# MonoPong

When I saw this amazing 1D-Pong-Game at Hack-A-Day, I thought "What a great idea - I want to make one". In fact it is a good projects for using microcontrollers, but I also think it is a great project for using logic ICs. I am fascinated by the simplicity of these ICs, and I was wondering if I could make a 1D-Pong-Game without a µController.

Here it is: MonoPong involves a CMOS NAND Gate (4011), a 4510 up/down decade counter, 4028 BCD to decimal decoder chip and as an oscillator an NE555 in astable mode.

The Game
is a 1D-version of the famous PONG game. The "ball" moves from left to right. The player has to push the button at the right moment to strike it back. If he misses the "ball" the other player wins one point.

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## Step 1: How it works

Instructables is not only about how to make something, but also about learning how something works. So, let me first explain how the circuit works.

IC2 in the schematic is a CMOS 4510 up/down counter. Driven by IC1 which is a NE555 in astable mode it counts from 0 to 9 in BCD code. Normally it counts from 0 to 9, but it can be switched to count in the opposite direction by b setting pin 10 to HIGH.The BCD code is converted into a decimal code by the CMOS 4028 (IC2). This one drives the display and gives out the counted number in form of one of 10 LEDs lighting up.

The last IC is a 4011 NAND gate. Two of the NAND gates are connected to work as a RS flip flop. The inputs of the other two NAND gates are connected to the buttons and LED1 or LED10. The outputs are connected to the RS flip flop. If you push the button at the right moment, which means for example when LED10 lights up, the output of the NAND gate sends a LOW signal to the flip flop which changes its output state (eg. from HIGH to LOW or vice versa). This signal goes to pin 10 of the 4510 to change the direction of the count. The "ball" bounces back.
dmark21 month ago

I thought about some developments for a possible future build of my own: narrow pulse one-shot generator for each button (to avoid cheating/holding) and 4017 decade counters for score (each time the 'score' LED lights, a clock is sent to the counter) and some sort of tone being triggered by the 10th step opening. I imagined just a simple AND gate opening a tone and one has to reset the circuit to restart the game. I really REALLY like that this is just based on logic! very clever done!

Fenris781 year ago
First of all, Thanks for share your Schematics!

I have a couple of doubts about the materials:

R3 (10k) is not in the list
In the Schematic, i see 8 Leds but in the list i only see 1 resistor of each type. I have supposed that it are 8 resistors of 470 Ohm, or a big one of 3.7K.

am i supposing correctly?

mischka (author)  Fenris781 year ago
Hey Fenris, thanks for your comment. Let me explain...

R3 was the pulldown resistor for the reset button. In my final design I left the reset button because there was no need for it.

I also changed the 8 current limiting resistors for one, because only one LED lights up one time. So you just need only one resistor between the cathodes of the LEDs and GND. (See Step 4).

Cheers Mischka
Ploopy1 year ago
Cool project, I just think it would be good to put the speed switch in the middle with the power switch.
swartable2 years ago
This is great fun, much better than having to download a program to a microcontroller. I don't have a 4510 or 4028 but I found a 4017 decade counter in my son's electronic kit, which unfortunately only counts up, but at least I don't need to decode anything. I was thinking of using two more 555s to fix the cheating problem (and maybe adding another two counters and 7-segment LED decoders to keep score). It starts to get complicated, and my son says we should just use an Arduino, but I'm having fun.

