How to send a pulse from GPIO header to add credit to an arcade machine?

[nortski]

Hi guys, I'm new here a little out of my depth but this is a bit of a pressing matter.

I'll get straight to the problem. How can I send a pulse out from a raspberry pi to the pcb of a video arcade machine so that it adds a credit?

Now the long bit:

In the coming months I'll be opening a retro amusement arcade and I want to use RFID technology so that customers can come the the counter and purchase an all day pass, or half day, or hour, and use an RFID card to play on the machines as many times as they like during one of these time frames.

As it stands; I'm testing with a raspberry pi zero w with a RC522 RFID card reader. I've been using Tkinter with python to develop a backend that activates rfid cards, sets a chosen time frame, initialises a 2 minute cooldown period (so customers can't just load credit on a bunch of machines so his/her mates can all play for free too). Considering I'm a newbie at programming, I am pretty chuffed with what I have achieved so far

Now this is where I am stuck. If all the conditions are met I need to now actually send out the pulse to add the credit to the machine. I know zero about electronics so I don't even know where to begin here. Can someone please point me in the right direction?

[DaOld Man]

I'd probably use an optoisolator, keep both systems isolated from each other.  Very cheap and is basically a small integrated circuit and a resistor.

[PL1]

How about a solid-state relay?

Like this . . .

http://www.instructables.com/id/Controlling-Any-Device-Using-a-Raspberry-Pi-and-a-/

. . . or this.

http://www.susa.net/wordpress/2012/06/raspberry-pi-relay-using-gpio/

Be sure to consider the amount of current needed to operate the relay -- IIRC the 3.3v GPIO pins can only provide a rather limited current flow. (~16 mA?)


Scott

[nortski]

Thanks for the reply guys. I've been getting some help from Reddit. One guy recommended:

All you need is something like these (many vendors sell them):
https://www.amazon.com/WINGONEER-KY-019-Channel-Module-arduino/dp/B06XHJ2PBJ

Hook up any pi digital output and ground to the input pins (and power to the +), and bypass your coin slot through the relay NO/GNDCOM terminals.
More info. https://arduinomodules.info/ky-019-5v-relay-module/

But it is basically doing what his circuit does. Just integrated.
Actually, I've read those often need 5V to trigger, so just find a 3.3v version, like https://www.amazon.com/Icstation-3-3V-Optocoupler-Trigger-Development/dp/B01300ZY5M

[DaOld Man]

Sounds good, but an opto isolator and a resistor would be simple and cheap.

The chip itself is smaller than a US quarter coin.

Would require some soldering though.

[nortski]

Sounds good, but an opto isolator and a resistor would be simple and cheap.

The chip itself is smaller than a US quarter coin.

Would require some soldering though.

Could you please explain more, I really don't know the first thing about electronic components. Starting from an output pin on the pi GPIO header (pins 1, 6, 19, 20, 21, 22, 23 are being used by the RC522 RFID card reader)

 

[DaOld Man]

an optoisolator is a small "chip" that has inside an LED and a photo transistor.
Applying power on the led terminals, through an appropriate current limiting resistor, turns on the led, which turns on a photo transistor, which acts like a switch.
You wire the LED (input) pins of the chip to your RPI ground and an available GPIO output pin. The current limiting resistor goes between the chip and the GPIO output, same as any ordinary LED.
The transistor (output) pins of the chip wire to your arcades coin switch input and ground.
Polarity is important on both input and output for the opto isolator to work correctly.
In drawing below, I show how it would wire into both RPi GPIO and arcade coin switch. (If you have no coin switch, the Opto Isolator output will wire into the arcade board like the switch did.)
Of course it will be up to your software to turn on that output to simulate a coin drop.

[PL1]

Mouser lists the TIL 119 as obsolete so it might be hard to find a vendor.

Would a PC817 be a suitable substitute? (datasheet here)


Scott

[DaOld Man]

Probably, as long as the coin input on the arcade board dont draw over 50 MA, which I would bet it doesnt.
The PC827 is basically the same, just two circuits in one package, if his arcade machine has P1 and P2 coin inputs, this one chip (and two resistors and two GPIO outputs) could activate P1 and P2 credits.
Not sure if he needs that though.

