hello, i'm starting to have some fun with electronics with my kids.
we build a small light aeroplane with wheels and put a 12v dc motor on it with a propeller.
Hope was to see it moving ahead not yet flying, but the motor starts turning nicely and after about 1 seconds
stops working. If i remove the propeller it works perfectly, if i put it back, it stops again.

I tested the same circuit with a 1,5 v battery and propeller, and then the motor works slowly but nicely,
what's going on?

thanks
alex

 

hi,
Post details of the 12V battery, depending upon the type ie: current rating it may not be able to supply the required motor current to drive the prop.

E
A quick check would be to measure the 12V battery with and without the prop.

 

actually it was a 9 V battery, standard duracell from any shop.... i tried also to put two of them in series to get 18V, and got same result.
What do you mean by current rating? i guess there is nothing written on the battery, but shall i measure current flow with amperometer ?
Also the DC motor was bought over internet and came without any data sheet, only specification was 12 volts.

if the current is not enough, shouldn't the prop just spin slowly, i mean it should not give enough push to move the aeroplane, but still moving the prop as a little fan ?
why 1,5v works like that but 9v stops it?
thanks!

 

hi,
Is the 9V battery a PP3 type, rectangular approx about 1 inch * 2 inch,? If so I would say it cannot produce sufficient current to drive a medium/ heavy current motor..

A 1.5V AA size battery can supply 1 to 2 Amps for a short period.

Measure the current drawn by the motor from the 1.5V battery, this will give you a rough guide to the current required at 12V
Use Ohms law to get an approx value for the motor resistance...
E

 

ok thanks, I'll do that.
this actually makes a lot of sense. any suggestions where to find a proper battery?

 

any suggestions where to find a proper battery?

We don't know where you live, but any reputable electronics store/supplier would have one.

 

You could get two battery holders for say 4 * 1.5V [ AA] so 6V each holder.
Depending on the capacity of the planes fuselage you may get them to fit inside.

 

If that's brushless motor used for RC planes than he is rated in Kvs.They are normally run with 3,7V.

 

thanks everybody for helping!
i live in Helsinki Finland, so an online store would be best.

I was thinking about the 2 x four batteries holder solution as well, i was just thinking about the extra weight,
but i'll try and let you know !

it was a general purpose dc motor, cheap, just for testing with kids what we can do

alex

 

That kind of motor can't power planes since it doesn't have enough RPM,you can build a car or some kind of tracked vehicle.

 

Post a pic of the motor if possible, if this is a brushed motor, you can spin it by means of a drill chuck etc and read the DC generated, if it is supposed to be a 12vdc motor then see if you can produce 12v, this voltage will be proportional to the actual rpm produced by the chuck.
Max.