Powering electric motors

[Chippychap]

Hi Guys,

I wish to turn a battery powered little motor into a mains fed device.
Obviously I will use a, what I call, mains adaptor.
Do I "bin" the chargers for the ni-cad ones or could they be used as a power supply?
Are there rules of thumb or must each be considered separately?
One motor used a "D" cell so it uses 1.5v according to the battery, do
I need to check what the motor wants and needs as opposed to what
the battery gives?
If this is covered fully in a tutorial then the links would be gratefully received.
Thank you.

 

[colin55]

All the chargers will deliver about 250mA. But the motor wants 2amp to 10 amp depending on the load.
That's why you leave the batteries in place and charge them as much as possible while you are using the device.
The charger will keep up at the rate of about 10%.

 

[crutschow]

If you check the motor current under load, you will know how big a power supply you need to power the motor.

But it will likely be difficult to find an adapter that puts out 1.5V or so.

 

[MikeMl]

Just a minor warning about Wall-Warts:

Some are AC (no rectification)
Some are half-wave rectified DC (with, or without an internal filter capacitor)
Some are full-wave rectified DC (with, or without an internal filter capacitor)

Most are unregulated, and in fact they purposely have a high output impedance so that they will not burn up if shorted (part of UL Certification)

Some are regulated, but have fairly modest output current ratings.

Most are not suitable for running low-voltage, high-current motors...

 

[ronv]

It would be best to know what the motor wants and needs. We know the voltage --1.5 volts. If we knew the current we would almost be there. (even the resistance would tell us the locked rotor current)

 

[vlad777]

It's dangerous
but if you overload 300 mA wallwart it will give higher current and lower it's voltage.
It will operate with lower coefficient of efficiency and it will heat (and give more watts then labeled).

Transformer can stand up to 70 deg Celsius.

Of course , wire can burn out , diodes fail, or you can cause a fire.

 

[Chippychap]

WOW ! So plenty to think about then.
So when it's on a cell it has a stabilised input?
What about a constantly re-charged ni-cad where the charging current
is just floated over the cell, or s'pose may as well just use it powered by the cell itself.
Some of us don't know how dumb we are until we ask.
Then again, on the plus side, I was smart enough to not only ask, but know who to ask.
Bless you guys.
As Arnie said, "I'll be back" hopefully before the fire.