Has anyone grabbed the 12v rail and powered a Raspberry Pi?  

Re: Has anyone grabbed the 12v rail and powered a Raspberry Pi?

Hi there, I think it's been already discussed somewhere else in the forum. There is an additional connector under the black PETG cover of the PSU where you can attach a couple more wires for getting +12v and ground. You can use a step down like this ( http://www.ebay.co.uk/itm/401265883616 ) and get 2A, (3A peak) out of it.

It should be safe enough, since the PSU remain sealed.

Re: Has anyone grabbed the 12v rail and powered a Raspberry Pi?

yep, only 4 of the 6 terminals are already used, so there are two left "for other purposes". simply attach an ordinary buck converter, or such a 2x 5V USB Adapter, designed for cars, bikes or boats with 12-24V board supply voltage.... as i did at my own clone.

Re: Has anyone grabbed the 12v rail and powered a Raspberry Pi?

Awesome! Thank both of you for the info. One last question, how do I get the black bottom off the PSU without unsealing the PSU?

Re: Has anyone grabbed the 12v rail and powered a Raspberry Pi?

Interesting you should ask. I just did this yesterday.

I installed one of these in a reprinted/modded power supply holder.

https://www.amazon.com/gp/product/B01HPSYBKE/ref=oh_aui_detailpage_o04_s00?ie=UTF8&psc=1

I located it on the side with the plug and power switch, moved to power switch to the back. Powering my Pi just fine. Of course it's only been a day 😀

I haven't posted the STL files anywhere yet.

Re: Has anyone grabbed the 12v rail and powered a Raspberry Pi?

Yeah so I got this today:

https://www.amazon.com/gp/product/B00BMIVFK8/ref=oh_aui_detailpage_o01_s00?ie=UTF8&psc=1

I took the bottom off the PSU, but I haven't installed it yet as I don't have a spade/fork crimp terminal handy. I'm going to pick one up tomorrow. I'm so impressed how this PSU is laid out! It's nicely labeled and conveniently has an extra terminal.

I'm not sure what sized spade terminal to get, but I'll just have to get a few sizes.

Re: Has anyone grabbed the 12v rail and powered a Raspberry Pi?

Now I feel like a dope. This morning it dawned on me that in order for this setup to work I'd have to keep the printer plugged in and on the entire time. Currently I have a Wemo switch that I turn on/off via a octoprint. This works great, except I have no outlets close enough for the power cable so I'm using a battery pack at the moment. Additionally I wanted the setup to be as clean as possible which was why I was investigating pulling power from the PSU. I completely forgot that when the Wemo switch is off the PSU won't get any power either (DUH!)! I'll end up cutting the power to Octoprint as well as the printer.

So now I'm back to square one. How have others solved this? I want a clean solution where Octoprint can stay powered and I can turn the printer on/off at will.

Re: Has anyone grabbed the 12v rail and powered a Raspberry Pi?

So now I'm back to square one. How have others solved this? I want a clean solution where Octoprint can stay powered and I can turn the printer on/off at will.

I have 2 MK2's that are powered by the printers psu but I have a 3rd printer that I ended up using the standard pi power adapter to accomplish what you want to do. The pi and the printer are both plugged into a UPS.

Re: Has anyone grabbed the 12v rail and powered a Raspberry Pi?

I think I figured out how I want to do this, but I need some help in understanding relays more. What I'm thinking about doing is have the PSU always on and splice a relay between the two 12 volt rails going to the mini rambo. So my question is, the 2 channel 12v relay below, am I understanding relays correctly that it will support 12 volts on each channel? If yes, then my plan would work correct?

https://smile.amazon.com/SMAKN-Channel-Isolated-Optocoupler-Trigger/dp/B00PFA83RW/ref=sr_1_1?s=electronics&ie=UTF8&qid=1492706180&sr=1-1&keywords=2+channel+12+volt+relay+module

EDIT: I believe I'm misunderstanding what the 5v or 12v means in the name. Correct me if I'm wrong that isn't the max voltage the module can support, it's the voltage needed to trigger the switch.

