RPi 3 power

[RonRN18]

I’m sure this is out there but I’m not seeming to find the correct key words. How much power is supplied by the OpenSprinkler board to power the Raspberry Pi? I believe I’ve seen something about people having power issues with the Raspberry Pi 3. I have disabled the HDMI port and have disabled the built-in WiFi and Bluetooth, as none of that is needed. I could disable the LEDs but the savings from that is tiny, so likely un-needed. This new OSpi is replacing my old OSbo. I ordered both a RPi3 and OSpi last week and OSpi arriving tomorrow. I’m hoping I have no power issues. Another little question I have is heat. I’ve never thought much of heat and the Raspberry Pi but when I ordered the RPi 3, it came with two heatsinks. I installed them because why not; I don’t see any harm in doing so. I’m guessing that the processing of OpenSprinkler barely breaks a sweat. As the RPi 3 is sitting on my desk, the CPU temp is 45.0C.. it will be warming in the garage and in a case but I doubt it will be an issue.

[Ray]

OSPi was originally only designed to deliver 500mA output current. In practice it can probably go up to 800mA, but the problem with RPi 3 is that it can draw a lot more depending on the processes running on it. So we recommend powering it additional using a USB adapter and microUSB cable.

Actually, more recently we found that the 3.3 ohm (3R3) resistor that’s inline on the 24VAC line is limiting the amount of output current. By bypassing that resistor, or replacing it with (or stacking) a 0 ohm resistor it will work much more reliable with RPi 3 without additional USB power. Because most of our RPis are already packaged it’s going to be a pain to replace these ourselves. So you can do it on your own if you have a soldering iron.

That resistor used to be a 500mA PTC fuse, but as soon as RPi 2 was released, we found that RPi 2 draws more current than RPi 1 and can sometimes trigger that fuse. So we replaced it with a resistor. After that, RPi 3 was released and that resistor also became a problem, so next time we will have to just remove it. It’s hard to keep up with the RPi releasing game, and the ever increasing power consumption 🙁

[ShawnHarte]

The RPi will have zero issue with heat, it will throttle the processor if it starts to become too hot. Even throttled it will run the OSPi just fine. If you really want to reduce power consumption you could under clock the processor quite a bit. Remember the RPi uses an processor that is used in cell phones. If you haven’t had to add a heatsink to your phone adding one to the RPi isn’t needed either. If fact some of the fancy colored, anodized aluminum heatsinks can actually cause overheating issues.

By underclocking my RPi3 and turning off HDMI and Bluetooth I was able to get it to run at just about 1.5A, much less than the 2.5A it requires with the base settings. I did it for a weather tracking project that automatically looks for and takes pictures of reported storms near my house. It gets some great shots of storm clouds, but I digress. It sounds like you know your way around the Pi so if you want to avoid the soldering iron just go for underclocking and you’ll be fine.

[lumihei]

Hi,
I have a version 1.3 of the OSPI board, so far always used Raspberry Pi 1 B. This now broke and I have to replace it – I would really like to replace it with a Raspberry Pi 3 and use that for multiple other things (WiFi AP in the garden, etc…).
As this is all in a box with underground cables attached, delivering the 24V and LAN, there is no (easy) way to get another 5V cable or 230V for powering the Micro USB. Also, the box is pretty crammed, there is not a lot more space available.

Therefore, powering the RaspberryPi 3 through the Ospi board may be my best (read: only) chance. The transformer I use to supply the 24V (hager ST312) delivers 25W, thus I guess that should not be the limiting factor.
Thus my question:
Can you help me identify what to change on board Ospi v. 1.3 in order not to limit the power delivery to the Pi? I did not find the resistor R3 you mentioned above.

Thanks for your support!!

[Ray]

Did you mean the OSPi 1.3 board broke? If so, it’s gotta be fixed first, right? Or did you mean the RPi broke? Anyways, the main limiting factor on OSPi 1.3 is an on-board 500mA PTC fuse. It should look something like this:
http://www.sellifuse.com/pptc/imges/2016_big.jpg
If you want you can just solder a small wire (or a 0 ohm resistor) across it to bypass it.

[lumihei]

Thanks Ray, will try to find that.

For clarification: the ospi works still fine, but the RasPi broke, thus want to replace the RasPi.

Thanks

[esigler]

In case anyone else is contemplating a new system with a Pi3, I thought I’d share my experience. So far I haven’t noticed any power issues with the stock OSPi board and a RPi3. I did disable the HDMI port, Bluetooth, and the Pixel desktop, but haven’t needed to modify the Ospi board.

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