Reference designator for components

[hammy]

Hi

a question to professional pcb designers in this forum:

What is the standard for the reference name of electronic components in circuit and pcb designs? (R1 = Resistor, D1 = Diode, K1 = Relais ...)
I was pointed to DIN EN 81346-2 that replaced the old DIN 40719-2.
Example: The new standard says a Diode is now "R" and not "D".   

Any thoughts about this? Do you follow this new standard?

Thank you!
hammy

[ataradov]

Example: The new standard says a Diode is now "R" and not "D".   

This must be some sort of mistake.

Any thoughts about this? Do you follow this new standard?

I don't design boards professionally, but I look at a lot of boards designed by others (but mostly in the US). In my experience, people just do whatever works for them and faster. The only real reason to mess with standards is if you are doing some government or military stuff. And that's the reason many prefer to avoid government or military contracts.

[hammy]

Example: The new standard says a Diode is now "R" and not "D".   

This must be some sort of mistake.

"R" is now used for diode, zener-diode, choke and resistor.
"K" is now used for transistor, voltage regulator, relay.

There are a lot changes between the old and new standard. 

[ataradov]

Wikipedia says that

EC 61346 has been WITHDRAWN. It is replaced by IEC 81346.

And it is really not worth my time to investigate how those dummies propose to name resistors in a new one.

[nctnico]

AFAIK the IEC has been trying to make the world adopt their symbol standards for several decades now without much succes. It's only goal seems to be different to what people have been using for decades. 

In my experience the list below is the most commonly used 'industry standard':
R=resistor
D=diode (sometimes zeners have a Z)
C=capacitor
L=inductor
Q or T=transistor
TR=transformer
IC=chip
REL or K=relay
J=jumper/header
P or CON=connector
F=fuse
TP=test point

[hammy]

AFAIK the IEC has been trying to make the world adopt their symbol standards for several decades now without much succes.

That was my impression too. I had a look into IEEE Std 315 (Graphic Symbols for Electrical and Electronics Diagrams) and the last pages lists a cross-reference to IEC Publication 113-2. The IEC standard is from 1971. This comparison is quite old but already shows the conflicts we still have nowadays with EN 81346. Anyway ... it is a mess! 

@ntnico: I agree with your list. Its the same I was taught years ago.

The whole topic popped up, because I would reference a crystal oscillator with "X" or "XTAL" and the other guy said we should use "G".
Go figure!

[tszaboo]

AFAIK the IEC has been trying to make the world adopt their symbol standards for several decades now without much succes.

That was my impression too. I had a look into IEEE Std 315 (Graphic Symbols for Electrical and Electronics Diagrams) and the last pages lists a cross-reference to IEC Publication 113-2. The IEC standard is from 1971. This comparison is quite old but already shows the conflicts we still have nowadays with EN 81346. Anyway ... it is a mess! 

You can safely ignore any standard, where electrical and electronics systems are both covered.
And dont listen to anyone who claims to understand single-line diagrams. They are like the flat earth society, who werent informed about the Kirchoff law.

[Mattylad]

On top of it there is also  IPC-2612-1.

315 and ANSI are obsolete - however that is what the rest of the world still uses, it's what the symbols in the CAD packages were drawn with many years ago and they have not changed and are not going to.
The guy that taught me used ANSI, the guy that taught him used ANSI, the guy that taught him used ANSI.

So we use ANSI.

EN 81346 - whats that?
It's titled "Industrial systems, installations and equipment and industrial products -- Structuring principles and reference designations -- Part 1: Basic rules"
Doesn't sound like schematic diagrams to me.

You pick your symbols in a company and woe betide anyone that wants to change it.

There is another En standard for schematic symbols - looks very similar to ANSI - it is also very badly drawn, I certainly would not be using many of the symbols from it.
Just like the IEEE symbols.

Try using 

http://www.pcblibraries.com/downloads/Guidelines!Reference_Designators.asp

- this is what the IPC-7351 (the current footprint standard) recommends AFAIK.

[sdguy12]

I tend to follow the standards in this table for the most part.  The only thing I do differently really is use X for crystals instead of Y.  For ICs, I mainly use U as the refdes and not IC. 

