I don't know if it's the perspective or not, but your antenna wire looks a tad short.
Otherwise, good job!
Tom
From the board to top it currently measures around 75mm. It keeps being shorter everytime the antenna breaks at the base from too much twiddling around. Once the boards are stable on a box I plan to add an SMA and an antenna, which I think is going to be an adventure on itself...
Yes, this is exactly what I suggested.In this case, you could use another NPN transistor and use it as a voltage follower. As a 'follower', the collector is tied to Vin. The base is tied to 3.3V, the emitter to the power supply of the relays. I did not check on how much current the relays draw, but if it's a lot (which it may be, being low voltage relays), then you'll need a Power NPN transistor and possibly a heat sink if you do plan to operate from 12V. You can calculate power as W = Ir * Vd, where Ir is total current of the two relays (in Amps), Vd is the voltage drop across the power transistor and is equal to Vin - (3.3-0.7) 0.7 is the voltage drop from the Base to Emitter. The advantage of this circuit is very low quiescent current when the relays are off.
Tried the voltage follower (although, I do not understand why it works, which is bad) and it worked as described. Got the reference voltage minus 0.7. But boy did the NPN heat up when power was going through (that was at 9V). When I went to the shop to ask around for a Power NPN and a heat sink, they recommended instead a voltage regulator fixed at 3.3V, together with a heat sink. It wasn't really expensive, so I went with that too (LM 1117T-3.3
http://www.ti.com/lit/ds/symlink/lm1117.pdf). Tested it and it works, 800mA is more than enough for the two relays. On the PDF there are some reference circuits using two condensers (a 10uF and a 100uF) on the input and output, connected to the ground. I guess the condensers keep the input and output stabilized.
At this point I have many questions. Is a voltage regulator just a voltage follower with a diode somewhere to tune the reference voltage and some heat protection? I have seen some diagrams on voltage followers on the internet and they all include a zener and some resistences to tune the reference voltage. Maybe a regulator is just a voltage follower with all these things packaged. Otherwise, is there any pros or cons on using one or the other?
The other question is: does the voltage follower (an NPN, maybe with a heat sink, with base connected to Vref, collector to the Vin and emitter as Vout, being Vout = Vref - Vd) have any other components involved (resistors maybe?). I want to know more about this circuit, it looks really useful. All things I found on the internet about this have zeners and resistors to tune Vref.
Attached the current revision of the 'master' board.