Powering RaspberryPi with 12vdc (12v-5v voltage regulators)

[David Vandenberg]

Hey guys,

I need to power my raspberry pi via a 12vdc PoE recevier.
The reason being that I have 12vdc peripherals, so I want to use the 12vdc output from PoE and use a regulator to get the 5vdc that I need for the Pi.

I'm currently using a Hobbyking 5v UBEC successfully, but I want something in a more discrete package that can be mounted on a PCB.
http://hobbyking.com.au/hobbyking/store/__14310__HobbyKing_UBEC_3A_2_6s_LiPO.html

 

I’ve tried using these:

 

SPR01L-05 – http://www.meanwell.com/search/spr01/SPR01-spec.pdf

 

7805CT - http://www.jaycar.com.au/productView.asp?ID=ZV1505

 

But they both ran too hot and didn’t output enough voltage. I bought these from Jaycar without checking the specs ( they were closing), so I don’t think they can output enough current. But they’re just generally too inefficient anyway.

 

Can anyone recommend something that is PCB mountable, efficient, and less than $5?

 

 

 

David Vandenberg

Director | EngineRoom

Director | Fishburners

e – da...@enginerm.com

m – 0416 16 32 64

 

[Tim]

The 7805 should work, if it's too hot you might have to use a heat sink. It is by far the simplest method.

If you wanted a more efficient regulator, look for a switch mode regulator (pretty much the same as the ubec), they don't burn the excess power off as heat.

Just Google "switch mode 5v regulator" and work from there!

Tim.

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[Madox]

Hi,

Why do you want it to be PCB mount?  It is hard to beat the Hobbyking UBECs (I use a different one) on price and efficiency since they're switch-mode and VERY cheap.  With linear regulators like the 7805's you're down at less than 50% efficiency, with most of that wasted as heat as you've now found out.

I like the Hobbyking UBECs :)

These were Kean's rough measurements with their 3A one.

"Good results with 12V in.

 

No load 4.95V out 0mA in

500mA load 4.92V out 160mA in 78% eff

1000mA load 4.89V out 380mA in 93% eff

2000mA load 4.82V out 840mA in ~100% eff

3000mA load 4.76V out 1330mA in 89% eff"

[Terry Dawson]

On Mar 9, 2013 7:22 PM, "David Vandenberg" <da...@thelab.com.au> wrote:
>

> I'm currently using a Hobbyking 5v UBEC successfully, but I want something in a more discrete package that can be mounted on a PCB.
> http://hobbyking.com.au/hobbyking/store/__14310__HobbyKing_UBEC_3A_2_6s_LiPO.html
>

Wow, that UBEC looks great! I've not seen those before.

thanks
Terry

[Iain Chalmers]

Hey David,

I'm pretty sure you aren't going to find anything that'll beat the pricepoint on the HobbyKing uBecs.

I've seen a lot of people talking about these:

http://www.pololu.com/catalog/product/2103

but they're almost 3 times the price of the HobbyKing things ($10 each), and they're only good for 600mA (which might be marginal for a B model 'Pi, they reckon on 700mA if the 'Pi is providing ~100mA to both USB ports).

 The LM7805 should happily provide the 700mA you need, but it's going to need to dissipate almost 5W as heat - so you're going to need 4 or 5 square cm of heatsink at a guess,  which kinda makes their "pcb mountability" a moot point.

I'm almost certain I read an article recently about pin-compatible drop-in switch-mode voltage regulator replacements recently, but I can't find any bookmarks and Google's not showing me the webpage I'm certain I remember reading...

I think your best short-term solution is to buy every uBec HobbyKing has in the Aus warehouse...

big 

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"I say we take off and nuke the entire site from orbit.
That's the only way to be sure." - Ellen Ripley

[Nick Johnson]

On Sat, Mar 9, 2013 at 3:38 PM, Iain Chalmers <big...@mightymedia.com.au> wrote:

Hey David,

I'm pretty sure you aren't going to find anything that'll beat the pricepoint on the HobbyKing uBecs.

I've seen a lot of people talking about these:

http://www.pololu.com/catalog/product/2103

but they're almost 3 times the price of the HobbyKing things ($10 each), and they're only good for 600mA (which might be marginal for a B model 'Pi, they reckon on 700mA if the 'Pi is providing ~100mA to both USB ports).

 The LM7805 should happily provide the 700mA you need, but it's going to need to dissipate almost 5W as heat - so you're going to need 4 or 5 square cm of heatsink at a guess,  which kinda makes their "pcb mountability" a moot point.

