neděle 15. února 2015

ENC28J60 library, GM counter - part II

I continued with what I was working on yesterday. First task today was to get the SW SPI library working with ENC28J60. I used the old goold Ethercard library by Jeelabs, and the porting went pretty well. I did not care to port it properly, with defines and stuff, I just wanted to verify if it works. It does, despite the fact I am using digitalWrite, and the demo properly displays the web page. I'll polish the library in upcoming days, test it on Due (I used Uno for tests today), and will put it into SVN repository.
I also finished the hardware of the GM counter. Nothing big, just small change of the hardware, and adding Arduino Pro Mini and Nokia display, plus some small changes of the HV power supply. I tried to replicate the other power supply, hoping to get the power consumption under 1mA, but no matter how I tried, it stays around 2.5mA unloaded. I don't get it, the power supply is the same, just the transistors are different, and the capacitors are actually smaller - 6.8nF instead of 18nF. Anyway, the whole thing is not supposed to be switched on for extended period of time, and Arduino and display also consume some power, so there's no need to keep it low... but still. I am really curious what causes this. I found some reasonably prices disc ceramic capacitors on eBay, and those should be smaller than the ones I am using (size-wise), which, combined with a small tube like SBM-21 could make a nice pocket geiger.
I put a very simple software into the Arduino, basically just to find out how it performs, and added basic CPM -> dose calculation based on the SBM-20 datasheet for Ra226. The hottest ore sample I have shows 4 mR/h (on the picture). I bought it as uranocircite, although I guess that there's some torbernite in the sample that's much more active, because the most active part of the sample does not fluoresce, so that's most likely not uranocircite. The reading depends on which value of the CPM -> dose I choose, there are some similar values for Cs137 and Co60, but the final number will be around those 4-5 mR/h.
I have a few ideas for the software, based on these kits. That's definitely something I want to finish next week!

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