The .58VDC represents an optimal temperature and I want to keep the thermistor voltage at that level while the 18F4550 continually checks the analog voltage once every 5 seconds. If the voltage is between .58 and 2VDC, the 18F4550 should force the voltage level (that is the issue I'm describing in this thread) to .58VDC. Below .58VDC and above 2VDC the thermistor value will not be forced. What did you have in mind?

I've gotten two methods to work, for the most part, but there are a couple of issues. The one I like the best is using a voltage divider from the PIC. I use two outputs and those pins are connected to the 18F4550 pins. It works really well and the voltage divider I'm using only consumes 10mA. Here's the problem and hopefully someone can point me in the right direction. When I put the pins as inputs, there must be a low impedance connection within the PIC because it pulls the voltage to ground. The pins I'm using are PORTE.1 and PORTE.2. I've tried PORTB.6 and PORTB.7. Can I configure something with the pins where they are truly in a high impedance state?

I've also used a zener diode (1N5352B) but only because it's all I had laying around. It worked better than I thought but it doesn't pull the voltage low enough. I'm going to look around, perhaps even Radio Shack, to buy some different types and play with them. I don't understand how to use a zener diode correctly in this application but I suppose it's not meant for it anyway. I will try the normal diode experiment when I get my hands on some. I know I have about 30 of them somewhere.....