compact design (same exact form factor as 2x16 display)
scratchpad proto hole area (plated thru .1-spaced holes)
realtime clock chip (ds1302) with supercap backup
high quality double layer ground-planed pc board
6pin header for FTDI serial/usb cable
breakout pads for all the digital and analog ard. pins
power and pin-13 leds
reset switch
pin assignment and headers for IR-remote sensor
pin also assigned for pwm-based lcd backlight
contrast pot for lcd onboard
I got tired of building the same thing on proto board (by hand) and so had a friend help me with the pcb layout. we are expecting samples from the first shipment in a week or two. once the beta-test is done, we expect to have full production boards stocked at his e-store (amb.org/audio)
I'll have the schematic and pcb images ready for review shortly. the prototype has been built and has been working for a while now, so its only the layout stuff that needs testing at this point.
one side faces the lcd (once its assembled) and the other side faces the inside of your box or chassis and that's where I envisioned the 2 leds, lcd contrast pot, reset switch and 6pin FTDI download cable header. also a 3 pin molex header for an IR TSOP receiver module (since I tend to use IR remotes as my 'multi button pads' these days).
since this is intended to be built by hand (not wave soldered, etc) I don't see a problem with parts being on both sides. do you?
No problem, of course.
You could have reduced the thickness of the whole assembly if you had all parts soldered on one side (the back side, where the LEDs are now).
You could have reduced the thickness of the whole assembly if you had all parts soldered on one side (the back side, where the LEDs are now).
but then, how does the user SEE the led status if it faces inward toward the sandwich?
similarly, the reset button is a user accessible item; if its inside the 2 board sandwich, its impossible (or hard) to get at.
there's nothing essential (other than the contrast pot) on the back side of the board. the reset button is not NEEDED for the thing to work and neither are the leds. I suppose you could argue that the contrast pot could be set once and then left alone; but I'm not sure if we had room 'inside' for the pot so it went on the back side.
I think I was not clear. What I was saying is that you could have had all components on the side where the LEDs (and pot, reset button) are now, with none of the parts between the sandwich. Just an opinion, maybe you would consider it in revision 2
my thought was to make good use of the 'internal room' between the boards. that won't get compressed too much anyway if you use the arduino style female sockets and male pin headers. all the sockets I've seen are of the same general thickness and the pin headers don't get that much smaller, either. they are needed to help secure the 2 boards together (you can ignore the screw holes in many installs and only secure the main lcd to the front panel and let this board hang off the top row of pins). on my proto, I had a bottom row of 3 (say) pins just to keep things tight; but not all lcd's have the dual rows of top and bottom pins for soldering to.
maybe this will help; it was my early prototype before I made the board layout:
I suppose shorter pins and sockets could be used to combine the 2 pc boards and then you'd HAVE to mount the parts only on the back side of the board
do you really think that much space would be saved this way?
OK, I see.
In this case, you may bring the pot, leds and button to the sides, so they are accessible.
You can find right angle push buttons, like this one:
Pot can be rotated from the side, and LEDs, this is the question, how do you handle those?
You can either right-angle them, so they could be visible from the side, or use SMD on the back.
Again, just a suggestion; may be helpful when you want to encase this project; just two sheets of plexiglass would sandwich the board(s), sides open, so you have access to everything.
just two sheets of plexiglass would sandwich the board(s), sides open, so you have access to everything.
I can visualize that, I think.
the 6pin download header has to be easy to access and have secure mounting (with all the plugs and unplugs it will see in its lifetime).
the pot could be a lesser accessible thing since you'll usually find the right spot for your lcd and leave it there.
there's a 3pin header for the IR input sensor. I didn't want cables coming out of the side since I wanted the lcd module group to fit inside the smallest case that would hold the actual lcd size, itself (plus some room going back). we kept the width and height of the board to exactly what our model 16x2 had. my partner suggested we go a bit bigger (to allow mounting of the IR input module, for example) but I really wanted to know that 'if the lcd will fit in the box, so will our module, behind it'. I didn't want the backpack mainboard being larger than the daughter lcd board. and that meant that things coming out the side would be impossible for me to get to
one proto went into an spdif switch that I built:
I realized that with this popular hammond box, that its still a tight fit with just the lcd by itself. having stuff come out the sides would not be a good idea for this kind of mounting.
and this is one of the primary use-cases I had in mind. some hammond or similar box with a minimal front panel.
all the app-specific stuff would go inside either right behind the lcd sandwich (the shield idea, but to the lcd display form factor) or via cables to a horizontal mount board (my spdif switch was like that).
its a very common hammond box, from digikey, mouser, newark. the audio guys (I do a lot of DIY audio stuff) use these all the time
the top slides off (its metal) and I slipped in some plexiglas. its not the strongest thing (the thickness I used) but it gives great demo (lol).
the front was done with hand tools and its abs plastic so the finish isn't perfect. I may have panels made on a cnc and make some kits up, depending on interest. the neat thing about this kind of design is that you can get away with generic front panels (just square cutout for lcd and round for a single IR sensor). if you have a big enough IR remote, you have a bazillion buttions there at your disposal for the cost of cutting 1 round hole in the front panel. big win
a lot of people put DACs and headphone amps and specialized 'audio grade' power supplies on those hammonds boxes; and you do see quite a few with the clear top show-off window.
I'm also working on a board for the SPDIF switch guts. that will be one of the first 'apps' for the LCDuino infrastructure.