So I'd really need this:
https://smile.amazon.com/SunFounder-Channel-Optocoupler-Expansion-Raspberry/dp/B00E0NTPP4/ref=sr_1_3?s=electronics&ie=UTF8&qid=1492708774&sr=1-3&keywords=2+channel+relay+module

Re: Has anyone grabbed the 12v rail and powered a Raspberry Pi?

those relays are rated at 10amps, your heatbed may draw around 15 amps.

I suspect the relay will not normally be used to switch or break the rated current as I expect the switching will occur when the printer is idle. so you may get away with over rating the contacts.

as far as I know, the two feeds tot he Rambo are handled separately on the Rambo, so there is no current sharing to reduce the heated bed load on one of these relays. you may find the PCB racks inadequate for the proposed current load...

just things for you to look out for. you never know the board may be over engineered... however a couple of amazon customers commented on poor connector quality on the second item mentioned.

best wishes, Joan

Re: Has anyone grabbed the 12v rail and powered a Raspberry Pi?

Thank you! I didn't consider that! jeez this is why I'm asking all these questions. So 15 amps minimum, got it.

Is there anything else I need to consider?

EDIT: This appears to be what I'm looking for:

https://www.amazon.com/KKmoon-2-channel-250VAC-Module-Trigger/dp/B01N406CCJ/ref=sr_1_1?ie=UTF8&qid=1492728427&sr=8-1&keywords=2%2Bchannel%2Brelay%2Bmodule%2B30A&th=1

Supports 30 amps and triggers between 1.5-5v. Can anyone do me a favor and confirm this will work for me? I've never used relays before and I'm also an electrical engineering newbie. I still have a lot to learn!

Re: Has anyone grabbed the 12v rail and powered a Raspberry Pi?

I posted my modified power supply box to Thingiverse. It allows the installation of a USB socket connected to the 12V rail of the PS.

http://www.thingiverse.com/thing:2264196

Re: Has anyone grabbed the 12v rail and powered a Raspberry Pi?

Awesome job! What did you print the base in? I think the original comes on PETG, not sure if PLA would matter or not.

Re: Has anyone grabbed the 12v rail and powered a Raspberry Pi?

I printed it in PETG but I agree that PLA would probably be fine. Not much heat below the power supply.

Re: Has anyone grabbed the 12v rail and powered a Raspberry Pi?

For the person looking to implement a relay, you may want to try something like this https://smile.amazon.com/BIQU-Power-Module-Expansion-Printer/dp/B01HEQVQAK/ref=pd_bxgy_147_img_3?_encoding=UTF8&pd_rd_i=B01HEQVQAK&pd_rd_r=GWVY5TR09NDWWCBSPVCX&pd_rd_w=Onert&pd_rd_wg=DxGbl&psc=1&refRID=GWVY5TR09NDWWCBSPVCX#feature-bullets-btf

It's solid state and designend for the purpose. Rated to 25 Amps.

Re: Has anyone grabbed the 12v rail and powered a Raspberry Pi?

I've powered my OctoPi directly from the Rambo board. Wire from the socket indicated by the purple to the GPIO pins 4 and 6 on the Pi

Re: Has anyone grabbed the 12v rail and powered a Raspberry Pi?

I've powered my OctoPi directly from the Rambo board. Wire from the socket indicated by the purple to the GPIO pins 4 and 6 on the Pi
...
💡 hmmm... i wouldn't recommend this, because it puts additional load to the 5V voltage stabilizer, which will probably lead to a slightly different voltage when the raspberry is on or off. even so that the voltage change will remain in the limits of the circuit (+/-5%) will the change affect the sensitivity of the p.i.n.d.a. probe.

➡ so you'll probably encounter that different live-z adjustment values are required, depending on whether the OctoPi is running or not.