schematic interchange

updated 2005-12-02.

This file contains information about electronics schematics interchange as well as a few small schematics I drew.

This is just something I threw together that I thought you might find useful. comments?


related files:


design tools: schematic and layout editors

[FIXME: comb through next section[s] of this file and move appropriate links to this section]

design tools: digital logic simulation

design tools: digital logic simulation

see also vlsi.html for VLSI design tools.

"open" schematic interchange file formats

DAV: I *really* want to make it easy to freely exchange electronics schematics and MEMS designs. (See my "To Do List")

Others agree: "Finding: An extensible standard digital data interchange format or language is needed for MEMS."

EDA Industry Standards Roadmap

filip at (Filip M Gieszczykiewicz) has some really nice pages. His FAQ Corner and /* was */ has info on DTMF, MIDI, data compression, and other useful things. (with lots of ASCII schematics).

From: filip at (Filip M Gieszczykiewicz)
Newsgroups: sci.electronics,,alt.comp.hardware.homebuilt
Subject: ASCII Schematics V0.1
Date: 27 Jul 1995 17:48:12 GMT
Organization: Medical Informatics, Pittsburgh PA, USA
Sender: filip at
Summary: let's see if we can get this concept rolling here...
* Please feel free to DONATE (attribution and credit is, of
  course, fully supported) any ASCII schematics you may have
  to my address: <filip at>. Thanks!
* I refuse to e-mail any of these. I AM working on an e-mail
  to WWW interface so, some fine day, even BBS users will be
  able to grab these (yes, I have Agora src :-)
* I AM also accepting GIF/JPG/PS schematics BUT, I'd prefer
  ASCII. Please get an RMA number first :-) Don't just blindly
  send me a 200K uuencoded file, pretty please!
+-->Filip "I'll buy a vowel" Gieszczykiewicz | E-mail: filipg at
| | Sci.Electronics, RC, Misc FAQs + MORE!
| Enjoy your job, work within the law, make lots of money : Choose any two.
| Making money with CS and spending it on robotics, life & friends. !NOT(!PC) /* was */

WWW Repair Notes /* was */ includes

-Steve Walz   rstevew at
-Lots of New FTP Electronics Stuff!! 700 Files/40 Dirs (Full Mirror ==> *)
-Steve Walz  rstevew at *
Europe:(Italy) *
Oz: (Australia) *
(U.Cinci) *

Steve Walz

Chip Directory

Maintained by Jaap van Ganswijk <ganswijk at> (he's on the pci-sig at mailing list)

USA mirror of chipdir

Europe mirror of chipdir

Finally, DAV's schematics !

IR receiver

The typical IR receiver circuit I see has a op-amp configuration something like

 |       |
 | +--\  |  V1
 +-| - \ |  |
 D |    -+--+--|C|-+--Vout
 +-| + /           |
 | +--/            R
 |                 |
 gnd.             gnd.

Where the photodiode D is exposed to light, this "transimpedance amplifier" multiplies the photocurrent through the diode by Rf (typically a MegaOhm or so) to get a voltage, and the highpass RC filter blocks the ambient light -- both DC from sunlight and incandescent bulbs, and 120 Hz (100 Hz in England) from flourescent bulbs.

This uses the photodiode D in the "zero-voltage" or "photo-current" mode, rather than the "photovoltaic" or "avalanche" modes. (There's a long discussion about the pros and cons of these modes in a _1992 Amplifier Applications Guide_ book from Analog Devices). I prefer this configuration because it's very linear -- I double the amount of light, and it doubles the voltage at V1 (a very useful test point). I shine a IR remote control on photodiode D, and I get the same signal with the same amplitude (P-P) at Vout whether I'm in a completely dark room or if I have a high ambient light level (assuming that it's not completely saturated by sunlight).

The particular op-amp used is not terribly critical, though you must make sure that it's actually connected to the appropriate power supplies.

