Brian, I did not look at the photos but I have disassembled a few hot-air popcorn poppers and they all used the same approach with the line voltage dropped via a small heater coiled wired to a discrete diode bridge attached to the motor leads. I opened the first one up to investigate automation and had a few poppers die on me after extended coffee roasting. The ancient popcorn popper shown in the post below has been going strong for YEARS. They really do not make them like they used to. https://fettricks.blogspot.com/2018/10/roasting-coffee-with-hot-air-poppcorn.html
Most recently I had to work on the internals to by-pass a low-temperature thermal switch attached to the metal chamber. It seems some manufacturers do not want their hot-air poppers to be used for roasting coffee (I use these poppers only outside, on concrete, at least 12 feet from the house, I had an Alpen Roaster (linked below) experience a software glitch that caused a fire so I am cautous and always keep an eye on the roaster). I needed a fix for the poppers because I had bought a box of four. https://legacy.sweetmarias.com/library/prod.swissmar-alpenrost2 I did expect that using an Arduino's pin 5 or 6 with a 960 Hz PWM, when combined with the inductance of the motor, the inertia of the fan blades and thermal inertia of the heater, would provide a response to varied PWM duty cycle that is more than smooth enough for the application. The greater failure in my recommendation was a failure to point out that the MOSFET must be rated to standoff the peak rectified DC voltage from the 120 VAC line, roughly 170 VDC, that will be present on the circuit when the MOSFET is off. So you would need something like a 200 volt DC rating for the MOSFET or DC solid-state relay in this application. So all in all, it does look like an AC Solid-State relay would be the simplest way to go for modulating the second heater coil and fan! Cheers! Shane On Tue, Jan 7, 2020 at 12:56 PM Brian via TriEmbed <triembed@triembed.org> wrote: > Annnnd just a bit more: > > I realized that my thoughts on PWMing an unfiltered DC waveform are > unfounded, after playing around with a circuit in a simulator[1]. If > the PWM period is sufficiently higher than the power waveform's period > (a couple orders of magnitude at least), then the noise averages out. > > I stand by my suggestion of using an AC switching element instead of > trying to tie in between the bridge rectifier and the motor, though, > simply on the grounds of ease of work. It's a lot easier to just cut a > wire. :-) > > -B > > [1] Check out https://falstad.com/circuit > > here's the circuit I used: > http://tinyurl.com/yfssghhk > > _______________________________________________ > Triangle, NC Embedded Computing mailing list > > To post message: TriEmbed@triembed.org > List info: http://mail.triembed.org/mailman/listinfo/triembed_triembed.org > TriEmbed web site: http://TriEmbed.org > To unsubscribe, click link and send a blank message: mailto: > unsubscribe-triem...@bitser.net?subject=unsubscribe > > -- [image: photo] *Shane D Trent* Patent Agent 919-348-0061 | shanedtr...@gmail.com ShaneTrent.com | Skype: skype:shane.trent1 <#SignatureSanitizer_SafeHtmlFilter_> Raleigh, North Carolina <http://www.linkedin.com/in/shanetrent> <http://twitter.com/sdtrent> Create your own email signature <https://www.wisestamp.com/signature-in-email/?utm_source=promotion&utm_medium=signature&utm_campaign=create_your_own>
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