[T3sl4co1l]

Hmm, I typically use:
A   XSPICE models (nothing physical)
B   battery
C   capacitor
D   diode (any kind except LED)
E   SPICE dependent source (nothing physical)
F   fuse
FID   fiducial
G   SPICE dependent source (nothing physical)
H   mounting hole or lug connection
I   SPICE current source (nothing physical)
IC   integrated circuit
J   connector, female
K   relay (infrequent)
L   inductor (sometimes including multi-winding types)
LED   light emitting diode
M   nothing specific; various abbreviations (see above)
P   connector, male
Q   transistor, SCR
R   resistor
RLY   relay (most common)
SW   switch
T   transformer
TP   test point
U   integrated circuit (infrequently)
V   valve (tube)
X   SPICE subcircuit (nothing physical)
XTAL, Y   crystal
Z   SPICE general impedance; RF planar structures

I don't use BT, CR, VR, TZ or W, or at least very rarely.

I've seen lots of things before, some on the above list, some not.  I don't much care at this point.    I'm going to look at what the part is (MFG, PN and datasheet) before I decide what its actual function is.

Tim

[sdguy12]

Yeah, there is some personal preferences when it comes to designators in PCB design.  The only thing that was annoying at times for me was when I first got started with PCB design, there would be an IC like a comparator or something and in the schematic I would label that thing as like U1.  But then when I want to simulate with the thing using the macromodel, the spice model is going to be a subcircuit and so it's going to be designated as X and it's just kind of like why isn't there more overlap between the spice designator vs the schematic refdes.  But you get used to it pretty quickly I suppose.

[T3sl4co1l]

Since schematic driven simulation took over (gosh, this must be 2-3 decades ago now? ), you usually have the name of a component on the schematic (e.g., "U1"), and the SPICE type is prepended to it to generate the netlist line (e.g. "XU1 1 2 3 4 5 COMPARATOR_LM339").  The user never sees the netlist (well, unless they look at it), it happens transparently.

Tim

[james_s]

Example: The new standard says a Diode is now "R" and not "D".   

This must be some sort of mistake.

"R" is now used for diode, zener-diode, choke and resistor.
"K" is now used for transistor, voltage regulator, relay.

There are a lot changes between the old and new standard. 

Is this a joke? Why on earth would someone use "R" to indicate a diode?? Must be on some good drugs.

[Len]

Is this a joke? Why on earth would someone use "R" to indicate a diode?? Must be on some good drugs.

I guess you'd do it if your company told you to follow the ISO/IEC 81346 standard. I don't know how many companies require that for electronic schematics.

Note that this standard is not just for electronics, it's for "objects in all technical areas, e.g. electrical, mechanical and civil engineering".

[james_s]

I'd ask my boss what he was smoking if I were asked to use such ridiculous designations.

As of yet I've never seen anything like that used in any of the equipment I've been inside, and I've certainly never done that on my own designs.

[capt bullshot]

I don't know which particular standard they adhere, the CAD people at my workplace use:

V - Diode / Transistor
H - LED
R - Resistor
C - Capacitor
L - Inductor
D - integrated circuit (more digital nature)
N - integrated circuit (more analog nature, but often seen on digital ICs also)
U - Photo couplers and the like
T - Transformer
X - Connector

It's quite confusing if you are used to more common designators like D - Diode, U - IC, T or Q - Transistor
I just don't care and treat them as unique identifiers for the components without information

[hammy]

H - LED

Any idea why "H"?

Cheers
hammy

[ataradov]

Any idea why "H"?

  Soviet standard prescribes LEDs to be "HL", there must be a common reason for this.

Come to think about it, regular indication lamps are "AL", and tubes are "VL". So may be it is just arbitrary letters that were still available .

[sdguy12]

Since schematic driven simulation took over (gosh, this must be 2-3 decades ago now? ), you usually have the name of a component on the schematic (e.g., "U1"), and the SPICE type is prepended to it to generate the netlist line (e.g. "XU1 1 2 3 4 5 COMPARATOR_LM339").  The user never sees the netlist (well, unless they look at it), it happens transparently.

Tim

Back when I was still doing IC Design many moons ago, we used a schematic capture tool from a PCB tool suite to create the schematics and then generate the netlists from the tool and ran simulations in good old SPICE.  I had to look at spice decks all day, .cir files, and prepare netlists for LVS, SVS, LVL

...I looked at a lot of netlists back then.....

