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I’ve built an OpenSprinkler 3.0 from scratch, and just working around a few bits of errata that appear to be missing from schematics.
1) On the master PCB, the schematic shows 0.1uF for C4, but presume this is placeholder and is meant to be something else? I was getting odd RTC behavior until I noticed this. I’ve left it out for now, presume NTP will fix any drift anyway.
2) Looks like the resistor LT and RL aren’t populated on master PCB?
3) On DC driver PCB, I missed that the final drive FETS were supposed to all be AO3400, I ended up using BSS123 since this is what pops out of BOM given not all parts are labelled correctly in Eagle. That was kinda dumb on my part since should have known BSS123 can’t handle that much current, but just putting it out there in case it helps others that likewise get confused.
Is there anything else to watch out for? All seems to be working correctly otherwise.
Many thanks for your post. I was struggling with the RTC not working, and this made me aware of the issue and the trivial fix.
I am an electronic n00b, and this was my first project putting together a PCB&circuit, so I feel rather satisfied now that everything works!Here are a couple more hints:
On point 2), Resistors LT and RL, used in the current sensor circuit, must NOT be mounted on the PCB. They lift the ADC input voltage above 1V and permanently saturate it. Found it the hard way and ended up simulating the circuit before I understood the problem. Leave them out and the circuit becomes a rectifier of the input voltage as intended.4) The LM1117 linear regulator on the Master PCB is a fixed 3.3v model. I mistakenly bought an Adjustable model and it obviously did not work (BOM does not specify and not knowing there were different kinds of LM1117..).
The AC driver board worked fine by just following the schematic. There seems to be no issues there.
1) On the master PCB, the schematic shows 0.1uF for C4, but presume this is placeholder and is meant to be something else? I was getting odd RTC behavior until I noticed this. I’ve left it out for now, presume NTP will fix any drift anyway.
==> In the actual product, C4 is NOT populated. It’s there because it’s what the datasheet recommends, but it should be a very small capacitor that accounts for the PCB parasitic capacitance. It should definitely not be as large as 0.1uF, and in fact just leave it unpopulated.
2) Looks like the resistor LT and RL aren’t populated on master PCB?
==> These are not populated, you are correct. They are there to form a light sensor, because we use the same OpenSprinkler top-level circuit board for other purposes (RFToy WiFi version, a WiFi light sensor, and the WiFi thermostat that we’ve been working on). For OpenSprinkler, these are not populated at all.
3) On DC driver PCB, I missed that the final drive FETS were supposed to all be AO3400, I ended up using BSS123 since this is what pops out of BOM given not all parts are labelled correctly in Eagle. That was kinda dumb on my part since should have known BSS123 can’t handle that much current, but just putting it out there in case it helps others that likewise get confused.
==> You are correct it should be AO3400. Apologies for the inconsistency, I really should carefully check the component values before publishing them.
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