Small 5V supply from AA batteries - Page 1
Forum section: electronics / beginners

author: spacedementia87
author_rank: Contributor
timestamp: August 24, 2016, 08:57:31 am
content: So I built a thing!It runs off USB 5v at the moment but I want to make it more portable and run of AA batteries.I have done a bit of research and seen that I need a switch mode boost supply.I have found a couple of build tutorials, would these be ok and efficient enough?http://www.instructables.com/id/Adjustable-Voltage-Step-up-07-55V-to-27-55V/?ALLSTEPShttps://learn.adafruit.com/minty-boost/overviewSent from my ONE A2003 using Tapatalk

author: Psi
author_rank: Super Contributor
timestamp: August 24, 2016, 09:01:12 am
content: impossible to say without knowing how much current your "thing" draws.

author: krolu
author_rank: Contributor
timestamp: August 24, 2016, 09:12:30 am
content: You don't have to use SMPS in boost configuration. It all depends on how many batteries you want to use. If you join 4 AA batteries in series you will get 6V total when they full so no need for boost. You could use buck/boost controller if you want to use 4 AA and get them completely dead before your project will be out of power.

author: jpanhalt
author_rank: Super Contributor
timestamp: August 24, 2016, 09:13:23 am
content: A simple boost reulator might work for you. The NCP1402 gives a compact device. Sparkfun sells a pre-made version for about $6.00 (https://www.sparkfun.com/products/10968). Others are on ebay and banggood.Of course, as already mentioned, you need to know your required supply current. The SF booster can provide 200 mA, but at that maximum, your AA batteries won't last more than a few hours.John

author: Zero999
author_rank: Super Contributor
timestamp: August 24, 2016, 09:17:27 am
content: Quote from: krolu on August 24, 2016, 09:12:30 amFor how long?The batteries won't stay at 6V for long. Even with fresh batteries, at heavy loads the voltage will drop to below 1.25V per cell immediately.Rather than a boost converter, use six AAs and a buck converter, for maximum battery life.

author: BradC
author_rank: Super Contributor
timestamp: August 24, 2016, 09:28:12 am
content: Quote from: Hero999 on August 24, 2016, 09:17:27 amBatterizer to the rescue!

author: spacedementia87
author_rank: Contributor
timestamp: August 24, 2016, 09:54:55 am
content: Quote from: Psi on August 24, 2016, 09:01:12 amIt is a small analogue clock using smd LEDs.I haven't tested but it can't be more than 100mAWill test it soon.I guess I am asking a more theoretical question.Most efficient way to provide 5V without wasting power in the power supply circuit.Sent from my ONE A2003 using Tapatalk

author: alanb
author_rank: Frequent Contributor
timestamp: August 24, 2016, 10:01:06 am
content: Redesign to work within the voltage range of the chosen batteries. There is probably no need for a 5 volt supply.

author: jeroen79
author_rank: Frequent Contributor
timestamp: August 24, 2016, 10:52:23 am
content: What kind of "thing" did you build?Must it have exactly 5V?Or could it also run on 4,5V (3cells) or 6V (4 cells)?

author: spacedementia87
author_rank: Contributor
timestamp: August 24, 2016, 11:24:37 am
content: Quote from: alanb on August 24, 2016, 10:01:06 amWhat if there is a need for 5V?Sent from my ONE A2003 using Tapatalk

author: Zero999
author_rank: Super Contributor
timestamp: August 24, 2016, 11:32:49 am
content: Please post the schematic for the clock.

author: alanb
author_rank: Frequent Contributor
timestamp: August 24, 2016, 11:40:24 am
content: Quote from: spacedementia87 on August 24, 2016, 11:24:37 amIf it has to be 5V then you will need to have a regulator, either buck or boost depending on the supply voltage. In your earlier message you mentioned that you are using LEDs. This is what made me think that you could possibly redesign for the available voltage. Without seeing the circuit it's not possible to be more specific.

