Weekly Project: Voltoids; Or, How to Make 5V From 1.5V




Introduction: Weekly Project: Voltoids; Or, How to Make 5V From 1.5V

Yes, you read that project title right; this simple circuit will enable you to generate 5V DC from a single 1.5V DC AA battery. How can you pump 1.5V up to 5V, you ask? It's simple with a little piece of electronic steroids from MAXIM IC.

The MAX1674 IC is a DC-to-DC step-up converter that can take in voltages as low as .7V and crank out a digital circuit enriching 5V. Or, for more finicky projects, the MAX1674 can also output 3.3V. A simple pin-selectable preset determines the output voltage.

There is one small caveat with this project, however. Whether a blessing or a curse, the MAX1674 generates a steady-state output current ranging between 180-420 mA. Therefore, high current projects involving motors won't be able to benefit from this voltage amplifying circuit.

On the other hand, powering lightweight projects involving TTL/LS circuitry or LEDs are ideal applications for Voltoids. In fact, with such a low operating current, the MAX1674 is able to drive a 3.3V LED without the ubiquitous power-limiting resistor. All from a single 1.5V AA battery.

If this project seems beyond your talents, but the benefits of powering a digital circuit from a single 1.5V DC power source sounds enticing, you can opt to purchase a similar circuit from Spark Fun Electronics. Costing less than $10, this clever little device which is designed by Bodhilabs.com is housed discretely on the back of an AA battery holder.

Unfortunately, with this commercial product you are limited to a fixed 5V output and it isn't housed in a cool Altoids tin. Enter Voltoids.

Step 1: How to Build Voltoids

Time: 4 hours
Cost: $15.05
Difficulty: Difficult

Parts List

  • (1) MAX1674 (Digi-Key #MAX1674EUA+-ND; $5.06 NOTE: this is a uMax device)
  • (2) .1mF ceramic capacitor (All Electronics #104D50; $1.00/10)
  • (2) 47mF electrolytic capacitor (Electronics Goldmine #G13761; $1.00/20)
  • (1) 100K resistor (Electronics Goldmine G497R; $3.50/100)
  • (1) 22mH inductor (Digi-Key #308-1533-1-ND; $1.17 NOTE: this is an SMD)
  • Or, try this 20mH inductor (Electronic Goldmine #G1325; $1.00/5)
  • (1) rotary switch (Electronics Goldmine #G13928; $1.00/4)
  • (1) knob (Electronics Goldmine #G14481; $.99)
  • (1) Altoids tin (salvaged)
  • (1) two-position header pins (BG Micro #ACS1019; $.33/2x17)
  • (1) AA battery holder (Electronics Goldmine #G16152; $1.00)
  • (1) small perforated prototyping board - optional
  • (1) 8-pin uMax adapter prototyping board - optional

NOTE: Before you begin this project, read and understand the MAX1674 datasheet.

Step 2: Board or Freeform?

You can build this circuit on a small piece of perforated prototyping board. If you elect to go this route, you might also want to use an 8-pin uMax adapter for holding the MAXIM chip. Be forewarned, this adapter is not the same as the more common 8-pin IC socket. Although untested, try this MSOP-8 adapter from Digi-Key #33108CA-ND.

If you're more adventurous, you can build this entire circuit freeform. In other words, solder all of the components together without using a board to hold them. Please note that a soldering iron can and will burn off a leg on the MAX1674 with too much heat.

Either way this project is for the advanced electronics builder. Just go slow and don't burn your fingers.

Step 3: Can It

A circular Altoids tin is ideal for holding a retro-looking rotary switch. Drill a 3/8-inch hole in the center of the tin for holding the rotary switch. Make sure there is enough clearance inside the tin for the depth of the switch.

Attach the 2-position header pins at the 12-oclock position around the outside of the tin. Be careful that only the plastic portion of the header pin touches the metal sides of the tin. Glue these header pins into place.

Also, line the inside the tin with an insulated material. An Xbox Jewel Case skin from Gamer Graffix is a perfect fit for this round tin.

Step 4: Get Out(put)

Wire one pole of the rotary switch to pin 8 (OUT; for 3.3V) and another pole to pin 6 (GND; for 5V) for generating the proper output voltage. This switch sets the output voltage that is produced at VOUT.

Wire the battery holder's ground terminal (negative) to the circuit's ground. Connect the battery holder's positive terminal to VIN.

Step 5: Power Up

Double-check all of your wiring and connections. Be especially critical of your solder connections on the header pins. None of your circuit should touch the metal box of the Altoids tin.

Rotate the rotary switch to the desired output and insert one fresh (or, even not so fresh) AA battery into the holder. Using a meter, measure the output from the header pins. It should match the voltage that you selected with the rotary switch.

Step 6: Low-Battery Output Option

There is an optional feature of the MAX1674 that enables an AA battery to supply usable voltages down to .7V. This option is called Low-Battery Output.

