Oatley K241 regulator questions

[northrun]

I am a newbie building my first windmill, an Ametek-style setup with an Indiana 36VDC motor.  For a dump load controller, I chose to build an Oatley K241 kit (without the 3 phase rectifier portion).  http://secure.oatleyelectronics.com/files/K241notes.pdf Seeing as how this is my first circuit board soldering job, I am hoping that it is put together correctly.  I am a little confused about some things.

For connecting a dump load, the instructions say " a resistive load ...can be connected across the two pads (two long pads on the underside of the board near the MOSFETs).... "  I have done that.  I have set the switching voltage to 14V with the trimpot, using a DC power supply that puts out 13.8V (I set it a hair over the 13.8V point).  

To see what happens when the regulator switches to dump mode, I have turned the trimpot down so that at 13.8V, it is in dump mode.  The green "charged" LED comes on.  When I do this, I see a voltage of 4V across the long pads.  Is this what I should be seeing?  

I am unclear on the concept of the dump load diversion.  For example, in the above case, if the trimpot is set to switch at 13V, the battery voltage is above this so the power is diverted to the dump load, and the generator is putting out an open circuit voltage of 18V, would I expect to see 18V - 13V = 5V across the dump load pads?  Or is the voltage I see always held to the voltage of the batteries (in this case it would be 13V) so I should see 13V across the pads?

The other question is the red "charging" LED.   This is not on when the regulator is hooked up and the battery voltage is below the switching point (actually it is very faintly lit, visible in a dark room).  I have replaced the LED and it's the same.  I have checked all the soldered connections and they seem fine.  Any troubleshooting tips?

Thanks.

[Nando]

I am not familiar with that controller but I have the impression is just an ON/OF switch.

When dumping the load it may stay for a fraction of a second or several seconds, all depends how the battery is charged and what extra current is coming in and it is just applying a load across the battery to keep it from going above the 13.8 volts settings you say you have.

You should see the battery voltage across the dump resistors and very low value across the MosFet pads ( a good design should read around less than 0.3 Volts

The Charging LED, normally should be bright when ON, It may be that you have a high value resistors, it should be in less than 3 Kilohms if a high intensity LED or could be a minor error in the build up.

Nando

[Flux]

I think that circuit diverts the source before a blocking diode. To use with a brushed dc generator you should use a dump load resistor that will dump just more than the full current expected from the generator. Alternators can be shorted in some cases and may stop during the diversion period but repeated direct shorting of a dc machine will be bad for the brushes and commutator.

Because of the blocking diode you will not see the battery voltage at the dump load resistor. The 4 v that you see across the pads should be the volt drop across the dump resistor. You need to choose a resistor that will drop about 10v at the maximum output you expect from the generator, at less than full current out, the volt drop will be proportionally less.

It seems from the description that it is working.

Personally I would not have chosen that mode of control for a dc machine but with care I expect it will be ok.

Flux

[northrun]

Thanks to both of you.  I will install the regulator in my system and watch the battery voltage carefully to ensure that the dump diversion is happening when it should.  

As for the red LED, I can live without it coming on, unless it's a symptom of something more serious.  As long as the green one is off when charging and on when dumping that should be all I need.

[Nothing40]

The red LED is lit,but very faintly?

There's probably a resistor in series with the LED somewhere,Is it the correct value resistor?

[northrun]

I checked it, and it's the corect one (15K).