Vout usually goes to more filtering and demodulation circuits to extract the actual bits. Most TV, VCR, etc. remote controls have a 40 KHz squarewave that is turned on and off to send one and zero bits, so most receivers send Vout to a narrow bandpass filter tuned to 40 KHz, then AM rectify the bandpass output to extract the bits.

The semi-commercial site seems to have even more detailed information.

bi-directional optoisolator

What if you want to isolate a digital signal ? You use a optoisolator, of course. What if you want to isolate a bi-directional digital signal ? Optoisolators only handle one-way communication, so one won't work -- obviously you need (at least) 2.

Here's a really clever circuit that does this.

      |   |    (+5V)-R2--+   gnd
      |   |              |   |
      +|<|+               \ /    -
        |                 ---     \(optoisolator chips)
       --- IC1             |  IC2 /
       / \               +|>|+   -
      |   |              |   |
    gnd   +--R1-(+5V)    |   |

 -|>|- == diode

Circuit by Jerry Steele (National Semiconductor), _EDN_ 1996 Jun 6 p 122. It references "Isolate data acquisition on a bidirectional bus" article by Jerry Steele in _Electronic Design_ 1995 Nov 6. ASCII schematic drawn by David Cary.

(If you want bidirectional I2C communication between chips at different voltages -- often 3.3 V signals on one side and 5.0 V signals on the other side -- but they don't need to be completely isolated, use the "two resistors and a mosfet" circuit on the SDA line and another one for the SCL line -- see "Sensor Interfacing" tutorial by Nathan Seidle ).

We assume that everything else on the (left) and (right) bus is a open-collector pull-down device. (I don't *think* that it hurts if there are other pull-up resistors besides the 4.3K R1 and R2 in this circuit).

To build a complete isolated bidirectional I2C bus, you build one of the above circuits for the SDA line and another one for the SCL line; and you need a isolated "gnd" and +5V power supply. Steele's component list looks like


"Assume an initial high state on the [left] serial-data (SDA) bus. The normal rest state for both the SDA and SCL (serial clock) lines of the I2C bus is high.

The LED in IC1, which has a current path from its anode via R2 [...], is off. As a result, the [turned-off] IC1's output transistor transmits (via IC2's photodiode in parallel with D2) [a high] to the [right] SDA [...]. Grounding the [left] SDA line causes current to flow in IC1's LED, thereby activating IC1's output transistor. The transistor's low state transmits to [right SDA] via [...] D2, [...], limits the reverse-bias drop to the typical 0.4V of a Schottky diode. This arrangement prevents the low condition from circulating back across the barrier, [which avoids] causing the circuit to latch.

When [something pulls the right SDA bus low], the mirror image of the above scenario occurs. When IC5 pulls the SDA line low, it turns on the LED in IC2. When IC2's output transistor pulls [left] SDA low, it does so in such a way that it applies a reverse bias to IC1's LED [keeping it turned off], with a current path via D1 (again, to limit the drop to 0.4 V) preventing a recirculating condition. In short, when you take the left-side SDA low, the right side goes low. When you take the right side low, the left side goes low. ... without latching."

[DAV: I've taken the liberty of replacing Steele's terminology "photodiode", "forward biased", "inactive" with the more-understandable-to-me terms "LED", "turned on", "turned off", even though I know the LED in a optoisolator doesn't emit visible light.]

(A similar bidirectional isolator circuit is listed in the I2C FAQ )

The only flaw is that many optoisolator chips have rise and fall times of at least 10 us, meaning maximum bit rates below 50 KHz. (Which I find very odd, because you would think that optoisolator chips with their fixed, tiny separation would have a much *higher* bandwidth than the 4 Mbps over IrDA ).

Here's a random assortment of "fast" (faster than 10 Mbaud) isolator chips and their approximate price (Newark, Digikey, as of 2006-03): ( )

For true isolation, these optoisolators also require isolated power supplies on both sides. A few random examples:

Daisy's theorem: standard op-amp design

[see also

"Designing with op amps: Single-formula technique keeps it simple" article by Dieter Knollman, PhD, Lucent Technologies and and /* was */ local mirror: ../mirror/designing_with_op_amps.pdf covers "Plato's gain formula" and "Daisy's theorem" .

