometimes it redraws the summary screen and goes back to working fine again
- other times, it draws the new screens also rotated 90 degrees and reversed text. It does still seem to be working ok otherwise, though - I can cycle through the screens and see them being updated to the TFT - it's just all scrambled on the screen.
Had anyone else seen this and can anyone suggest a cause? I'd be grateful if anyone could help.
I'm going to try placing the TX further away, and see if the screen glitch still happens.
As you'll see in the photos, the ribbon cable is about 25cm long, and runs 10cm from the TX unit (could be interfering with the serial connection to the screen?). I've wired the screen up following instructions in Wizza's build thread (thanks!). I didn't make a connection to the SDO (MISO) pin on the LCD, as per Wizza.