compatibility with Rasberry pi 3b+

[framar97]

I have a OpenSprinkler Pi running with a Raspberry Pi 3. Now I have to replace the model 3B with a new one. Can I buy a new model 3B+ ? Is it fully compatible? Or it is better if I take an old model 3B (without plus)?
Thank you, Francesco

[Ray]

Yes it’s compatible with 3B+. The only thing you should be aware of is that if you have USB devices connected to 3B+, the power supplied by OSPi may not be sufficient to drive those, so in some cases you may have to plug in a microUSB cable connected to a USB power source to provide additional power. Other than that, all software/hardware features are the same across all RPi versions.

[rszimm]

Ray, what am I missing regarding powering the 3B+. It seems the LM2596 supplies up to 3A of current. The Opensprinkler Pi hardware only draws minimal current from the 5V, so nearly 3A for the pi and peripherals seems like way more than enough.

[Ray]

The issue is not so much with LM2596, rather, it’s the fact that this is deriving power all from the 24VAC power supply, and it might not have sufficient power to drive both solenoids and RPi. For example, the 24VAC adapter we sell is only rated 500mA — so that’s about 15Watt, while at peak power RPi B+ could draw close to 15Watt, leaving no room for solenoids.

[bdmartens]

Hi All,
I’m a bit late to the party, and trying to put together the pieces.
I have an OSPi FirmWare 2.1.9(3), connected to a RPi 3B+ running on wifi.
I had some hiccups trying to update the software with git update /upgrade that I haven’t seen before, but those resolved with powering the RPi separately for that process. (never had any undervoltage icon, though)

I now have it running fine off the 24AC / OSPi board power, but no CPU load/solenoid load.

Looking at the above comment from @Ray, it seems that if I source an AC adapter rated for (much) higher current, it may be sufficient to power the RPi3B+ as well as the board – is this correct?
If not, then of the posts I’ve seen, it seems it may be required to un-solder a zero ohm resistor somewhere on the ospi board to decouple the pi from the springklerpi board – is this the case? Is there a more ‘official’ page from Ray/team directing how to best do this? If this were to be required, I’d be powering the pi from a simple USB ac-5vDC adapter.

Thanks
–
I’ve played with pi’s for the past 8 years, most recently largely limited to openhab (openhabian/raspbian). Otherwise, I like to tinker with microcontrollers and custom circuit boards, when I’m not climbing something or playing in the dirt.

[Ray]

Desoldering the 0 ohm resistor is the best way to decouple the 5V coming from OSPi with 5V coming from USB. However, in most cases it’s fine if you don’t desolder the 0 ohm resistor. The reason is that these different 5V power sources are all based on switching power circuit, which means there is a feedback loop that monitor’s the actual voltage on the 5V line — if the voltage is higher than the internal reference, that particular switching power circuit will turn off. So whichever 5V power source is outputting the highest voltage will take over. For example, if the USB adapter normally outputs 5.01V, and OSPi’s switching circuit normally outputs 4.97V, when they are put together, USB will take over as it has the highest voltage.

[Author]

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