vending machines

@bharathpb-FtEhYi • Jan 15, 2026

Jan 15, 2026

2.0K

Just saw the vending machine post below and had a doubt...

Many auto -vending machines have the feature of accepting coins and delivering the required item from the store..

Mostly it will something that the machine accepts coins of 1,2,5 Rs.

How does the machine distinguish between coins..??

Is it using any microcontroller..??
or any logical interpretaion of weight of coin (like that).??

And how exatly may be the working of this item

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narayana murthy

@narayana-z4W16q • Feb 6, 2011

I think it depends on weight and there will be a micro control program to manage according to it
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POOJA JAIN

@pooja-jain-oSNzRK • Jun 21, 2011

What I think is, there may be a sensor, sensor which senses the different coins, and if there are 1,2,5 rs coins, there would be three different sensor for detecting them each.
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Harshad Italiya

@harshad-ukH5ww • Jun 21, 2011

POOJA JAIN
What I think is, there may be a sensor, sensor which senses the different coins, and if there are 1,2,5 rs coins, there would be three different sensor for detecting them each.

As said by Pooja they used IR based sensor which detects the size of the coin and performs the function according to that.
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limestone7000

@limestone7000-AV88z8 • Jun 24, 2011

godfather
As said by Pooja they used IR based sensor which detects the size of the coin and performs the function according to that.
But the size of the coin can be changed right! it already has!!
1 rupee, 2 rupees, even 5 rupees sizes arent fixed!
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Saandeep Sreerambatla

@saandeep-sreerambatla-hWHU1M • Jun 24, 2011

Vending Machine works on different principles:

I have got a change to look into a vending machine at our office, and I have got the wonderful chance to open it and check its working, why I opened I will tell at last.

So, As far as I have learnt. The machine has a optical sensor which has a camera (small) which takes the picture of the bills you have inserted. It then sends the information to the calculating box ( A microcontroller and a computer). SO all the bills you have inserted are scanned.

Next comes the interesting design , the identification of coins. The passage section of coins has series of wires with electric supply. So there will be magnetic field in the section. When a coin is inserted it cuts the magnetic field which depends upon the thickness and material of the coin which is different for different coins. So it differentiates like that!

And if you order a coke, there will be a electric motor which moves the section where you have selected. It gives you what you want.

I accidentally inserted 20 $ bill and It got stuck. So I have to open it then I learnt about it.
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qaisarpk1

@qaisarpk1-6Lfp0G • Jun 26, 2011

Vending machines read coins according to their individual characteristics, mainly their thickness, diameter, and the ridges on their edges.
e.g US quarte dollar is .995inches in diameter, .069 inch thick and 119 ridges on the outer edge.
paper currency is printed with magnetic ink, so it is scanned using a magnetic scanner that looks for the magnetic ink that is unique to each denomination.
some vending macines read credit card.credit card is printed with a magnetic strip on the back of the card. vending machines are suported with magnetic strip reader.data read from this strip is fed to small processor for further processing like card no etc
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bharathpb

@bharathpb-FtEhYi • Jun 26, 2011

Nice Explanation English -Scared..

But I still have something fishy in my mind.
As you said:

When a coin is inserted it cuts the magnetic field which depends upon the thickness and material of the coin which is different for different coins. So it differentiates like that!
What if we have a dupli coin ..acting as same thickness and material...??I havent tried....but what if..
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PraveenKumar Purushothaman

@praveenkumar-66Ze92 • Jun 26, 2011

Wow awesome... But in case of 1 re telephone booths, I guess this is not the way, coz I inserted 2 rs coin and made a call for 1 re! 😔 I didn't have any change and I had to do it... 😔
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William Fields

@KzET4EN • Jan 15, 2026

Thanks for this idea.

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