Easy/tidy way to supply power for mini-bartop

[GSXRMovistar]

Working on my current project which is a mini-bartop driven by a Raspberry Pi. I need a 5v 2.5 amp for the Pi and a separate 12v feed for the 9” display it is hooked up to.

I wan’t to avoid having two external power adaptors going into the cab and due to the small size of the machine I also don’t want to have both power adaptors being housed internally and feeding in a mains supply.

I was thinking I could maybe feed 12v into the cab and then power some sort of USB hub which the Pi could hook up to but from those that I’ve looked at most don’t seem to provide the required 2.5 amps.

I’m capable with a soldering iron so happy to have a go at wiring something up but need help with the components/diagram, any suggestions?

Thanks

[JDFan]

Could use a DC - DC Buck Converter Step-down ( EBAY  LINK -- http://www.ebay.com/itm/DC-DC-CC-CV-Buck-Converter-Step-down-Power-Supply-Module-7-40V-to-0-8-35V-8A-DE-/172141501255?hash=item28146edb47:g:rygAAOSwvFZW770W )



They can be used to take a DC input and step down the voltage ( this particular one can take anywhere from 7 to 40V and step it down to anywhere from 0.8-35V and can handle up to 8A) they make smaller units but since you want 5v 2A output from a 12V source it will create a decent amount of heat in the process so using something designed to disperse the heat is best and for the $4 it doesn't cost much for the overkill.) SO you would just use your 12V input hooked to this and then adjust the output level to 5V to send to the Pi by adjusting the small screws using a jewelers screw driver until you get the desired 5V on the output side.

[DeLuSioNal29]

Yup.  Use that in conjunction with this external molex 12v power supply and you're in business.

Added bonus:  No fans so it will be completely silent in there!   

http://www.ebay.com/itm/External-MOLEX-Power-Supply-US-SELLER-12V-DC-4-Pin-Adapter-Cable-Cord-NEW-/360170366699?hash=item53dbd3a6eb:g:~4sAAOxy4YdTWwr0

DeL

[JDFan]

Yup.  Use that in conjunction with this external molex 12v power supply and you're in business.

Added bonus:  No fans so it will be completely silent in there!   

http://www.ebay.com/itm/External-MOLEX-Power-Supply-US-SELLER-12V-DC-4-Pin-Adapter-Cable-Cord-NEW-/360170366699?hash=item53dbd3a6eb:g:~4sAAOxy4YdTWwr0

DeL

Though that one is a bit underpowered at only 2A :

Please note: This device is only intended to power a single device (2A or less) like hard drives / disc drives so pin #2 is not grounded. Some devices (I.E cathodes, case fans, video cards) require pin 2 to be grounded. Please check your device before purchasing.

So might want to get one with a bit more output depending on the display requirements. For example this listing has a 5A unit with US plug for $9.39 shipped ( http://www.ebay.com/itm/Power-Supply-Adapter-AC-To-DC-12V-24V-2A-3A-5A-6A-10A-5050-3528-LED-Strip-Light-/262010038401?var=&hash=item3d0103e881:m:myz7cVlmLctVD835ROH0gyg )

[dmckean]

Won't a supply like this provide both the 12v and the 5v he needs?

http://www.amazon.com/T-Power%C2%AE-adapter-4-Pin-Acomdata-Model/dp/B00EFIVJ62

[JDFan]

Won't a supply like this provide both the 12v and the 5v he needs?

http://www.amazon.com/T-Power%C2%AE-adapter-4-Pin-Acomdata-Model/dp/B00EFIVJ62

Maybe !!   -- While it shows output of both 5V and 12V it does not list the Amperage of those outputs so no way to tell if there is the required 2.5Amps of output on the 5V for the Pi (as mentioned by the OP most USB replacement 5V sources only output 1-2A instead of the 2.5Amps the pi3 requires) So would need to check the specs to ensure there is enough 5V output before using that one

EDIT : Here's another listing for that one ( http://www.amazon.com/T-Power%C2%AE-adapter-4-PIN-Replacement-switching/dp/B00EFIVFDE/ref=sr_1_24?s=pc&ie=UTF8&qid=1459273838&sr=1-24&keywords=12V+and+5V+output+external+power+supply ) and as suspected it shows the specs as :

T-Power® Ac Dc adapter for 4-PIN - Welland 12V 5V PA-215 4pin NexStar (+5V - 1.5A Max / +12V - 1.8A Max)

So only 1.5A 5V output max so would not work for his use !

