Going from Breadboard to Project Case - Page 1
Forum section: electronics / projects

author: larrybud
author_rank: Contributor
timestamp: February 21, 2024, 09:19:43 pm
content: I've done a number of smaller projects on breadboards and then made project boxes and etched my own PCBs, and I haven't really considered size before because the components were small enough and I the enclosure was always much larger than the PCB.However, I've built this LCD clock for S&G and want to make a permanent version. I haven't routed anything or done any board layout yet.My question is in consumer design, is the board made first and the case to fit, or the case/button layout made first and the board to fit, or do the two departments get together and design everything together?

author: Shay
author_rank: Regular Contributor
timestamp: February 21, 2024, 10:10:31 pm
content: I believe it varies between companies and the nature of company structure. Logically, it makes sense to design the PCB while considering a rough idea of how it will fit into an enclosure, avoiding unusual shapes unless necessary.

author: sparkydog
author_rank: Regular Contributor
timestamp: February 21, 2024, 10:22:58 pm
content: I'm just a hobbyist, so take this with averylarge grain of salt, but... I expect the usual case would be that the product itself has some requirements that might be relevant to the board design. If not, however, I'd guess that it's typical to just try to make the board as small as possible and then look at your enclosure options. If that doesn't work out, iteration may need to occur.If your schematic is essentially fixed (that is, when you've determined that you can't achieve the desired goal with fewer and/or smaller components), that's going to give you a rough idea of the minimum board size. Within those constraints, smaller is almost always better, and adding 'dead' space to a board (e.g. to make mounting holes line up) is probably easier than starting over. (Exceptions may apply if you're dealing with high frequencies.) Also, if you're doing enough volume, a custom case may not be a big deal.You mentioned an "LCD clock". That suggests an LCD panel in an enclosure; probably one you don't want to be terribly much larger than the LCD. That in turn suggests you ought to know, or be able to figure out, likely size constraints.

author: Ian.M
author_rank: Super Contributor
timestamp: February 21, 2024, 10:45:03 pm
content: In a sane world, the EEEs come up with or are asked to do a proof of concept to show marketing, the product external design team and the beancounters. They then answer size and functionality vs cost questions taking care *not* to underestimate their requirements, and the project either gets sh-tcanned or given the go ahead. A costing structure for changes to the specification is agreed. All teams then design their part to the agreed specification's constraints.However many (if not most) companies are not sane . . .e.g. A client asks for something technically ridiculous, sales says "Yes, delivery next quarter" without even talking to engineering, and the sh-t show begins.

author: larrybud
author_rank: Contributor
timestamp: February 21, 2024, 11:11:44 pm
content: Thanks all. I've attached a pic of the circuit just to give an idea of what I'm doing. The only couple of changes in making this permanent is the 44 PLCC for the LCD Driver chip (AY0438) and probably a surface mount 555. The Lipo battery with corresponding charger board is not pictured here either.So with the large footprint of the LCD and several buttons and switches which I will expose to the outside of the case, I do have to work with a little bit more constrained dimensions than I normally would.I was a cool project, as I didn't know much about raw LCD displays before this (this display just happened to be in my parts bin for YEARS).

author: sparkydog
author_rank: Regular Contributor
timestamp: February 22, 2024, 06:18:30 pm
content: Whee, lots of breadboard fun! Thanks for sharing!I think the first question that should be asked is, is there an existing, off-the-shelf case that will fit that panel and the buttons you need? If "yes", you could at least try to make an educated guess whether the necessary boards and other components can be made to fit in said case, which would imply designing the boards to the case.If "no", you're going to need a custom case anyway and might as well design the case to the boards.That driver chip ishugeand I'm not sure how well you're going to be able to cram in all the necessary traces even if you go with a smaller chip. That being the case, I might seriously consider planning on two boards. One is just for the display, and would have the actual display soldered to one side (possibly using castellated holes) and the driver on the other side. You'll also need something to connect it to the "main" board. A surface-mount header or even ribbon-cable connector might allow you to keep the board no wider than the display. OTOH, you mightwantto go wider than the display in order to add mounting holes. If the LED is intended for the user and you want it on the same face as the LCD, you could use a surface-mount LED on the display board, or you might want to leave aholein the display board for a taller THT LED to poke through. In the latter case, you might consider using a male-male pin header to connect the boards if you don't mind the connection being very permanent.Your other board will probably have buttons/switches on an edge that stick through the case.What you'll end up with is a sort of "sandwich", with the display and display board, a 'main' board, and the battery. Depending on sizes, the latter might be stacked or next to each other.