[PL1]

Probably, as long as the coin input on the arcade board dont draw over 50 MA, which I would bet it doesnt.

Agreed.

IIRC he can confirm that by setting his multimeter to Amps, touching the red lead to the coin input, and touching the black lead to ground ==> PCB registers it as a coin insertion + meter displays the current draw, right?

Should be easy to check at the coin microswitch NO (Normally Open) and COM (Common) tabs.

The PC827 is basically the same, just two circuits in one package, if his arcade machine has P1 and P2 coin inputs, this one chip (and two resistors and two GPIO outputs) could activate P1 and P2 credits.
Not sure if he needs that though.

Good point.

He might even need 4 pins + 4 resistors + one PC847 or two PC827 or four PC817 for 4-player games like TMNT or Simpsons where the coin slot determines which player postion gets the credits.
-----------
Another thing to consider, Nortski, is if any of your games need more than one credit to start, you should check the dipswitches and service menus.

With most games you can set coins/credit to 1 coin/1 credit, but some newer games might require 2/1. (or more)

In that case, you'll want to have the code output more than one coin pulse per RFID scan.


Scott

[nortski]

Thanks for the info guys. I don't have any arcade machines yet so I can't do any testing. I was hoping to bypass the coin mech altogether and wire straight to the arcade pcb. I see that the JAMMA harness have two wires indicating coins, coin 1 T switch and coin 2 16 switch, I was wondering if I can just hook into them? Also; am I right in thinking that the arcade board provides the power so I'll I have to do is activate the optoisolator or relay?

[DaOld Man]

Thanks for the info guys. I don't have any arcade machines yet so I can't do any testing. I was hoping to bypass the coin mech altogether and wire straight to the arcade pcb. I see that the JAMMA harness have two wires indicating coins, coin 1 T switch and coin 2 16 switch, I was wondering if I can just hook into them? Also; am I right in thinking that the arcade board provides the power so I'll I have to do is activate the optoisolator or relay?

Im not sure about the wire numbers on the board, but I would say touching the coin wires to GND or COMM should register a coin credit, but you might want to research that to be sure before trying. I would not want you to fry your arcade board.
You might ask on here (there are a lot of original arcade experts on here), or google wiring diagram for your board.
As far as the opto isoltor, if you wire it correctly, your software on the RPi should make the output turn on for a few milliseconds to simulate a credit on the arcade board.
Your software will also have to assign the pin(s) you are using as output(s)
No other power supply should be necessary, just what the Pi requires and what the arcade board requires.
You will need available outputs on the Rpi, I really dont know if the Pi zero has same GPIO configuration as the Pi2 and Pi3?

[nortski]

Im not sure about the wire numbers on the board, but I would say touching the coin wires to GND or COMM should register a coin credit, but you might want to research that to be sure before trying. I would not want you to fry your arcade board.
You might ask on here (there are a lot of original arcade experts on here), or google wiring diagram for your board.
As far as the opto isoltor, if you wire it correctly, your software on the RPi should make the output turn on for a few milliseconds to simulate a credit on the arcade board.
Your software will also have to assign the pin(s) you are using as output(s)
No other power supply should be necessary, just what the Pi requires and what the arcade board requires.
You will need available outputs on the Rpi, I really dont know if the Pi zero has same GPIO configuration as the Pi2 and Pi3?

I believe it's the same 40 pin GPIO header as the other pi's and it looks straight forward configuring a pin for signal output. I'm waiting for the tech guy of an arcade refurb company to get in touch with me next week, I'm sure he should be able to tell me exactly which wire/s on the JAMMA harness I need to be connecting with.

It's so annoying that everywhere is closed for the long weekend, want to get some components together so I can start testing!

[nortski]

an optoisolator is a small "chip" that has inside an LED and a photo transistor.
Applying power on the led terminals, through an appropriate current limiting resistor, turns on the led, which turns on a photo transistor, which acts like a switch.
You wire the LED (input) pins of the chip to your RPI ground and an available GPIO output pin. The current limiting resistor goes between the chip and the GPIO output, same as any ordinary LED.
The transistor (output) pins of the chip wire to your arcades coin switch input and ground.
Polarity is important on both input and output for the opto isolator to work correctly.
In drawing below, I show how it would wire into both RPi GPIO and arcade coin switch. (If you have no coin switch, the Opto Isolator output will wire into the arcade board like the switch did.)
Of course it will be up to your software to turn on that output to simulate a coin drop.

