DIY 'Coin Mech' (Simple Coin Acceptor)

[smithers18]

Hi. 

I thought I'd make a thread regarding building your own coin mechanism since I couldn't seem to find one. 

So I have built a small cabinet and after I got finished with it I thought "wouldn't it be nice to have a coin mechanism on there!". Unfortunately there is not enough space to add a real coin mech and even those cheap silver coin mechs are a little too big to fit on the front bezel (and would be awkward to retro fit into the cab). So I had the thought of building a simple coin mechanism instead. My plan is to use an Optocoupler Module to sense the coin being inserted and that will be linked to a relay that makes a connection to a pair of wires coming from the 'zero delay' encoder in my cabinet, telling it to press the '0' button (insert coin). 

I have tested this out and it seems to work perfectly so in theory all I need to do is make a short coin chute or rather a channel that carries the coin past the sensor on its way down to the hopper. The downside to doing a coin mech this way is that it is a 'dumb' system in that it doesn't know what you have inserted, only that something has broken the light path between the 2 poles. So that means if you were to insert a button or a stick or a coin, it wouldn't care and it would always pass the 'keyboard 0' signal through regardless. This is fine for me as the machines I like to play are all £1 in and £1 out and I will be using tokens instead of real cash, but if you wanted something that recognises the denomination then this isn't for you. 

Parts used so far: 

• Optocoupler Module Photo Interrupter Sensor (£6.59 for 5 pcs)
• 5V 1 Channel Relay Board with Optocoupler Isolation (£6.99 for 4pcs)
• Metal coin accepter (£6.50)

 

I will update this thread as I make progress and would love to hear if anyone else has done something similar already and can share some tips, especially on how to make the coin channel! I will also make a wiring diagram if anyone is interested although its pretty straight forward. 

Here is a video showing the proof of concept: 

 

 

[woodsy]

BRILLIANT STUFF

[slotsmagic]

Seems like a good idea! My plan (before using actual coin validators instead) was going to be similar- but using a leaf switch, and relying on the mass of the £1 coin being sufficient to trigger it, but yours is more elegant and (I assume) less likely to fail / jam.

Edited September 20, 2025 by slotsmagic

[smithers18]

Yes I considered doing that too, like you say using a leaf switch, I have some that are really sensitive. It would be the simplest way to do it but would have to reliably bounce off the switch each time. Also, I plan on using tokens which are thinner and likely less heavy than a pound coin (I haven't actually received them in the post yet so I am just surmising based on the dimensions!). 

Im just currently trying to decide on the best way to make the coin slide. The gap in the optocoupler is 6mm so my thought is to try building the 2 sides using 3mm acrylic and then using 2 thin strips glued together to form the base piece, 6mm thick in total, which the coin will roll down. Then I'd leave the top mostly open in case of jams. 

I might experiment with the optocoupler sensor too, unsolder it off the board and split the 2 sides apart. Would make it easier if I can just glue them on each side of the clear perspex instead of fitting the whole unit into the slide.  

[smithers18]

Quick update with some progress on this. I am still waiting on the coin insert being delivered, not ideal, but in the meantime I have decided on a simple idea for the coin chute and have made a POC:

 

All I done was get some 3mm perspex, heat it up with a heat gun, placed it into my vice with a 6mm gap and slowly pushed it down to fold in on itself. The result (once cooled) is a very sturdy coin slide. 

I then cut a slight angle at one end (the coin insert end) to ensure a small incline downward and i also cut in a slot that was big enough to fit the optocoupler sensor poles either side. All the cutting was done on my table saw. 

I then hot glued the sensor in the slot I made, making sure the poles weren't intruding into the coin slide path, and then the concept is complete. Using hot glue isn't ideal in the long term of course as if the sensor were to fail then it'll be a pain to replace so ideally I need to attach it in a non-permanent way. I'll think about that at a later date.

Testing has shown it works perfectly so far. The slide leaves plenty of room for a £1 coin to slide down at an upright, consistent angle and it passes through the poles each time since it is positioned on the bottom of the slide rather than the top so it really doesn't have a choice. The perspex is glossy enough to allow the coin to freely slide with no resistance. Here is a video showing it in action:

https://youtu.be/3hYykQa2PlA?si=K-ceT51ZQCTH-1PI

So this is the design I think I'll go with, I just need to figure out how to attach it to the coin insert so fingers crossed the bloody thing arrives soon! 

Happy to hear any comments or suggestions from people on improvements etc. and again I will aim to upload a wiring diagram soon. 

All the best,

Steve

 

[Ginge]

Looks like a homemade 2p pusher slide . Nice work 

[smithers18]

Since I last posted the coin slot has arrived, hurrah, so I set to work fixing it all up this afternoon. 

I measured the mounting holes and then cut a line down the middle of the perspex slide to the correct length and then heated the 2 sides at the start of the cut and bent them out at right angles so they would splay out and act as mounting lugs. I then drilled bolt holes in and trimmed down the lugs so it was just enough for the bolt to grip:

I next made a rectangular mounting plate out of perspex and attached it to the slide with an improvised bracket (rough and ready but it works and its more future proof than hot glue is!)

Next I had to drill a hole into the bezel and through the plastics on the all-in-one pc (luckily it was an empty cavity where the speakers used to be mounted), and then I was able to slot it in after a bit of dremel tweaking!