author: harerod
author_rank: Frequent Contributor
timestamp: February 22, 2024, 08:39:30 pm
content: Quote from: Ian.M on February 21, 2024, 10:45:03 pmI just sent five boards for dimension and placement approval to a client. The case had been designed before the electrical requirements were finalized. Several months after the case design I got the contract for the electronics.Due to space limitations we had to break up the electronics into five separate chunks, which are interconnected by ribbon cable. One Board is 91mm x 34mm, with the center resembling a swiss cheese of mounting holes and a pass-through hole for pneumatics. We route sensor signals of 4mVpp from the left to the right of that board, plus four different supply voltages and several digital signals, including a data bus. The widest routing channel is 2.5mm. Well, the client is king, but I put my concerns in writing.This is a repeating pattern. I still havefondmemories of a disastrous automotive project (custom communication device), where the injection molds had been built before the electrics had been specified. That project actually killed that client.

author: larrybud
author_rank: Contributor
timestamp: February 23, 2024, 01:09:49 pm
content: Quote from: sparkydog on February 22, 2024, 06:18:30 pmThis is just a one-off home hobbyist project, so I'm going to 3d print the case myself. This is totally being done as a learning process.I do plan on having the LCD on a separate PCB with a ribbon cable connecting between that and the main board. I had planned on having the driver chip on the main board and only the lcd on the secondary board, but now you've given me food for though of having the driver and lcd on one board, the other rest on the main board. I will have to try it and play around with it.The driver chip comes in two flavors. The 40 pin dip and the 44 pin plcc. It will be interesting to see if one is any easier to route than the other.

author: sparkydog
author_rank: Regular Contributor
timestamp: February 23, 2024, 06:56:40 pm
content: Quote from: larrybud on February 23, 2024, 01:09:49 pmIf you're going to print the case yourself, I woulddefinitelydesign the boards first, although I'd probably also have an idea in mind what Iwantthe case to look like that I'll be thinking about while designing the boards.For example, for one project I knew that I wanted "as small as possible", butparticularlyI had one dimension that was dictated by other components, so I knew I wanted to keep the boardwidthto about that dimension (and also that making the boardnarrowerwasn't very purposeful), while the boardheightwas more flexible. I also planned to incorporate a 25mm "vandal switch" which, given mydepthgoal, was going to have the switch right up against the board (or even require a cutout), so I had to keep that in mind. (That project ultimately ended up significantly redesigned, which goes to show that even when youthinkyou know what the case will be like, requirements can change at any time.)...But you asked about whatprofessionalsdo. My impression from the other replies is that thesmartones (or at least the ones that get any say in the matter) design the boards first. 🙂 I'd be surprised if they don't sometimes have the same problem with changing project requirements, though.Quote from: larrybud on February 23, 2024, 01:09:49 pmHave a look at the many, many LCD/LED "modules" in the tinkerer community. You'll almost always find a display directly soldered to a carrier board that contains the driver circuitry, with something like a 4-pin data/power connector. You already need a board to mount the display; whynotput the driver IC on the same board (back side, obviously!) so as to minimize the number of connections you need to the main board?

author: Ian.M
author_rank: Super Contributor
timestamp: February 23, 2024, 07:58:38 pm
content: Don't forget to consider *how* you are going to mount the PCBs when you design them. e.g.If using mounting screws, you need screw holes, with clearance round them for the screw head, and preferably no tall components, or tiny fragile passives immediately adjacent so you don't need tweezers to get the screw into place and a miss with a screwdriver isn't instant death for your circuitIf it slides into PCB guides, you need those edges to be smooth so no protruding panalization mouse-bites etc. and no components close to the sliding edges, to have enough clearance to slide.If it clips in, you need clearance for the clips to land, and to get a tool in to release them, places you can push near the clips to get the board in without damaging tall or fragile components, and unless you can get to the other side of the board, or the clips are designed to lever the board out when released, you may need holes or edge recesses so you can hook the board edge or hole to get it back out of the clips.I've seen too many hobby projects and a few cheap and nasty commercial products with boards mounted on double sided sticky tape because how to mount them wasn't considered till the boards were built and the case nearly done!

author: larrybud
author_rank: Contributor
timestamp: February 24, 2024, 12:13:30 am
content: Good stuff on some considerations for the PCB mounting! I've done a few simpler projects, but nothing with interconnecting boards.The idea of putting the driver chip on with the LCD is great. I've gone and designed my schematic for the LCD board today and am finalizing that. It definitely simplifies the interconnect between the two boards, that's for sure!I will post updates as I continue with this project if that is ok!