Friday, May 31, 2013
Tuesday, May 21, 2013
Demonstration of Geiger Tube emulation with DDS generator and DIY Geiger Counter with NOKIA 5110 LCD
Here is the video where I connected DDS generator for Geiger-Muller tube emulation. It starts from 1Hz (60 cpm) and goes up to 4000Hz (240000 cpm) The accuracy is better for low background cpm. Maximum cpm error is 4% on the highest values. Counting ability for this prototype is 500000 cpm. In real life condition with SBM20 tube we'll be able to register about 1mSv/h (or 175000 cpm) because of tube limitation (the tube has physical limitation for cpm counting).
Saturday, May 11, 2013
I have changed the LCD design for this project. The dose now displayed with bigger font and the CPM value with smaller numbers. Dose now has only 3 digit with float point and it displayed by auto in uSv/h or mSv/h (depend on the value). Maximum value that can be displayed is 9.99 mSv/h; minimum value is 0.01 uSv/h.
Sound on/off and battery indicator was added. I also made a lot of work with internal code optimization. High voltage is supported by auto to 400V app. and it independ from battery voltage changes, so it stay stable even if batteries will go down to 4V.
I thinking if it will be right or not, to use Li-poly battery with 5V step-up IC and charge circuit. Personally I like this option, but it will require SMD components to be installed on the PCB. I still thinking about this. It can reduce weight of the final product when installed to the box. Anyway 4.8V Ni-MH battery will do the job perfect.
Saturday, May 4, 2013
New 1.01 version of Logger software available. Please re-install the application if you use our Geiger Kits.
Several bugs was fixed:
1. Logger crash fixed after random device ot TTL module detach.
2. Default factor math error fixed that was caused by regional settings in Windows.
New features added:
1. Now measurement period can be longer that 5 minutes.
Wednesday, May 1, 2013
It starts here, but now I tried to work with Nokia 5110 graphic LCD. The problem I met was there no ready library for my PIC compiler! It's mean that I was forced to write my own procedures to initialize the lcd, clear screen, write texts and etc. After searching the web I found some arduino examples from sparkfun and lcd datasheet. With Arduino library it was very simple to run this display, but my project build with PIC16F876A and I started to transfer the principles to my mcu. This forum thread was helpful for understanding how to write main display procedures. The results are in the current video. This is diy geiger counter prototype. It use only PIC16F876A for controlling all dosimeter functions. I transferred almost all program functions from version with 16x2 lcd to this version of the board. The hardware include voltage reference IC for precision voltage measurements.
The prototype work started from this:
And comes to this:
1. PWM control high voltage, the output can be tuned with 2 keys from 300V to 600V.
2. Measurement period automatically changes, depend on radiation level. See on the video how it happen when level goes up and down. Long period is better for the background.
3. Fast response scale on the display will show immediately levels changes, even before the measurement period will end. It useful when prompt response is required. The bargraph scales up to 800 cpm.
4. As before UART, Arduino, Geiger Bot communication
5. Calibration menu (not presented in the current video) allow to changed conversion factor, alert threshold, high voltage and save all settings.
This work still in progress. Because the signal captured from tube cathode there is some problem with sensitivity to static electricity (if you touch the tube it will cause false counting) I think I need to make some small circuit changes. But if enclosure is used its unnecessary.
follow for updates...