author: spacedementia87
author_rank: Contributor
timestamp: August 24, 2016, 11:49:10 am
content: Quote from: alanb on August 24, 2016, 11:40:24 amThe IC requires 5V, min 4.5v which is why I want 5V.But I also want to learn how to build an efficient circuit to provide 5V from a lower voltage.I am currently looking at the max1674Sent from my ONE A2003 using Tapatalk

author: spacedementia87
author_rank: Contributor
timestamp: August 24, 2016, 11:51:22 am
content: Quote from: Hero999 on August 24, 2016, 11:32:49 amThe IC has a min input voltage of 4.5VI am looking at how to make a circuit to efficiently provide 5v from AA batteries.I might use it for other applications like an arduino.It is me learning and in the future I might want to build 3.3v or other.Have you ever used the max1674?Sent from my ONE A2003 using Tapatalk

author: mariush
author_rank: Super Contributor
timestamp: August 24, 2016, 11:58:34 am
content: I've made in the past a boost regulator using LT1307 which can take in anything between 1v and around 10v and outputs a higher voltage at a maximum of 100mA :http://cds.linear.com/docs/en/datasheet/1307fa.pdfThe datasheet is very good, explains in detail the purpose of all components and how should be chosen and even shows how you would wire everything (see figure 12) and example circuits, it's a piece of cake to make it yourself.It's expensive compared to other regulators (being Linear part) but as it works at high frequency it can work with ceramic capacitors and small inductors and it's also available in DIP package. LT1308 is the beefier brother, which if i remember correctly can do up to 1A.

author: alank2
author_rank: Super Contributor
timestamp: August 24, 2016, 12:21:49 pm
content: I've got one of these:http://www.proto-advantage.com/store/product_info.php?products_id=2120002

author: Zero999
author_rank: Super Contributor
timestamp: August 25, 2016, 08:02:34 am
content: Quote from: spacedementia87 on August 24, 2016, 11:51:22 amWhich IC? Do you have the part number or data sheet?

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: August 25, 2016, 08:39:50 am
content: Could you just use a usb battery pack?

author: spacedementia87
author_rank: Contributor
timestamp: August 25, 2016, 09:51:00 am
content: Quote from: Hero999 on August 25, 2016, 08:02:34 amIt has an NE555 timer"Input supply voltage, 4.5 V to 16 V. (SE555 maximum is 18 V)"But anyway, I would like to learn how to create an efficient 5v battery supply.Sent from my ONE A2003 using Tapatalk

author: tszaboo
author_rank: Super Contributor
timestamp: August 25, 2016, 10:06:38 am
content: You use a buck-boost or a boost converter. Buck boost if your input voltage voltage is below or above 5V, boost if it is below. I suggest the Texas Instruments simple switcher family. That is like the complexity of a linear regulator + an extra inductor. If you want to learn, learn how to select the correct one. We will help.You can also use a pre built module, sold on ebay.This is an example:http://www.ebay.com/itm/DC-DC-Step-Up-Boost-Power-Supply-2V-5V-to-5V-2A-Stable-Fixed-Output-/331949748204?hash=item4d49bf2fec:g:HDYAAOSw6n5Xs6Y2I will mention, this: The NE555 is not going to be high precision. You will be told about this by a dozen other forum members. Just a heads up.

author: sleemanj
author_rank: Super Contributor
timestamp: August 25, 2016, 10:11:10 am
content: Ideally, efficiency speaking, series up batteries to sufficiently higher than you need which will still be higher than you need when "flat", then use a buck converter to go down to 5v. 8 AA cells in series will be 12v full 6.4v empty.Thats ideally speaking, because buck is a bit more efficient than boost. But the practicality is that efficiency of a converter depends on so many things that it really isn't going to matter what you choose, boost, or buck (or sepic, or cuk or....), you are going to get somewhere in the area of 75 - 95% efficiency.So the answer is less to do with efficiency, and more whatever is most convenient for the capacity you require - how many cells do you want to fit in to your space and what cell holders are available to fit that space, is most likely to dictate your choice.

author: Zero999
author_rank: Super Contributor
timestamp: August 25, 2016, 01:13:09 pm
content: Quote from: spacedementia87 on August 25, 2016, 09:51:00 amThen use six AA cells in series.Or you could replace the NE555 with an ICM7555 or TS555, which will work at lower voltages and use less power.As stated above, the 555 timer has a poor tolerance and is not very stable enough to keep accurate time.

