Tuesday, July 29, 2014

The Software Has To Get Better

So why are we "pushing" Forth on single chips? To get you prepared to do it on an array of 144 Forth Engines on a chip.

Engineering is the art of making what you want from what you can get at a profit.

Monday, July 21, 2014

I2C RH Sensor 21May2014

This is a Relative Humidity and Temperature Sensor that attaches to the I2C Bus. It has a relative humidity accuracy of 3% a precision of .2% and a resolution of .1%. You can buy a higher accuracy version (2%) if you need it. Be sure to get the 5V version. For temperature the accuracy is .3°C and the precision is .01°C. There are two versions of the sensor. One is powered up continuously and the other just powers up for each reading. You can learn more by having a look at the family data sheet. The part number I tested the board with was the CC2D35. Any of the 5V parts in the family should work.

Soldering is not difficult (for surface mount). I normally mount the 4.7uF capacitors first and then mount the ICs. Mounting the TVS diode package before the capacitors and sensor is probably a good idea. The connector should get mounted last. You can get the parts list, schematic, and parts layout at I2C RH Sensor 21May2014 - Documentation. I also have software that will read out the sensor to 4 digits at I2C RH Sensor 21May2014 - Software For The LPC812 FISH Forth.txt. As you can tell it is designed to be run with our LPC812 board. The software is mainly a how to do it minimal package. Also note that the readout for this software is 4 digits (at room temperature and less than 100% relative humidity) with no decimal point. You can use other Forth routines to add a decimal point and add one more decimal place of resolution but I wanted to keep the software simple so it is easy to understand. For systems use you will probably want to add time outs and other things so a defective or missing sensor does not hang up the system.

This board is available from OSH Park for $3.05.

Engineering is the art of making what you want from what you can get at a profit.