TOD: Diode Matrix ROM intro (7-segment display) by guyfrom7up
Tons
Of
Diodes

A new series of instructables that will be using tons and tons of diodes. No IC's are aloud, the only semi conductors are diodes and transistors. The only passive components aloud are capacitors, resistors, switches, inductors, and potentiometers (variable resistors for those who don't know). Another rule is it must have more diodes then any other component. I made this all up, and I made up this group to see how creative people can be with electronics without resorting to IC's. My next one (this one is just a little wimpy intro) might use up to 2000 diodes.

This is an intro to Diode Matrix Roms, basically it takes a signal in (switch) and gives an output (number on the display)

NOTE: I couldn't complete a project designed by myself because my breadboard is way too small, but That'll be fixed in later instructables.
 
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Step 1: Parts

100_2770.JPG
7x 68 ohm resistor or higher (I used somewhere 110 I think)

1x 7-segment display

1x 10dip switch (I could only find an 8, just less characters to display)

23x signal diodes (cheapest you can find), I had 23, but I could only fit 9 on my board

1x breadboard, preferably big (unlike mine)

Some jumper wire

some sort of power supply, like 2AA or AAA's

wire cutters help
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Ehsan Al Aani says: May 1, 2013. 6:04 AM
thank you very mach
Meran Eng. says: Jan 12, 2013. 9:40 PM
what you're doing with these instructables, is just awesome :)
timitrisanto says: Apr 9, 2012. 7:27 AM
May I have a layout for printed circuit board?
ashraf sallah says: Jun 21, 2010. 5:59 AM
sry 9 bits
ashraf sallah says: Jun 21, 2010. 5:09 AM
plz i need help.......how can i connect (9 digits)binary to seven segment? without decoder (9 -512)??????????plzzzzzzzzzzzzzzz help meeeee.thnx
dungeon runner says: Apr 27, 2010. 6:22 PM
Okay, correct me if I'm wrong, but with diodes it's possible to make non-volatile (won't lose it when the power goes off completely) memory cells? Right?

This is just what I need for my project. At first I thought about capacitors, but deemed it way too complicated. Also, where would I find a tutorial on doing this?

(By the way, I love what you're doing with these instructables, and I hope you keep going. I prefer transistors to diodes, but still awesome).

-Y
thrashbarg says: Jan 26, 2008. 4:12 PM
There's a PDF about DEC logic modules used in PDP computers. It's full of information about using DTL to make stuff, including adders, etc. The link is here

I made a 2 bit plus carry adder out of DTL a few months ago, but I can't find any pictures of it. There were about 15 transistors and 28 diodes.
guyfrom7up (author) says: Jan 27, 2008. 7:43 AM
thanks for the link! I'll look at it once it's done downloading (25 MB!)

I'm making a 2 digit adder (xx + xx = xxx) only from diodes

the schematic is a pain in the butt.
microman171 says: Jan 27, 2008. 1:04 PM
I been working on DTL aswell. I have figured out every gate I could find info about. NOT, OR, AND, NOR, NAND, XOR, XNOR. Are there any that I have missed? When I have got a full set I'm goin to make an instructable on it.
dungeon runner says: Apr 27, 2010. 6:15 PM
Nope. That's all of 'em.
asa-tech says: Feb 12, 2009. 10:40 AM
Perplexing question!

Hello

Dr. asked me a question related to the university b Markp ROM on the design of the type of ROM through the Diode Matrix

