i was woundering about making one of those DC meters to monitor tempreture in my case... can any 1 reccomend what i need to do i found a 5A DC Meter that has the sort of display i want... as in it shows a blue curve going onto a red one... i was going to use something like a Thermistor to "gather" the heat... so to speak.. and if possible a couple of LED's to show when its ok and when its getting hot.. any help?
Well, you could use a thermocouple, http://www.picotech.com/applications/thermocouple.html and then an op-amp in a comparator configuration. Basically, a comparator compares the voltages of the two inputs and sends the appropriate supply voltage to the output. If the voltage at the inverting input is higher, the negative supply voltage is sent to the output, and if that of the non-inverting input is higher, the positive voltage rail is sent to the output. You might want to brush up on op-amps if you don't understand what I'm saying. The key here is to have a reference voltage at one of the inputs. The other input comes from the thermocouple. If this voltage is higher than the reference voltage, the output reflects this. At the output side, you could have two LEDs, one opposed from the other--so tie the cathode of one to the anode of the other, and the anode of one to the cathode of another. When negative voltage is applied at the output, one LED--the reverse-biased LED--turns on. When positive voltage is applied, the other LED turns on. As for your temperature measuring instrument, I'd need more information to help you.
