build a multi-voltage portable power supply you can take anywhere

8/17/2019 Build a Multi-Voltage Portable Power Supply You Can Take Anywhere

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Build a Multi-Voltage Portable Power Supply You Can Take Anywhereby j_thompson (/member/j_thompson/)

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PSU (/tag/type-id/category-technology/keyw ord-

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Voltage Regulator (/tag/type-id/category-

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travel (/tag/type-id/category-technology/keyw ord-

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Portable M obile Charger

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My implementation is a composite of three linear regulator circuits, giving three

readily available voltages. The basic (one voltage) circuit shown below, is the

standard circuit used everywhere. Here (https://youtu.be/GSzVs7_aW-Y) is a

really good video explanation of the basic circuit and the theory behind it, produced

by Afrotechmods (https://www.youtube.com/user/Afrotechmods).

The supply subsystem picture above shows you the basic linear regulator circuit.

The circuit gives you a nice even voltage that is great for low-load applications,

such as your Arduino projects. Linear regulators are commonly rated up to 1A.

This build is made up of four subsystems. The first is the DC power supply from the

battery pack, with the first filtering capacitor (leftmost C1 in the basic circuit) and a

power switch (power subsystem diagram). The filtering capacitor does the job for

all the regulator subsystems, so we only need it once.

(http://cdn.instructables.com/F8M/VYZT/I8YBJTEC/F8MVYZTI8YBJTEC.LARGE.jpg)

(http://cdn.ins tructables.com/FWN/RW14/I8YBJTHY/FWNRW14I8YBJTHY.LARGE.jpg)

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(http://cdn.instructables.com/FEG/73MH/I8YBJTFU/FEG73MHI8YBJTFU.LARGE.jpg)

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Next is our 9V regulator circuit (9V subsystem diagram). This produces our 9V

output rail, which the 9V connectors or leads will connect to.

The 5V subsystem input connects to the same place as that of the 9V subsystem

(5V subsystem diagram). These operate in parallel so that load on the 9V rail

cannot compromise the 5V supply. The output is a good place to put your power

LED. You can see the 5V regulator is preceded by a 9V regulator. The greater the

voltage drop, the greater the heat output from the regulators. As such, going from

12V to 5V will cause some heat buildup. We can share the load and thus heat

output by using an intermediary voltage step with the 9V regulator, only loaded bythe 5V regulator. The capacitor between them helps to prevent any ripple

superposition between the two regulators (just for good measure). The 5V and 3.3V

rails should only really be supplying light-current circuits; nothing too strenuous. So

finally, the 3.3V supply can be stepped off the 5V rail, giving us the fourth

subsystem (3V3 subsystem diagram).

Each output rail has two capacitors to filter high and low frequency noise (ripples)

from their respective regulators. A shotkey diode can also be put in reverse,

parallel with the output capacitors on each rail. This ensures circuits producing

back-building voltages don't blow anything up. Put it all together and you end upwith the total schematic shown above.

Step 2: Soldering


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When you do your soldering, space the individual regulators apart to aid heat

dissipation. A few centimeters is fine. You'll want to keep your filtering capacitors

as close to their regulators as possible, preferably in front if you want to attach a

heat-sink to the back (flat) side. Your regulator's 'GND' pin should be in the middle,

so also ensure the negative (striped) pin on the 10µF capacitors orients to the

middle of the regulator. If you have side-by-side tracks on your perf board, you

can place the 'GND' and 'OUTPUT' pins on the tracks. All this can be seen above.

When soldering the battery compartment, I recommend a way of making it

detachable from your main board. If you have the 9V connector on the battery

holder and the connector that is fine. If not, I recommend putting connectors

between the battery box and the board. That way, you can detach the whole battery

holder without desoldering it. If you decide to use PCB headers to output your

voltage rails, solder them onto a separate board so that you can mount them flat to

the inside of your project box. Now you know how much room you need for your

(http://cdn.instructables.com/F5Z/4WOU/I8YBJTEJ/F5Z4WOUI8YBJTEJ.LARGE.jpg)

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board, heat-sinks and batteries, it's a good time to get your project box. Don't forget

you need room to mount your switch, LED and ports, as well as allow heat buildup,

so ensure you have some excess room.

Step 3: Mounting the components

(http://cdn.instructables.com/F1N/GPK2/I8YBJS4T/F1NGPK2I8YBJS4T.LARGE.jpg)

http://cdn.instructables.com/F1N/GPK2/I8YBJS4T/F1NGPK2I8YBJS4T.LARGE.jpg


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I'll leave the external layout and aesthetics to you. Just remember to use heat-shrink

tubing whenever you solder cables to terminals (like on the power switch) to avoid

shorts. It's also a good idea to allow your PCB to be removable. Sticky cable clips

can be used to make a slot for my board to sit into.

You can also see that the board acts as a divider. That way, if the batteries movethey don't damage the upright components. If your layout matches the one above,

add a block of sponge to the battery section for cushioning. That way the batteries

are elevated above the external cables' ports and pressed to the lid, securing them

once closed. Remember, the batteries together are heavy so need to be secure.

