LED
THERMOMETER |
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| This
device is a novel LED electronic thermometer for use in a home as a
means of monitoring room temperatures and the operation of your homes
heating and/or air conditioning system, greenhouse, attic, or cellar
temperatures, or almost any location where a temperature readout is
needed. It is a good science or experimenter project demonstrating the
operation of bar graph LED displays and the LM34 Temperature sensor.
It has a range of 60 to 78 deg F and uses ten LEDs as a readout. The
temperature is indicated in 2 deg F steps by the particular LED lit
or by the number of LEDs that are lit. This project, while useful, is
also a good one to learn about LEDs, bar graph displays and drivers,
and temperature sensors and their applications. It also makes an interesting
conversation piece if packaged appropriately. The circuit can be calibrated
for other temperature ranges and spans as well (i.e. 60-70F, 50-70F,
70-90F, 60-100F, etc) by simply readjusting internal potentiometers
The project uses an LM34 temperature sensor, an LM3914 dot/bar graph
driver, and ten LEDs, and a few small parts. This project is low frequency,
low voltage DC operated and can run from 7 to 9 volts of battery supply,
and only a voltmeter is needed to calibrate the circuit, so it is suitable
for beginners. It is built on a small PC board 1.75 X 2.75 inches in
size. Current drain is about 33 milliamperes, which is mostly LED current.
The driver IC and the sensor circuit require about 10 milliamperes.
It is also feasible to operate this project from a small "wall" transformer
providing 7 to 10 volts DC. More voltage is unnecessary and is not recommended
as it will result in increased dissipation and resultant heat generation.
The circuit tolerates supply ripple well and a few volts of this is
permissible. In addition, a 9V transistor radio battery or a pack consisting
of six AA alkaline cells can be used for power. |
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| Price
$27.50 USD
Kit |
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| Price
does not include shipping and handling (See Order
Form) |
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| NORTH
COUNTRY RADIO |
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| PO
Box 200, Hartford NY 12838-0200 |
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| EMAIL:
support@northcountryradio.com
Tel 518-854-9280
Internet
http://www.northcountryradio.com |
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