# Vending Machines?? **URL:** \ **Category:** Factual Questions\ **Created:** [December 22, 1999, 3:35am UTC](https://boards.straightdope.com/t/vending-machines/5508 "1999-12-22T03:35:00Z")\ **Posts on this page:** 8\ **Page:** 1
**Author:** ![chief](https://avatars.discourse-cdn.com/v4/letter/c/df788c/32.png) [@chief](https://boards.straightdope.com/u/chief)\ **Post date:** [December 22, 1999, 3:35am UTC](https://boards.straightdope.com/t/vending-machines/5508/1 "1999-12-22T03:35:00Z")
how do vending machines recognize whether the coins are correct? also what about dollar bills? * * * Chief’s Domain - [http://www.seas.ucla.edu/~ravi](http://www.seas.ucla.edu/~ravi) ---
**Author:** ![RealityChuck](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/realitychuck/32/195_2.png) [@RealityChuck](https://boards.straightdope.com/u/RealityChuck)\ **Post date:** [December 22, 1999, 3:39am UTC](https://boards.straightdope.com/t/vending-machines/5508/2 "1999-12-22T03:39:00Z")
Used to be, they checked the size and weighed the coins. It may be possible to make a slug the same size and weight of an actual coin, but not worth the effort for a soda. Bills, OTOH, are printed with magnetic ink. The reader checks the magnetic pattern to see if it matches. * * * “East is east and west is west and if you take cranberries and stew them like applesauce they taste much more like prunes than rhubarb does.” – Marx Read “Sundials” in the new issue of Aboriginal Science Fiction. [www.sff.net/people/rothman](http://www.sff.net/people/rothman) ---
**Author:** ![mikan](https://avatars.discourse-cdn.com/v4/letter/m/cc9497/32.png) [@mikan](https://boards.straightdope.com/u/mikan)\ **Post date:** [December 22, 1999, 3:40am UTC](https://boards.straightdope.com/t/vending-machines/5508/3 "1999-12-22T03:40:00Z")
Try [http://www.howstuffworks.com](http://www.howstuffworks.com) (I think that’s the url, anyway). ---
**Author:** ![funneefarmer](https://avatars.discourse-cdn.com/v4/letter/f/9fc348/32.png) [@funneefarmer](https://boards.straightdope.com/u/funneefarmer)\ **Post date:** [December 22, 1999, 1:02pm UTC](https://boards.straightdope.com/t/vending-machines/5508/4 "1999-12-22T13:02:00Z")
Didn’t see it on How Stuff Works, but try this site. They make the coin recognition equipment and state that it tests 6 parameters and compares it to what was entered during the programming stage. [http://www.coges.it/English/eur10b.htm](http://www.coges.it/English/eur10b.htm) ---
**Author:** ![funneefarmer](https://avatars.discourse-cdn.com/v4/letter/f/9fc348/32.png) [@funneefarmer](https://boards.straightdope.com/u/funneefarmer)\ **Post date:** [December 22, 1999, 1:05pm UTC](https://boards.straightdope.com/t/vending-machines/5508/5 "1999-12-22T13:05:00Z")
Ooops, forgot about bills. Same company, bill recognition. [http://www.coges.it/English/TP95A.HTM](http://www.coges.it/English/TP95A.HTM) ---
**Author:** ![mikan](https://avatars.discourse-cdn.com/v4/letter/m/cc9497/32.png) [@mikan](https://boards.straightdope.com/u/mikan)\ **Post date:** [December 23, 1999, 6:28am UTC](https://boards.straightdope.com/t/vending-machines/5508/6 "1999-12-23T06:28:00Z")
Hmm, I’m pretty sure I saw a short piece about the various techniques used for the recognition of paper money at howstuffworks, probably in the daily questions archive. Too lazy to look it up, though. ---
**Author:** ![funneefarmer](https://avatars.discourse-cdn.com/v4/letter/f/9fc348/32.png) [@funneefarmer](https://boards.straightdope.com/u/funneefarmer)\ **Post date:** [December 23, 1999, 1:23am UTC](https://boards.straightdope.com/t/vending-machines/5508/7 "1999-12-23T01:23:00Z")
Mikan, it could very well be there. All I did was type vending machine into the search function. It came up with zilch. ---
**Author:** ![Alan\_Smithee](https://avatars.discourse-cdn.com/v4/letter/a/2acd7d/32.png) [@Alan\_Smithee](https://boards.straightdope.com/u/Alan_Smithee)\ **Post date:** [December 23, 1999, 8:03am UTC](https://boards.straightdope.com/t/vending-machines/5508/8 "1999-12-23T08:03:00Z")
When I was in Jr. High school (about 10 years ago) I had a friend who would photocopy dollar bills and put them in the school Coke machine. They worked fine. Not only did he get a free soda, he got 50 cents back, too! Vending machines are undoubtedly a lot more sophisticated now than back then (paper money probably is, too), so I doubt this would work today. I just know one of you clowns is gonna try it, now, “in the interest of science.” Don’t. If I were less lazy, I’d quote “Dr. Strangelove” now.