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Author Topic: Convert 3.7v to 5v DC  (Read 13304 times)
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Hi,
  I have a battery that outputs 3.7v, but part of my project requires 5v. Does anyone know of a simple and most importantly small method of doing this? I have read about taking apart cell phone chargers but am not sure that, that is the best solution. I have seen the step up converter sparkfun, however I was wondering if anyone had any better ideas? Thanks in advance.
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The step up converters are DC-DC switching regulators which is the most efficient way to achieve what you want to. Most phones run at 3.3v or less nowadays, so you are unlikely to find anything useful in there. Even if you do, they will work on the same principal as the ones Sparkfun and others sell.

I am guessing from the voltage that you are using either a Li-Ion or Li-Po battery, in which case something like this will work well whilst also protecting the battery for being over discharged:
https://www.sparkfun.com/products/10255
« Last Edit: August 18, 2012, 07:17:45 pm by Tom Carpenter » Logged

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ok. I will stick with something like what sparkfun sells.
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ok. I will stick with something like what sparkfun sells.

Much better prices on boost switching voltage regulators on E-bay from Asian sellers. I've bought several types and have never had a problem with them. Here is just one example:

http://www.ebay.com/itm/DC-DC-3V-to-5V-1A-Voltage-Step-up-Power-Regulator-Transformer-Module-500KHz-NEW-/251080856072?pt=LH_DefaultDomain_0&hash=item3a7595d208

Lefty
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would it not be easier to buy a wallmart 5v dc wall supply?... or rescue old cell phone charger?..
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This pololu unit is both small and inexpensive
http://www.pololu.com/catalog/product/798
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ok. I will stick with something like what sparkfun sells.

Much better prices on boost switching voltage regulators on E-bay from Asian sellers. I've bought several types and have never had a problem with them. Here is just one example:

http://www.ebay.com/itm/DC-DC-3V-to-5V-1A-Voltage-Step-up-Power-Regulator-Transformer-Module-500KHz-NEW-/251080856072?pt=LH_DefaultDomain_0&hash=item3a7595d208

Lefty

 Have you tested the step-up regulator with much of a load? I ask because I would like to run about 140ma of blinking LEDs of a minimal Arduino using a 3.7 lipo battery. It would be awesome if the regulator could truly supply 1A at 5V.
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ok. I will stick with something like what sparkfun sells.

Much better prices on boost switching voltage regulators on E-bay from Asian sellers. I've bought several types and have never had a problem with them. Here is just one example:

http://www.ebay.com/itm/DC-DC-3V-to-5V-1A-Voltage-Step-up-Power-Regulator-Transformer-Module-500KHz-NEW-/251080856072?pt=LH_DefaultDomain_0&hash=item3a7595d208

Lefty

 Have you tested the step-up regulator with much of a load? I ask because I would like to run about 140ma of blinking LEDs of a minimal Arduino using a 3.7 lipo battery. It would be awesome if the regulator could truly supply 1A at 5V.

I don't own that specific regulator, I just posted it as an example of what is avalible from Asian sellers on E-bay and there are many many others to choose from. I have bought similar regulators (step up and step down models) and have had no problems with them. Their main advantage is their higher efficiency ratings Vs linear regulators and when powering a project from batteries that higher efficiency is a real benefit. The output current rating from that ebay listing shows:

Quote
Input voltage:1-5V
Output voltage :5.1-5 .2 V
Output current: rated 1A-1.5A, 1.5A maximum
Conversion efficiency: up to 96%

So I see no reason it can't meet it's 1 amp stated rating.

Lefty
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Just started playing with some of these recently, they work well, are easy to use, don't need a lot of external components and certainly are SMALL! You don't say how much current is required, these will only go about 350mA at best, but that's plenty for a lot of my needs.

http://www.microchip.com/wwwproducts/Devices.aspx?dDocName=en547080
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There are a lot of designs out there on the interwebs for low budget 555 timer-based boost converters and charge pumps.
Here's some:
http://www.benjscott.com/2009/07/555-boost-converter/
http://electroschematics.com/648/555-voltage-doubler/

Also have a look for "joule thief" designs -- which are simply boost converters

These are low budget things that you might have the parts on-hand for.
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Love the title on that 555 article, "555 Timer Based Boost Converter (Spoiler: Not Very Useful)". The OP may want a boost regulator, which the 555 circuit is not.

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What do you think about using the MAX1708?
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Have you tested the step-up regulator with much of a load? I ask because I would like to run about 140ma of blinking LEDs of a minimal Arduino using a 3.7 lipo battery. It would be awesome if the regulator could truly supply 1A at 5V.

I wouldn't bother generating 5V and then wasting 1.5V or more in the series resistor, instead I would drive each LED or bank of LEDs from the 3.7V supply using a simple unregulated boost converter. To make the converter, you can adapt the joule thief circuit (but then you need to wind a transformer), or use a PWM pin driving a transistor and inductor, or use one of the many ICs that are available for this application.
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I have bought similar regulators (step up and step down models) and have had no problems with them.

Yep.  +1 for eBay boost boards. They really simplify the design of battery powered gadgets.


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