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Connecting a motor to mains

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nic_marshall

New Member
howdy all. I have a 3v-9v motor that i want to connect to my 240v mains. I bought a maplin "DC 9V (2A) Switched Mode Power Supply", which i thought would do the trick.

However the motor doesn't run constantly. It powers up for a second, then switches off, then powers up again for only a second, working intermittently like this. Why does this happen? How can I solve it?

I've also bought 2 "Miniature Dual Gang Linear Potentiometers" at values 10k and 100k, but when i wire it up the moving slide switch has no obvious effect. Please see attachment for images. If there's a specific way to wire this bad boy up, or if its a wrong component can someone say because i know there's other types of potentiometers.

thanks
 

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Styx

Active Member
when you say the motor powers up then switches off, does it come to a complete stop or does it stop accelerating

Also do you have a multimeter? might be worth probing the 9V while the motor is running
 

Pommie

Well-Known Member
Most Helpful Member
Looks like your motor draws more than 2A. Must be a big(ish) motor. More details would be good.

Mike.
 

colin55

Well-Known Member
A motor cannot really be 3v - 9v. This voltage range is too large.
If it is a 3v motor and you supply it with 9v, it will run too fast.

If it is a 9v motor and you supply it with 3v, it will be very weak.

You have to be more specific.

If it is a 9v motor and the data sheet says 800mA, it will take more than 2A during the time when it is starting-up. This may be overloading the power supply and it is switching off.

You may need to put a large electrolytic across the motor.

These are some of the things you have to consider.
 
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crutschow

Well-Known Member
Most Helpful Member
If it is a 9v motor and the data sheet says 800mA, it will take more than 2A during the time when it is starting-up. This may be overloading the power supply and it is switching off.

You may need to put a large electrolytic across the motor.
A cap across the motor will increase the starting surge current, not reduce it. You want the cap at the power supply output, in front of a switch to the motor. This allows the cap to charge before you turn on the motor.
 

nic_marshall

New Member
I've given you all the info that's been given to me colin. Maplin is awful for supplying details, the potentiometer came in a clear plastic bag and that's it. I think you're right about it drawing to much power.
I've also tested it out Styx, it the power supply gives a steady 9V. I'll put a cap on it after the switch as crutschow says.
 

Styx

Active Member
I've also tested it out Styx, it the power supply gives a steady 9V. I'll put a cap on it after the switch as crutschow says.

ok it might be an instantaneous dropout,
Is the motor unloaded. I can't imagine an electrical machine would need 2A just to spin unloaded???
 
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nic_marshall

New Member
well i've had fun burning out caps, i better buy the right kit now. The motor's very small, that's why i thought this power supply would be ample. The motor runs intermittently like this regardless of the load (although my load's small anyway).

I've also found out that if i tap the wires together the motor sort of powers up and begins to work. How fun! But unfortunately impractical.
 

Mr RB

Well-Known Member
The motor might be drawing TOO LITTLE current. Some of those little motors only use 50mA to 100mA with no load and your 2A SMPS supply might have a minimum current value.

It's also possible the motor generates enough line noise it is causing the SMPS to shut down, I would try connecting a large cap across the motor, maybe 220uF or larger.
 
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