Howdy, Beginner electronics hobbyist here. Mechanical engineer as a day job though. I bought this motor to use as a generator. I have been running some test to see what kind of power i can get from it. At rated speed it claims 15W however i am only seeing 27V .25mA. Currently using a power drill to spin the motor, tach to measure the speed, and multimeter to get the volt and current. Currently the two leads of the multimeter are attached to the two contacts of the motor.

Question:
Does the circuit need a load in order to effectively measure current and voltage? Or is it more possible that the motor is defective? My research has said that a brushed dc motor does not need rectification, is that correct? I have tried a blocking diode just in case but did not change anything except for eliminate one rotational direction of power. Troubleshooting is difficult when little is known about the subject. Hopefully will be learning quickly though.

Thanks,
Ag

 

It is a 12vdc motor so if you back-drive it and measure the output for 12vdc, this will be the rated RPM of the motor/generator.
How are you measuring the current? What load?
I doubt the motor is defective if it is outputting 25vdc!
Current depends on load connected across the generator.
Max.

 

Current measurement set up is the same as voltage measuring set up, which i know is wrong. I tried adding a few resistor in series with the motor and meter to act as a load but it also didn't change anything

 

If you are seeing a voltage output and a load results in little or no current then you have something miss-connected, if you overloaded it the voltage would collapse some.
The load has to go ACROSS the output.
Max.

 

Try a 1-2 ohm 15w power resistor or a 15W 12V (automotive) bulb directly across the generator output and measure the voltage.

 

Try a 1-2 ohm 15w power resistor or a 15W 12V (automotive) bulb directly across the generator output and measure the voltage.

I was actually in the process of finding a auto bulb but it seems to have disappeared.
I drew up a very poor diagram of what ive tried so far. All situations had same result of very little current. The motor was not driven.

 

As has been stated, you cannot connect the load in series with the meter, if the meter is measuring voltage.
The meter has a megohm or more of impedance, so obviously you are not going to get much current through it.
You need to place the load in parallel, directly across the generator output.

If you want to measure current through the load then you put the meter, set to measure current, in series with the load.

 

As has been stated, you cannot connect the load in series with the meter, if the meter is measuring voltage.
The meter has a megohm or more of impedance, so obviously you are not going to get much current through it.
You need to place the load in parallel, directly across the generator output.

If you want to measure current through the load then you put the meter, set to measure current, in series with the load.

Thanks for the reply, I am trying to measure current, as the lack of current is my problem. And all the diagrams are in series with the load correct?

 

Update: Fuse is blown on multimeter Oops, that may be the problem XD

 

Thanks for the reply, I am trying to measure current, as the lack of current is my problem. And all the diagrams are in series with the load correct?

If the meter is configured to measure current, yes.
What is the meter setting?

 

Update: Fuse is blown on multimeter Oops, that may be the problem XD

Generally done if you connect the ammeter across the generator with no load in series.!
As in your 1st example, it should be the second.
Max.