Welcome to our site!

Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

  • Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

Air hockey scoring system

Not open for further replies.


New Member
Hi all

For my A level DT project I'm making an air hockey table. I would like to make it coin operated with a fully electronic scoring system. The only problem is that I'm new to electrnics although I would much like to learn. I would gradually learn everything I need for this out of books, but as I need to make it fairly soon I have turned to your expert help.

Without going any further, here is an idea of a circuit to be used (please point out glaring mistakes) :


The main part of the circuit is the intergrated circuit which would be turned on by SW1 which is a coin pressed micro switch. The IC would then activate the relay to turn on the four fans ran in parallel. SW 2 and 3 would register goals by the puck and count up on DISP 1 and 2 which are 7 segment LED displays.

When 6 goals are scored on a certain side, a lever would move to make a barrier to trap the puck on the next goal scored for that specific side. Once the 7th goal is scored for either side, the fans would stop and the two displays would flash the scores for a while before turning off.

This would be a complete cycle, it would begin again when SW1 is pressed again, and the levers would release to let the puck out.

Hope that is sufficently clear :eek:

Main questions:
Is this even doable?
Is 1 IC enough? Or would you need more?
Does the rest of my circuit make sence?
Is 5v correct? How many amps would I need?
Can you give model numbers I would need of the somponents? (IC and relay especially)
The only way I can think of making the levers is a very short burst on a motor, surely there is a better way?
How/where can I learn how to program the IC?

And anything else you feel like telling me :)

One more thing, as its for my schoolwork, if you help me can you add your name and any electronics qualifications if possible so I can credit you for help? If not don't worry, all help is appreciated.

Thanks in advance.



Well-Known Member
Its doable

just depends how far you want to go
A PIC is perhaps the easiest way to go but you need to write then program a PIC chip.
another method is simple TTL or cmos
just have two up counters that count to 7
when 7 is obtained it turns off the fans and traps the puck (thats the hard part or perhaps have a trap door that opens then traps the puck.
upon inserting a coin the puck drops to a tray and play begins (kinda like a billard table)
look up using google or ? for up counters with a single digit
take the outputs and using gates (IC chips like 7400 or 4011) you analyze when 7 is reached.
another method would be a simple counter like the 4017 and a few gates to analyze the outputs into 7 segment digits.
If wanting to use a PIC then PCB Heaven has a one digit counter but the circuit and code would need to be written (lots of work if never used a programming language.
micro switches at each goal to instantiate the counters.
metal pucks are an easy way to count the goals or infrared red sensors.
micro switches would work but IMO would wear out very quick and not as reliable??
if you could get a PIC programmed then you could cut your costs down.
my eatimate = 1-4518 counter(2 counters in one package,
2-4511 BCD gate,decoder/driver,
1-4013 gate
couple of transistors, couple of relays, switches and you have it.
now go do a search
look up decimal counting unit


Well-Known Member
use a 4023 to decode outputs

a 3 input nand gate to decode when 7 is reached then take enable on the 4518 low to stop count and turn fan relays off.
look up cd4518, cd4023, and 4511


New Member
Im back again after more help :)

But first off I'm ashamed I never thanked you MrDEB, although I did add to you reputation if that helps at all? You were a great help and following your replies I went off to learn a lot more about electronics.

I have a lot more of my circuit completed, as seen here:


Any mistakes/suggestions will be greatly appreciated.

The counters work and flash when they reach 7, but if you notice the exor leading to the big gap in the middle, this is where I would like to make some type of delayed pulse that takes a logic level 1 input from the exor, then approx. 10 seconds later send a continous pulse to the blanking pins on both 4511 ICs.

I guess a good way of doing this would be with a 555 multivibrator system with some capacitors and resistors but I have no clue how to lay this out. I have looked on the internet for diagrams but can only seem to mainly find delayed on circuits, and for some reason they never seem to work in circuit wizard.

Any help would be greatly appreciated on this and please could you try and include resistor/capacitor values as I can never seem to work them out.

Many thanks,


New Member
look for one shot controlling an astable.
its there LM555 Timer Circuits
then calculate your desired time.
I like this calculator better
555 Calculator
let me know if you need more help but the link I sent you should help.

Thanks loads but sorry, but I'm having problems again. :(

I've tried building a few of those circuits off the first link but none of them are working for me.

Heres one:


Tried building it again in another program but still not working, all that seems to be happening is 10.95mA flowing into pin 8 and 3.95mA flowing out pin 1.


New Member
My circuit is finally finished :D All working on the simulator, I just hope it behaves the same when built. :ermm:

Here it is for anyone interested:


(full size here)

Many thanks MrDEB for all the help, I truely couldn't have done it without you. May I credit you in my project folder? (If so can I have your name and any electronics related qualifications)

Thanks again,
Not open for further replies.

Latest threads

EE World Online Articles