Vending electronics

Question

I am building a One-off vending machine for limited used. I am looking to re-purpose the best/most appropriate/ economical / off the shelf package or group of components with Credit Card only payment system (no cash or coins) that I could string together to send a current (up to 60 seconds) to one of up to 64, 24VDC electric fail secure locks (and maybe light an LED light above the lock that was triggered). After that lock was opened once, it would display “sold out” and not activate that lock again until item was refilled and reset. Anything out there that can be adapted to accomplish this? I was hoping that I could adapt current commercially used items that would simplify troubleshooting, repair and replacement and increase durability but am open to starting from scratch if there is nothing out there.

paulyvee · Accepted Answer

A thought re the power pack. the ATX or the ATX2 packs - with or without -5v not now used - are very easy to mod to power up on application of power. Simply take the switching wire low. However I have played with a few, making power packs for all sorts of bits and pieces and have found the if connected to the supply with the power output active they can tend to go bang. My experience is that a short while is needed before switching on the output or the start surge kills the main diodes . I find that if you use a normally closed relay with the contacts wired across "power on" and 0 volts and the coil wired between 0 volts and the auxiliary supply with an electrolytic of 500uf or so in series when switching on the coil is activated by the current through the cap and pulls in. deactivating the supply. After a short while - millisecs to seconds depending on the cap value and coil resistance the cap[ charges - the current drops to zilch and the relay drops out - activating the supply. Thus this delays switch on and reduces instantanious surge, Depending on the current in the non-vending phase of operation you might have to introduce a bit of load to stabilise the pack - put lots of pretty lights on the machine as an example. Pull 500 ma to an amp and the pack will be happier. This is one time when you have power to waste. Also if you use a credit card company for collecting the money you will have to have a phone line near the machine.

michaelkellett · Answer

I'm in the UK - I think you'll need some local knowledge to get hold of bits - are there any vending machine suppliers/breakers near you ?

For a ready made solution to driving the loads I would look at using a PLC.

http://en.wikipedia.org/wiki/Programmable_logic_controller

The hardware could be done a lot cheaper if you make it yourself and don't count your time. PLCs are reliable, replaceable etc but not really cheap.

MK

michaelkellett · Answer

Do you need a PLC output for each lock and light or can you route these outside the PLC.

PLCs with perhaps up to 8 inputs and outputs are common and cheap, once you add IO extenders to get up to 128 outputs it will be a bit more pricey. It's a good while since I played with PLCs so I can't actually recommend one. Farnell sell a good range of them. I'd start by looking at the Siemens ones.

MK

Vending electronics

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