Q) Design an adoide matrix read only memory that stor the following 20 words:
1-10111101
2-00101011
3-10111100
4-01000011
5-11101000
6-10011001
7-10111011
8-01100111
9-11101001
10-10111101
11-10000110
12-00010111
13-11001100
14-11111000
15-11001101
16-11000001
17-11001111
18-01100110
19-00101011
20-11111111
How to answer it and drawing with diode matrix read only memory??!!
hotwaterwizard says: Dec 13, 2008. 2:27 PM
Is there a way to make this circuit to have a +5v input at each point instead of the switch? In other words input a +5 volt signal at any point and display the corresponding number on an LED 7 segment display. This would tell you which one has the +5v signal at its input.
hotwaterwizard says: Dec 17, 2008. 9:47 PM
Will this one work? it only puts power to the circuit when needed.
Push to digit Com Cathode.GIF
Llamarama says: Oct 9, 2008. 2:34 PM
Nice one! How refreshing is is to see some real (!) electronics! Funnily enough im working on a diode matrix ROM to form a BCD to HEX decoder.
AzN1337c0d3r says: Oct 7, 2008. 3:55 PM
Good luck building anything more complicated than a 7 segment display, you make EEs and electrical technicians everywhere cringe with that mess. Also you use way too many diodes where they are not needed.
engmohammed says: Sep 11, 2008. 11:01 AM
plz show where intersections are.....
engmohammed says: Sep 11, 2008. 10:55 AM
it will be much easier by using the sn74ls47 ic(only 4 inputs)
GorillazMiko says: Apr 24, 2008. 5:32 PM
1 question- how do you know this stuff?!
guyfrom7up (author) says: May 9, 2008. 6:40 PM
books, and thinking, then researching to see if there's something similar to my original intentions
guyfrom7up (author) says: May 9, 2008. 6:40 PM
oh, and of couse, asking on forums ;)
GorillazMiko says: Feb 9, 2008. 9:02 PM
Kind of a retarded question, because I don't know much about schematics and stuff, but what do diodes do? :P
guyfrom7up (author) says: Feb 10, 2008. 6:36 PM
diodes only let electricity pass one way, likea one way valve for water. I use diodes here so that the signal doesn't backtrack.
GorillazMiko says: Feb 10, 2008. 6:55 PM
Oh. Wait up! Aren't you supposed to be taking a break from Instructables? :-O
guyfrom7up (author) says: Feb 14, 2008. 8:20 PM
I'm taking a break from taking a break, lol. I pretty much accomplished everything I wanted to do in my break, so I'm back.
GorillazMiko says: Feb 14, 2008. 8:27 PM
Welcome back. :P
Fernbot says: Jan 26, 2008. 12:50 PM
Holy power consumption!

As it stands now, your circuit consumes more power when the LEDs are off than when they are on*. Looking at your schematic, what if you pushed the LEDs to the top (next to the resistors) and then disconnected the cathodes of the LEDs from ground? You could then use your diodes to ground the cathodes of the LEDs. Since the LED + diode is a larger voltage drop, you'll probably have to reduce the size of the resistors to keep the same LED brightness.

It's fun to work with the basic components, isn't it? =D

*Your diodes turn the LEDs off because they have a smaller voltage drop (~0.7v) than the LEDs (~1.3v), right? This creates a larger voltage drop across the resistor when the LED is off, which leads to a larger current, and therefore higher power consumption.
guyfrom7up (author) says: Jan 26, 2008. 1:35 PM
you are right! I'm glad you pointed this out! I don't get exactly what you're describing, could you make a schematic?
Fernbot says: Jan 28, 2008. 11:14 AM
Ok, here is what I was thinking. Notice that now you put the diodes where you want the LED to be on instead of off. I just randomly put my diodes in the schematic, so the output would probably be meaningless, but hopefully it gives you the idea.
led_schem.bmp
guyfrom7up (author) says: Jan 29, 2008. 12:55 PM
ohhhhh so the switches are normally on, but when you flick the switch off so do the leds.. I'm going to post that schematic as a better way of doing it on my instructable
guyfrom7up (author) says: Jan 26, 2008. 1:36 PM
btw it is fun to work with basic components ;)
dungeon runner says: Apr 27, 2010. 6:13 PM
So true :). I just got done designing an ALU that can add, subtract, do all of the boolean logic operations, and now I'm working on bit-shifting. Once the design is done I'm going to hard-wire it all up.

-Y
guyfrom7up (author) says: Jan 26, 2008. 1:29 PM
you make a good point, I'll check with my multimeter, be back in a jiffy!
Einsteins Circuitry says: Jan 26, 2008. 7:48 PM
I guess you like doing things the hard way right? Fun at first but it would probably get boring after a couple thousand diodes. :p
guyfrom7up (author) says: Jan 27, 2008. 7:42 AM
thats what she said probably, but it'll be like a piece of art!
GorillazMiko says: Jan 26, 2008. 4:17 PM
Dang, nice job 7up man! Haha, so this was the Instructable you were working on when Instructables crashed, eh?
guyfrom7up (author) says: Jan 27, 2008. 7:41 AM
yep
guyfrom7up (author) says: Jan 26, 2008. 12:36 PM
the schematic should be the 2nd step, but whenever I try to reorder them I get a NULL error. Just if you're wondering.
chooseausername says: Jan 26, 2008. 4:24 AM
Nice work !
You should add schematics into the instructable too.
=o)
guyfrom7up (author) says: Jan 26, 2008. 8:33 AM
oops, my bad, forgot to add it in, I'll fix it. This is my second draft of this instructable, I must have forgotten to put it in my bad
rmd6502 says: Jan 25, 2008. 9:01 PM
How many diodes would be needed to make an adder? Could it even be done without transistors, or would the losses add up too quickly? I suppose with schottky barrier diodes with very low Vf it could be done...
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