Ok so I have gotten some components together. I have some 150ohm resistors, a breadboard, jumper wires and I have bought some PC817 Sharp optoisolator photocouplers. Now I do not know if these will be ok, I have attached an image, mine are the same except mine are marked 'D2' in the top right corner.

They didn't come with a datasheet but I found this one: http://www.sharp-world.com/products/device/lineup/data/pdf/datasheet/pc817xnnsz_e.pdf

I also have some 2.2v LEDs as I would like to test my code lighting up one of these before I try it on the arcade board.
Can these components be connected for testing? Would I just replace the coin switch in your diagram with the LED?

[DaOld Man]

Im sure that will work. Make sure you connect it correctly, and if it doesnt work, try a smaller resistor. (You can add another 150 ohm resistor in parallel with that 150 ohm one to make total resistance 75 ohms.)

On the test led side,  Im not sure I understand what you are doing. You can connect the opto to the led, but you will need a power source and appropriate resistor for that led.
You say replace led with coin switch? im not sure that will work. you might try putting the led in one wire going between the opto and the coin switch. (In series).
I dont think you will need a dropping resistor for that led if you do it that way, still not sure if your arcade board will have enough current to light the led.

No matter what you do, you still need the resistor between the opto and the RPi.
Think of the opto isolator as a fence between the RPi and the arcade board. Each side of the fence dont care what the other side is doing. As long as the arcade board gets its signal through the fence to do what it is supposed to do.
And in this case, that signal is light, even though the light is inside that chip and you cant see it.

Heres a diagram showing how I would hook this up for testing, using the RPi 5VDC GPIO pin as power for the led. If it works, remove LED and connections to the pi and wire it to your arcade board like in the first diagram.

[nortski]

Im sure that will work. Make sure you connect it correctly, and if it doesnt work, try a smaller resistor. (You can add another 150 ohm resistor in parallel with that 150 ohm one to make total resistance 75 ohms.)

On the test led side,  Im not sure I understand what you are doing. You can connect the opto to the led, but you will need a power source and appropriate resistor for that led.
You say replace led with coin switch? im not sure that will work. you might try putting the led in one wire going between the opto and the coin switch. (In series).
I dont think you will need a dropping resistor for that led if you do it that way, still not sure if your arcade board will have enough current to light the led.

No matter what you do, you still need the resistor between the opto and the RPi.
Think of the opto isolator as a fence between the RPi and the arcade board. Each side of the fence dont care what the other side is doing. As long as the arcade board gets its signal through the fence to do what it is supposed to do.
And in this case, that signal is light, even though the light is inside that chip and you cant see it.

You need a diagram showing how I would hook this up for testing?

I would love a diagram thanks!
I'll try and clear up what I mean. Because I do not have any arcade cabs yet I can't test if my python code works so I thought can I use an LED after the opto isolator and then when I send a signal out form the GPIO header to the opto, the LED would light up? I then realised that I would need to power the led. Oh that reminds me, does the opto isolator get it's power from the GPIO signal out and ground pins (my ignorance shining bright here)? And if so, why can't the LED also?

The diagram was confusing me as there's no switch between the pi and the jamma harness. But then I bought a cheap coin acceptor and noticed that it has a switch on it that can be set to NC or NO so it looks as though I need a relay switch after all (I'm now assuming that it what you are referring to on your diagram?)

Annnnnd, looking at the pin layout of jamma, there are two wires, coin A and coin B. At first I thought one was for the signal and the other was ground but now I'm thinking its for two separate coin acceptors for player 1 and player 2? If that's the case then this would mean I need to double up on my set up for each 2 player machine right? ARGHHHH

Sorry for all the questions, all your answers are helping me understand much more clearly!

[DaOld Man]

Im sure that will work. Make sure you connect it correctly, and if it doesnt work, try a smaller resistor. (You can add another 150 ohm resistor in parallel with that 150 ohm one to make total resistance 75 ohms.)