[aldub516]

I actually have a lot of input with this issue and have been having a lot of problems.  A while back i started building a whole fleet of mini-dedicated machines out of old icades.. using a pi inside. I also have the screen, led strip and speakers i need to power and wanted to keep it clean and have 1 power plug going in. So, i ended up going through a lot of variations of "power supplies".. made a few breadboard type power supplies. Used different step down converters as above, used voltage regulators. A whole bunch of proto types.. Currently i have a power supply taking in 12 v, and eventually give me about 5.20v on the last rail.. BUT it seems no matter what, through all the machines i have almost finished, the pi always resets or gives me issues! Im heading out right now but ill be back shortly with more details.. simply put, what youre trying to do, ive been trying to do with the pi for quite awhile, with some very knowledgeable people on my side.. and im still having pi issues.. the pi is getting 5.20v at 2.5a (even had a 4.5a plug to try) and the pi always at some point, resets. I may have too much going on with the power supply, as ill show u when i return home.. im powering a few things and maybe some surge is knocking it out? Ive been through it all.. i hope we can find a solution. It seems the pi does not like home rigged power hook ups.. but yea, i been working on this for a while..

[GSXRMovistar]

Thanks for the suggestions guys and and looking forward to the extra info aldub516.

At the moment I've got some cheap old power adaptor powering the screen and an iPad PSU powering the Pi (with zero delay controller hooked up, all seems very stable regardless of what I run.

[Jamesbeat]

My next project is going to be a pi-powered barstick, and I'm seriously considering just using a pc power supply.
It would give me 5v for the pi and 12v for the amplifier.
I'm also toying with the idea of disconnecting the fan and seeing what happens. The pi and an amplifier (from some old pc speakers) isn't going to draw anywhere near the current that a pc would, so it's quite possible that it would be ok without forced air to cool it.

My original plan was to just use a power strip and plug two wall warts into it. I still might take this approach as it would likely be smaller and lighter than the pc power supply.

If you're using a pi in a bartop, you should have plenty of room for two wall warts and a power strip, plus you could plug the monitor into the strip and thus only need one power cable coming out of the machine.

This is the exact setup that I am currently using in my bartop, and there is still loads of room inside.

[aldub516]

Ok.. im going to copy and paste my post from the pi forums.. it basically describes exactly what im going through, so i figured no need to re-type it. i also included a pic of the power supply.. here goes my post from the other forum...



 I am building little mini replica arcade machines, such as pacman, etc. they are coming out incredible. They boot up to the original game via the pi and play with original buttons hooked up and such.. But here is my issue. There are several internal electric components that i wanted to have a very clean hookup to.. I didnt want 3 power plugs coming out the back. And for some reason, i cant seem to give the pi sufficient power. It keeps dying and resetting sporadically. So here are the internal components and their voltages

9" screen-12v
pi-5v
led strip-12v
speakers-5v
coin light-5v

there is also a control panel with buttons and a joystick, running through the gpio board and pins.

To power everything, i created a bread board which has incoming 12v, then using some diodes and a  voltage regulator in place that takes in the 12v and steps it down, im able to create a roughly 5.20v output on the other side of the bread board. Here is my issue. I took the micro usb charger for the pi, snipped off transformer end, and connected it to my breadboard. SOO. theoretically, i have between 5 and 5.5v running into the pi from my bread board. But it seems that i keep having my pi die and reset. I made 4 machines but different methods for powering them, as i went through prototype ideas. 1 machine works well so far, 1 machine worked but crapped out but it seems that was a loose wire, so i changed out the whole breadboard to my new one, and that now dies on me.. machines 3 and 4.. yup, die on me. 1st thing i noticed was my transformer was 12v but only 2 amps.. besides that i only had a 12 v 4.5a transformer.. even if thats over kill (there is a fuse in line for safety) the pi still dies with incoming 5.45v at 4.5amps. Can someone shed any idea on whats happening or what could be? its partly pi based, partly electronic knowledge. The behavior of the pi is weird though. for instance.. i can have the arcade running for an hour on attract mode and its fine.. i can play for 5 minutes or 5 seconds. and it will just die randomly. The other day i noticed, whenever i would try to escape to a setup menu it would keep dying as well. With the pi plugged into its own separate 2.5a 5v power into the wall its fine.. i just cant understand why it keeps dying on me when run through the bread board if its getting 5.45 or so volts. For electric know hows out there, can i check some kind of continuity with a meter i can check or something and see if that 5v line on my breadboard is dipping under somehow? What are the EXACT requirements of a pi to run consistently? Ill be happy to add any info if needed. Im just stumped.The pi should be getting enough power? I dont want to burn it out either.

as of right now, the power on the line going to the pi is exactly 5.17v.

 here is a crappy pic of my power supply. I did it quick, but to explain.. its taking in 12 volts on the right where the yellow is, it goes through a 1 amp fuse for safety, then it runs through the step down converter which brings it to about 6.4v. i then use a little diode to cut down the voltage a tiny bit more.. once its under load, it gives me a nice 12.37 v on the 12 v line, and 5.17 volts on the 5v side.. that should be sufficient for power..

i am considering getting something like that above posted, a molex connector giving 12 and 5 v.. my issue is, if its already getting the proper power, why is it not working? makes me feel like even a power supply giving 5 and 12v would cause this issue


screen shot windows 7

[Jamesbeat]

Can you put a meter in between the pi and the power source to see how much current it's drawing?

