Vintage car cellphone charger and grip

I have a Volkswagen beetle and it (oviously) doesn't have a cellphone charger... and I play Ingress.

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Well there are a couple of DIY projects about this but they're no quite right:

Sadly my car doesn't give exactly 12V, when the car is on , the alternator makes the voltage of the whole circuitry go up almost 1.5V.

So I need a different solution tha t keeps the output in 5V despite the input voltage.

  • 1 × LM7805 (The TO-220 packaged) Power Management ICs / Linear Voltage Regulators and LDOs
  • 1 × Heatsink for the LM7805 Electronic Components / Misc. Electronic Components
  • 2 × 1N4731 Discrete Semiconductors / Diodes and Rectifiers
  • 1 × 100nF @ 16V or Higher Ceramic or tantalium capacitor / Electronic Components
  • 1 × 10uF @ 16V or Higher Electrolytic capacitor / Electronic Components

View all 10 components

  • First version: Single voltage regulator and LED indicator - Did not work properly

    Daniel Mejía Raigosa03/12/2015 at 04:28 0 comments

    As a first version of our car cellphone charger we used a circuit like this:

    As Gerardo pointed out, this circuit produced a variable voltage output between 5V and 5.5V. We do not desire such behaviour in our cellphone charger since the battery lifespan might be severely reduced.

    The main source of such voltage variation lies on the car's voltaje drops between the low and high RPM of the alternator, a phenomenon noticable on old cars (like in my 94' car for instance).

    We think that a pair of zeners reverse biased in series could clamp the voltaje at the output in around 5V.

    The fuse at the input of the circuit (not shown on schematic) prevents it from passing more than 500mA to the output, that is, our charging cellphone.

    On the LM7805 voltage regulator

    You must check that the LM7805 regulator you choose can handle currents of about 500mA or more since there is a LM7805 version that can handle up to 100mA. 100mA is a low corruent and the regulator should malfunction due to the high current load. We recommend using the TO220 version.

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Daniel Mejía Raigosa wrote 03/12/2015 at 04:15 point

We value your suggestions, although We are looking for "cheap" and easily found component alternatives, since the electronic parts availability is different for every country and we're looking for a quite universal solution.

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