Enclosure ideas
This project originally started with trying to source an LCD touchscreen that I could mount between the top/bottom screw pattern in a standard workbox. The Nextion panel selected was the only option I found which would fit (and for which I could actually program against without enormous effort), but even then it only barely fits. I’ve been designing against the common blue-plastic workbox you see everywhere along with some online dimension drawings I’ve found for the same. I’ve been running a single HASP device in my office which fit fine, but now that I have some PCBs I’m ready to start deploying these around the rest of my house and have found that the existing design is a very tight fit in some of my other boxes, to the point where I had to dremel one out to get the case in. This doesn’t seem ideal.
I’ve also been monkeying around with how I can better enclose this thing such that there are no exposed components in the finished design for safety reasons while still fitting between those two screw holes.
With the current published model there are two places where we have holes open to the outside that aren’t going to be easy to address (the USB access port is simply for dev work and with OTA updating is no longer necessary). These are the openings for the LCD PCB and 4-pin XHP connector, and the opening for AC power connection.
AC Power connection
The incoming power connection sticks out of the top of the unit and has a pretty large gap to insert wires. This is a huge safety problem, it exposes the only high-voltage contacts in the system and opens them facing upward, perfect for dust or whatever to fall directly into the box. This seems bad so I’ve been kicking around some ideas to address it.
I started with designing a retainer plug and printing it in semi-flex TPU to clamp in the wires, fill the gap, and provide some modicum of strain relief. This approach actually worked OK but it still has cables egressing out of the top of the device in what is already going to be a cramped box. Pics below show the design and printed results along with another part I’ll be discussing in a moment:
While chewing this over with @zombu2 on Discord he suggested running the power cables out of the back. The more I thought about this approach the more I like it. I have a rigid surface back there with room for a grommet, it moves the cables away from the already-tight perimeter, and it wouldn’t require a change to the PCB. I can simply remove the screw connector, insert the incoming AC cables from the back side and solder them to the PCB on top. I’ve ordered some grommets to test fit some ideas around strain relief, but I think this approach might be how I move forward with the design. It neatly solves the safety problem, provides for sturdy cable capture, and removes the cable harness from the already-cramped top/bottom of the box making for an easier fit in your existing box.
I don’t have those grommets quite yet so I’m testing printing a basic design with holes for the wires. Note the much deeper cutouts for work box screw mounts, something possible now that I’ve moved everything out of the way top/bottom. With the screw connector gone I can also put the 4th screw mount for the LCD and front panel back in place which is a nice bonus.
LCD PCB and connector
In the current design the top and bottom edges of the LCD panel are exposed. On the bottom this is simply due to room between the screw mounts and saving myself a single mm by leaving just that edge exposed to the outside. On the top it also has the 4-pin JST-ish XHP-kinda connector up top which we never have been able to use. All existing builds (at least those that have been put into a box) have required soldering the wires directly to the solder pads of the connector. That doesn’t bother me so much, but having the connector itself exposed to the outside top of the box is problematic for all the reasons outlined above (only this time w/ 5VDC instead of 120VAC).
My first approach to solving this problem was the same as above - print a semi-flexible plug that I can stuff into the connector as a dust cap and hope for the best. While this covers the exposed pins it still leaves open gaps around the perimeter and takes up a fair bit of real estate. After stewing on this for a bit it occurred to me that this whole thing would be better if the connector itself were simply gone. A few moments with the hot air station proved this out pretty well:
With the connector out of the way I am now able to fully enclose the case such that no conductive parts are exposed to the outside which is critical for safety. We can do it without changes to the HASP PCB (which is handy because I’ve already sold a handful) but at the cost of requiring the assembler to have access to some means of removing the connector which is going to be tricky with a standard soldering iron. You’re really going to want a hot air station to make that happen.
I’m still running some prints and have some parts on the way (grommets/screws/etc) to test out some ideas, so this is all very much work in progress. If anyone has any thoughts or ideas to share, I’m all ears!
