Cheatsheet & Glossary

This volume distills the nine that precede it into a single dense card. Nothing here is new — every value is carried forward from the IV-9 tube data (Vol 2), the driver and timebase chapters (Vols 3–4), the worked Nuts & Volts six-digit clock (Vols 5 and 8), and the build article’s parts list and Resources section. Where a number could be mistaken, the source volume is named in prose. Print it, laminate it, keep it by the iron.

10.1 IV-9 quick spec

Table 1 — 10.1 IV-9 quick spec

Parameter	Value	Note
Technology	Incandescent (tungsten filament)	Not neon, not LED — a vacuum tube with no electron emission
Operating voltage	~5 V	Same rail as the logic; no high-voltage supply anywhere
Segment current	~23 mA per segment	At ~5 V
Digit height	~13 mm	Small Soviet tube
Elements	7 segments + 1 decimal point (DP)	Standard seven-segment layout
Connection	Fly leads (flexible wires)	Solders straight to the board — no socket
Common polarity	Positive, negative, or AC	A filament is purely resistive — direction-agnostic
Getter	Silvery patch at the top of the envelope	A vacuum indicator: white = vacuum lost = dead tube
Origin / family	Soviet ИВ- (“IV-”) series; IV-9 (ИВ-9)	Larger sibling: IV-13

Full-digit current. A complete “8” lights every element: 7 segments + the decimal point = 8 elements at ~23 mA each ≈ 184 mA per tube. (Without the DP, the seven segments alone draw ~161 mA.) The build article uses the seven-segment figure for its worst-case supply math — see 10.6.

10.2 IV-9 pinout

Pin numbering and segment assignments per the construction manual (notation is the same a–g standard used for seven-segment LED displays).

Table 2 — 10.2 IV-9 pinout

Pin	Function
1	Common
2	RH decimal point (DP)
3	Segment b
4	Segment c
5	Segment a
6	Segment f
7	Segment g
8	Segment d
9	Segment e

Standard seven-segment layout (a–g). The seven segments form a figure-eight: a is the top bar, g the middle bar, d the bottom bar; f and b are the upper-left and upper-right verticals; e and c are the lower-left and lower-right verticals. The DP sits at the lower right.

     aaaa
    f    b
    f    b
     gggg
    e    c
    e    c
     dddd  . (DP)

10.3 The “can’t multiplex” rule

A Numitron cannot be meaningfully multiplexed: a filament has thermal mass, so a low duty cycle just dims it — every digit needs its own continuous driver. By contrast, the worked clock’s 60-LED ring is heavily multiplexed (never more than 8 lit at once, fused by persistence of vision).

The two display technologies in the same clock therefore demand opposite drive strategies — the instructive heart of the build (Vol 3).

10.4 CD4511 quick reference

The CD4511 is a BCD-to-seven-segment decoder/driver with a built-in latch, designed for LED displays but driving the IV-9 directly because its ~25 mA output rating covers the tube’s ~23 mA per segment at ~5 V. One per tube (six total in the worked build).

10.4.1 BCD → segment truth table (0–9)

Active-high outputs; 1 = segment ON. (CD4511 blanks for input codes 10–15.)

Table 3 — 10.4.1 BCD → segment truth table (0–9)

Digit	a	b	c	d	e	f	g
0	1	1	1	1	1	1	0
1	0	1	1	0	0	0	0
2	1	1	0	1	1	0	1
3	1	1	1	1	0	0	1
4	0	1	1	0	0	1	1
5	1	0	1	1	0	1	1
6	1	0	1	1	1	1	1
7	1	1	1	0	0	0	0
8	1	1	1	1	1	1	1
9	1	1	1	1	0	1	1

10.4.2 Control inputs

Table 4 — 10.4.2 Control inputs

Pin	Name	Active	Effect
LE	Latch Enable	LOW = transparent	LOW: outputs follow the BCD input. HIGH: latch holds the last value (lets the worked clock fan one data bus out to six decoders, latching only the selected one)
LT	Lamp Test	LOW	All seven segments ON regardless of BCD — used for the startup/reset flash and to test the tubes
BI	Blanking Input	LOW	All seven segments OFF (ripple-blanking / display blanking)

Priority in the part: BI overrides LT, which overrides the decoded data.

10.5 Worked-clock IC roster

The Nuts & Volts six-digit clock (Bill van Dijk, September 2016), one-line roles.