Summary: When designing new op-amp circuits, use this design procedure:


Design procedure:

Some op-amp circuits need a resistor to ground from the op amp's inverting input. Others need a resistor to ground on the noninverting input. The sign of the ground gain determines where to place the ground resistor.

If the desired gains add up to one, a ground resistor is unnecessary.

(see )

current-to-voltage circuit

Ways to convert a current to a voltage (convenient for feeding into a ADC):

voltage-to-current circuit

voltage-to-current circuit

Subject: Re: Testing solar cell performance w/computer assistance?
From: whit at (John Whitmore)
Newsgroups: sci.electronics
Keywords: Solar cell
Date: 16 Dec 92 06:28:50 GMT
Article-I.D.: u.1992Dec16.062850.11638
Sender: (USENET News System)
Organization: University of Washington, Seattle
dnwangus at flash.LakeheadU.Ca (Dave Angus) writes:
>bill at (Bill ODonnell) writes:

>>     If extreme accuracy isn't a major concern you may
>>want to consider using the game port on the Apple.  The
>>Apple II series and the Apple IIGS both use a 4 channel
>>A/D converter to read the voltage (via a variable resistor)
>>at the game port.

>Sorry; that ain't correct.  The Apple ][ game ports work almost exactly
>like the IBM game ports:  they use a 558 quad timer chip to generate
>time delays proportional to RC time constants.  The C is built into
>the game port, the R is provided by the joystick or paddles'
>potentiometers.  The game ports can measure resistance, but not

	There is a workaround for this problem; the timer requires
an input current, and a resistor and two PNP transistors makes
a pretty good voltage-to-current converter.

           +5V o------+----------+
                    |/         |/
             R    | |\         |\
                  +---+          |
                                 +(to game port)

The transistors should be the same type, and at the same temperature
(glue them together).  There is some slight temperature-dependence
due to the Vbe of the transistors, but it is possible to calibrate
the system for near-room-temperature conditions.  It's hard
to draw in ASCII, but the emitters of the two transistors
are connected to +5V (and they must be PNP).

	You want R to be roughly 220 k ohms for 0 to +5V inputs,
and 400 k ohms for -5V to +5V inputs.  The +5V power
is available, of course, at the joystick connector on the
game port.

	John Whitmore

design tips and style guides

[FIXME: what about the IPC and other standards organizations ?]

The Printed Circuit Board (PCB) Layout explains PWB design to total beginners ... say, high-school or college freshmen.

When designing a PCB board, you might want to consider the "Murrietta Circuits Design Layout Standards" to avoid designing something impossible to manufacture.

oscillator schematics

See also robot_links.html#servo . [FIXME: consider moving this section to has a nice audio oscillator schematic. has detailed instructions on building a handheld oscillator.

MICRO OSCILLATOR, INC. sells entire oscillators much smaller than most quartz crystal resonators.

pointers to more schematics

[FIXME: probably should be further organized: digital logic, communication, small-signal analog, high-voltage analog, ... etc.]

tons of ASCII schematics at

Ideas for Design /* was */ Lots of clever circuits here. (You can get $100 cash for submitting your clever circuit).


unsorted stuff. [FIXME: delete the cruft, sort the rest into the appropriate section.]

EDIF Technical Centre

edif-support at

"EDIF (Electronic Design Interchange Format) is a means of moving design information between design systems, from a design system to manufacturing, and for archiving. ... EDIF Version 3 0 0 (ANSI/EIA Standard 618) ... EDIF Version 4 0 0 will be released ... in October/November 1995."

IBIS Open Forum

founded to update and promote the IBIS standard. Currently no dues.

IBIS is an emerging standard for specifying analog I/O characteristics of digital ICs. "It protects vendors' intellectual property by providing models that reveal no proprietary information" "IBIS behavioral simulations run much faster than any corresponding structural models"

Portable to many simulators (including SPICE) on many machines.

