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digital thermometer help

Here's what I'm looking to build.......hopefully someone has some good
advice or maybe even has already built something similar.

I've build circuits to detect temperatures in the past but I'd like to
take it to the next level. I want to build a small, inexpensive
circuit that will detect ambient air temperature changes, display temps
to a small digital display, and even better, somehow log temp data (per
second or so). My initial thoughts are to use a usb flash drive since
they are small, inexpensive, and easily used with a desktop PC for
later analysis of the temp data. Basically I want to place the
thermometer at a location, leave, have the temp data logged, and be
able to later review the temp data on a computer.

Anyone have any advice on this one?

Thanks!!!

Steve
 
S

Spehro Pefhany

Jan 1, 1970
0
Here's what I'm looking to build.......hopefully someone has some good
advice or maybe even has already built something similar.

I've build circuits to detect temperatures in the past but I'd like to
take it to the next level. I want to build a small, inexpensive
circuit that will detect ambient air temperature changes, display temps
to a small digital display, and even better, somehow log temp data (per
second or so). My initial thoughts are to use a usb flash drive since
they are small, inexpensive, and easily used with a desktop PC for
later analysis of the temp data. Basically I want to place the
thermometer at a location, leave, have the temp data logged, and be
able to later review the temp data on a computer.

Anyone have any advice on this one?

Thanks!!!

Steve

You'll need a fairly powerful (micro)computer to talk directly to a
USB peripheral. You might do better with a CF or SD card.
 
I

Ian Stirling

Jan 1, 1970
0
Here's what I'm looking to build.......hopefully someone has some good
advice or maybe even has already built something similar.

I've build circuits to detect temperatures in the past but I'd like to
take it to the next level. I want to build a small, inexpensive
circuit that will detect ambient air temperature changes, display temps

Define small, define inexpensive, and how long do you want it to log
for?

As a quick hack, I'd be looking at a MP3 player, with external RAM.


Encode the sound in some form that the MP3 player can read.
 
T

Tim Wescott

Jan 1, 1970
0
Spehro said:
You'll need a fairly powerful (micro)computer to talk directly to a
USB peripheral. You might do better with a CF or SD card.
Or include some flash in the thermometer and make _it_ a USB peripheral.
USB masters are hard to make, but slaves are fairly easy if you don't
try to cross every 't' and dot every 'i' in the plug & pray mechanism.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Posting from Google? See http://cfaj.freeshell.org/google/
 
I

Ian Stirling

Jan 1, 1970
0
Tim Wescott said:
Or include some flash in the thermometer and make _it_ a USB peripheral.
USB masters are hard to make, but slaves are fairly easy if you don't
try to cross every 't' and dot every 'i' in the plug & pray mechanism.

Or if you just pretend to be a serial/parallel port, and use one of the
canned chips, which present an 8 bit 'friendly' bus.
 
My definition of small would be handheld size. Inexpensive is because
I'll want to make like 5 of these, and hopefully it could log data for
2 hours or so, 1 hour minimum. I'm sure there's a way to make an
electronic thermometer (I remember doing it in electronics class) but
getting it to work with some sort of data logger is my big problem. I
guess I'd like to see any circuit diagrams others might have come up
with if they are willing to share.

Thanks

Steve
 
M

Martin Riddle

Jan 1, 1970
0
Omega has data loggers just as you describe. I believe under $100.

Cheers
 
A

artie

Jan 1, 1970
0
Here's what I'm looking to build.......hopefully someone has some good
advice or maybe even has already built something similar.

I've build circuits to detect temperatures in the past but I'd like to
take it to the next level. I want to build a small, inexpensive
circuit that will detect ambient air temperature changes, display temps
to a small digital display, and even better, somehow log temp data (per
second or so). My initial thoughts are to use a usb flash drive since
they are small, inexpensive, and easily used with a desktop PC for
later analysis of the temp data. Basically I want to place the
thermometer at a location, leave, have the temp data logged, and be
able to later review the temp data on a computer.

Anyone have any advice on this one?

Thanks!!!

Steve

Take a look at http://www.onsetcomp.com/index_ppc1.html

Hobo data loggers. USB or serial.
 