I beg to differ. ;)

 

I'm almost certain I read an article recently about pin-compatible drop-in switch-mode voltage regulator replacements recently, but I can't find any bookmarks and Google's not showing me the webpage I'm certain I remember reading...

Murata make some, the 78xx series, with up to 1A output. They're more expensive than the ubec, though.

[tALSit de CoD]

You can get a pin-compatible Recom SMPS that does 1A, but those are over $12, like the R-78C5.0-1.0. But it's quite nice!

[headingwest]

I had the same issue with my 12V chicken gate. The LM7805 --> 5V chewed through the 12v batteries in no time while on standby. I needed 12v for the gear motor to lift the gate and 5V for the microchip.

I've bought about 6 of these ebay buck converters:

http://www.ebay.com.au/itm/360503007953?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649#ht_2649wt_1039

I did consider building my own version, but for the cost and convenience I'd rather just bolt these onto my existing board.

[Madox]

Hi Big,

You might be referring to this :- http://www.dimensionengineering.com/products/de-sw050

Which is rather expensive.  They're the makers of the motor controllers a lot of the robot guys use I believe.

[Matt Callow]

There was also a project in elector to build a 7805 pin compatible switch mode regulator.

http://www.elektor.com/magazines/2012/november/farewell-7805-7905.2292144.lynkx

Matt

[ivanjh]

I find the cheap LM2596 modules do a reasonable enough job.

e.g. http://www.ebay.com.au/itm/330646303458

Solder a couple of header pins thru the supply/output pads and it's PCB mounted.

There's adjustable current limited versions too...

[Iain Chalmers]

On 10/03/2013, at 8:20 AM, Madox wrote:

> Hi Big,
>
> You might be referring to this :- http://www.dimensionengineering.com/products/de-sw050
>
> Which is rather expensive. They're the makers of the motor controllers a lot of the robot guys use I believe.

Yep - I think you're right, the picture looks familiar. I vaguely recall seeing it by following a link/headline/blogpost titled "never use a 7805 again", but I'm pretty sure now that it either linked to or swiped images from that page - and that price is probably why I didn't bookmark it.

big

>
> On Sunday, March 10, 2013 2:38:22 AM UTC+11, big...@mightymedia.com.au wrote:
> Hey David,
>
> I'm pretty sure you aren't going to find anything that'll beat the pricepoint on the HobbyKing uBecs.
>
> I've seen a lot of people talking about these:
>
> http://www.pololu.com/catalog/product/2103
>
> but they're almost 3 times the price of the HobbyKing things ($10 each), and they're only good for 600mA (which might be marginal for a B model 'Pi, they reckon on 700mA if the 'Pi is providing ~100mA to both USB ports).
>
> The LM7805 should happily provide the 700mA you need, but it's going to need to dissipate almost 5W as heat - so you're going to need 4 or 5 square cm of heatsink at a guess, which kinda makes their "pcb mountability" a moot point.
>
> I'm almost certain I read an article recently about pin-compatible drop-in switch-mode voltage regulator replacements recently, but I can't find any bookmarks and Google's not showing me the webpage I'm certain I remember reading...
>
> I think your best short-term solution is to buy every uBec HobbyKing has in the Aus warehouse...
>
> big
>
>
> On Sat, Mar 9, 2013 at 7:21 PM, David Vandenberg <da...@thelab.com.au> wrote:
> Hey guys,
>
> I need to power my raspberry pi via a 12vdc PoE recevier.
> The reason being that I have 12vdc peripherals, so I want to use the 12vdc output from PoE and use a regulator to get the 5vdc that I need for the Pi.
>
> I'm currently using a Hobbyking 5v UBEC successfully, but I want something in a more discrete package that can be mounted on a PCB.
> http://hobbyking.com.au/hobbyking/store/__14310__HobbyKing_UBEC_3A_2_6s_LiPO.html
>
>
>
>
>

> I’ve tried using these:
>
>
>
> SPR01L-05 – http://www.meanwell.com/search/spr01/SPR01-spec.pdf
>
>
>
>
>

> 7805CT - http://www.jaycar.com.au/productView.asp?ID=ZV1505

[Kean Maizels]

David,

 

It is hard to beat the Hobbyking UBECs or cheap ebay units for prototyping/hacking.

 

I’ve used these Murata modules in a couple of designs.

http://au.element14.com/jsp/displayProduct.jsp?sku=1814499

They replace a 7805 with a mini switching regulator, and can supply 1.5A at 5V (also a 3.3V version).