On the test led side,  Im not sure I understand what you are doing. You can connect the opto to the led, but you will need a power source and appropriate resistor for that led.
You say replace led with coin switch? im not sure that will work. you might try putting the led in one wire going between the opto and the coin switch. (In series).
I dont think you will need a dropping resistor for that led if you do it that way, still not sure if your arcade board will have enough current to light the led.

No matter what you do, you still need the resistor between the opto and the RPi.
Think of the opto isolator as a fence between the RPi and the arcade board. Each side of the fence dont care what the other side is doing. As long as the arcade board gets its signal through the fence to do what it is supposed to do.
And in this case, that signal is light, even though the light is inside that chip and you cant see it.

You need a diagram showing how I would hook this up for testing?

I would love a diagram thanks!
I'll try and clear up what I mean. Because I do not have any arcade cabs yet I can't test if my python code works so I thought can I use an LED after the opto isolator and then when I send a signal out form the GPIO header to the opto, the LED would light up? I then realised that I would need to power the led. Oh that reminds me, does the opto isolator get it's power from the GPIO signal out and ground pins (my ignorance shining bright here)? And if so, why can't the LED also?

The diagram was confusing me as there's no switch between the pi and the jamma harness. But then I bought a cheap coin acceptor and noticed that it has a switch on it that can be set to NC or NO so it looks as though I need a relay switch after all (I'm now assuming that it what you are referring to on your diagram?)

Annnnnd, looking at the pin layout of jamma, there are two wires, coin A and coin B. At first I thought one was for the signal and the other was ground but now I'm thinking its for two separate coin acceptors for player 1 and player 2? If that's the case then this would mean I need to double up on my set up for each 2 player machine right? ARGHHHH

Sorry for all the questions, all your answers are helping me understand much more clearly!

No problem about the questions, thats what we are here for, to help each other all we can.
I dont think you will need a relay, the opto isolator should just take the place of the coin switch and wire the same as it would have, to the arcade board.
But, if it dont work, you could try having the optoisolator turn on a relay. But that opens up more variables.
relay coil cannot draw over 50 ma, and it will need a diode across the coil leads to protect the opto isolator transistor from CEMF generated by the relay coil.
Why dont you try just opto isolator and if that wont work we can look at adding a relay.

Yes, those wires go to a coin switch each, the other sides of the switches probably connect to ground or common on the board.
You have to decide if you want Player 1 AND Player 2 coin inputs, and if you do, yes, you will need to double the circuit.
If you use relays, this can get expensive if you have a bunch of machines, so hopefully just the simple circuit using the opto isolators will work for you.

I posted a quick and dirty diagram on last post. Let us know how this project is going. Very interesting.

[nortski]

Ah ha right I think I actually understand that diagram! I need 1 x 5VDC from pi, 1 x available out pin, and 2 x ground pins?

Believe me, I don't mind spending a bit more on relays if I have to because I was quoted £20,000 for a cashless solution from Ideal! Hence why I'm making it myself haha!

[nortski]

Could you please check my breadboard set up, first time EVER using one. Thanks

[DaOld Man]

Looks good to me.

When you test it, setting the output on the Pi high should turn on  the led. Making it low should turn it off.
If your software acts different (low to simulate coin drop), you just need to rewire the input on the opto a little different.

[DaOld Man]

Ah ha right I think I actually understand that diagram! I need 1 x 5VDC from pi, 1 x available out pin, and 2 x ground pins?

Believe me, I don't mind spending a bit more on relays if I have to because I was quoted £20,000 for a cashless solution from Ideal! Hence why I'm making it myself haha!

Yes, but the grounds can connect together and tie back to one pin, since all the gnd pins on the RPi connect together. But thats only for testing. When you connect this to your arcade board, no wires at all should connect between the board and the RPi.
If you want to use relays, thats pretty simple too, but if you really need to use relays, you might want to consider some of those that PL1 posted a while back.
I would try the optos though, cause I am a old tight wad. LOL

[PL1]

Could you please check my breadboard set up, first time EVER using one. Thanks

The only problem I see is the LED has both leads on the same rail as pin 4 of the optoisolator and one end of the resistor.

The outer rails connect full-length vertically and the center rails connect horizontally.

Move the resistor and the + lead of the LED to a different rail and you are good to go.   


Scott

[nortski]

Could you please check my breadboard set up, first time EVER using one. Thanks

The only problem I see is the LED has both leads on the same rail as pin 4 of the optoisolator and one end of the resistor.

