I would like to switch on a point light (increase the emission strength from 0 to 100). Then turn it off again after a number of frames. I would like to realize this with animation nodes. Is that possible?
You can do it animating the light's strength.
(I did it in Cycles)
I couldnt add the screen shots that i took :/
First, select your lamp
Then go to the frame that you want the strength 0
Go to light settings and set the strength to 0
Press the 'i' key with your mouse cursor over the strength value and it will gets yellow
Go to the frame that you want the strength to be 100, set the strength to 100 and press the 'i' key again with the mouse over the number
Everything can be animated in the animation nodes. If you want to animate the strenght of a light in the internal blender renderer, you have to change the energy value found in the properties panel of the object.
The debug panel at the top shows the property changed was bpy.context.object.data.energy = some_value. A handy thing about blender is that the programm allows us to access almost every property of every object through it's data path. I will assume you are not familliar with the blender api (me neither but I will do as if I was :) ). Just think of a data path as the way (path) to access a property.
Now you can right click on the property and copy it into the Object Attribute Output Node. Now you can add an animate number node in order to animate the value.
If you are doing it with the cycles renderer the process is simpler because there is a special node for it. I use a developpement version of the A-N, and I don't know if this node is present in the master build. If it is not, just use the same process than before. The node is the cycles material output. You cant use this for a point lamp because it can only modify the material and the lamp has no material, but built-in strenght and color values. If you want to use the cycles output nodes just replace the point lamp with a tiny ico sphere or any mesh-you like. Trough this node you can access the icosphere material (make sure you click on the button Use Nodes to use it). Then use the emission shader. From there you can access the material through the AN node. Select your material, than below Emission; then the strength value.
P:S I found very few documentation on the an, but I am sure there is a growing community using it so if you have any more questions, make sure to ask them.