Introduction.
We are currently (August, '98) developing a number of tutorials related to making various weather measurements using the BASIC Stamp 2. This is a spin off of our effort in developing the PIC based Morgan Weather Measurement System.
Please note these two are different.
The Morgan Weather Measurement System is a full system where the various PICs have been programmed to perform two temperature measurements, two relative humidity measurements, barometric pressure, a user A/D, wind direction, wind speed and gust and rainfall. This has a 9600 baud serial interface and was developed for hobbyists who desire to interface their PC or similar with an inexpensive and yet high quality weather measurement system.
The details of how the measurements are made is hidden from the user. For example, the PIC assembly language implementation, the details of interfacing with an LTC1298 A/D and the Dallas 1-wire interface. Rather, this system was developed for people who desire to use their creativity on the PC or similar side in writing C++ or Visual Basic to log, determine trends, develop amazing graphics and put weather measurement results on the Web.
BASIC Stamp 2 Tutorial Series.
This effort with the BASIC Stamp 2 will consist of a number of tutorials that illustrate how various weather measurements may be implemented. In many cases, the techniques are very similar to those used in our PIC based system. The measurement of atmospheric pressure and wind direction using the Linear LTC1298 dual 12-bit A/D is an example. In other cases, the approach is quite different. For example, our PIC system uses the Dallas 1-W interface to measure temperature. The Stamp is too slow and thus we illustrate how the Analog Devices TMP04 temperature sensor may be used.
Each tutorial is designed to stand on its own. However, these are not cookbook tutorials. Every attempt is made to develop the programming concepts and to discuss the hardware. Various other topics are also included as appears relevent. For example, the tutorial related to temperature measurement includes storing signed calibration constants in EEPROM, the timing distortion caused by the exponential charge and discharge of long cables and the use of balanced pairs. The tutorial related to barometric pressure discusses the details of the LTC1298, techniques for dealing with noise and the use of twisted pair cable. That is, each tutorial is intended to teach concepts in the context of a practical application.
The text associated with each tutorial will be placed on the Web as soon as it is developed. However, I do not have the manpower to do the Figures and thus a paper copy of each tutorial will be inexpensively priced at nominally 10 cents per page.
Please consider that Parallax will sell you an Applications Kit for the LTC1298 for $26.00 or you can buy the same thing from Mouser for $35.00. I haven't seen it, so I can't comment on its quality. One certainly hopes it is pretty darn good.
For $2.50 you can buy a 25 page tutorial from us which treats the LTC1298 in the context of a simple user input, interfacing with an MPX4115 pressure sensor and with a 360 degree dual wiper potentiometer to measure angular position. Hopefully, it is as good. For another $8.00, you can purchase an LTC1298 device or for $20.00 you can purchase three.
Parts.
It is difficult for a hobbyist to find parts and this can be frustrating and costly, and all the more so for rather specialized parts.
Thus, in developing each tutorial, we strive to acquire and sell the parts that are discussed in the tutorial. Thus, we now sell such parts as the TMP04, ADM485, MPX4115 and LTC1298 and we strive to make them as inexpensive as possible, hopefully cheaper than you will find them any place else.
The whole idea of this effort is to encourage people to tinker and provide them with affordable materials to do so without me having to sell the house or have my wife take a second job.
Planned Tutorials.
Over the next month, we hope to have the tutorials in the following areas;
Over time, we may add to this with different measurement techniques and perhaps branch into such areas as environmental monitoring.
We have no plans to pull this all together into a cookbook for you to assemble your own full weather system. However, we are paying attention to IO assignments and will offer thoughts on you doing so, but, we don't want to rob you of that satisfaction. Rather, we will provide low cost tutorials on how to perform many types of measurements and hopefully, a number of different options and leave the fun for you.
Current Tutorials
Measuring Atmospheric Pressure and Wind Direction