The outer rails connect full-length vertically and the center rails connect horizontally.

Move the resistor and the + lead of the LED to a different rail and you are good to go.   


Scott

Thanks man! I'm gonna give this a try right now!

[nortski]

Ah ha right I think I actually understand that diagram! I need 1 x 5VDC from pi, 1 x available out pin, and 2 x ground pins?

Believe me, I don't mind spending a bit more on relays if I have to because I was quoted £20,000 for a cashless solution from Ideal! Hence why I'm making it myself haha!

Yes, but the grounds can connect together and tie back to one pin, since all the gnd pins on the RPi connect together. But thats only for testing. When you connect this to your arcade board, no wires at all should connect between the board and the RPi.
If you want to use relays, thats pretty simple too, but if you really need to use relays, you might want to consider some of those that PL1 posted a while back.
I would try the optos though, cause I am a old tight wad. LOL

Gotta look after them pennies 

[nortski]

Blurry, but it's the most beautiful thing I've ever seen!
I might actually pull this off! Just need the arcade machine now

Thanks to everyone that helped, I'll be sure to post updates

[DaOld Man]

Could you please check my breadboard set up, first time EVER using one. Thanks

The only problem I see is the LED has both leads on the same rail as pin 4 of the optoisolator and one end of the resistor.

The outer rails connect full-length vertically and the center rails connect horizontally.

Move the resistor and the + lead of the LED to a different rail and you are good to go.   


Scott

Thanks PL1, that slipped right past me.

[DaOld Man]

Blurry, but it's the most beautiful thing I've ever seen!
I might actually pull this off! Just need the arcade machine now

Thanks to everyone that helped, I'll be sure to post updates

Cool! Looking forward to seeing your writeup on this project.

[nortski]

Cool! Looking forward to seeing your writeup on this project.

I'll make sure I do. It will be a while though, still tonnes of work to do. Got to get my business plan handed in, get the funding, find suitable premises, purchase the arcade machines, finish coding the back office, hook the pi's into the machines.......I'm going for a lie down.

[chopperthedog]

Seems like you're trying to open a restaurant with no experience of ever cooking a single egg. I'd be interested to hear more details, i.e. how many games you plan to have, what type of games, will you serve booze, can you live off your savings for the next 4 years and so on?


good day.

[nortski]

Seems like you're trying to open a restaurant with no experience of ever cooking a single egg. I'd be interested to hear more details, i.e. how many games you plan to have, what type of games, will you serve booze, can you live off your savings for the next 4 years and so on?


good day.

I'm sorry, I didn't realise this was a business forum (who rattled your cage?), I came here for electronics help which the guys above have so generously provided. But if you must know I have budgeted for 10 arcade machine, a pool table, an air hockey table, and a fussball table. I will be charging corkage fees for people who want to bring their own alcohol. I own my own successful online retail business that has kept a roof over my head and fed and watered me for the last 5 years.




good day

[chopperthedog]

No cage rattled here. Was just a couple of honest questions. You should call it "Rusty Quarters". 


good day.

[nortski]

Hi guys, back again :p
I have an arcade machine arriving on Friday, Tekken 4, and I just want to clarify something before I hook in the pi and rfid reader.
On the diagram on reply #6 above, do I just need to connect pin 3 of the opto isolator to the gnd/common wire of the jamma harness and pin 4 to the coin 1 wire?

Thanks.

[DaOld Man]

Yes I think that is correct.

[PL1]

On the diagram on reply #6 above, do I just need to connect pin 3 of the opto isolator to the gnd/common wire of the jamma harness and pin 4 to the coin 1 wire?

Pin 3 isn't used in that TIL119 diagram.


If you're talking about using a PC817 (datasheet here) instead of the TIL119 in the diagram, you got your pin numbers and connections right.

- Pin 4 emitter (arrow) on the TIL119 ==> Pin 3 emitter on the PC817 -- connect to JAMMA ground

- Pin 5 collector (straight line) on the TIL119 ==> Pin 4 collector on the PC817 -- connect to JAMMA Coin 1


Scott

[nortski]

Thanks guys.
Yes I'm using the PC817.
I've modified the diagram slightly to reflect exactly what I'm doing...