# Voltage help

Discussion in 'General Electronics Discussion' started by graves4412, Nov 12, 2014.

1. ### graves4412

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0
Nov 12, 2014
Hey guys, I'm really new to the world of electronics building and have a question that would be quiet basic to all of you but I need help. I have a 3v motor that needs to fit in a compact space along with a battery. I also need to hook up an on off switch as well. Is it possible to hook up a 12v battery to a 3v motor or will it blow the motor?

2. ### davennModerator

13,865
1,956
Sep 5, 2009
hi
welcome to the forums

what do you think would happen ?

yes its likely to burn it out

cheers
Dave

5,164
1,087
Dec 18, 2013
Probably not a good idea. You need to drop the voltage. What motor is it, how much current does it draw?

4. ### BobK

7,682
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Jan 5, 2010
If it has to fit in a compact space why are you using a 12V battery? It will take more space than a 3V battery with the same current capacity. Is there something else that needs to run off 12V? If so, how much current?

Bob

5. ### Gryd3

4,098
875
Jun 25, 2014
Something to help when working with electronics is knowing what voltage and current actually is... and how it behaves.
For simplicity sake, I will not go into this, but remember these:
-When voltage is being provided, it will be 'pushed' to the device you want to power.
__a 12V battery will put all 12V on a 3V motor, which is 9V higher which would most likely kill it.
__a 3V battery will only be able to put 3V on a 12V motor, this could strain the battery (or other source) and kill the battery (or other source... like a AD/DC adaptor)
-When current (amperage) is being provided, it will usually show you the upper limit it can provide. The device you want to power will pull the current it needs.*
__a 3A motor will only take 3A from the wall adaptor.. even if the wall adaptor is rated for 100A**
__a 5A motor will attempt to take 5A from a wall adaptor even if it's only rated for 3A, this could damage the adaptor.

So. Match voltage exactly (or very close to), and you can bend the numbers for current.
ie, a 3V 1A adaptor will power a 3V 200mA motor with ease.

nitty gritty notes:
*There are such things as "constant current sources", which will increase the output voltage to force the current through the device... You are unlikely to find one at a local radioshack. They are usually found on bench power supplies, or as small integrated circuits on circuit boards.
**Be careful here.. as some wall adaptors are built cheaply. When you pull current from a source, the voltage will droop a little. The more current you pull, the more the voltage drops typically. Some power supplies will start at a much higher voltage than advertised so when the advertised current it pulled from them, they 'droop' down to the advertised voltage. It would be wise to always double-check the voltage from a power supply prior to using it with a sensitive device.

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