Finally decided to automate my sprinkley system and settled on the PSF-B04 purchase via ebay.
Using the following guide as a start was able flash with Tasmota firmware:
Only to add to the above notes, instead of soldering necessary programming wires directly to the ESP8285 which can be challenging, GND, GPIO0 and 3.3Volts are easily accessible on other parts of the board as I’ve marked below , in addition GPIO0 and GND are conveniently position next to each other on a header.
Initially purchased two of the boards, one worked perfectly that is all 4 relays could be switched on at the same time but the other wouldn’t play ball. That is, switching on each individual channel on/off worked fine, but attempting to switch on all 4 relay channels would lose connectivity and device would reboot.
As I wouldn’t be switching on all 4 channels for my sprinkler system not an issue, but curious as to why this was occurring. Also purchased an additional board as a spare, but it also exhibited the same fault.
After eliminating several possible causes, power, shorts and PCB track variances between the boards nothing obvious stood out.
Curiously couldn’t understand the purpose of a mystery chip as shown circled above with all marking removed. All 4 relay output pins from the ESP8285 entered this chip and another 4 pins went to the digital input pins of the ULN2003, therefore not sure what the purpose of this chip performed and couldn’t see any reason why if removed and bypassed the board would still function the same….So I did!
Once mystery chip was removed and using the now free chip pads and wired as shown below was able to drive the ULN2003 directly without any issues and able to then switch on all 4 channels.
Hence still wondering what the purpose the chip serves but suspect it’s some sort of microprocessor/buffer with maybe a firmware bug as one of the three did work??
Be interested if anyone else has more info. on this chip.