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I made a voltage divider using 2k4 and 4k7 resistors.

If I check the voltage with the multimeter, the voltage is correctly converted from 5V to 3.3V however when connect a consumer(small electric motor that should work with very low power) it does not work.

Why would this happen?

yonutix
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    The current is limited by the resistors. Get a voltage regulator instead. – Dejvid_no1 Jun 15 '17 at 08:43
  • I don't think it's about the current, I used also a 5V 12A generator, still not working – yonutix Jun 15 '17 at 08:45
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    The current that your motor draws is too much. So it **is** the current. By placing a motor (of for example 100 ohms) in parallel to the 4.7 k resistor you made a different voltage divider of 2.4 k ohm and (100 ohm in parallel with 4.7 kohm). – Bimpelrekkie Jun 15 '17 at 09:07

2 Answers2

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You need a voltage regulator to drop 5 volt to 3.3 volts if you want to provide a decent enough current to drive an electric motor. A resistor divider will produce 3.3 volts open circuit but, as soon as you connect a load, you draw current and largely destroy the potential dividers ability to deliver a constant 3.3 volts.

Use a voltage regulator.

Andy aka
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The problem is that a voltage divider made with simple resistor can not guarantee a fix voltage output if a load is apply. By adding this load, the resistance of the circuit change and then change the output :

schematic

simulate this circuit – Schematic created using CircuitLab

\$V_{out} = V_{in}*\frac{R_2 // R_{load}}{R_1+R_2//R_{load}}\$

As you can see, \$V_{out}\$ may change if you add a load.

As said @AndyAka, you remplace the voltage divider by a voltage regulator. It's extremely easy to use (few resistor and capacitor) and it will fit your need.

M.Ferru
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