Concept for the electronics (pdf)

Right now I am concentrating on the control software and the 0.9 version of the electronics. The V0.9 is basically the signal generator combined with the low-power backend. In this version I had the split between the microcontroller and DAC + amplifiers. In V1.0 the DAC is together with the microcontroller, because it is more likely that the amplifiers will be replaced than the DACs.


Bill of materials:

The following list provides the required material to build one mainboard and one addon board with two channels.

2 1 nF, 0603 Capacitor, AD converter
2 10 nF, 0603 Capacitor, USB power filter and reset signal filter
12 100 nF, 0603 Capacitor as current spike filter next to every IC
2 10 uF, MLCC, 0603 Capacitor for Voltage stabilisation
1 NFE61PT Noise filter, maybe not necessary, replace by a piece of wire?
1 P8X32A, VQ44 Parallax Propeller
1 24LC256, SO-08 One I2C EEprom stores the program. The other one seemed to be a good idea, when I designed the board. But I think it is not needed right now.
1 FT232RL, SSOP28 FTDI USB to serial converter: talking to the PC & getting programmed
1 LT1117-3.3, SOT223 800mA and 1A Low Dropout (LDO) Positive Regulator
2 LM339D Low Power Low Offset Voltage Quad Comparators
3 LED, 0603 RX, TX, and status, choose any color You like ...
1 MCP4922-SN 12-Bit DAC with SPI Interface
1 AD8644 Quad 18 V R2R Operational Amplifiers
1 Crystal CTS406, 5 MHz Anything that says "5.000 MHz" on the housing
2 82 Ohm, 0603 Resistors, horizontal and vertical sync signal
5 270 Ohm, 0603 Resistors for the LEDs and PS2
3 430 Ohm, 0603 Resistor, RGB voltage DAC
3 820 Ohm, 0603 Resistor, RGB voltage DAC
2 4k7 Ohm, 0603 Resistor, reference voltage stabilizer in add-on boards
20 10k Ohm, 0603 Pull-up / pull-down resistors for every occasion
1 33k Ohm, 0603 Resistor, voltage divider for comparator, replace with 10k to get voltage right. (see below)
1 100k Ohm, 0603 Resistor, AD converter
2 270k Ohm, 0603 Resistor, AD converter
1 BC847, SOT23 NPN Transistor, any NPN from the "TUN TUP DUS DUG" tables works
1 PN61729-S USB connector (Berg)
1 MDSSV-BC06 PS2 connector
1 F15HDH Sub-D, VGA connector (15 pol)
1 WAGO 233-104 Wago connector, or solder the wires directly onto the board
1 SW-SCHURER Reset button

Bugs found in version 0.9:

Schematic - page 1

Schematic - page 2

Schematic - page 3

Schematic - page 4

Schematic - page 5


The board is made to fit a Frame Case from FISCHER Elektronik: