Hi all,
Some updates:
Field testing is underway for the Deluxe, and I am already receiving some very useful feedback, which I am applying back to the design. Thank you, field testers!
I discussed the new input filter/debouncing circuit in my the last post, so I won't really revisit it here except to say that the first field test units were sent with the previous circuit - as the new circuit didn't exist yet - so I will be sending out some revisions soon so we can properly test the new circuit. It is a simpler, safer circuit that doesn't require a separate power supply (certainly some sibilance in that sentence!), so it's unlikely to cause any further issues, but it still needs to be tested. I may have a bit more to say about it -
- but I'm saving that for a future post.
The main thing I want to talk about in this post is heat! As my field testers are reporting,
these little heaters are pretty good at heating things. To keep you safe and allow it to work for a long time, the heaters have thermal fuses that will shut them down if they get too hot. Too hot means a work coil temperature greater than 110°C (the sensor is positioned to be within 1mm of the work coil). This feature is bound to annoy some people, but it's there for your safety.
Remember, this is a full power heater in a very small package. Treat it with respect, as you would treat a sharp knife. Or a hot Dynavap.
You can absolutely use this device to heat your Dynavap session after session, but if you plan on going "full Reefer Madness" with it in a short period of time, you will probably need to lift its lid occasionally to vent some of its heat. Blame physics, not me. For that matter, you can also use it with the lid off, and it will be fine. In any event, the keys to using this device for longer sessions are to either slow down a bit, and/or occasionally lift the lid.
If you leave the lid on, the heater will get hot, and you will likely hit the thermal limit before you would like to. "Hitting the thermal limit" presents itself as a loss of power until the fuse cools down. The thermal fuse is tied directly to the positive power lead, so when you cross its limit, you lose power. The thermal fuse makes a soft click when it passes over its heat limit - and you lose power, of course - and it makes another soft click when it cools. Cooling takes ~10 seconds with the lid off. Once cooled, cycle the power to reset it (switch it off, then back on) and it will be ready to go again.
The KSD9700 thermal fuses I use are rated for 10,000 cycles at 5A @ 250V. The Deluxe uses ~5A @ 12V, so you can bounce off of the thermal fuse without too much concern. It is better to manage the heat, though. You don't get any extra points for activating the thermal fuse.
To repeat:
This is a full power heater in a very small package! It can get hot, and it has safety features that are intended to keep you (and it) safe. Treat it with respect. If occasionally lifting the lid during a longer session sounds like too much hassle, this device may not be a good fit for you. Just sayin'...
The road ahead: I would like my field testers to have a few weeks to test the current design before I start cranking these out again. I want to make sure these are put through their paces before I make too many units, as I want happy customers and I don't want to discover a need for big revisions once I start making these for real. Please be patient while we find and address those things that need to be fixed!
Finally, despite the hard focus on the Deluxes, I have not forgotten about the Mother Fluxers! I need to build out some Mother Fluxers and get those into the hands of my Mother Fluxer field testers. I can do that now that the debounce circuit is stable. I hope to get to those out by Friday or Saturday. If you agreed to be a Mother Fluxer field tester, I will be in touch with you soon.
Thanks again for the outstanding support you have shown me in this thread! I think these heaters are coming along nicely, in no small part fo the advice you have shared with me. Thank you! I am confident these will make at least
some of you happy when you finally get the chance to have one in hand.
Here are a few pics of the Deluxe with the larger vent holes. Keen-eyed observers of this project may spot the new input buffer circuit in the "circuitry exposed" pic, immediately to the right of the PWM relay's blue PCB:
Cheers!