Increase voltage output on a photodiode

Hi all.
First, PLEASE forgive me, my electronics knowledge is poor, but I do have a HUGE interest in it...
My Question:
I am building a device to continually track the sun. The 'sensing' part is a photo diode, which I want to link up to a Moeller PLC controller.
If I link the one leg of the photodiode to a 'analog-output' of the device and the other to 'analog input', the voltage read by the PLC changes with light intensity- this system works, but I'm trying to not use any external power(is this possible?)
Second way I have set it up is to have the one leg of the photodiode the analog input, and the other connected to ground. I only get a tiny change in voltage.
I have been fiddling with a transistor, and have been pouring over a circuit diagrams. Problem is; I theoretically grasp the diagrams(to some degree) but don't then know how to apply that to my Real system(which leg is which). Symbols are one thing, but I fall short when it comes to actual components.
In really really basic terms, can some one explain which Leg of the diode i must connect to the transistor, and where must I plug it in to my PLC.
Thanks
Sebastian

you can use op amp. its a practice way

You may want to look at the circuit presented on this page. I would play around with the value of Rf (the feedback resistor) and try various gains while looking at assorted light levels as to the analog voltage out.

Ron

Taos makes an all in one light sensor package. One model has an amplified analog readout, for a microcontrollers a-d inputs, look them up.

Thank you!
Nickelflippr, in my meanderings, I actually did find them! I want to build the thing myself though
And Ron, are you suggesting I, like mrdauz, that I use an op amp? [that is an op amp right?]
Is is not possible with a transistor?

Cbas said:

Thank you!
Nickelflippr, in my meanderings, I actually did find them! I want to build the thing myself though
And Ron, are you suggesting I, like mrdauz, that I use an op amp? [that is an op amp right?]
Is is not possible with a transistor?

Click to expand...

It is possible several ways. I was under the impression you wanted an analog output signal. So I suggested the circuit I linked to. If you just want an output that is high or low then I would suggest a comparator circuit. Really depends on what output you want. A transistor could also be used.

Ron