ICL7107 and LM35 based 7-segment thermometer Answered
I'm trying to create a digital centigrade thermometer based on an ICL7107 3 1/2 digit 7-segment driver/ADC and an LM35 linear centigrade temperature sensor but I'm having a few problems. There doesn't seem to be much online about using the ICL7107 with a LM35 and most of the schematics available are for volt meters, but that's not a massive problem as the LM35 gives 10mV/C linearly. I'm just trying to go based on the few schematics I have found but I'm wondering about the supporting components for the LM35 which seem a little too simple. The first schematic I found was from a Hungarian electronics forum and seems to depict a diode and amplifier being used for the temperature sensing which seems like a bad idea to me. The second seems more like what I'm trying to do.
The other few things are the negative voltage source, the first schematic shows an inverter being used as does the datasheet, but the second schematic shows an LMC7660 voltage converter which seems like a better option to me. The second one does also show three diodes in series used to drop the voltage for the LED displays which doesn't seem like the best idea, but I can't think of a better way to do it without attaching resistors to each one as the number of lit segments will be variable.
The supporting components for the ICL7107 seem pretty consistent between the two and the schematic so I'm confident those are correct, but I'm looking for some advice on how to connect the LM35 in a way that will give me an accurate readout.