Finally starting on this convection oven -> reflow oven conversion project

[coppercone2]

You have a scrap of metal in one of your banana plug holes that can potentially come lose and make a short circuit, get that fixed ASAP. Typical drilling near metal stampings problem, take a close look


If you want 'cleaner' holes in shitty metal, you can think about this tool:
https://www.amazon.com/Astro-Pneumatic-Tool-1442-Setter/dp/B003TODXQW/ref=asc_df_B003TODXQW/?tag=hyprod-20&linkCode=df0&hvadid=312174136943&hvpos=&hvnetw=g&hvrand=13597386352196417469&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9004235&hvtargid=pla-338189070626&psc=1&tag=&ref=&adgrpid=63790029762&hvpone=&hvptwo=&hvadid=312174136943&hvpos=&hvnetw=g&hvrand=13597386352196417469&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9004235&hvtargid=pla-338189070626

you can put nuts into the chassis, drill out the thread, and seat the banana plug in it, if you want it in a neat grommet


you might want to look at getting cable harnesses or at least looking at pin and socket for those wires so you can unhook the boards without a soldering iron, its starting to look hairy. You don't need the cable housing, you can put aviation pins on the PCB and crimp or solder sockets on the wires. not sure whats going on in there, maybe you soldered them to headers

[mindcrime]

You have a scrap of metal in one of your banana plug holes that can potentially come lose and make a short circuit, get that fixed ASAP. Typical drilling near metal stampings problem, take a close look

Thanks, I was able to grab it with a pair of needle-nose pliers and yank it out.

If you want 'cleaner' holes in shitty metal, you can think about this tool:
https://www.amazon.com/Astro-Pneumatic-Tool-1442-Setter/dp/B003TODXQW/ref=asc_df_B003TODXQW/?tag=hyprod-20&linkCode=df0&hvadid=312174136943&hvpos=&hvnetw=g&hvrand=13597386352196417469&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9004235&hvtargid=pla-338189070626&psc=1&tag=&ref=&adgrpid=63790029762&hvpone=&hvptwo=&hvadid=312174136943&hvpos=&hvnetw=g&hvrand=13597386352196417469&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9004235&hvtargid=pla-338189070626

you can put nuts into the chassis, drill out the thread, and seat the banana plug in it, if you want it in a neat grommet

Huh, interesting. I'll definitely look into that for future use. So far the best way I've found to drill decent holes in think/weak metal is to sandwich the metal between a couple of sacrificial pieces of wood, clamp the wood down tight, and drill through the whole mess. I didn't have enough room to do that that here though. 

you might want to look at getting cable harnesses or at least looking at pin and socket for those wires so you can unhook the boards without a soldering iron, its starting to look hairy. You don't need the cable housing, you can put aviation pins on the PCB and crimp or solder sockets on the wires. not sure whats going on in there, maybe you soldered them to headers

Sorry, I'm not following you. You can unhook everything now with no soldering. 95% of the board to <anything else> interconnections are done with dupont header pins and corresponding connectors. The couple of exceptions are the USB connection to the Nano, and the input to the power supply board, which (when I finish that bit) will terminate at the banana plug end with some ring connectors that can be connected/disconnected from the banana plug.

Heck, even the couple of IC's I added are socketed. I am very big on making things that are easy to disassemble / modify / repair.

One problem I have, although not one I care enough about to "solve" is that I'm using pre-made / store-bought jumpers to connect things, and in many places they are much longer than they need to be, so I wind up with a rat's nest of wire coiled around in there. At this point my innate laziness / apathy kicks in, and I doubt I'll ever bother addressing that. If I were making a product to sell, I would absolutely worry about that. For a one-off tool built for my own use? Nah. Not gonna sweat it.

[coppercone2]

then its fine, too many pictures failed to load and I thought it was soldered together. if the wiring in mine was all soldered together I would possibly throw it out if it breaks because its just too much

the wood trick works but sometimes if you are drilling a stamping its very hard not to tear it and the only way to get a 'good' hole is to put some kind of grommet in it like a shower curtain

I built 'cool' projects before that I thought could work like paint can mini variac and there is a perpetual problem with getting banana plugs into the metal to sit nicely, the only way is some kind of reinforcement, and you get this problem a little with certain tins (like foodstuff for cookies or soup cans or whatever).

I made a somewhat nice paint can variac and the banana plugs and stuff kept getting loose every few months, so as a rare use item every time I went to use it it needed some kind of maintenance

If I had the tool I linked you when I made it, I could put thick stable deformed metal nuts into the thin crappy metal to have a really good place to put the connectors on stable surfaces. I would just need to drill the nuts out a little bit. 