In my experience, the pi draws a lot more current than you'd expect, and needs a pretty beefy psu.

Try hooking it up to a pc psu and see if you still get the problem.

[aldub516]

someone said there are spots on the pi u can check for voltages, i have to try that.. i cant check exactly what the pi is drawing right now, but i do know that the power coming from the breadboard, through the micro usb and into the pi is 5.17v at anywhere from 2.5-4.5 amps with different power plugs tried..

[Jamesbeat]

It's insane how much current those things draw isn't it?

I remember when it was first launched, they implied any old phone charger would work.

Is it possible that the microusb cable is causing a problem? A lot of those have extremely thin conductors inside.
I had a problem with a phone taking ages to charge on one particular charger, when my wife's was charging just fine on her identical one.
I tried using hers with my phone, and it charged fine.

Turns out it was't the charger at all - it was the cheapo cable that I had used to replace the one on my charger when I damaged the microusb connector.

They do sell charging-only cables. The idea is that eliminating the data wires means that the power wires can be thicker.

[aldub516]

so i got a lot of feedback from the pi community. In my personal case, it SEEMS that the "linear regulator" im using is overheating, and/or just not the proper thing to use. I need to use a dc/dc buck converter to step down the voltage. Which is funny, because as i noted i went through several "power supply" ideas.. and the only machine that worked was the one with one of these converters. So im going to now order some of these http://www.amazon.com/ZPS-Lm2596-Adjustable-Converter-Module1-3v-35v/dp/B00IJYDJTS

but i want to make sure it can handle the pi drawing on it. Its rated current is 2amp and 3amp maximum. The pi draws 2.5 amps, so im worried it may overheat again. If so i will find a beefier dc/dc converter, such as the one posted above. But for now, my long standing power problem has been singled out to be cause by that 12v to 5v regulator shown in my bread board.. i need a "switching regulator" instead of the "Linear"....  I

atleast i have something to work with now

[ark_ader]

I would use a travel power brick.  It should last a few days on a full charge.

Then you have a portable mini bartop.

[JDFan]

I need to use a dc/dc buck converter to step down the voltage.

 So im going to now order some of these http://www.amazon.com/ZPS-Lm2596-Adjustable-Converter-Module1-3v-35v/dp/B00IJYDJTS

but i want to make sure it can handle the pi drawing on it. Its rated current is 2amp and 3amp maximum. The pi draws 2.5 amps, so im worried it may overheat again. If so i will find a beefier dc/dc converter, such as the one posted above. But for now, my long standing power problem has been singled out to be cause by that 12v to 5v regulator shown in my bread board.. i need a "switching regulator" instead of the "Linear"....  I

atleast i have something to work with now

I'd go with the beefier ones -- seeing that the linked ones state :

Output current:Rated current is 2A,maximum 3A(Additional heatsink is required)

SO even at their stated output which you will be pushing - they already tend to overheat unless an adequate Heatsink is added to them - So get the beefier one that is already designed for the output up to 8A rather than 2-3A and has the heatsinks required instead of needing you to add them ! 

ANother option if you already ordered those - use 2 of them and drop the 12V first to around 9V with the first and then take in the 9V and drop it to the 5V with the second -- that way each unit will be creating less heat to dissipate ( since the heat is generated when discarding the extra Voltage that you do not use ) and those smaller units might then be able to handle it (though the 2.5A the pi requires may still push them )

[aldub516]

so i ended up with that 8a drok converter.. and im waiting for it in the mail to come this morning.. basically i built 5 awesome working replica mini-arcades, and have been battling this power issue since day one. if this doesnt work, feel free to come and grab all 5 machines off of my curb.... im done

[aldub516]

so it appears that the new converter i got has fixed my issue!  I bought the d-rok one that handles up to 8a. Easy hookup into my breadboard. just removed the old regulator and jumped this one in. I can steer you my way if youd like for the power solution, but i believe you can find something a lot easier and out of the box instead of making a breadboard. there are plenty of power supplies that output 12 and 5v lines.. just make sure they are powerful enough and proper to power the pi. If you hit a dead end ill happily make or instruct you to make one of the power supplies i made. Gives me plenty room to add and power anything i need