Amazon’s got a lot of complaints about broken cooktops so ours came packaged inside another massive box stuffed with brown paper. The cooktop was intact. Initial impression is below K-Mart grade but above say, Harbor Freight grade. Plastic is cheap and soft with flash on seams and the general ill-fitting warpedness you see on poorly made kid’s toys. Buttons are that nasty hard plastic membrane that cracks after a year and the display is red, 7-segment LED. Classy!
The device seems to be a rebranded generic induction cooktop from China – the Better China Corporation, to be exact. www.better-china.com Model BT-180K. Their resonant circuit is awesome, so two thumbs up on power management. Two thumbs down on everything else, tho – sorry guys!
7 screws on the back separates cooktop side from interesting side. Remove a ribbon cable connecting the two halves and you’re home free. Our pic of the two open halves is blurry so it’s not going up – sorry. The next pic is looking down into the bottom of the device to the power side. This big coil is mounted above the PCB and fan all in the base of the unit.
Fig 4 – Inside the Base. Are belong to us
The work coil is 20 turns of stranded (Litz) wire. 10 gauge-ish? Who knows, a lotta strands tho. It sits on a plastic platform with a couple of embedded ferrite rectangles in the bottom. This probably keeps the inductance reasonable when no pot is applied so the resonant frequency doesn’t go to 10MHz or anything. The coil attaches to the driver with a couple of lug screw connections marked IN and OUT.Interestingly, the INside of the coil goes to IN and the OUTside turn goes to OUT. Unlikely that it matters, but it’s the little things that entertain us.
The coil measures about 55uH with no metal nearby and about 25uH with a big steel cooking pot sitting on it. The white pedestal in the center seems to be a thermistor spring-pressed against the cooking glass for overtemp protection. And a lot of thermal grease.