Bill of material. This is the bill of material from Mouser. Please note that some component like the multiturn trimmer and the audio IC are missing. The trimmer was bought from a stock on eBay, same thing the IC CM108AH. The low leakage zener diode on the feedback circuit was bought from a german military surplus stock. Hard to find part, search on eBay.
This is my first didactic 8bit – Z80 based computer.
I’ve made it because I was interested into homebrew such type of computer since high-scool times but never do it. I was intrigued by the idea of better understanding of PC architecture and I wish to learn programming with assembler language.
My project starts copying Grant Searle’s magnificent project: Grant’s 7 chip Z80 Computer Please note that I’ve changed the way of the UART/RS232 converter is wired. In fact I’ve lost a lot of time following Grant’s schematic: everything double cecked but no data received to the serial port… uhm… I’ve solved in this way:
No jumpers between DB9 connector pins or other RTS shit… just a simple straight RX-TX converter between 6850 UART and DB9 connector.
I’ve build it using point-to-point wire soldering on a veroboard prototyping board. At the moment it comunicate with me via a RS232 serial link.
The schematic is the same of the Searle’s website except I’ve modified the clock source and the init.asm code that drive the 68B50 ACIA.
I’m using a 1.8432Mhz crystal oscillator at first for cpu and ACIA then switched to drive the cpu via a 10.240Mhz crystal oscillator. The 1.8432Mhz crystall just drive the ACIA.
I’ve benchmarked it’s performance via the Mandelbrot generator provided by the RC2014 project.
This is a γ-selective Geiger counter from the “M” professional serie used also in demonstration devices for measuring the age of minerals by the activity of the isotope potassium-40. It’s a classic all-glass construction with platinum cathode.
·Radiation determine: (γ) gamma soft/hard
·Voltage of start of counting: 720 – 780V ;
·Operating voltage (recommended): 820 – 880V;
·Length of flat part of counting curve (plateau): 200 V
·Slope of the counting curve: < 0.1 %/V;
·Sens. background: < 65 counts/min;
·Maximum counting range: 5*10E4 counts/min
·Load resistance: 8 – 15 MOhm
·Counter resistance: 4 – 8 MOhm
·Allowable stray input capacitance: < 25 pF
·Working temperature range: -40…+50 C
·Anode material: Platinum (Pt)
·Cathode material: Copper (Cu)
·Dimensions: counter length 175mm, diameter 21.5mm
This is the smalles geiger tube I could find. It’s so cute but… so insensitive to the background. It’s a good tube to build around it a personal dosimeter. It’s not suitable to monitor background radiation.
·Radiation determine: beta soft/hard; gamma
·Voltage of start of counting: 260V - 320V;
·Operating voltage (recommended): 380 - 420V;
·Length of flat part of counting curve (plateau): 100 V
·Slope of the counting data: < 0.15%/V;
·Own background: < 0.2 imp/s;
·Max. counting range: 650 imp/s;
·Sensetivity: 6.5 - 9.5 imp/uR standard 137Cs, p = 10 uR/s;
·Working temperature range: -50…+60 C
·Dimensions: counter length 21mm, diameter 6mm