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One of my projects required the testing of aquastats, and we needed to monitor voltage (12-14vac) as well as temperature. I originally started with a TMP36 analog temperature sensor, but was unhappy with the output. It varied a few degrees every few seconds with no  obvious change in the environment. I changed it out for a DS18B20 didgital sensor. I offer both versions here for your enjoyment.

For more info on this and other related projects see:

http://arduinotronics.blogspot.com/2011/03/monitoring-voltage-of-dc-battery-supply.html

http://arduinotronics.blogspot.com/2012/04/voltage-monitor.html

http://arduinotronics.blogspot.com/2013/06/ac-voltmeter-and-temperature-monitor.html

http://arduinotronics.blogspot.com/2013/06/volt-meter-temperature-monitor-part-2.html

Step 1: The case

I dug out an appropriate case from the dumpster, milled out a rectangular hole for the lcd, and drilled holes to mount the LCD and the Arduino. I used brass standoffs and fiber washers to prevent shorts. Then I gave the whole case a quick spray of flat black to cover the scratched and scraped gray that originally covered the case.
<p>is this voltmeter have a feature of Auto-ranging???</p>
It uses a voltage divider, so it can measure whatever max your voltage divider is set for. You could add manual ranges with additional resistors.
<p>hi ..i am doing the same project my design a little different may i ask u some qustions in ur project how can i contact u ?</p>
email me at greentrust@gmail.com

About This Instructable

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Bio: Professionally, I'm an IT Engineer (Executive Level) and Electronics Tech. I'm a Amateur Radio Operator (KK4HFJ). I lived off grid, with Solar (PV ... More »
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