author: spacedementia87
author_rank: Contributor
timestamp: August 25, 2016, 05:45:14 pm
content: Quote from: NANDBlog on August 25, 2016, 10:06:38 amThanks for the tips, I will start to look at that range and see what is available.Quote from: sleemanj on August 25, 2016, 10:11:10 amThanks for the tips. I will look into the possibilities.Quote from: Hero999 on August 25, 2016, 01:13:09 pmBut surely 6AA in series the internal resistance is starting to get pretty high. I was always taught that linking up cells in series is a pretty inefficient way of getting higher voltages.They also won't give a level voltage. What if I have another project with a tighter working voltage range?Sent from my ONE A2003 using Tapatalk

author: Zero999
author_rank: Super Contributor
timestamp: August 25, 2016, 07:04:21 pm
content: Quote from: spacedementia87 on August 25, 2016, 05:45:14 pmThe internal resistance does rise but so does the voltage so the power and energy available still increases.Yes, it's true that the voltage won't be regulated but a 555 timer can work at much higher voltages so that's not a problem. If you have another project with tighter voltage requirements, then perhaps you could built a voltage regulator into said project, so it no longer needs exactly 5V?

author: spacedementia87
author_rank: Contributor
timestamp: August 25, 2016, 10:37:00 pm
content: Quote from: Hero999 on August 25, 2016, 07:04:21 pmOk, but hypothetically what would be an efficient way of doing that. A 7805 needs a higher input voltage and burns up excess energy as heat as it is a linear regulator.Are the ti range of switching regulators a good choice?Sent from my ONE A2003 using Tapatalk

author: ebclr
author_rank: Super Contributor
timestamp: August 25, 2016, 10:50:44 pm
content: 0.39 USDhttp://www.aliexpress.com/item/Free-Shipping-1PCS-0-9V-5V-to-5V-600MA-USB-Output-charger-step-up-Power-Module/32701204969.html?spm=2114.30010308.3.2.pTvogs&ws_ab_test=searchweb201556_0,searchweb201602_3_10057_10056_10065_10037_10055_10054_301_10059_10058_10032_10017_107_10060_10061_10052_414_10062_10053_10050_10051,searchweb201603_2&btsid=75d06c0a-80bb-4d90-80c8-dfc14269da63

author: ez24
author_rank: Super Contributor
timestamp: August 26, 2016, 12:13:01 am
content: Quote from: ebclr on August 25, 2016, 10:50:44 pmThis is the cheapest thing I have seen with free shipping.

author: ebclr
author_rank: Super Contributor
timestamp: August 26, 2016, 01:21:39 am
content: I have one, if you want i can do some tests you may want

author: ebclr
author_rank: Super Contributor
timestamp: August 26, 2016, 01:23:59 am
content: 50W for sure is typo, 1A 5V = 5W

author: sleemanj
author_rank: Super Contributor
timestamp: August 26, 2016, 02:48:02 am
content: Quote from: wilfred on August 26, 2016, 12:49:11 amThey are fixed 5v output and can do up to about 600mA tops, I'll leave you to do the math :-)They do work OK and are good for low current demands from even a single AA cell (or parallel cells) as they will run down to a very low voltage.

author: Keysight DanielBogdanoff
author_rank: Unknown
timestamp: August 26, 2016, 03:35:04 am
content: Quote from: mikeselectricstuff on August 25, 2016, 08:39:50 amThis.

author: ez24
author_rank: Super Contributor
timestamp: August 26, 2016, 03:50:20 am
content: Quote from: Keysight_DanielBogdanoff on August 26, 2016, 03:35:04 amAre you sure you don't mean "that"

author: Zero999
author_rank: Super Contributor
timestamp: August 26, 2016, 08:27:11 am
content: Any voltage regulator uses extra energy. It's true that a linear regulator is less efficient than a switched mode but it still uses more energy.

author: tszaboo
author_rank: Super Contributor
timestamp: August 26, 2016, 09:08:49 am
content: Quote from: Keysight_DanielBogdanoff on August 26, 2016, 03:35:04 amA lot of the battery packs are designed to charge phones. If you dont load them with, say 50mA, they shut down. Forget using the cheap and excellent Xiaomi power bank to run an Arduino for example. Others use DC-DC converters with quiescent current higher than your actual load.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: August 26, 2016, 03:33:33 pm
content: Quote from: NANDBlog on August 26, 2016, 09:08:49 amThat's a possible issue,but as a quick & cheap solution it's worth a try. I've used them for various random stuff and I don't recall having switch-off issues above about 50ma. Ymmv of course.

author: Chalcogenide
author_rank: Regular Contributor
timestamp: August 26, 2016, 05:49:58 pm
content: I have a few of them. When you remove the built-in LED, the quiescent current is <0.5mA which is still quite significant. It also increases fairly rapidly when the voltage gets lower than a couple of volts. BTW, the USB connector is awful quality, but for the price I don't even know how can they afford to have one.