Supermarket self-service machines: how do they know......

[betty swollocks]

what combination of coins to give as change?
Just been in Tescos, paid a tenner and got £1.66 back, as follows:- x1 £1, x3 20p, x1 5p, x1
1p.
Why this combination of coins, if say, all its reservoirs of coins are full? What if they aren't......some are more full than others, or some are empty even?
Is there some complex maths involved?

 

[Globalti]

That's what the small bloke inside the machine had in his hand at the time.

 

[MontyVeda]

for the most part, I refuse to use them because eventually they'll replace staff... however since Globalti pointed out there's a small bloke inside, I might start using them as it must be hard to get a job outside of panto if you're only that big.

 

[betty swollocks]

.....we're edging closer to the answer then......

 

[Nantmor]

I once put my card into an ATM and a voice from inside said, "Its empty." So I replied, "I never really believed that there is a little man inside." "There isn't!" said the voice.

 

[col]

A simple note and coin recognition, if there isnt enough change it will say correct change only, well my works coffee machine does?

 

[ColinJ]

It would be simple to write the software to do that. I would program it to use the minimum number of notes/coins from what was available in the machine.

Ideally, £1.66 = £1 + 50p + 10p + 5p + 1p but if the 50p pieces had run out then the next best option is £1 + 20p + 20p + 20p + 5p + 1p.

It wouldn't take long to enumerate all the acceptable combinations of coins for the pence (1-99p), and pounds (£1-£19, assuming that the machine didn't accept notes greater than £20 in value). I would suggest no more than 9 of any given coin i.e. 9p in 1ps, 18p in 2ps, 45p in 5ps, 90p in 10ps, £1.80 in 20ps, £4.50 in 50ps, £9 in £1s and £18 in £2s

Things could get silly if only small value coins were available so I would either set a fixed limit on the number of coins which would be given out, or give the customer the choice of accepting a large number of coins or of going to a different machine. I'd probably set the limit at about 15 coins, but ideally the company would have already asked customers how many coins they would find acceptable.

"Sorry, but your change will be made up of 23 coins - press the Okay button to Accept or Cancel to decline and try another machine."

 

[betty swollocks]

It would be simple to write the software to do that. I would program it to use the minimum number of notes/coins from what was available in the machine.

Ideally, £1.66 = £1 + 50p + 10p + 5p + 1p but if the 50p pieces had run out then the next best option is £1 + 20p + 20p + 20p + 5p + 1p.

It wouldn't take long to enumerate all the acceptable combinations of coins for the pence (1-99p), and pounds (£1-£19, assuming that the machine didn't accept notes greater than £20 in value). I would suggest no more than 9 of any given coin i.e. 9p in 1ps, 18p in 2ps, 45p in 5ps, 90p in 10ps, £1.80 in 20ps, £4.50 in 50ps, £9 in £1s and £18 in £2s

Things could get silly if only small value coins were available so I would either set a fixed limit on the number of coins which would be given out, or give the customer the choice of accepting a large number of coins or of going to a different machine. I'd probably set the limit at about 15 coins, but ideally the company would have already asked customers how many coins they would find acceptable.

"Sorry, but your change will be made up of 23 coins - press the Okay button to Accept or Cancel to decline and try another machine."

Thanks: thought it'd be something along the lines of least amount of coins possible.

 

[marinyork]

Vending machines originally used an area of Maths called automata theory. Simple vending machines and ATMs are loved examples in this area.

 

[Cubist]

Why do Klix machines give everything out in 5ps? Bloody things.

 

[Beebo]

the vending machines in my university halls of residence were used mainly to purchase crisps and chocs when students had the munchies. Being poor students most purchases were made in very small change and coppers.

i once made the mistake of buying a 25p packet of crisps with a £1 coin, and had to catch 75 1p's as they were ejected in change.

 

[BigonaBianchi]

no idea...I just think it's sad when I have to buy an apple with a bar code on it.

 

[marinyork]

no idea...I just think it's sad when I have to buy an apple with a bar code on it.

Shops have things called PLU codes for fruit and veg. There is an international standard set out by the International Federation for Produce Coding.

 

[brokenflipflop]

I only use the self service tills if there are Jews in the queue for the manned tills....I've made that mistake before - time is a precious commodity and watching those tight buggers pay for their groceries very slowly in small change and then proceed to check every item/price on their till receipt ain't no fun.

 

[vernon]

I only use the self service tills if there are Jews in the queue for the manned tills....I've made that mistake before - time is a precious commodity and watching those tight buggers pay for their groceries very slowly in small change and then proceed to check every item/price on their till receipt ain't no fun.

"Look after the pennies and the pounds will look after themselves." as my uncle Reuben used to tell me every day as we made our way to the Mikveh.

It works. We all have an Audi Q7 4.2 DTI Quattro S-Line each in our familiy, paid for in cash, in penny and tuppenny pieces.

Our beards grew by two inches while the Audi dealers counted the money.