Dallas Semiconductor sells temperature loggers as part of their iButton
line which can be placed wherever you want records. They come in a can
about the size of a quarter. You can also purchase a USB interface,
which you can connect the temperature logger into to get the data out
of it, and set the parameters to sample the data in the first place.
See http://para.maxim-ic.com/cache/en/results/4872.html for the USB
interface, and http://para.maxim-ic.com/cache/en/results/4871.html for
the loggers themselves.

Starter kits are available from
http://www.maxim-ic.com/quick_view2.cfm/qv_pk/2820; this kit for $60
includes the USB interface, and a thermocron (which might be for the
wrong temperature range). The thermocrons typically have a 10 year
lifetime.

I've strapped these to water heater output lines and watched the usage
patterns of hot water. Software for windows XP is free for download.
If you're trying to use this with Linux, try the "One Wire File System"
software.

Thanks - I checked out their site - A bit technical, but it seems that the
iButton line is aimed at temperature/humidity logging. I would also need to
know when compressor switches on and off - For this, I would ideally use
current measurement (0-10A DC), voltage (0-30V) or even something like
sound. Two temperatures would be better than one.

Because of this, the buttons made for monitoring transportation
temp/humidity, may not be the best choice. The multi port dataloggers would
be great, but cost is a bit high for a one time experiment. There are units
that interface with a computer that are aimed at school science projects
that are more reasonable, but my laptops CDROM just failed!

http://www.drdaq.com/

I would prefer a stand alone unit for data collection that I can connect to
my desktop computer for downloading. The Onset Hobo would do the job, but by
time software and sensors are added, it becomes a bit pricey for a 1 time
job.

GBM

wrote in message
ps.com...
Dallas Semiconductor sells temperature loggers as part of their iButton
line which can be placed wherever you want records. They come in a can
about the size of a quarter. You can also purchase a USB interface,
which you can connect the temperature logger into to get the data out
of it, and set the parameters to sample the data in the first place.
See http://para.maxim-ic.com/cache/en/results/4872.html for the USB
interface, and http://para.maxim-ic.com/cache/en/results/4871.html for
the loggers themselves.

Starter kits are available from
http://www.maxim-ic.com/quick_view2.cfm/qv_pk/2820; this kit for $60
includes the USB interface, and a thermocron (which might be for the
wrong temperature range). The thermocrons typically have a 10 year
lifetime.

I've strapped these to water heater output lines and watched the usage
patterns of hot water. Software for windows XP is free for download.
If you're trying to use this with Linux, try the "One Wire File System"
software.

simpler is to take a couple of turns of the positive feed to the
compressor round a reed switch. Pump on, reed closes, pump off reed
opens. A lot simpler than having to read the current.

Ian M

Some of the dataloggers have the possibility of monitoring an event such as
a switch on/off, but not all.

I think I have finally come up with a simple method - I will just use two
independent temperature loggers. One in the ice-box and one just above the
condenser fan. The latter will get an upward spike in temperature when the
compressor comes on. This way, I should be able to plot box temperature vs
compressor on/off cycle. This should do it.

Thanks for the input.

GBM

"nimbusgb" wrote in message
oups.com...
simpler is to take a couple of turns of the positive feed to the
compressor round a reed switch. Pump on, reed closes, pump off reed
opens. A lot simpler than having to read the current.

Ian M

A much better idea would be to find a datalogger that can monitor 0 to 5VDC
and an amploc hall effect current sensor.
http://www.ampsense.com/AMP25.html These things cost about $5 and need a
stable 5V power source like an Artesyn AFC5-12S05F, 2 little resistors and a
small capacitor. Loop one of the compressors power lines through the sensor
and you can monitor not only when it turns on but how many amps it is
drawing. With that information you can adjust the speed of the little
Danfoss compressors to get the most cold for the least amps.

If you can't find the Artesyn you can have one of my spares for $12.

--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

"GBM" wrote in message
...
Some of the dataloggers have the possibility of monitoring an event such
as
a switch on/off, but not all.

I think I have finally come up with a simple method - I will just use two
independent temperature loggers. One in the ice-box and one just above the
condenser fan. The latter will get an upward spike in temperature when the
compressor comes on. This way, I should be able to plot box temperature vs
compressor on/off cycle. This should do it.

Thanks for the input.

GBM

"nimbusgb" wrote in message
oups.com...
simpler is to take a couple of turns of the positive feed to the
compressor round a reed switch. Pump on, reed closes, pump off reed
opens. A lot simpler than having to read the current.

Ian M

"Glenn Ashmore" wrote
A much better idea would be to find a datalogger that can monitor 0 to
5VDC
and an amploc hall effect current sensor.
http://www.ampsense.com/AMP25.html These things cost about $5 and need a
stable 5V power source like an Artesyn AFC5-12S05F, 2 little resistors and
a
small capacitor. Loop one of the compressors power lines through the
sensor
and you can monitor not only when it turns on but how many amps it is
drawing. With that information you can adjust the speed of the little
Danfoss compressors to get the most cold for the least amps.

If you can't find the Artesyn you can have one of my spares for $12.
Glenn Ashmore

Thanks for the offer Glenn!

I did consider this approach, but because I am just troubleshooting on a
1-time basis, I am trying to keep the cost down! The Hobo unit becomes
expensive because of the software cost as do several of the other makes. I
don't really need current logging. I have borrowed a Kleton AC/DC clamp on
meter that will allow me to check out startup & run current.

I am thinking about just buying two of the button type temperature loggers
but even that will cost US$120.00 or so. Something that would display and
log icebox and condenser fan exit temperature would probably be more useful
in the long term - still looking for this! I do already have a display using
a wireless indoor/outdoor thermometer, but no logging.

GBM
GBM