To get IBIS information, chose one of

  send your e-mail address to <ibis-info at> (domain;
  anonymous login or anonymous ftp to the VHDL International BBS (414.335.0110)
  or to

To get on the IBIS Open Forum e-mail list, send a request to

  ibis-request at

-- information from EDN March 16, 1995, "I/O buffer modeling spec" article by Duehren, Hobbs, Muranyi, and Rosenbaum.

the IBIS(I/O Buffer Information Specification) ANSI/EIA-656-A Homepage

IBIS article by Dr. Howard Johnson (?) 1997

ISA, EISA, PCI, VME, and other plug-in cards

Um... actually most of my PCI information is over at vlsi.html#pci .

a few scraps of information about

This ISA (industry standard architecture) has nothing to do with ISA (instruction set architecture). (I talk about that over at )

This ISA is fast becoming obsolete, being replaced by


PC/104 and IEEE P996 are mostly-compatible variants of ISA.

X-Mas lights for your CAR

X-Mas lights for your CAR

             X-Mas lights for your CAR
             Mon, 01 Dec 1998 23:59:00 EST
             "K.C." <Iamnot at>
             We'll Wire Anything!

Home-brew Project: Automotive Christmas Lights!
 by: K.C.

DISCLAIMER:  The author assumes no liability, implied or otherwise, for
the results of attempting the modifications described in this text. 
While this procedure is fairly safe (12V electrical systems are fairly
harmless), I do not guarantee the safety or suitability of this procedure
for any purpose.  Do it at your own risk, and be smart! 

Now that that's out of the way:

This year I set out to decorate the interior of my car with XMAS lights!!
With a couple of simple modifications you can connect household XMAS
lights to your car's 13.8VDC electrical system.

For the project I bought a $0.99 set of 35 multicolored household lights
from the XMAS display at K-Mart. 

The important factors for this project are: 

 => The lights must be wired in series. (If one goes out, they all go out.)

 => The bulbs must be the 3 - 3.5V kind. (See labeling on back of package)

 => No special controls, sequencers, etc.. (We'll be re-wiring the lights.)

The 35 bulb set from KMart is perfect, since 35 bulbs at 3.5V each, 
wired in series is ~ 122V (household current.)

Now for the wiring.   Household Christmas lights are usually wired in a
large series loop, twisted together, so that you end up with:

      >---\ /----[B]----\ /----[B]----\ /----[B]----\ /----[B]-------\
AC IN      X             X            X             X               [B]
      >---/ \-----------/ \-----------/ \-----------/ \--------------/

          [B] = bulb                            X  = Twist in wire

Now, for the ~14V automotive system, the most you can reasonably get away
with is 5 bulbs in series on a single strand.  (3V each is enough to light
a 3.5V bulb fairly brightly, without producing much heat.)

So- there are two ways to accomplish this with the above set of lights.

-----// The First Method: //---------------------------------------------

Trace the wires from the plug to the first few lights, and make sure 
they are wired in an alternating series pattern, as shown above.  
(If not, you'll have to use the second method.)

1 - Cut the plug off the beginning of the cord. 

2 - Then, count the lights and cut both wires halfway between the 10th 
    and 11th bulb.  You then should have a strand of 10 lights, with two 
    cut wires on each end.  (You should trace the wires to make sure you
    aren't going to end up with 6 on one strand and 4 on the other.)

3 - Strip back the insulation from the pair of cut wires at each end and 
    twist the pair together.

Now you have two sets of 5 lights in series, connected together in 
parallel.  Go on to the next part: Connecting the lights.

-----// The Second Method: //--------------------------------------------

1 - Cut the plug off the beginning of the cord.

2 - Untwist the wires until you end up with one long cord, with bulbs 
    in series along it.  

3 - Count the bulbs and cut the cord halfway between the 5th and 6th 
    bulbs.  Repeat after every 5 bulbs, so that you end up with several 
    strands of 5 bulbs.

Now you have several usable 12V strands of Christmas lights!

