Hi,
I got a question from a friend. Its way out of my knowledge, so i hope someone can shed some light ion this. This information is somewhat limited, but maybe enough to understand whats going on.
They have a electronic thermostat. It communicates (RF 433 MHz) with a heating system, via a MICROCHIP MRF49XA. Now the signal seems to be unreliable. Looking at the design we see a 220V AC wires being 'routed over' (there is a gap of a few mm) the RF chip.
The box is roughly 15cm x 8 cm. The power input is on the left, the power switch is on the opposite side. So the AC wires (2x) go into the switch (crossing the RF chip, and 'hanging' free inside the case), and then back to the PCB. On the PCB the 220 is switched via couple of relays to the heating elements, and there is a voltage regulator that powers the PCB). So, basically the 220V is passing the RF chip twice.
My question: could this 220V AC be a cause for interference (and with that unstable RF link)? Shouldn't you need to keep the AC lines as short as possible?
Moreover, and now it get really weird. The box has vent holes for cooling. For some reason, when you switch on the box, and wipe your hand over the box (touching the cooling holes), the signal is lost. This can be repeated with same result. My initial thought would due that you create some static electricity somehow. But maybe thats too far fetched? Curious if this 'effect' is something common?
Thanks!