We would need drivers anyway; logic outputs do not produce enough current to
drive relays. I suggest ULN2803A driver chips:
http://www.ti.com/lit/ds/symlink/uln2803a.pdf
I believe we have some in the shop.
- Bob
On Feb 6, 2016, at 10:12 PM, Joachim Hall <jjoachimhall@xxxxxxxxx> wrote:
Hmm then we are going to need to have some extra components if we use
Raspberry Pi. The relays we need to drive are 5 volt so we are going to need
some kind of buffer/driver or transistors. I'll see if we have any of those
74HC logic chips next time I'm down at the shop.
-Joachim
On Sat, Feb 6, 2016 at 9:51 PM, Robert Berger <bob@xxxxxxxxxxxx> wrote:
74LS logic is not compatible with the 3.3 volt logic used on Raspberry Pi.
74HC logic is.
I would use shift registers interfaced to the SPI port. 74HC165 for input,
74HC595 for output. They can be cascaded for multiples of 8 signals.
- Bob
On Feb 6, 2016, at 8:40 PM, Joachim Hall <jjoachimhall@xxxxxxxxx> wrote:
You mentioned using a multiplexer. When I was going through the logic IC's
and looking up random part numbers I noticed we had some 8 line to 1 line
data selector/multiplexer (I think the part number was SN74LS151). Would
that do the trick? We also have 3 line to 8 line decoder/demultiplexer
(probably part number SN74LS138) I also have a tube of SN74LS138's if we
can't find them at the shop. They are pretty common though so I'd be
surprised if there are none at the shop. I would like to help with any
logic circuitry that may be needed. However I do have school so please
don't hold the project up on me if I'm not able to come down to the shop.
BTW we still have the original coin accepter from the vending machine.
It's either on the bottom or second from bottom shelf across from the
arcade machine. If nothing else it's got some pretty cool and complicated
mechanisms that you(Simon) would probably find interesting.
-Joachim
On Sat, Feb 6, 2016 at 6:03 PM, Simon Heath <icefoxen@xxxxxxxxx> wrote:
On 02/06/2016 04:58 PM, John Lewis wrote:
I have a Raspberry Pi B+ already reserved for that propose, I can have
it formatted today with rasbian and bring it too you if you need it now.
Sounds good, though I don't need it now. If you leave it in the machine
with whatever software you want on it, I'll start hacking on software for
it.
On 02/06/2016 05:09 PM, Steven Owens wrote:
I'll be happy to take a crack at that, I need to work on cutter/CNC
design.
Speaking of that, if anybody has any recommendations (tutorials,
videos, apps) I'm all eyes.
Steve
Awesome! What we need really isn't all that complicated, as long as it
fits, looks cool, and has convenient places to bolt a Pi and maybe power
supply. We're going to need to run all the ethernet and power cables
along the bottom of the vending machine's doors, so we can open it without
ripping a bunch of wiring out.
I've gotten the button panel wired up and connected to terminals in a
vaguely sane fashion, including the power wires someone so inconsiderately
snipped off. It might still need ground wiring, I don't know? It looks
like the buttons pull low when closed, but honestly I didn't test it that
much... I'd appreciate it if someone who knows what they are doing looked
at it.
Thanks,
Simon