-----// Connecting The Lights //-----------------------------------------

The various strands of lights created as described above can be connected
to your car's 13.8V electrical system in any method as long as you
don't connect multiple strands in series.  You can, however, connect
the strands together in parallel.   

Care should be taken to insure that the circuit you are wiring the lights
to has a fuse installed, whether it is an existing circuit or installed
by you.  Fuses and fuse holders can be found in most auto-parts stores,
or in the car audio section of home electronics stores. 

*** FOR AN EASY displayable way to connect the lights in most cars: ***

On each side of the rear windshield, you will find the terminals for the
rear-window defrost circuit.  Disconnect the terminals. (In my Saturn,
and my girlfriend's Honda, this simply involved pressing on a square
plastic tab while pulling downward on the connector.) 

By connecting each side of the strands of lights to the wires, you have a
safe, easy way to switch them on and off from the dashboard using the
defrost switch.   In my car I left the defrost terminals disconnected.
Since I park in a garage, I don't use the defrost circuit often.

In my girlfriend's car, we reconnected the terminals after wiring the
Christmas lights to them.  This way, the defrost circuit is still
operational, albeit while the lights are on. 

Another advantage of this setup is that it enables you to flash the
lights with a switch on the dashboard.  Also- since the defrost 
circuit in most cars won't operate unless the car is "on", you can't
accidently drain your battery.

Well, by now you should have some festive automotive lights!  Enjoy
them and have a MERRY CHRISTMAS!!!

If you see a green saturn with a "Get a grep" and "Free Kevin" sticker
in the back and Christmas Lights, be sure to honk and say hi!


flash memory cards

[FIXME: move to ]

(from "Putting the squeeze on flash memory" article by Mike Elphick, in _Computer Design_ magazine 1998-05)

package name dimensions (mm) maximum capacity (MB) number of contacts type of contacts
Miniature Card 38x33x3.3 64 60 flat edge contacts
Serial Flash 15x45x <1 2 8 flat contacts
CompactFlash 43x36x3.3 48 50 circular pins
MultiMediaCard 32x24x1.4 10 7 flat surface contacts
Memory Stick 21x50x2.8 32 10 flat contacts
SmartMedia 45x37x0.76 8 22 flat surface contacts

more info:

working with surface-mount components

See also "surface-mount components" robot_links.html#surface_mount

flight computer

rocket computer

DAV: these are long and skinny, to fit in those rocket tubes. It might be interesting to try to reduce the diameter even further, so it can fit even smaller rockets).

Does it make any sense to combine these 2 projects, to make one CPU that does both? (data collection during the flight; recovery beacon after the flight).

If I put a digital camera on the rocket, is it better to combine it with (a) lots of memory to hold the snapshots, or (b) real-time television broadcast ?

board house

(I've moved my long list to )

logic probe

I've been fascinated by logic probes. I think they were the first "wearable electronic devices". I think in the future there will be lots of devices that have been miniaturized to the "hi-lighter size form factor". I know enough about SMT to think I could build a few of them myself, but I haven't gotten around to it.

[FIXME: build a few small devices in pen-size form factor ... strobe running off 2 AAA batteries ?]


Newsgroups: sci.electronics
From: (Sid Boyce)
Subject: Schematic editor for UNIX/linux ???
Keywords: schematics unix linux
Reply-To: (Sid Boyce)
Organization: Amdahl Corporation, Sunnyvale CA
Distribution: WW
Date: Tue, 6 Sep 1994 11:14:31 GMT
Lines: 7

   I recently got the sources for the pcb editor from
in /pub/cae/pcb and it compiled and ran fine with the demo file, just
have to do some reading on how to use it.
   Does anyone know of a schematics editor that will run under linux,
hopefully available for ftp.
Sid... G3VBV ... Amdahl(UK) ...
Dave Dunfield <> (ddunfield on BIX)
Newsgroups: sci.electronics
Subject: Re: emailing schematics
Date: 9 Sep 94 11:30:56 GMT



, a small drawing editor/viewer for 640x480 VGA graphics, and an ascii-encoder/compressor for packing them for email.

