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Motors and stepping down voltage?

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lee_hdi

New Member
Hello,
This is my first post and just need a little help and to be pointed in the right direction.

My car has electrically folding mirrors, but they've stopped working so I took them to pieces and noticed that the motor had rusted up (common problem on a Peugeot 206, sadly)

Anyway I'm going to buy some new motors, the only problem is that the only ones i can find that will fit are 3v rather than 12v.

So I've done a bit of searching and found out i need a voltage regulator and found this one LM317 3-Terminal Adjustable Voltage Regulators : Voltage Regulators : Maplin which i think would work.

But when i've read through the description it says you need two resistors adding to the circuit to get the desired voltage output. Now that just goes straight over my head and i don't even know where to start looking for the correct resistors. So i was wondering if you know what resistors i would need.

Thanks in advance,
Lee
 

ke5frf

New Member
Lee,

All I will suggest is that, aside from specific design characteristics, a 3V motor is rarely going to generate the torque a 12V motor provides. And I imagine car mirrors are fairly heavy and cumbersome things to actuate even with a 12V motor. I may be wrong, I've never tried it, but it seems to me...

So before trying to re-engineer everything, I would dig a little deeper into finding an more suitable replacement. I would definately consult the datasheet for both motors for current, power, and torque specifications. Otherwise, you may find out that 3V motor only stalls after all the work to fit it.
 

ke5frf

New Member
Oh, just to add another tidbit.

If I WERE to attempt to run a 3V motor from a 12V source, A simple, cheap alternative might be to drop the voltage with some DC light bulbs, Three 3V, a 9V, or a 6 plus 3V. You do understand voltage dividers I assume? I think you would need to determine the power rating of the motor and the bulbs to comply with Ohms law (proper impedances). This would be a series arrangement.

Bulb-Bulb-Bulb-Motor or Motor-bulb-bulb-bulb. Either way. Build a little box to hide the bulbs in.

I mean, this is a car battery and is constantly recharging so energy consumption isn't a priority right?
 

giftiger_wunsch

New Member
Anyway I'm going to buy some new motors, the only problem is that the only ones i can find that will fit are 3v rather than 12v.

Did the original motors have any markings which might indicate their model numbers / manufacturers etc.? If you can't find a 12V motor which will fit in the enclosure then your best bet is to look for the one 12V motor you know will definitely fit.
 
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