Sphere U6DNC Series Скачать руководство пользователя страница 13

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SCHEMATIC:

Look at the Schematic of the clock and remote displays before starting work, and be sure

you understand how the clock is designed. The smaller U6DNC-ND version is just a subset of the main
schematic, with the drivers and display tubes deleted. The microprocessor (UP1) (and its crystal clock) do all the
timekeeping and counter control. BCD (Binary coded decimal) data (4 lines) is sent from the microprocessor to
the Nixie driver chips, which can be 74141 or K155ID1 types, which convert the 5V logic to the HV line control
required by the Nixie tube. The 7441 can not be used, as it does not support blanking, which is required in many
modes. Other Nixie tubes can be used and hard wired into the board pads

. Note that the pads indicate the

function of the pad, NOT THE PIN NUMBER

. A is for Anode, 1-9 and 0 for the specific cathode element, and

DP for decimal points. Tubes like the IN-16 are easy substitutes. The remote display boards are essentially
identical, with the tube footprints being the major difference between them. All the remote boards have 6 tubes,
and display drivers, plus neon lamps for the colons.

POWER SUPPLY CONCEPTS:

To get the required HV to run the IN-14 Nixies, at least +150VDC is

needed, and to insure adequate element coverage, +170-175V is ideal with the supplied 22K anode resistors.
Some tubes need a bit more to give crisp digit focus, and up to +200VDC can be used with no difficulties on most
tubes, but life will be reduced if the tubes are run too bright.

The 12VDC bus is converted to +170VDC by the switching converter formed by 555 timer U100, MOSFET Q100,
and the following rectifier/filter parts on the board. Parts selection is semi-critical, so stick to our specified items to
avoid problems. The HV level is adjusted by measuring the +170VDC test point (J1) to DC common (J5), and
adjusting trimpot R104. If no tubes are present, the voltage can go quite high (over +250VDC), so care must be
used to set it to +170VDC as a starting value. “HV present” is indicated by neon lamp DS3 being lit. +5VDC for
the digital circuitry is provided by regulator U9 via R18, and its presence is indicated by LED1. A keep-alive
+5VDC for the clock is maintained by the supercap C11 via D6, and fed to UP1 and the oscillators. This keep-
alive voltage must be present for any CPU operation, and it prevents time loss during momentary primary power
interruptions.

JUMPERS/OPTIONS:

Jumpers at U10, D1 and D5 are installed (and D2, D4 delted) when the primary

power is a nominal 12VDC, these parts are required if primary power is AC or if it is over 12V average. C18 is
required ONLY if a low drop-out 12VDC regulator is used at U9.

BITE INDICATORS:

Because the board is dangerous when excited with HV, a caution light is added,

(DS3), to warn you that HV is applied. This can be very important during troubleshooting. A 5VDC green LED is
also supplied (LED1) which warns when the logic supply is present. A crowbar Zener is across the 5V power
supply to clamp any excess voltage applied by mistake, and as a static shunt. If this part shorts, or is installed
backwards, the 5V bus will never rise above about 0.7VDC, and the FI polyswitch fuse will open (self-resetting
when power is disconnected). The 12VDC to 170V converter has its own polyswitch (F100) to protect that circuit,
and a green LED D101 monitors primary power to the HV converter, it will be ON when primary power is present,
and the F100 polyswitch has not opened.

POLYSWITCH FUSES:

These kits use a Polyswitch for low voltage DC protection rather than a glass

fuse. Primary AC line protection is still by a one-shot glass fuse for fire safety within the wall wart. Polyswitches
are conductive as long as the current is at or below their specified holding value, but go essentially open circuit
when the current is too high. They are reset back to proper conducting operation by removing the short, and/ or
resetting the primary power. The 5VDC light will go out when the primary Polyswitch opens. This technique is
used because many assembly problems may create a “short”, and this would be very inconvenient for you if you
had only one glass fuse available. In addition, R18 is a fusible resistor, in series with the 5VDC regulator, it limits
current to the regulator if a problem is present on the 5VDC rail, if it gets hot, remove power, and search for the
problems.

CABLES:

Connection to the setting switch assembly is via a short length of ribbon cable, which can simply

be soldered to each end. The remote displays are connected by 3 individual 20 pin ribbon cables, plus at least 3
additional wires for the colons and HV connection. The ribbon cables are designed with redundant parallel pins,
so that cable construction is not affected by many types of mis-alignment and orientation. As long as the
connectors are not plugged in offset, or reversed end-for end, they will work. It is also possible to solder the wires,
if preferred.