Everything But the Kitchen Sink

I'm been giving thought to what would be a set of reasonable requirements for a temperature sensor/datalogger. Here are some of my first thoughts in general order of importance:

• Very Low Power Consumption
• Best powered by a 3V lithium battery
• Active: < 1mA, Sleep: < 50µA
• Long Recording Period
• At least one week to several months
• Reasonable Recording Intervals
  • Event recorded every 15-60 minutes
• Rugged Construction
  
• Wide Operating Temperature Range
  
• Small Form Factor
  
• Easy Downloading of Data
  
• Inexpensive (<$50US)
  

That all should be easy, NOT! Considering I sometimes still put diodes and transistors into my protoboard backwards this could take awhile. It's a good goal though. This may sound a little sad, but this project has be more excited that any software project I've been involved with for the last few years.

How Hot Was It?

A couple of years ago a new car came into the household and my workhorse Integra lost it's privilege of parking in the apartment's underground parking area. Now exposed to the elements I was surprised this summer when I found a couple of hard candy tins had become so hot, even out of the sunlight, that the hard candy had at one point melted into a near liquid and later resolidified.

The lowest melting point for a sugar I found was 85^oC (185^oF). That's at the low end. Common sucrose doesn't melt until nearly 150^oC (over 300^oF)! So my question is: How Hot Was It?!

I don't care about the candy, but I do care about my digital SLR camera. I couldn't find the recommended storage temperatures on the camera's spec sheet. I did find the Compact Flash cards are only rated to about 80^oC (176^oF), storage maximum, not operation. I suspect the camera is much more sensitive.

It's obvious storing the camera in the car during the summer is a bad idea. Yet when might it be a good idea? Could I keep some extra doses of my prescription medication in the car for those time I forget to take them with me? Would my chocolate truffles ever be safe in my car!?

This rather unimportant question kept running around in my head. How could I measure and store the temperature minimums and maximums? I once used a high/low mercury thermometer when I grew indoor plans. But with how I throw things around the car I'd end up crushing it and getting mercury in the upholstery. I could drive around with mercury vapors too! Weeee to dying brain cells.

So this is where the new training comes in. Could I build a temperature sensor/datalogger that would record the ambient temperature over a period of weeks or months? Sure I can! For the ignorant everything is easy!

Tomorrow I'll consider the requirements.

Welcome to BlinkingBoxes

Who am I and what is this about?

The name is Dave and after working in the Software/IT business for over 22 years I needed to make a change. Being a Web Engineer during the DotCom Crash also helped make the decision for me.

About two years ago I returned to school at a local community college, the College of San Mateo, to experiment and see if this aging dog could learn anything new. I tried some work in Graphic Design; it was fun but I couldn't see any future earning potential for myself. I also checked out a new program in Computer Forensics.

At the last moment one of the Computer Forensics classes was postponed until the following semester. I looked around and discovered that there was an opening in "D.C. Electronics". This triggered some good memories.

When I was a teenager I'd played around with building digital circuits. I enjoyed it and most likely would have continued the hardware work, except I lost my most valuable components in a power supply failure. At the time the value of the lost circuitry was maybe $150, but it was 1977 and I was 15. I couldn't recover from that large a loss. I dropped the electronics hardware and stuck to the software side using a Tandy TRS-80 microcomputer. This simple start eventually lead to my 22 year software career.

Now with the goal to explore, I took the "D.C. Electronics" course. The rest, as they say, is history. I continued with the classes and am now less than a year away from finishing the technical portion of an A.S. in Electronics Technology. Who knows, a BSEE could follow someday.

It's been very frustrating and amazingly rewarding. I've come to remember the joy of learning and getting in touch with yet another aspect of my inner geek.

Right now I'm so green I glow in the dark. My hope is to learn, talk about what I learn, develop electronics projects and ask questions. Then maybe I'll glow a little less brightly.