Before we look at preparing the Arduino/Freeduino microcontroller for connection to the nixie tube driver modules described in Part I and Part II, you can build this power supply to provide the high firing voltage required by the nixie tubes. This switch mode power supply easily outputs 50 mA, which is more than most, and offers a variable output from 150 to 220 VDC, when driven by a 9 to 16 VDC source.
Step 1: About the Circuit
A 12 volt source at one amp will easily drive this nixie tube supply. There is sufficient power produced by this switch-mode supply to drive at least eight of the nixie tube driver modules (I've had 12 of the nixie tube driver modules running off of one of these boards, that's 24 IN-12A nixie tubes!).
A typical nixie tube power supply offers 170 to 250 VDC at 10 to 50 mA. A switch-mode power supply is desirable because it's small and very efficient. You can fit it inside your clock and it won't heat up. The schematic for the project is taken directly from the MAX1771 datasheet, however, because of the large voltage jump from input to output, board layout and low ESR type components are critical.
Step 2: Parts List
The Following are Digi-Key Part numbers for all components:
CAP TANT 100UF 20V 10% LOESR SMD
CAP CER .1UF 25V Y5V 0805
CAP 4.7UF 450V ELECT EB SMD
CAP TANT 10UF 25V 10% LOESR SMD
CAP .1UF 250V PEN FILM 2420 5%
CONN TERM BLOCK 2POS 5MM PCB
J1, J2, J3
INDUCTOR POWER 100UH 2A SMD
RES 10.0K OHM 1/8W 1% 0805 SMD
RES 1.5M OHM 1W 5% 2512 SMD
RESISTOR .050 OHM 1W 1% 2512
TRIMPOT 5K OHM 4MM SQ CERM SMD
IC DC/DC CTRLR STEP-UP HE 8-SOIC
MOSFET N-CHAN 300V 14A TO-220F
DIODE ULTRA FAST 3A 400V SMC
Step 3: Preparing Parts for the Printed Circuit Board
These parts I Ieave to solder conventionally after I've got all the smaller surface mounts parts on the board.