Table 5 — 10.5 Worked-clock IC roster

Ref	Part	Role
IC1	PIC16F876A-I/SO	8-bit MCU — runs everything (time, display scan, UI, EEPROM) at 4 MHz
IC5–IC10	CD4511 (×6)	BCD-to-7-seg decoder/latch, one per Numitron tube
IC4	SN74HC164N	8-bit shift register — selects which CD4511 latch to update
IC2	CD4017BE	Decade counter — selects the active LED row of the 60-LED ring
IC11	ULN2803A	Darlington array — sinks the full LED-row current (beyond the CD4017’s rating)
IC3	LM2575T-5	Switch-mode buck regulator — provides the single 5 V rail

(The part list prints a typo — IC11’s Mouser line reads a CD4511 number — but the device named is the ULN2803A Darlington array, IC11 in the schematic.)

10.6 Power & timebase quick facts

Table 6 — 10.6 Power & timebase quick facts

Item	Value	Note
Wall wart	≥1.5 A at ≥9 V, AC or DC	Bridge rectifier accepts either; parts list suggests 12 V or 15 V
Peak current	~966 mA	Startup flash: all six tubes lit (7 segments × 6 = 42 × ~23 mA) — close to 1 A
Rail	5 V from LM2575T-5 buck	Behind a bridge rectifier + 1000 µF tank cap
System crystal	4 MHz	Runs the PIC program
Timebase crystal	32.768 kHz watch crystal	Critical for accuracy — do not salvage/substitute blind
Load caps	2 × 12 pF (0805), matched to the crystal	Set frequency accuracy; change them if you change the crystal
Accuracy	~1 s/day or better	When crystal and load caps are properly matched

10.7 LED pattern codes

The 60-LED ring’s selectable patterns (user manual). Mode is saved in EEPROM and survives power loss.

Table 7 — 10.7 LED pattern codes

Code	Pattern
0	Cycle — randomly changes patterns 1–7 every hour (default)
1	Single LED clockwise, ring fills as the minute progresses
2	As 1, but counter-clockwise
3	Single LED running clockwise (no fill)
4	Counter-clockwise running LED, ring fills as the minute progresses
5	As 4, reversed
6	Pendulum
7	Newton
8	Rain

10.8 Supply & current formulas

• Segment series/limit resistance — R = V / I. For a ~5 V drive at ~23 mA, the per-segment current path works out to roughly 5 V / 0.023 A ≈ 217 Ω of total path resistance (largely the hot filament itself; the CD4511 drives the IV-9 directly, with the optional dimming diode below).
• Full-clock peak current (startup flash) — 7 segments × 6 tubes × 23 mA = 42 × 23 mA = 966 mA (≈ 1 A). This is the worst case the supply must meet.
• Per-tube full-”8” current (with DP) — 8 elements × 23 mA = 184 mA.
• Dimming-diode drop — placing a series diode (D2, a 1N4001) in the common path and shorting it with jumper JP2 trades brightness for current. With the jumper off, the segments see roughly 5 V − 0.7 V = 4.3 V (one diode forward drop), dimming the tubes slightly and shaving the current draw. With JP2 on (or the diode replaced by a wire), the tubes run at the full ~5 V.

10.9 Source URLs and in-hub file locations

10.9.1 External resources (from the build article)

Table 8 — 10.9.1 External resources (from the build article)

Topic	URL
The build article	Nuts & Volts, “Build the Numitron — A Six-Digit Clock,” September 2016 (Bill van Dijk)
Switch debouncing discussion	www.eng.utah.edu/~cs5780/debouncing.pdf
Free EagleCAD	https://cadsoft.io
Microchip MPLAB / PICkit3 IDE	www.microchip.com/pagehandler/en-us/family/mplabx/home.html
Numitron lifespan (RCA DR2010)	www.rfcafe.com/references/popular-electronics/images2/rca-dr2010-numitron.pdf
Numitron history (March 1970 Popular Electronics)	www.rfcafe.com/references/popular-electronics/numitron-readout-march-1970-popular-electronics.htm
Cathode poisoning (nixie contrast)	www.tube-tester.com/sites/nixie/different/cathode%20poisoning/cathode-poisoning.htm

10.9.2 In-hub files (02-inputs/TheNumetron/)

Table 9 — 10.9.2 In-hub files (02-inputs/TheNumetron/)

File	What it is
_extracted/build_article.txt	The article text: parts list, Resources, ratings
_extracted/construction_manual.txt	Assembly tips and the IV-9 pinout chart
_extracted/user_manual.txt	Pattern list, accuracy, operating instructions
IV-9 (Numitron).pdf	The IV-9 datasheet
Schematic / Eagle + Gerber board files	Full design files (201609-Dijk.zip)
Firmware (60L-Numitron.asm + HEX)	MPASM source + production HEX
Pattern video	The LED-ring patterns in motion

10.10 A–Z glossary

BCD (binary-coded decimal) — a digit 0–9 encoded in four bits; the value the PIC sends to a CD4511 to select which numeral to display.

