View Full Version : Anyone got an SD-card or USB drive data logger?

05-25-2006, 08:43 PM

Am looking for a dirt-cheap general purpose data logger.

Was thinking that, by now, there ought to be some really cheap loggers on the market, what with SD memory coming in so cheap, and USB flash drives and MP3 players.

Two applications:

A friend has a micro-hydro scheme / other alternative power generators and wishes to log power output over time.

I figured all one needed to do was find something that would produce a comma-separated-variable file on SD card that one could upload to Excel. Any common SD card would have more than adequate storage for such purposes.

So, wondered whether one could DIY it. Or, indeed, whether someone had already done so - might even be a sale in it!

Also, for my own purposes, was wondering about similar cheap logging for weather recording. Was thinking standard parameters, but was also curious to log visibility. In 1997, visibility recording in the UK changed, as it went automatic to point measurements, and no-one bothered to log 'present weather codes' so that data after 97 cannot be compared with data before.

See my web site for more on this story and links to relevant people/groups:


I live in Norwich, UK.

Over the· last few years, the visibility has got worse and worse, and I'm beginning to get worried about it. This year, it seems to have become a problem a lot earlier, and far worse. The other day, despite strongish winds, the haze would not go away - ie: there was miles and miles of air containing it.

So, one additional parameter I was curious about was visibility.

I had a quick peek at projects file, and did·a search, here, but found nothing.

Was curious about pointer alignment project (Beau) as it might be sort of thing that could be useful if aligning eg: a laser to measure visibility (eg: by absorption). (I used to write about control and instrumentation engineering, on a (now dead) magazine, called 'Control & Instrumentation', and once wrote about a system called 'Lidar' that did this sort of thing, looking at various species in air.)

If no projects that do this, now, I'd be curious to know whether this is the sort of thing these systems could do (and if so, which). How much would a kit to build one set you back? How much I/O could you get in? (A to D, digital, etc)?

Please excuse extreme ignorance of post - I was a journalist - I made a living by asking stupid questions.

Hoping you can help!

Jeremy Jones.

05-25-2006, 09:14 PM
Wanted to add more, but session in library ended.

Would also be curious to know of any projects for:

Power measuring plug/socket - was thinking it might be useful, for when assessing power use at home, to have a socket that one could plug AN Other domestic device through to indicate power. If combined with a logger, possibly even more useful. And/or, depending on how ambitious one can be, timer/switch, or, thermostat (eg: heater), PID?.

(Excuse ignorance of computing resources available/required)

Unless it would be simpler to use some form of clamp-on ammeter to a logger. My ammeter only reads to 10A.

Also wondered why immersion timer switches don't have a simple 'run for half an hour' button.

Also occurred to me that an alternative controller for stanard domestic washing machines would be a good idea. They never do quite what I want them to do. If you could produce a user-programmable alternative that would allow you to specify a cycle: eg: pre-wash for 30 minutes at 60, spin, wash for 30 minutes at 90, spin, rinse five times (I have bad skin and like the idea of being able to make sure there is absolutely no soap left - terribly unGreen, but there you go.) Or just something that you could plug in when the original goes.


05-25-2006, 10:04 PM
You may want to look at the SD-card reader mentioned in this topic over at the Propeller forum:


It won't be easy to use it, though, as you must create your own routines, if you use a BS2.

There may be other alternatives.
(I think I've seen at least one which only needed simple serial commands to create and update DOS-compatible files, relatively recently either in the Propeller or the Sandbox forums)

Switching power may be best done with a X-10(I think it is) system.
These are 'intelligent' addressable units that can be controlled by signals sent though your AC-lines.

Measuring the power...

You could use a clamp-on ammeter, but they aren't very exact.
Maybe you could hack and adapt one of those meters you plug into the wall-socket, then plug the appliance into, and which also reads out the usage?
(They typically cost about £15 - 20)
The only problem I have with the one I own is that it only measures the usage when the appliance is active.
(I KNOW that my thermostat-controlled panel heater draws 600Watts, I want to know for how long it does that... How else can I know if my energy-saving methods actually work?)
Hacking it and reading out the data would help...

Of course, messing with the innards of such things tends to be frowned upon by the manufacturer, fire-departments, insurance companies...

Washing machine controller?
Most of us guys have problems handling the default set of programs, and you want to expand it?

If the machine has a machanical rotary system it shouldn't be too hard to replace, just stuff a whole lot of relays(or maybe thyristors?) in there to connect or break the circuits.
If you look in an auto parts shop, or well-stocked electronics store, you may find some plastic cuffs which clamps onto a wire and pierces it with a forklike metal blade to connect a second wire to it. A fistful of those should allow you to connect the relays without having to yank out the original switch system.

The more modern 'digital' systems shouldn't be much more problems, except that you don't have that nice disc from the mechanical system, to read the old program out of.
(A bit more guesswork, then)

Don't visit my new website...

05-25-2006, 10:14 PM
In the beginning of June I will have an SD data logger for sale.
I'm getting production PCBs today, then I will send samples out next week.

You can check it out at www.sddatalogger.com (http://www.sddatalogger.com)


Cheap 4-digit LED display with driver IC·www.hc4led.com (http://www.hc4led.com)

COMING SOON "SD DATA LOGGER" www.sddatalogger.com (http://www.sddatalogger.com)

"I reject your reality, and substitute my own." Mythbusters

05-25-2006, 11:34 PM
To monitor power, a digital multimeter with a serial port would do the job inexpensively as long as you have a PC available. Here's one for $39.50 elexp.com/tst_s345.htm (http://elexp.com/tst_s345.htm)

For weather data logging, Dr. Tracy Allen (who's a regularly visit this forum) has a few solutions www.emesystems.com/ (http://www.emesystems.com/)

05-27-2006, 01:06 AM

Thanks for all responses!

Pretty lazy of me not to check out the obvious. first!

Have found interesting units from Lascar on RS site


and on Lascar site.

Temp and humidity logger, USB drive output

(RS reference # 490-1064) £39. UK

Will get back later. This just quick thanks. Other things to do right now!

SD logger looks interesting!