Unfortunately they are about $8-$9 ea from e14, but Digikey do them for under $5 + shipping.

 

Kean

 

From: sydney-h...@googlegroups.com [mailto:sydney-h...@googlegroups.com] On Behalf Of David Vandenberg
Sent: Saturday, 9 March 2013 7:22 PM
To: sydney-h...@googlegroups.com
Subject: [RnD] Powering RaspberryPi with 12vdc (12v-5v voltage regulators)

 

Hey guys,

I need to power my raspberry pi via a 12vdc PoE recevier.
The reason being that I have 12vdc peripherals, so I want to use the 12vdc output from PoE and use a regulator to get the 5vdc that I need for the Pi.

I'm currently using a Hobbyking 5v UBEC successfully, but I want something in a more discrete package that can be mounted on a PCB.
http://hobbyking.com.au/hobbyking/store/__14310__HobbyKing_UBEC_3A_2_6s_LiPO.html

 

I’ve tried using these:

 

SPR01L-05 – http://www.meanwell.com/search/spr01/SPR01-spec.pdf

 

7805CT - http://www.jaycar.com.au/productView.asp?ID=ZV1505

 

But they both ran too hot and didn’t output enough voltage. I bought these from Jaycar without checking the specs ( they were closing), so I don’t think they can output enough current. But they’re just generally too inefficient anyway.

[Iain Chalmers]

Hey David,

I just noticed these:

700mA for $3.40: http://dx.com/p/03100226-breadboard-dedicated-power-module-compatible-with-5v-3-3v-black-yellow-194498

2A for $4.90: http://dx.com/p/2596-dc-dc-voltage-step-down-module-green-dc-5-36v-193446

Expect those to be "ISO Standard Deal Extreme" specs, which are only loosely based on reality, but they're sub $5 (and DX ship the, for free).

big

On Sat, Mar 9, 2013 at 7:21 PM, David Vandenberg <da...@thelab.com.au> wrote:

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[tALSit de CoD]

Kean, if that's the Murata that I think it is, the 3.3V version needs a minimum of 7V, not the expected minimum of 5V!

[Luke Weston]

Modules based around the LM2596 buck converter chip seem to be really, really common in the cheap Chinese eBay/DealExtreme/AliBaba etc. industry. There must be a factory somewhere using hundreds of thousands of LM2596s in some high-volume commercial gadget, and they probably go and sweep up the lost ones from under the pick-and-place machines to make these boards, because the cost is really good, just for the LM2596 and the inductor alone.

To get realistic specs of voltage ratings and output power, just go directly to the LM2596 datasheet. (Also at high input voltages, check the voltage rating of the input capacitor on the board.)

Those "breadboard power supplies" just use a pair of LD1117 LDOs, one for 5V and one for 3.3V, so their input voltage will be limited by power dissipation, and again, the best way to get an idea of realistic specs is to go to the LD1117 datasheet.

[Kean Maizels]

True, they are intended for 7 to 36V in.  But unless you “high” current, stepping down from 5V to 3.3V is probably better done with an LDO – switching regs tend to be quite inefficient at low current.

 

Most of my designs use only 10’s of mA at 3.3V, but sometimes a lot more at higher voltages (LCD backlighting, excitation/indicator LEDs, relays, etc).

 

Kean

[Arik Baratz]

On 17 March 2013 19:39, Kean Maizels <Ke...@kean.com.au> wrote:

True, they are intended for 7 to 36V in.  But unless you “high” current, stepping down from 5V to 3.3V is probably better done with an LDO – switching regs tend to be quite inefficient at low current.

 

Most of my designs use only 10’s of mA at 3.3V, but sometimes a lot more at higher voltages (LCD backlighting, excitation/indicator LEDs, relays, etc).

I may be missing something obvious here; but if you want to get 3.3V out of a 5V power source, can't you simply take a couple of silicone diodes in series? The voltage drop on each one is 0.7V, together it will give 1.4V which would get you from 5V down to 3.6V, within 10% of 3.3V. If you want to go down to 3.4V add a germanium diode in series to the previous one (0.2V drop).

Or better yet - a 1.7V zener diode in series. For the currents you're dealing with, they will take the load easily.

-- Arik

[Kean Maizels]

Arik,

 

Yes, you can potentially use diodes to drop some voltage.  But diodes have varying forward voltages depending on current, so they are not overly suitable way to do things.  Many zener diodes also don’t regulate very well at low currents.

 

If running a microcontroller or sensors off the 3.3V supply, you want a very stable voltage (better than 5%, often 1%) – especially if using it as a ADC reference.  If aiming for ADC or analog circuit accuracy a separate precision reference is a good idea.

