Another batch of toys I have to play with

metron9

It was my birthday and I grabbed the allelectronics.com catalog and ordered about a hundred bucks worth of stuff.

One of the items is a Motor/Generator Cat# DCM-310
http://www.allelectronics.com/cgi-bin/item/DCM-310/search/MOTOR_GENERATOR_B_9060_.html

I see it has 4 wires and the web page says red and black for input and yellow for output. I see I get an ac voltage on the yellow wires. I am a little perplexed as to its use though. What is the point of using DC voltage to run a generator that gives you an AC output? Is this something that was used before inverters·were invented?

Using it as a wind generator though it looks like i can use both sets of wires for power conversion. A quick spin on the scope shows the red line as the black and red wires and the yellow wires are the blue plot.

This is why a scope with two channels is a real boon to understanding how things work.


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Think Inside the box first and if that doesn't work..
Re-arrange what's inside the box then...
Think outside the BOX!

Bruce Bates

metron9 -

I suppose it's legitimate to call it a "generator output" in some circles, but I'd bet the manufacturer designed it as a TACHOMETER output. I _think_ motor controllers like the Solutions Cubed Motor Mind series (MM-B) can even accept a tachometer output for speed feedback. I'd have to check the datasheet to see if it will accept an AC tachometer input however.

As to your other query, yes, motor-generators were and are used to develop voltages and frequencies from the input side and produce them on the output side. It's actually quite efficient and may be the only way to develop certain voltages or frequencies. One notable example is creating three phase current from a single phase source. Once you have two AC phases, you can develop as many phases as you wish using transformers. However, if you only have a single phase source a motor-generator is an excellent method for producing the three phase power needed.

Another place one often sees motor-generators is on larger airplanes to develop 60 cycle current from a 400 cycle source, or visa versa. They also may be used in off-grid applications. 12 VDC input and 120 VAC 60 cycle output. The 12 VDC may be coming from batteries, solar panels, wind generators, fuel cells or any other converted power source.

Regards,

Bruce Bates

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James Long

Metron,

A car alternator actually puts out ac, that is rectified to DC· (I actually think it is a pulsed DC).

So things like this are really around everywhere.

Most of the time if you jump start a car with a dead battery and take the jumpers cables off too quick you will kill the alternator of the car with the dead battery. This is usually due to the alternator putting out more amps than the recitifer circuit can handle ( it blows the diodes ).

I do think it is interesting the input changes with the output.

I do not think you would really need the input voltage with a permanent magnet brushless motor.

I would think the black and red are for use as a motor....and the yellow are for use as a generator. But I'm guessing here.

Just would be a good test with the scope if you want to try it.

James L

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James L

Partner/Designer
Lil Brother LLC (SMT Assembly Services)

metron9

James, The scope output is the voltage comming from each set of wires, the red line is the output of the motor when spun by hand.

A DC voltage applied to the red and black wires (Red line) spins the motor and generates AC on the yellow ones.

Not sure how high of DC voltage can be applied but at 12V it only draws 90 mA and generates 8V output however it can only produce 10mA ac current so I think Bruce is right, it must be a signal generator. At 24VDC it draws 110ma and outputs 16V ac but I can put an led across the ac output with no resistor and it drops the voltage to 7.5V so an AC generator for power using wind is not a good option for this motor.

It has really nice bearings though at 24V it is silent (course I am a drummer who wears no ear protection).

I am going to order more of the NEODYMIUM magnets today though, if you have not played with these little buggers you should. The tiny NEO CYLINDER MAGNET is so powerful when you stick it to a piece of metal you cant pull it off without sliding it to the edge. They move each other at a distance of 6" when placed on a spindel you can move them from 3' or more. I have to get some of the 1" spheres. I know the slugs are used to make generators for home built wind generators.

I have a bunch of plastic test tubes comming today as well. I want to make some electronic fish with them and use the magnets on the inside and outside of the tube to move fins to propel the fish. I will also have a solar panel to recharge the dual A batteries that will fit in the tubes. Not sure yet if there will be enough air in the tube to float so i may need to add another tube.

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Think Inside the box first and if that doesn't work..
Re-arrange what's inside the box then...
Think outside the BOX!

stephenwagner

A very specific type of motor generator. Rotory Converter.
http://www.nycsubway.org/
http://www.nycsubway.org/tech/power/
http://www.nycsubway.org/tech/power/rotary.html

SJW

RobotWorkshop

That motor/generator is kind of a unique item to see these days. I wonder what it was intended for? I have seen a much larger version of this used on old WWII GE & Sperry Searchlights as a way to generate AC to run the servo system. They called it a Dynamotor. The whole set is powered from a large DC generator plant but the electronics (vacuum tube amps, etc) for positioning the light needed the AC. It's all really different method than what i'm used to seeing today. Not a lot of old examples are left intact but the ones that are left are pretty cool to see in action.

Robert

metron9

Hmmm perhaps it should be AC in and DC out as stephens link shows. I may try that with an AC wall wart.

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Think Inside the box first and if that doesn't work..
Re-arrange what's inside the box then...
Think outside the BOX!

ChrisP

Another notable use of motor/generators, very old school 2 way transceivers. Back in the tube days they used them to generate the upwards of 450 volts to run the tubes in place of transformers for mobile applications.