Boondog has a "user groups" page that has a lot of potential. Boondog is open-architecture. This means all of Boondog's schematics, PCB artwork and programming code is freely downloadable and viewable. Much like the shareware/freeware concept for software, Boondog believes open-architecture will lead to use and product adoption.


Date:   Tue, 3 Jun 1997 06:43:09 -0400 (EDT)
From: Matthew Haas 
To: Monte Bateman 
cc: Lloyd Sumpter ,
Subject: Re: SIMPLE PCB-drawing program


I haven't been following this thread since the beginning, and I have a
question (which I hope hasn't already been answered):

Is there a good PCB-drawing program for Linux console or Linux SVGALIB?

Thanks in advance.

On Mon, 2 Jun 1997, Monte Bateman wrote:

> >
> > ... I would like a
> > SIMPLE PCB design program.
> >
> > =========================================================================
> > Lloyd Sumpter                        E-MAIL:
> Take a look at xpcb.  It is quite robust, and has either PostScript or
> Gerber output.
> I did a two-sided COMPLEX microcontroller board with it in about a week,
> having never used it before.
> Cheers,
> Monte
> --
> ===============================================================================
>      Dr. Monte Bateman --- Research Physicist    |  InterNet: bateman @
>    Langmuir Laboratory for Atmospheric Research  #      Telephone: 505/835-5102
>         Campus Station, Socorro, NM  87801       #            FAX: 505/835-5707
>     WWW Homepage:    |        Amateur Radio: WB5RZX

From: Monte Bateman 
Subject: Linux PCB program
Date:   Tue, 3 Jun 1997 09:12:55 -0600 (MDT)
Precedence: bulk

Sorry!  When I posted yesterday about the printed-circuit board (PCB)
program, I neglected to include the FTP address.  For Xpcb it is:

And, on a related note, there is an X-windows schematics (and general drawing)
program that is simply wonderful.  It is called Xcircuit, and can be found at:

Hope this helps!


     Dr. Monte Bateman --- Research Physicist    |  InterNet: bateman @
   Langmuir Laboratory for Atmospheric Research  #      Telephone: 505/835-5102
        Campus Station, Socorro, NM  87801       #            FAX: 505/835-5707
    WWW Homepage:    |        Amateur Radio: WB5RZX then click on "Downloads" you can get the "Easytrax (DOS) freeware" PCB layout program and other demo programs.

A Miniature High-Rate Speed Control with Battery Eliminator Circuit (BEC) by Stefan Vorkoetter

The Electronics Documentation Project. A reference for electronics related software (freeware and commercial), electronic schematics and PCB layouts, service manuals and electronics educational resources. ... freely distributable schematics and PCB layouts

CyberCircuit sells a program that organizes "over 1100 circuits"; a "circuit of the day" and a demo with a few more circuits (such as a FM transmitter) are available for free on their web page.

TextModeCad: CAD system in text mode environment (ASCII Circuit CAD ?) lots of electrical circuit tutorials. and schematics: Crystal radio, One Watt Class C Amplifier The Curious C-Beeper


a bunch of standard electronic symbols are available at

EDA Today ???

Electronic Design Automation Consortium (EDAC)

the Digital Music Zone (DMZ "schematics for guitar effects, electronic circuits, and recording tips & techniques"

"circuit of the day"

printed circuit design includes "Printed Circuit Artworks Gallery "

mp3 hardware forum[ST_chan=cpu]/cog.xp?j=mp3_hardware "this forum is intended to all people who decided not to wait for firms to create mp3 hardware, but build it by themselves. here you can interchange your ideas,documantations and infos. mp3 chips,controllers,dacs,cd-rom infos, circuit diagrams,mpeg layer3 format "

Started: 1997.027 Jan 27
Original Author: David Cary.
Current maintainer: David Cary.

Return to list of DAV's documents

Send comments, suggestions, bug reports to David Cary