 

BTW I’m not sure what forward voltage silicone diodes might have (vs. silicon).   But they sound flexible… ;P

 

Kean

--

[Arik Baratz]

Hi Kean,

They have the same forward voltage as silicon ones, and they seem to pass spell checks as well as be extruded from a tube.

You're right, if you need more than 10% accuracy, it's not appropriate.

-- Arik

[kris]

this might be a stupid question but...

could i use the hobby king ubec mentioned below to provide a constant 5V to my arduino if it is given a constantly wandering dcinput voltage between 5.5 and 26v?
say, from a bicycles dynamo/magneto?

I would not mind if the output current wanders around, i'll only ever need about .05 of an amp, but i understand attiny likes a nice steady voltage

--

[Patrick Barnes]

It does say '2-6S', meaning that's the number of cells it supports. Two
lipo cells make 7.4V, so 5.5V might be under the minimum that will work.

As for how well it will handle 'constantly varying', I'm not sure.

I've bought 10 of them though, so if you want to bring in a dynamo one
day, grab one, and see how a UBEC goes, great! I'd be interested in a
reliable 5V bicycle power source too.

-Patrick

On 20/03/2013 2:36 PM, kris wrote:
> this might be a stupid question but...
>
> could i use the hobby king ubec mentioned below to provide a constant 5V
> to my arduino if it is given a constantly wandering dcinput voltage
> between 5.5 and 26v?
> say, from a bicycles dynamo/magneto?
>
> I would not mind if the output current wanders around, i'll only ever
> need about .05 of an amp, but i understand attiny likes a nice steady
> voltage
>
>
> On 10/03/2013 12:21 AM, Terry Dawson wrote:
>>
>>
>> On Mar 9, 2013 7:22 PM, "David Vandenberg" <da...@thelab.com.au

[Kris]

Cool, will do, let me know when they come in and well run some tests.

--
Sent from my Android phone with K-9 Mail. Please excuse my brevity.

[Madox]

As usual I'll come in from left field and ask - Do you really need to power it from the Dyno?  If you're only drawing 50mA, wouldn't a bettery last you yonks?  What about a solar battery solution?

If you use the dyno and the Bec, will you have a battery/cap backup?  What happens to your program if you brown out?... 

But yeah, test and have fun :)  I've got maybe 30 of those buggers...

[Kris]

Hey Madox,
Its for an art installation, with a nod toward sustainability, no batteries are to be used, and they are to be powered by humans.
I'm not sure if a capacitor is allowed. Early days yet.
I'm assuming that the digi stumps, given too little current will simply not work as oppose to wiping their program or damaging themselves.

[Madox]

My 2 cents follows.

A nod to sustainability should consider practicality. If a "sustainable" idea is not practical then it is completely useless.

Yes yes I understand this is for "art" :) Just thought I will let that out.

[Kris]

:-) I'm with you on that.
"I don't know much about art, but I know when the curator says no batteries"

[ivanjh]

So, a mechanical KERS then... http://www.formula1.com/inside_f1/understanding_the_sport/8763.html

[Patrick Barnes]

But where do the rotating knives go?
http://www.intriguing.com/mp/_scripts/architec.php

-Patrick

On 21/03/2013 12:10 PM, ivanjh wrote:
> So, a mechanical KERS then...
> http://www.formula1.com/inside_f1/understanding_the_sport/8763.html
>
> On Thursday, 21 March 2013 09:30:49 UTC+11, Kris wrote:
>
> :-) I'm with you on that.
> "I don't know much about art, but I know when the curator says no
> batteries"
>

> Madox <madox.net <http://madox.net>@gmail.com <http://gmail.com>> wrote:
>
> My 2 cents follows.
>
> A nod to sustainability should consider practicality. If a "sustainable" idea is not practical then it is completely useless.
>
> Yes yes I understand this is for "art" :) Just thought I will let that out.
>
>
> --
> Sent from my Android phone with K-9 Mail. Please excuse my brevity.
>

[Jonathan Louie]

I know the people and magnificent revolution would have the ideal answer for you as they run sound systems and movies off pedal power - 

http://www.magrev.org.au/

There's also another mob who are related who will be running a workshop on bike power soon - 

MilkCrateEvents.com 0428830753

You could give Sarah there a ring - she said she was interested in running an event. In any case, there is a specific transfomer that is needed to transform varying current/voltage to stable voltage for running USB5v/Power pack 240VAC

J