My final product (above) had 9V and 5V outputs, with space to add the 3.3V

regulator and cables later if I decide to.

So, there you have it. A 9V, 5V and 3.3V stable supply that you can take anywhere

with no country adapters or spare cables. If you're flying and weight is an issue,

you can always pop the batteries out making it super light.Acknowledgements

Lots of thanks to Afrotechmods (https://www.youtube.com/user/Afrotechmods)for really great videos explaining voltage regulator circuits. I really recommendthese.Thanks also to this Altoids Tin build (http://www.instructables.com/id/Altoids-Tin-Portable-Breadboard-with-Power-Supply/) for your inspiring design.

(http://cdn.instructables.com/FX8/GE0A/I8YBJVIS/FX8GE0AI8YBJVIS.LARGE.jpg)

(http://cdn.instructables.com/FY5/YQJW/I8YBJS4W/FY5YQJWI8YBJS4W.LARGE.jpg)

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11/14

We have a be nice comment policy.

Please be pos itive and constructive. I Made it! Add Images Make Comment

(/member/The+Lightning+Stalker/)

4 hours ago Reply

(/member/MikeD11/)

10 hours ago Reply

(/member/Gelfling6/)

8 hours ago Reply

(/member/MikeD11/)

5 hours ago Reply

(/member/JRV31/)

yesterday Reply

The Lightning Stalker (/member/The+Lightning+Stalker/)

Using heatsinks will allow 1.25A output.

MikeD11 (/member/MikeD11/)

Using Analog regulators is a bit 1970. For instance with a 12 v input and 3.3Voutput Analog regulators waste 72% of your battery power (38% efficient). The

regulator will get hot which is another problem. Why not use a $1 eBay Digital

supply for each of your outputs and you can set these for any voltage you want!Search for DC-DC LM2596 on eBay. You'll then have a 92% efficient power

supply and your battery will last 3X longer. Beautiful job on the instructable tho!

Gelfling6 (/member/Gelfling6/) MikeD11

Mike, You'd be surprised, a lot of the ATX supplies have a couple of

analog regulators on the output side.. a fixed 7805 for the +5vsb, and7812, 7912, and IF it has -5V out, there is a 7905.. They still use them.

MikeD11 (/member/MikeD11/) Gelfling6

Hi Gelfling, maybe, but this instructable is powered by a 12v battery and

to waste 2/3 of the battery life by using an analog voltage regulator is notvery "instructable".

JRV31 (/member/JRV31/)

Very nice project.

Where did you find the case? I have real trouble finding nice cases for projects.

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12/14

(/member/tomatoskins/)

yesterday Reply


7 hours ago Reply

(/member/ValentinoM/)

8 hours ago Reply


8 hours ago Reply


8 hours ago Reply

tomatoskins (/member /tomatoskins/) JRV31

I agree, that's a great looking project box!

Gelfling6 (/member/Gelfling6/) tomatoskins

Replying back to both JRV31 & Tomatoskins, Radioshack Used to carry

project boxes similar, but I can't find any online anymore. (their regulatedsupplies for CB/Ham Radios used to have a similar design.) Your bestbet, would be finding an Electronics tool/connector/supply store nearby.

Closest to me is about 17 miles away, and a lot like RS Used to be.

(parts, more than toys/cell phones.)

ValentinoM (/member/ValentinoM/)

Nice project. I would have liked it better with a big 12V car battery :)

Also, you could get the 12V and 5V from a PC PSU (and even 3.3V, -5V and

-12V, but with low power).

Gelfling6 (/member/Gelfling6/) ValentinoM

Depends on the PSU.. Been noticing a lot of the ATX units have been

omitting the -5V in the past few years, Since the Pentium4. The older PCsupplies were strictly +/-5, +/-12. (and you could still trick them with a 33-

Ohm, 5-Watt across +5 to GND)

Gelfling6 (/member/Gelfling6/)

One thing I would advise caution about, Back-feeding the +5V, or the +9VDD.The trace from the Vin pin back to the barrel connector, I accidentally fried mine

with a temporary short across the Vin & GND pins (placed arduino Duemilinova

on a drop of solder on the bench. Thankfully, was able to re-bridge the trace.) Andthere has been plenty of notes on arduino.cc forums, that back-feeding the +5V,

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(/member/j_thompson/)

17 hours agoReply

especially on the MEGA models, can harm the switching circuit between the USB

+5V and the regulator chip output. (haven't found a reason why myself? ) I've been

using a modified ATX supply (+/-5V, +/-12V, 3.3V ), and feeding the Mini-Molex(Floppy power) to a 7809 to the barrel connector, and +5V to anything that

requires +5 to high-draw (More than 4 servos, which can overload the Arduino's

regulator enough to cause random resets) I like the set-up!

j_thompson (/membe r/j_thompson/) (author)Thanks. A1parts.com look to have a decent range. Mine was a small shop in

Akihabara, Tokyo.

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build a multi-voltage portable power supply you can take anywhere

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