[David Hess]

I roughly follow the Tektronix standard these days which is what I learned long ago anyway.  Using R for diodes is insane.  I also use the ANSI gate symbols instead of the IEC box logic symbols which are more difficult to distinguish.

B or BT   Battery
C   Capacitor
CR or D   Diode
DS   Indicator including gas discharge tubes like neon bulbs
J   Stationary Connector
K   Relay
L   Inductor
M   Meter
P   Movable connector
R   Resistor
RT   Thermistor
Q   Transistor and Thyristor
S   Switch
T   Transformer
TC   Thermocouple
TP   Test Point
U   Integrated Circuit
V   Tube
VR or Z   Zener Diode
X or Y   Crystal

[Chris56000]

Hi!

Coming from the "Old Skool" of circuit-diagrams, my preferences are:-

A:- Repairable assembly or module
AE:- Aerial (receiving or transmitting)
B or BY:- Battery, bridge–rectifier (English and non–English annotated diagrams)
Bu:- Commonly found continental prefix for female multi-pole female connector
CP:- Capacitor pack, hybrid/thick-film module containing small nos. of components
CR:- Common U.S. designator for semiconductor diodes & rectifiers
VC:- Customer variable-capacitor, e.g., tuning, bandspread, etc.
TC:- Preset trimmer capacitor
D:- Any semiconductor diode (modern), also continental nomenclature for predominantly digital integrated circuits
E:- True earth
F or FS:- Fuse
G:- Galvonometer or current detector, also signal source
GL:- "Glenrichter" – German designation for bridge–rectifier, occasionally half–wave rectifier as well;
H:- Continental nomenclature for LED/Optocoupler devices
HB:- Hybrid/thick-film circuit intended to replace many individual components
HY:- Circulator
IC:- Integrated circuit device
JK:- Jack socket
JP:- Removable jumper-plug, e.g., for setting options
K:- Relay, uniselector or similar magnetically operated switch
L:- Choke, Inductor (one or more windings)
LK:- Permanent link fitted during manufacture/setup then left permanently connected
LP:- Indicating or illuminating lamp
M:- Indicating or measuring instrument, motor
MR:- Still crops up from time to time for annotating bridge-rectifier modules - originally used for metal/selenium rectifiers
MT:- Recent prefix now incommon use as mounting-holes for PCBs that are usually connected to 0V or chassis-earth
N:- Continental nomenclature for mainly analogue integrated circuits
P:- Preset adjustment
PCC:- Photo-conductive cell or LDR
PL:- Plug with male contacts
PT:- RTD-type (resistance) thermocouple
Q:- Thyristor, triac or four-layer switching device
R:- Resistor
Ro:- (Rohenhere I think!) Continental nomenclature for thermionic valves
RP:- SIL, DIL or SMD resistor pack/array
RT:- Selected or trimmed resistor (NOT preset variable)
S:- Hall or other type sensor
S:- (obsolete) Very old Philips references for inductors
SK:- Socket with female contacts
St:- ("Stecker") Commonly found continental nomenclature for multi-pole connector with male plug contacts
T:- Transformer
TB:- Terminal block/strip, screw connected
TH:- Thermocouple (general)
TP:- Test-point for voltages, waveforms, etc.
TR:- Transistor (very old British practice was to use "VT" - I don't know how that originated!)
U:- Sealed non-repairable assembly
V:- Thermionic valves
VR:- Customer-operated resistive control, e.g., volume, bass, treble, speed, etc.
W:- Very old nomenclature used by some British manufacturers for semiconductor rectifiers - I think it came from "Westector"
X:- Temperature-sensitive resistor (thermistor, PTC or NTC)
XL or Y:- Quartz crystal
Z:- Voltage-dependent resistor, varistor or "Metrosil", also gas-discharge suppression tube

I know I'll probably be shot down in flames with that lot, but I've collected them from a forty-year-old study of electronics magazines, manufacturer's service manuals, British textbooks and looking in many assorted pieces of equipment over the years!

Note:- As well as my own personal preferences, I've also included a number of very commonly found continental prefixes for completeness!

Obviously if I'm drawing out a piece of gear where a PCB is silk-screened I follow the OEM's prefixes, but when drawing something out from scratch that's totally free-wired or devoid of any PCB markings, then the ones I use are as per the list above!

[David Hess]

A:- Repairable assembly or module

Ah, I always wondered about this one.