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Digital Thermometer?

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mankunnam

New Member
I want to build a digital thermometer with a 3 1/2 seg. LCD Display and IC 7106 included. can i have a circuit diagram please
 

rantreb

New Member
Hi, Does anyone have info on a digital fahrenheit thermometer that uses a 7101 and lm34. i am interested in the led readout and fahrenheit scale. please note that the lm35 is celcius and the 7106 is lcd. i do not want a pic. for some reason the digital fahrenheit thermometer with led readout is hard to come by.
rt
 

on1aag

New Member
Hi Rantreb,

rantreb said:
Hi, Does anyone have info on a digital fahrenheit thermometer that uses a 7101 and lm34. i am interested in the led readout and fahrenheit scale. please note that the lm35 is celcius and the 7106 is lcd. i do not want a pic. for some reason the digital fahrenheit thermometer with led readout is hard to come by.
rt
A Fahrenheit thermometer is easy to build. Use a centigrade sensor
(like LM35, 10mV/°C) and multiply it's output by 0,18 with a resistive attenuator (e.g. 82k & 18k). Short the "hi" input of the 7107 and apply
-32 mV to the "lo" input so that the reading is 32,0. Remove the short
from the "hi" input and apply the signal from the attenuator.
You don't have to be a rocket scientist to do that.

on1aag.
 
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rantreb

New Member
Thanks on1aag,

Thanks for the info but I want to use the LM34 and would also like it to work down to -40 F. So, I'm working with the LM34 and the 7107 (not 7101).

Rantreb
 

wsemajb

Member
rantreb

I share your pain!!! I've been pulling hair for a while trying to come up with an LED panel readout for fahrenheit. I have very little EE knowledge so I need nuts and bolts that I can put together. I have no programming knowledge either. I need LEDs in F. for a shop project. They are actually readily available, for 450.00 USD on up for the pair, in industrial/nasa quality units, but astonishingly very little is to be had in anything more affordable.

Problem is that the advent of LCDs, with their far lower power consumption, just about eliminated the use of LEDs available in cheap (often battery powered) consumer applications. There are backlit LCDs available, but I believe they still don't approach the visibility of LEDs. I could be wrong.

I ended up getting a second hand (but new) pair of Thermodyne gauges for automotive use off of ebay. 12vdc with thermistor sensors. Only good down to 70F. but that works for me. Sixty bucks for the pair with senders.

Prior to that I was looking at this pair...

http://www.allelectronics.com/cgi-bin/item/PM-120/385/3.5_DIGIT_LED_PANEL_METER,_20V_.html
http://www.allelectronics.com/cgi-bin/item/LM34DZ/search/FAHRENHEIT_TEMPERATURE_SENSOR_.html

...figuring that even a novice like myself could manage to get a 1mv/F. LM34 sensor to match up with a 1mv-199mv LED panel. It could be scaled from
-40F. to 160F. No? I'll never know now. Heck, I might just order the pair anyway out of curiosity. They're cheap enough for that!
 
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