In order to obtain this Low-Battery Output option, you will need to connect to resistors to pin 2 (LBI). The values for these resistors are calculated according to a formula supplied in the MAX1674 datasheet.



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    32 Discussions

    does anyone knows how to calculate the values of each individual components in the entire circuit (e.g value if resistor, cap etc).
    I interested in understanding the equation behind it...
    can anyone help? thankz

    2 replies

    It's based on the chip. I can't add the link to the datasheet here, but Search from Google: max1674 datasheet ...

    Typo! You mean microfarad (µF) rather than millifarad (mF), right?

    1 reply

    I've just tried to rebuilt this and it didn't work in the beginning, after checking the data sheet and confirming it myself i would say the schematics is missing a wire from SHDN to OUT (5->8). After connecting it it worked fine for me.

    So, I made it. U need to connect pin5 with pin 8 couse it is turning on when this connected. My problem is with output current. I mode an air core inductor (played with the roud count), but I can't get more than 300mA out, and then output voltage dropps to 4V. With the bigger coil it the coil is now cold. But no more then 300mA :( Now it's better than minty boost. couse with minty boost I can change my acer pda if it is turned off. Any ideas about increasing the output current?

    Hmm.... I just built this thing (minus the switch... I just made the thing permanent to GND, it's for a solar powered bot, so it'll always be on.) Anyways, thing is... it didn't go. I've got the MAX1674 and everything, but it's not working. the voltmeter is registering the voltage of the AA battery (that's what I'm testing it with) The only thing that could be wrong with it, would be the inductor, or I've burned ANOTHER chip... I don't think I've burnt the chip, as, I was VERY careful to keep it cool. I held it in my fingers while I soldered (that COULD be the problem, but, I made sure to even the charges while it was on the carbon foam. ) then there's the inductor... it's not 22mH, to be honest, I don't know what size it is... but it would probably be in the 20-50mH range. I don't know how much that would affect the circuit... but... it might... and one last thing, in the circuit diagram the pins LBI and LBN are connected, right? there's no dot saying they are, but they do seem to go to the same place on the drawing. Also, on the Vout, is the .1uF cap really necessary? considering it's right next to the 47uF cap, which generally would have more then a .1uF range of error. PS: oh, and you can just order samples of the MAX 1674, it's free.

    1 reply

    is you inductor in mH or uH? as that could be a cause to your problem, the datasheet calls for 10uH to 47uH.

    Is there someone I can pay $20.00 on top of fees to make me one of these? Thanks Dave Davetrader@aol.com

    1 reply

    Has anyone contacted you about this yet? Because I would be willing to build one for you. PM me or email me at jjanizek@gmail.com if you want one.

    I believe that Linear technology makes a very similar but more versatile chip called the LT1073. You can see the data sheet here. It has some more schematics detailing step-down converters. If you can't get pdf's just google "LT1073".

    So I'm just curious. How long does the battery last, roughly? Cool project, I'm adding it to my list. : )

    8-umax? Jeez, that's a bit much for a beginner project... try the LT1308, comes in 8-SOIC and has a 2A internal switch, so should be able to provide twice as much current as the max1675 without the tinytinytiny pins

    2 replies

    He never said it was a beginner project. In fact, he said "this project is for the advanced electronics builder. " Wow Limor, for someone who claims to advocate open source, you sure seem touchy when someone designs something similar. At least pretend you support the open source concept and compliment the guy on a nice design. You have no right to feel like mintyboost is being ripped off anyway, it's an overly simplistic project ripped right from the datasheet. Here's a little secret too; saying a project is for a beginner doesn't justify making it simplistic. In the case of mintyboost, it's a tiny, cramped circuti board that is not suitable for beginners either. Don't get me wrong, it's a perfect board for the project, but covering the simplicity by saying it's a beginner project just makes you look silly.

    Open source is about everybody contributing to the work and adapting it so it is as modular and effective as possible for the majority of the users. In this case ladyadas suggestion incorporates that. The suggestion gives you more current and is easier to solder plus has a better chance of staying soldered, since the pins are bigger there is more surface for the soldering alloying to ad·here to.

    A drop test reliability test would probably show that the 8pin SOIC has a better chance of staying on the board then a UMAX form factor.

    Also keep in mind note all user are familiar with what rosin core is (which is usually a purified pine tree sap) or what flux to use (voc free, halide, none halide, IPA (isopropanal). We use a soldering wetting balance at work all the time and are surprise by companies preheat times, ramp ups, flux choice and soldering alloy or paste. Not all of them result in good wetting. Tombstoning issues arrise and solder beading. All these cause beginners and even experts issues at all times. With RoHS and lead free solder this is even more of a pain. High heat required, the eating of the soldering tips, putting out soldering stations with nitrogen, whiskering and others.

    The easier it is for the end user the better =)

    Soldering small things makes the end user some times have a big headach. The comment was constructive.

    Quick note, on the internet telling sarcasm apart and the mood of the poster when he posted his information is hard to judge.