Blanking (BI) — the CD4511’s active-low Blanking Input; when low, all segments are off.

Buck converter — a switch-mode step-down regulator. Here the LM2575T-5 drops the rectified wall-wart voltage to the single 5 V rail; chosen over a linear regulator because it runs cooler and tolerates more wall-wart options.

Darlington array (ULN2803) — eight Darlington transistor pairs in one package; used to sink the full LED-row current the CD4017 cannot.

Decimal point (DP) — the eighth illuminable element of the IV-9, at the lower right (pin 2). Not used for timekeeping in the worked clock.

Decoder/driver — a chip that turns a coded input (BCD) into segment drive signals; the CD4511 is a decoder/driver with a latch.

Dimming diode — the optional series diode (D2) whose ~0.7 V forward drop slightly dims the tubes and trims current when its bypass jumper (JP2) is open.

EEPROM — non-volatile memory inside the PIC; stores the 12/24-hour mode and chosen LED pattern so they survive power loss.

Filament — the tungsten wire that forms one segment; passing current heats it until it glows. The Numitron’s defining element — it behaves like a tiny light bulb.

Fly lead — a flexible wire emerging from the tube envelope (the IV-9 has them), letting the tube solder straight to a board with no socket. Bending stress on a fly lead can crack the glass seal.

Getter — the silvery deposit at the top of the envelope that absorbs stray gas and indicates vacuum integrity. It turns white when the vacuum is lost — a white getter means a dead tube.

Incandescence — light produced by heating a material until it glows; the Numitron’s operating principle (vs. the nixie’s gas glow discharge or an LED’s electroluminescence).

Inrush current — the brief peak draw at power-up; here the ~966 mA startup flash when all tubes light at once, which sizes the supply.

Lamp test (LT) — the CD4511’s active-low Lamp Test input; when low, all segments light regardless of BCD — used for the startup flash and to verify tubes.

Latch (LE) — Latch Enable; when transparent (low) the outputs follow the input, when latched (high) they hold. Lets one BCD bus feed six decoders, updating only the selected one.

Multiplexing — rapidly switching among displays so persistence of vision fuses them into a steady image. Works for the LED ring; does not work for Numitron filaments (it just dims them).

Numitron — an incandescent seven-segment indicator tube (RCA, ~1970; Soviet ИВ- series). Runs at low voltage; segments are filaments, not gas or LEDs.

Persistence of vision (POV) — the eye’s retention of an image after the light stops, which makes a fast-multiplexed LED ring look continuously lit.

Seven-segment — the a–g segment layout (top, two upper verticals, middle, two lower verticals, bottom) used to form digits; standardized from F.W. Wood’s 1908 patent.

Shift register (SN74HC164) — a chip that clocks serial data into parallel outputs; here it generates the digit-select signals that pick which CD4511 to latch.

Watch crystal (32.768 kHz) — the low-frequency quartz crystal used as the accurate timebase. The single most accuracy-critical part — do not substitute an unknown or salvaged one, and match its load capacitors.

10.11 References (Vol 10)

• Bill van Dijk, “Build the Numitron — A Six-Digit Clock,” Nuts & Volts, September 2016. Held in 02-inputs/TheNumetron/ (build article, construction manual, user manual, full schematic, Eagle/Gerber board files, IV-9 datasheet, MPASM firmware + HEX, pattern video).
• IV-9 (ИВ-9) Numitron datasheet — 02-inputs/TheNumetron/IV-9 (Numitron).pdf.
• Extracted source text — 02-inputs/TheNumetron/_extracted/{build_article,construction_manual,user_manual}.txt.
• Cross-references: Vol 2 (tube physics & anatomy), Vol 3 (driving Numitrons / CD4511), Vol 4 (timebase, PIC, LED-ring multiplex), Vols 5 & 8 (the worked build).