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Topic: 1 battery pack for different voltages (Read 800 times) previous topic - next topic

shiznatix

My project consists of an Arduino Mini, a radio receiver, and a LED array that I am trying to run all off of a single battery pack. The issue is that each of these requires only 5V of current to run properly but if I put them all together, the current dips and some things stop working (such as the radio receiver).

My radio receiver only works within a 4.9 and 5.1V range so I have to be quite specific (I once accidentally put 9V through one and it burned out in seconds). Also, the Arduino shouldn't start to get faulty until the batteries are really dead so I can't go too low on that either.

I thought of putting 4 or 5 AA batteries through it all and putting a 5V regulator in front of each component. Then I read that the closer you get the the voltage regulators output, the lower the output actually is. This is a problem as the batteries start to drain obviously.

So, what is the best way to have enough voltage/current without burning anything out? I know the LED array would survive just fine with 6 - 9 V but I worry about putting more than 5.5V into the Arduino Mini 5V input and the same for the radio receiver.

Nick Gammon

There's a "drop out" voltage which is around 1V (but see the spec for the particular regulator). You have to have at least that gap. So having 5 AA batteries should be fine, however once you have too many then the regulator starts to get hot. So you don't want too few and you don't want too many.

Another approach might be a boost-buck converter which would take your batteries and output a set voltage, even if the battery voltage is higher or lower than what you require.

http://en.wikipedia.org/wiki/Buck%E2%80%93boost_converter

I'm no expert on using them but it sounds good in theory.
Please post technical questions on the forum, not by personal message. Thanks!

More info:
http://www.gammon.com.au/electronics

jack wp

Sorry but:
Quote
each of these requires only 5V of current to run properly
does not make sense, as voltage and current are two different things.
What is the voltage range, and current needed for each of your three devices?

Of the three devices, I would guess the LED array is drawing the most current.

You should have a separate power supply for the LED array.
Good luck, Jack

MarkT

Can you tell us what the existing battery pack is and what the individual loads are - or at least their current draws.

Its possible that several of the devices can run from the 5V output on the Arduino Mini - it sounds like the
LED module is tolerant of a higher voltage and doesn't require any regulation if the battery is of the right voltage?

A switching regulator (aka DC-DC converter) would probably help reduce losses and extend battery life as
has been mentioned, but with knowing what the existing battery or current requirements are its all guesswork
really.
[ I won't respond to messages, use the forum please ]

shiznatix

Well at the moment I am powering the Arduino Micro with a 9V and then powering the radio receiver off of its 5V output and then powering the LEDs with 4 AA batteries. I don't really like this since it doesn't do great stuff for the battery life (a few hours and the 9V is dead). I also don't want this to be super heavy with bunches of batteries.

The LED array is 24x15 (360 total). The array is run off of shift registers and the LEDs themselves are these: https://www1.elfa.se/data1/wwwroot/assets/datasheets/1383-2sdrd-s530-a3_eng_tds.pdf

Only 1 row of LEDs is on at a time but I cycle the rows really quickly (to create static images). This for sure draws the most current.

The radio receiver has a operating voltage of 4.9 - 5.1 volts.

What would be the best way to power this all with getting the max life and minimum number of batteries?

jack wp

Does this have to use batteries. There is no AC voltage close enough to use a power supply?
Why do you want to use batteries?
Good luck, Jack

dc42

I would use 8x NiMH AA cells or a 11.1v LiPO, and a 5v switching regulator, and run the LEDs off the 5V along with everything else.
Formal verification of safety-critical software, software development, and electronic design and prototyping. See http://www.eschertech.com. Please do not ask for unpaid help via PM, use the forum.

shiznatix


Does this have to use batteries.

Yes, it is a portable unit attached to a backpack.

@dc42 could you show me some product links? I have never heard of any of those things so I am quite lost.

dc42

#8
Aug 18, 2013, 01:52 am Last Edit: Aug 18, 2013, 01:54 am by dc42 Reason: 1

@dc42 could you show me some product links? I have never heard of any of those things so I am quite lost.


NiMH AA cells =  standard 1.2V rechargeable AA cells. Better at supplying medium to high currents than alkaline AA cells.

11.1V LiPO = 3-cell Lithium Polymer battery, as common used in radio-controlled models. More expensive than AA cells, and needs a special charger; but higher energy density.

5V switching regulator - also known as a buck converter, or step-down DC-DC converter. Here's an example: http://uk.farnell.com/xp-power/sr10s05/converter-dc-dc-5v-5w/dp/1861095?Ntt=SR10S05. Several types also available on eBay.
Formal verification of safety-critical software, software development, and electronic design and prototyping. See http://www.eschertech.com. Please do not ask for unpaid help via PM, use the forum.

shiznatix

Ok, I understand but is there any "easy" way to handle it? A voltage regulator here, another there, and losing 1 or 2 volts? I am trying to keep costs down to the max.

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