He is our third boy. So now we're 4 monkeys and wonder woman
And I've even managed to make some progress
OK.. A LOT of progress
To cut to the chase this this is ROCKING
My favorite new feature is incremental mode!
I like to start it at 98°C, and every time I remove the vapcap from the coil, the setpoint jumps up by 2 degrees. The system then waits in low power READY mode, only firing up the induction circuit 1% of the time to measure frequency (optocoupler schmitt trigger + extra diode and resistor work perfectly connected straight to the work coil). When it detects a frequency change indicative of vapcap re-insertion, it fires it up to two degrees hotter than last time, and so on. I just place the vapcap in the toaster between every puff, and it takes care of ALL the rest for me.
Now the click is a tricky thing with induction heating. If I set the thing to say 115°C, the cap will click pretty quickly, around when I measure 110°C, and I've even slightly charred a bowl in a race to just 120°C.
However, if I heat up much slower (incrementally between puffs), it only clicks when IR sensor reads 125°C. Either way, I've been finishing some bowls without even hitting a click at a measured 120°C.
I say measured a lot since I'm not claiming that that's the actual tip temperature where it touches the bud. This is obviously some science involving a bunch of coefficients I don't really want to start thinking about yet, but hey, it works
Dealing with the noise generated by the oscillator was a challenge. A bunch of bypass capacitors and I was over an annoying OLED image disruption almost every time the thing fired up. This will really benefit from a properly designed PCB.
The first set of MOSFETs that I tried worked but had some noisy switching issues. Either way, when I finally got the case I ordered, I was trying to squish everything in. I bent the mosfet heatsinks back and their pins broke
When I changed them to a different set, oscillations were MUCH smoother
Alas, the case is about 1mm too small inside. The clearance of the battery, the board, and the coil is a tad too tight for my comfort. I've come up with some ways to reduce coil thickness when I wonder about coil design..
Now the batteries.. Up till recently the work tank on this thing would consume about 7Amps while heating a vapcap. This is a problem since the voltage drop on the batteries internal resistance increases, and the BMS would shut off due to low voltage cutoff, as it should. I've since removed one of the two 0.22uF caps I was using, and it is now consuming a more modest 4 Amps. This should reduce BMS issues. She now oscillates at 430Khz while idle, and uround 465Khz while toasting a vapcap, compared to circa 340Khz with 2x0.22uF (
@Pipes you should experiment with this too, remove one of those 0.33s and check consumption and voltages under load). I'll be happy if it can consume even less.. Heat up speed does not seem to a problem, and if it goes a little slower battery life (BMS shutoff wise) will be significant longer.
So time to first setpoint is now about 10~15 seconds from cold. Re-heat after a puff or two even to the next incremental setpoint is very quick though, about 2~4 seconds, and since temp is maintained it's perfect to just place VC there between puffs. This is reeeally convenient and I'm loving experimenting. I just can't experiment as much as I'd love to since.. well.. life
but ya, I'm happy it's finally all working.
There are still so many little things to play with, so this will keep me busy for a while. I'd love to share it, though it really needs to be on a properly designed board and built properly to be safe in anyones hands, and that'll take a while at best ( Anyone wanna help?
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OKK... it's late but I'll go take some pics quickly. One day maybe even a video
..