I'm thinking of building a rheobus and I have a question. Okay, is there a way to check the output voltage of a rheostat so that if the voltage is at say 2V - 6V, a green LED will light up, but if it goes up to say 7V - 12V, the green one will go off and a red one will light up?? Thanks in advance and let me know if I need to be clearer on this. EDIT: Hmm... think a 3914 will work for this?? Use it as a dot display and run the leads into two LEDs.. send the lower half of the pins to the green LED and the upper half to the red LED. The question then is whether or not the 3914 will take a signal voltage of 12V. Thanks in advance.
That's the easy way to do it. AmPz suggested comparators over on [H], and that's essentially what goes on inside the 3914. There's 10 calibrated comparators in there, dividing the reference voltage into ten equal steps. The thing is, I wouldn't suggest just wiring those outputs together in parallel and then selecting dot mode. The pins that are off will be pulled high, while the on pin will be low, but you tied it to a high pin, so it may be indeterminate. I'd suggest an op-amp comparator, you shouldn't need dual voltage supplies when in comparator mode. The cheap LM741 has four op-amps in the package as I recall.
this diagram could be modified into ne thing that requires voltage controlled bar graph get the diag here
ooh, nice one. That's pretty much what's going on inside the LM3914. Just set up your voltage divider the way you want it. It doesn't need to be equal steps.
look i dont want to plug cpemmas site too much but its here oh and maplin dont have ne of the rotary switches in stock according to their website
Just one warning, that Diobus was the most fiddly soldering I've ever done, though it would be easy with 3 hands. Unfortunately, my wife objects to mild burns.
