I am trying to make a temperature gauge using LEDS and the LM3914 IC. I haven’t figured out how to build it so I thought I would ask the experts. I have a temperature sensor that has a ground, meaning that the signal goes from the gauge to the sensor then grounds out on the engine block. I would like to make it with the first one or two LEDs yellow for the warm up or low temp setting, then three to four LEDs showing normal temp, then another one or two yellow to show high temp, two red LEDs showing over temp and have it when the last red LED lights up the whole cluster flashes. The specs on the temp sender are at 68º Fahrenheit the resistance is about 2.45k Ohms, 122ºF about 0.811k Ohm, 176ºF about 0.318k Ohm, 230ºF about 0.142k Ohm, and at 266ºF about 0.088k Ohm. This is on a motorcycle and the voltage will vary from 11-14 volts, so some kind of voltage regulator may be necessary? As an added bonus it would be cool if, when the circuit is first powered up, the LEDs would turn on one by one in sequence, and then turn off in sequence, as a self test mode. Not necessary but would add a cool effect.

Thanks for any help you can provide.

 

Anyone?

 

You would probably need to find out if the sensors change in resistance is linear (at first glance it does not appear to be). If it's logrythmic, the LM3915
may suit you better.

The how much resistance/deg F. You'll have to use voltage changes to make the LM3914 to respond and the voltage changes are too small you may have to amplify them.

The following circuit link is a Battery monitor using the LM3914 and has trigger points for alerts:

http://www.mhennessy.f9.co.uk/battmon/index.htm

Here is a link to the LM3914 Datasheet:

http://www.datasheetcatalog.com/data...9/LM3914.shtml

P.S. I am not the "expert" you are looking for but thought I'd offer a few pieces of information.