Coin operated water dispenser help!

[spycbeef]

Hi

The interrupt pin is pin D2 and what's triggering it is a coin acceptor.

@lastchancename

What’s feeding the interrupt input pin..

Would that also be the case with coin acceptors? I did monitor the D2 pin with an oscilloscope. Everything is normal from the time the arduino is reading the impulse from the coin acceptor > turning on the relay > turning off the relay.

The only problem is sometimes after a cycle, my coin_imp variable goes up.

I tried inserting "Serial.println("Triggered");" in my interrupt code but it doesnt show in the serial monitor when i get the unwanted impulse.

@lastchancename

Contact bounce is a thing.

[J-M-L]

Try with coin_imp declared as a volatile variable and use à critical section

  noInterrupts();
  // critical section
  int coin_imp_copy = coin_imp;
  coin_imp = 0;
  interrupts();
  // work with coin_imp_copy

to work on a copy in the loop.

(also necessary for i (Which is a stupid global variable name)

[spycbeef]

@J-M-L

(also necessary for i (Which is a stupid global variable name)

haha yeah my arduino's millis function is loco so i just used i. pretty much just random letters i use as timers. sorry

anyway, thank you, all for all your inputs! it's working now, I just put a capacitor between my D2 (interrupt pin) and gnd.

i cant thank you all enough! =D

@lastchancename

Possibly adding a small capacitor on the input pin may help quench some of those ‘extra’ pulses.

[TomGeorge]

Hi,

@TomGeorge

Your circuit shows no bypass capacitors, especially at your Nano power pins or coin counter or hopper inputs.

Post #16.

Tom..

[spycbeef]

oh yeah sorry! =( forgot to quote you but yeah you we're the one who suggested it first.

Thank you sooooo much! =)

[J-M-L]

I would still suggest you declare your interrupts variable as volatile

[spycbeef]

i read what volatile is just now and ill definitely use it. thanks! =)

also, what use will the noInterrupt() function serve? also the coin_imp_copy variable?

[J-M-L]

If you have interrupts while the loop is using the variable your code might have weird behavior

[spycbeef]

@J-M-L

while the loop is using the variable

and by variable you mean...?

[J-M-L]

Those shared between the interrupt and the main code

[spycbeef]

oh ok. I think i get it.

so i just put the NoInterrupt() function on the loop right?

but since the Interrupt() function is called in the NoInterrupt() function wouldnt that call the interrupt() function without D2 having to call the interrupt?

[J-M-L]

Notice the s at the end

@J-M-L

noInterrupts();
            // critical section goes here
interrupts();

It’s NOT your function. This is to deactivate and then reactivate the interrupts, this way you are sure nothing bad happens to the bytes whilst your loop plays with the variables. Of course you want to minimize the duration of the critical section, so that’s why you just make a copy of the values and then work from the copies