And that's it, I've been testing and haven't had any issues at all thus far so fingers crossed its done. I tested it with pound coins and also a 5p and both registered each time. I will be using tokens that are a little slimmer than a pound but knowing that a 5p is fine then I know they will be too. Happy days! Short video below showing it in action:

Now I need to make a tube to guide the coin into the hopper, but I don't have the hopper yet so that's a problem for another day!

All the best,

Steve

 

[thealteredemu]

Nice work on this

J

[Ginge]

Great idea . Can I just ask where you bought the items from and please could you provide a wiring diagram.

[smithers18]

Yes of course, see breakdown below: 

Optocoupler Sensor Module: https://amzn.eu/d/hggmd4g

Optocoupler 1 channel High/Low Relay: https://amzn.eu/d/6gMmIYA (this isn't the exact one I bought, I've had them for years but this looks to be the same just lower amps)

USB Type A Connectors: https://amzn.eu/d/j5td0bc (you don't necessarily need this, if you have an old USB 5v phone charger plug then just hack the 'phone end' off and use that but I already had these so I used them)

Wires: Pretty much any wires will do, this is all 5v low voltage so again use the wires from an old phone charger if you have it. The optocoupler comes with a bunch of wires so all you need on top is 5v positive & negative plus a pair of wires to your keyboard controller. 

Coin Inserter: https://ebay.us/m/vts4DE (I would have rather used a proper fruit machine coin bezel like a Mars or Barcrest but I opted for this due to the mounting holes on the back)

3mm A3 Acrylic sheets: https://amzn.eu/d/7X04gaD (my local stores didn't have 3mm in stock and it was quite pricey and came in large sheets so I opted for Amazon again) 

(I went the quick and more expensive route by getting all this stuff from Amazon but you could get it much cheaper off Ali Express if you can wait for delivery).

 

Wiring Diagram:

Hopefully the above makes sense but any queries just let me know. Also just to note as I feel like its an elephant in the room but I imagine that a 3d printed slide would be a much more graceful solution and you'd be able to make a better connection from the coin insert to the coin slide to the cabinet. In fact I bet you could create an all-in-one solution that would just slot in and includes the coin slot itself along with slider and faceplate without the need to buy them separately. The problem is I don't have a 3D printer and I am not at all versed with 3D modelling (I tried using Sketchup for this but gave up as it was taking too long!). Just food for thought for anyone out there with 3D printing skills. 

All the best, 
Steve

Edited September 23, 2025 by smithers18

[Road Hog Mad]

Nice, I was thinking of something similar for my second build which is now for sale, but ended up putting a new door on the back to give me the room to fit an actual coin mech, which is now a top coin slot. 

[Ginge]

7 hours ago, smithers18 said:

Yes of course, see breakdown below: 

Optocoupler Sensor Module: https://amzn.eu/d/hggmd4g

Optocoupler 1 channel High/Low Relay: https://amzn.eu/d/6gMmIYA (this isn't the exact one I bought, I've had them for years but this looks to be the same just lower amps)

USB Type A Connectors: https://amzn.eu/d/j5td0bc (you don't necessarily need this, if you have an old USB 5v phone charger plug then just hack the 'phone end' off and use that but I already had these so I used them)

Wires: Pretty much any wires will do, this is all 5v low voltage so again use the wires from an old phone charger if you have it. The optocoupler comes with a bunch of wires so all you need on top is 5v positive & negative plus a pair of wires to your keyboard controller. 

Coin Inserter: https://ebay.us/m/vts4DE (I would have rather used a proper fruit machine coin bezel like a Mars or Barcrest but I opted for this due to the mounting holes on the back)

3mm A3 Acrylic sheets: https://amzn.eu/d/7X04gaD (my local stores didn't have 3mm in stock and it was quite pricey and came in large sheets so I opted for Amazon again) 

(I went the quick and more expensive route by getting all this stuff from Amazon but you could get it much cheaper off Ali Express if you can wait for delivery).

 

Wiring Diagram:

Hopefully the above makes sense but any queries just let me know. Also just to note as I feel like its an elephant in the room but I imagine that a 3d printed slide would be a much more graceful solution and you'd be able to make a better connection from the coin insert to the coin slide to the cabinet. In fact I bet you could create an all-in-one solution that would just slot in and includes the coin slot itself along with slider and faceplate without the need to buy them separately. The problem is I don't have a 3D printer and I am not at all versed with 3D modelling (I tried using Sketchup for this but gave up as it was taking too long!). Just food for thought for anyone out there with 3D printing skills. 

All the best, 
Steve

Thanks for this information Steve. Might have a play around at some point. I have a few of these 2p pusher chutes that use a a flag opto I could probably use them somehow.

[smithers18]

Yes I imagine they would be perfect for this, providing the slide is no more than 6mm wide? (the width of the optocoupler sensor area). 

Oh and just to mention, I am speaking to a chap on a Facebook group who is designing a 3D print for this for me so hopefully I will be able to share an improved version plus the print files. 

[aland888]

Where did you get the silver coin slot surround???exactly what I’m looking for—thanks 

[smithers18]

I got it off Ebay, here is a link:

https://www.ebay.co.uk/itm/135668273108?

 

Whilst I'm here, I have made a 3D printable version of this slide now if anyone would be interested in having the file?

[smithers18]

3D model for my coin insert has been uploaded here: https://makerworld.com/en/models/2049863-coin-insert-for-arcade-fruit-machine-pinball-etc#profileId-2212214

This is a full solution i.e. it incorporates the faceplate/bezel, the coin slide and a mounting point for an optocoupler sensor. All it needs is a 40mm hole drilled into your cabinet and it will slot inside with the faceplate covering the hole.