Yeah, it's this sort of stuff that I don't know about electronics! I'll
see if I can dig them up when I get a chance. Driving the relays will
probably be the hard part, since we should be able to use whatever
voltage we want for the switches, right?
Simon
On 02/06/2016 10:42 PM, Robert Berger wrote:
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 <mailto: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 <mailto: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
<mailto: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
<mailto: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