[mindcrime]

then its fine, too many pictures failed to load and I thought it was soldered together. if the wiring in mine was all soldered together I would possibly throw it out if it breaks because its just too much

Yeah, same here. That's a bit of a "thing" with me. I hate items that can't be taken apart without (desoldering|cutting wires|any other unnecessary effort). So it would be very hypocritical of me to build something like that myself!

If I had the tool I linked you when I made it, I could put thick stable deformed metal nuts into the thin crappy metal to have a really good place to put the connectors on stable surfaces. I would just need to drill the nuts out a little bit.

Yeah, I am definitely wanting one of those now. I had not seen those before, so thanks for pointing that out.

[coppercone2]

just check the dimensions to make sure its compatible with a banana plug, it was just a thought

Also, I am not sure how well it grounds for grounded BNC if you want to use it in other projects.

I just have had very bad experiences with reusing thin metal enclosures to the point where I will buy a box for small stuff. For large stuff like that tool is intended for, I prefer to braze on nuts with a torch, but it has its purpose if you don't want to disturb a paint job or are working on weird objects. for chassis work that tool is a game changer for certain things. and possibly a massive cost and weight reducer since it lets you use thinner metal that is normally avoided because its hard to fasten nicely (obviously it might have EMI issues but for standard lab equipment and tools its great)

I kind of wish I had it for my project because then I could put fastener holes inside of the toaster oven to bolt my box onto, I did something very difficult with nuts, pliers and crazy tight wiring that required a mirror and mini right angle tools (it will still disassemble but you might want to throw something)

However I did do a good job and the PID I have goes into a big socket so if it breaks I can theoretically replace it just undoing 2 screws

[beanflying]

Nutsert tools are great for panel work. The angled guns rather than the longer ones are more useful to get into small spaces. Add a set of step drills to your collection too if you don't already have them. Both used here for a run of M6 Stainless Nutserts to retain some acrylic screens on some food benches.

[mindcrime]

OK, putting the finishing touches on this. With one minor exception, all of the electrical/electronic work AND physical fabrication work is DONE for what I'm calling "Phase 1". There will be as subsequent "Phase 1.1" or something like that, and perhaps a "Phase 2", but this phase yields a usable tool, which was the goal.

The one remaining work item, besides tuning the software, is to add a heat-sink on my LM7805 voltage regulator. It's running a little bit warmer than I'd prefer. I thought I could get away with it as is, but between the Arduino and the LCD, it pushes it just hard enough to where it gets a bit warm.

Anyway, some pics of the progress to date.





Finally cleaning up the mounting of the boards, adding spacers to keep the boards from flexing, etc.



I built a couple of long banana-to-banana jumper cables out of unused extension cords. This way the controller can sit on the bench while I tinker with it, but actually run the oven "live" for testing.



And wired up those banana plug connectors on the inside.



And that's pretty much it. The whole thing, all packaged up and ready to use (modulo some software tweaks).





Powered up and displaying the default greeting on the LCD.



The view from behind.

Anyway, that's basically it. I'll add that heatsink, finish merging the bits of software that I had originally developed in different projects, reflash the Arduino, and I'll have a usable reflow oven.

Things for "Phase 1.1" - adding the piezo buzzer that will buzz when the profile run is finished. I'm just not motivated to work on that right now. I need a break from this for a little while.

Things for "Phase 2" - finally implement the automatic door opener, and maybe design a real PCB for the electronics, mill it out, and solder it **in this very oven** and then rebuild everything in what will hopefully be a much cleaner / more elegant fashion. The circuit board layout / design here was really ad-hoc and kinda "making it up as I go" and could be way improved. It works, but some of the choices I made wound up making things difficult in the final assembly phase, and don't lend themselves to making this easy to maintain / repair, etc.

"Phase 2" might also include heat-press-fitting threaded inserts where the board mounting screws go, and not have that stuff sticking through with those nuts on the outside. If I do, then I could turn around and use a little dab of epoxy / bondo / J.B. Weld / etc. to cover over the holes so everything looks nice and smooth from the outside.

Edit: also if anyone is wondering, no, I don't intend to leave the control box sitting on top of the oven when it's in use.  That's the whole reason for the long jumpers connecting the box to the oven, so I can set it off to the side while the oven is actually running. The one thing I should probably also consider, is using a longer thermocouple wire. I think the kit I ordered included two, the one seen here, and one much longer one. That is, if memory serves correctly. If so, I should probably swap it out, as right now that thermocouple is the limiting factor in how close the control box has to be to the actual oven.

[mindcrime]

Code for this project is up on Github.com now. See: https://github.com/mindcrime/ReflowOven

I kinda stalled out on this right after posting the last message above, and didn't get back to working on those last few software tweaks until last weekend. But now that I'm back on it, the software part should all be finished up in another day or two. All of the pieces are there, they just need to be integrated into a comprehensive unit and flashed to the Arduino.