I have a lighting controller that outputs 0-10 vdc control voltage. (sourcing)

The 40 LED fixtures it is to control dimming on, require a 0-10 vdc sinking controller. The LED driver control leads supply 24vdc which needs to be sunk down to 0-10vdc. Currently i'm using a 500 ohm pot (2watt) to dim the lights manually, which works fine, however we need to set up the controller to simulate sunrise/ sunset everyday.

With all control leads shorted together, (0vdc) the current through the control circuit is 31 mA DC.
Can anybody offer a cost-effective solution to make this work? (My budget wouldn't allow for a new controller) Thanks for any suggestions.

 

How much current does the 40 LEDs require?
What output will the controller provide to simulate sunrise/sunset?

 

How much current does the 40 LEDs require?
What output will the controller provide to simulate sunrise/sunset?

The controller outputs a regular 0-10vdc control signal.
The maximum current to be sunk will be 21 milliamp dc.