Easy USB Charger




Introduction: Easy USB Charger

About: Robots and video games...

This is an easy USB charger because you can get the electronic booster board already assembled. Just add the batteries, a couple of capacitors, the usb connector and nothing else.

Step 1: Materials

The main component is the PTN04050, it takes the 2.4 volts from the batteries and raise it to 5 volts for the USB. You can get it from the Texas Instruments site here.
You will also need:
2 100uf capacitor
1 USB female connector
1 battery holder

Step 2: Assembly

The assembly is pretty easy, just follow the scheme. Try to not overheat the terminal of the PTN04050 and be careful with the polarity of the USB connector.

Step 3: Finish

Find a nice case for your charger, an Altoids tin would be great, but I can't find one of that in my country so I will keep look for a case.
For testing the device at first I used my USB tester and then I tried it with my mp3 player, but there shouldn't be any problem if I were careful with the assembly.



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    40 Discussions

    does anybody know if this will damage an iphone 4s at all

    The data sheet for the PTN04050a says the minimum input voltage should be 2.9v. New alkaline batteries would output 3.0v, but as they are run down (or if you started with rechargeable batters putting out only 2.4v) you would have less than the 2.9v required. I'm assuming you tested this for a while and it worked, but this may put stress on the chip that will cause it to fail prematurely.

    Also (and perhaps more importantly), the data for that chip says that a resister is required between pins 1 and 4 to set the output voltage. If no resister is used, thoutputtdefaultsls to -1.79volts, which is not only wrong for USB, but is also outside the chipoperatinggn range. I don't see a resistementionednd in your write up at all, so how on earth did you get this to work?

    7 replies

    I took this picture from a datasheet just look in case of questions

    Cool Instructable by the way!

    Picture 2.png

    You are right with the voltage, but I made it and I have been using it with regular and rechargeables batteries for a few moths with no problem.
    The datasheet says "open" in the resistor for 5 volts, so you don't have to use any.
    Ragards, Bruno.

    If you can, when your batteries are dead please measure their remaining voltage. I thing you will find there is usable power In the dead batteries.

    So 3x AAA would be far more efficient.

    Good find on this chip. I scoured the TI site for something like this, but I guess I looked too hard under DC-DC and not this section. This chip looks really strong... Max 12W means you could adapt for an iPad charger.. Sweet!

    The trouble with using 3 batteries is that fully charged ones will run afoul of the maximum input voltage specification, which is the lesser of 5.5V (okay, that's not the issue) or the output voltage minus half a volt (i.e. 4.5 V).

    It's probably safer to undervoltage the input than to overvoltage it....and it's also one less battery. :-/

    I think you misunderstand something. The author was using 2 AA batteries and a boost circuit that maintains exact 5v output (from ~2x.5v input).

    Note that this Texas Instruments chip is designed to work with undervoltage... "anything" under 5V is boosted to 5v... but the more you undervolt, the less efficient the TI boost circuit will operate.

    I proposed making the input 3xAA or 3x1.5v (nominal 4.5v input). The advantage is twofold: greater capacity, and greater efficiency in voltage conversion by the boost.

    It's true that new batteries will contain > 1.5v (1.65v being common), but 3x1.65 = 4.95v. Even if the batteries were 1.7v, that is still 5.1v total which is far less than USB max of 5.5v.

    Did you read the TI datasheet? Please have a gander at the "input voltage specifications" part.

    lol, no it will not "put stress on the chip that will cause it to fail prematurely".

    What it does instead, is makes this instructable poorly thought out because you can't use more than a small fraction of the battery capacity. Instead of 2 x alkaline cells it should use 3, or a different boost circuit.

    Just as an FYI - You can order samples of this item if you have a company (or if you enter a company name in TI's registration fields). The samples are free. I DO NOT recommend abusing this. I simply think those who own electronics companies should know.

    I tried this and it did not work it couldnt even charge my motorola phone. the w765 or somehing.

    No Altoids tins in your country that is TERRIBLE!!!!!!!! that's like not having duck tape.

    I'm not very good with schematics. Is my terribly drawn in mspaint translation correct? and could someone fill me in on the ? I've placed in there? thanks!

    2 replies

    Pin 1 VCC (+5 V)
    Pin 2 Data-
    Pin 3 Data+
    Pin 4 Ground


    im a storm chaser and need to charge usb instermentsin my truck you should do one like this one but step it down from 12v car to 5v i would love to see that one

    1 reply

    Just FYI if you're really in need of something like that there are tons of devices out there like this https://www.dealextreme.com/p/universal-usb-ac-car-charger-adapter-27057

    However if you want to build your own you can check out this instructable https://www.instructables.com/id/12v-to-USB-adapter-12v-to-5v-transformer-great-/

    Why is the output capacitor placed on the USB connector instead of at the module? Quoting from TI's datasheet: "The stability of the module and voltage tolerances are compromised if the capacitor is not placed near the output pin."

    Granted, it's good practice to place an electrolytic close to the load, that's primarily to improve transient response (also as noted in the datasheet) though for charging applications, load transients may be minimal (but YMMV, as always).