I

Ian Stirling

Jan 1, 1970
0
My definition of small would be handheld size. Inexpensive is because
I'll want to make like 5 of these, and hopefully it could log data for
2 hours or so, 1 hour minimum. I'm sure there's a way to make an
electronic thermometer (I remember doing it in electronics class) but
getting it to work with some sort of data logger is my big problem. I
guess I'd like to see any circuit diagrams others might have come up
with if they are willing to share.

Ok.
What I would do, if I wanted to put one together quickly.
As it's only 2 hours, the storage problem is simplified.
Go to ftdichip.com, and find the link to the parallel 8 bit bus output
ones.
Now, two ways.
A) Take a small PIC, and a temperature measurement chip - maybe one of
the 'one wire bus' ones from TI, maybe not. Add an I2C LCD if you want,
and a I2C eeprom chip. Accumulate samples at the specified rate until
you can squirt them out the PC connected bus on demand.
B) Take a 16 bit counter, a oscillator to clock data into the RAM, a
32K*8 SRAM (62256), an 8 bit ADC, a suitable temperature probe (lm10?),
and again hook it to the ftdi chip, with some glue logic. When you turn on
the 'log' switch, it clocks the counter, samples the temperature, and
writes to the RAM.
When you plug it in, it resets the counter, and reads from the RAM on
demand from the USB port.
You add another gate or two, and it writes to the USB port too, enabling
you to wipe the memory to 0.
 
W

William at MyBlueRoom

Jan 1, 1970
0
My Cricket Thermostat could be modifed as a logger. Just use the I2C
temperature sensor and add an 24LC256 eeprom.

www.myblueroom.com

Bill
 
W

William at MyBlueRoom

Jan 1, 1970
0
My Cricket Thermostat could be modifed as a logger. Just use the I2C
temperature sensor and add an 24LC256 eeprom.

www.myblueroom.com

Bill
 
W

William at MyBlueRoom

Jan 1, 1970
0
My Cricket Thermostat could be modifed as a logger. Just use the I2C
temperature sensor and add an 24LC256 eeprom.

www.myblueroom.com

Bill
 
S

Spehro Pefhany

Jan 1, 1970
0
From the web page...
GENERAL SPECIFICATIONS
Measurement Capacity: 7943 readings

I wonder how that number came to be? 1f07 in hex doesn't help my
understanding.

Probably 8K less some overhead for calibration parameters etc.
 
G

GregS

Jan 1, 1970
0
Probably 8K less some overhead for calibration parameters etc.

My Fluke 189 has a variable width storage all depending on
rate of change.

greg
 
M

Michael

Jan 1, 1970
0
My definition of small would be handheld size. Inexpensive is because
I'll want to make like 5 of these, and hopefully it could log data for
2 hours or so, 1 hour minimum. I'm sure there's a way to make an
electronic thermometer (I remember doing it in electronics class) but
getting it to work with some sort of data logger is my big problem. I
guess I'd like to see any circuit diagrams others might have come up
with if they are willing to share.

Thanks

Steve


Take a look at: http://www.ubasics.com/adam/pic/picprog.html
Its a PIC (sorta) tutorial and a temperature-logging project I found some time
ago. Project uses a PIC16F84, 24C65 8-pin serial EEPROMs, and a DalSemi 1-wire
temperature sensor. This project inspired the design of my own temperature
logger. (I used PIC16F628 and 8 ea. 24LC256 EEPROMS though.)

IIRC, your temperature sampling is to be 1/sec. That might be too frequent to
implement with a 1-wire sensor, taking its conversion time, all software
overhead, and EEPROM write time into account. The DS1822, for example, takes
750 ms (max.) to do a conversion. My logger samples only once every 5 minutes,
so I didn't have to consider conversion time, software overhead, or EEPROM write
time in my design.
 
W

William at MyBlueRoom

Jan 1, 1970
0
Since you're using I2C eeproms it might be more efficent to use an I2C
temperature sensor and larger EEPROMs 24lc1024.
Only 2 I/O pins too.
 
W

William at MyBlueRoom

Jan 1, 1970
0
Since you're using I2C eeproms it might be more efficent to use an I2C
temperature sensor and larger EEPROMs 24lc1024.
Only 2 I/O pins too.

See my PIC projects at http://www.myblueroom.com
 
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