Thanks so much for this project. (BTW, what's the best place to get these old parts? Digikey?)
2 years ago
The cheating problem can be fixed with a 4013 dual D flip-flop I.C.
Connect the clock inputs to the push buttons and the D inputs to the decoder outputs (where the NAND gates' inputs are connected to in the original circuit) Then connect the outputs of the flip flops to the RS latch.
mischka (author)  swartable2 years ago
you can get them for example at mouser.com
mischka (author)  swartable2 years ago
sounds great, hope you will share your result! The parts are still very common. I bought them in a german store (Conrad) since I live in Germany ;-), but there should be sources in US.
nlcortana2 years ago
What happens when both players hold down the button? I think the game is cheatable, any simple solution around that? D-latch on the output 1 & 9 as memory for the last output stage?
Still very grate and simple circuit! A+
mischka (author)  nlcortana2 years ago
Yes you are right, it is defenitely cheatable. I wanted to keep the circuit simple, but it should be possible to avoid cheating. Feel free to hack it better and post your solution.
Higgs Boson2 years ago
This is very cool! I've done quite a few analog circuits and some arduino programming, but have always wanted to do digital logic (I enjoy the electronics building much more than the programming) and this seems like an excellent starter project.
mischka (author)  Higgs Boson2 years ago
indeed, I totally agree
tolstoyan2 years ago
maybe it would be nice if it has a directional LED not only for two players so that it can be more fun and exiting
Build_it_Bob2 years ago
Very nice project ...well done and nice to see the use of some of the components I grew up using ...and admiring each of their functions.
Build_it_Bob

I love this, and the way you've implemented it in discrete logic.  Maybe not a game you could play for hours on end, but a great novelty.  Sometimes I think microcontrollers make things too easy!
It reminds me of a game I built out of TTL chips literally 3 decades ago where you had to turn off a sequencing string of LEDs by pressing a button as each lit LED passed a marker.  Pressing at the wrong time would light an additional LED.
2 years ago
When I started serious (?) electronics TTL was still on the way in, we learned to build this kind of stuff with discrete components: many transistors, resistors and caps... My very first Noughts and Crosses (Tic-Tac-Toe) machine came out of a Bernard Babbini book (who remembers them?) and was made entirely from multi-layer multi-pole rotary switches and lo-voltage light bulbs. Microprocessors ... Pah!
2 years ago

The wonderful Babani Books!
The first circuits I ever made were a metal detector and a 'burp box' (4 cross-connected astables) from '50 Electronic Novelty Circuits'. And then a matchbox radio using the ZN414 from 'Practical Electronics'. Those were the days. Kids today . . . Don't know they're born #;¬)
2 years ago
So true! Now it's just 'plug an Arduino into a socket with 4 LEDs and a USB then program it to play "Happy Birthday" and, WOW, Howzat for clever?'! Still, machine-code programming was damn good fun when it first appeared too. Don't suppose you built a Nascom as well, did you! ;-)
2 years ago

Not a Nascom (oh the luxury of those Z80 16 bit registers), but an Ohio Superboard - 6502 based.  Came ready built (apart from case, PSU, modulator etc) and I built an extra RAM board and a speech synth for it.  Then came the brilliant BBC computer.
I've just received a Raspberry Pi I ordered a few months back.  Hopefully the Raspberry project should get a few more kids thinking about what actually goes on in that black box under the desk that they play games on.
2 years ago
It was the PIO that did it for us (gang of 3 all making Nascoms and then applying them). You could actually measure and control things - and boy, did we measure and control! Aaah, the memories...
I've sort of avoided the Pi though I totally agree that it is really needed to drag kids back from the X-Box way of thinking. Let's hope... Perhaps I should give it a whirl.
I think µControllers are very useful to make things easier. I mean you could make this pong game with much less wire connections and more features using an Arduino or a µC. But using discrete logic you can learn how digital circuits really work.
TheDivineImpulse2 years ago
so do i have to program the cmos ic's or not? i'd like to make one of these...
mischka (author)  TheDivineImpulse2 years ago
No, these ICs have implemented funktions. If you want to know more about digital logic see for example this website.
dspencer92 years ago
this looks hard. I don't have ANY of those basic skills...
M0HIZ2 years ago
Where did you get that box?
mischka (author)  M0HIZ2 years ago
got it in a 1 € shop
2 years ago
OK, thanks.
indiantinker2 years ago
Great Implementation..
Well Done!
Orngrimm2 years ago
Hahaha! How nerdy is that??? :)
I was like "Whaaaaat?!?" and i think i will build such a thing just to see the fun if i get it out and show to someone... The expression on theyr faces will be worth it for sure :)