Craig, The optoisolators allow the microcontroller to switch AC connected loads while isolating the microcontroller from the AC lines. Your AC solid-state relay for the heater coil has the optoisolation built-in. Actually you could use a DC solid-state relay for controlling the cooling fan as well. The only other components you would need to add are the input current limiting diode and the reverse-biased kick-back diode across the motor terminals. The IXYS DC solid-state relay below is $3 in singles (and IXYS makes nice parts). The diagram I shared in my previous message is basically how you would build your own solid-state DC relay.
https://www.digikey.com/product-detail/en/ixys-integrated-circuits-division/CPC1706Y/CPC1706Y-ND/3077519 Shane On Thu, Jan 2, 2020 at 7:00 PM Craig Cook via TriEmbed < triembed@triembed.org> wrote: > >I was actually talking about the voltage rating of the optoisolator used > to drive the FET gate. The image below more fully describes what I meant. I > expect your final circuit for the fan would include most of the items shown > below (I am not sure that you would need D2). > > Ah, I was working off this tutorial. > > > https://itp.nyu.edu/physcomp/labs/motors-and-transistors/using-a-transistor-to-control-high-current-loads-with-an-arduino/ > > Their example uses a 12V motor. Mine is ~20V. I thought I was "close > enough" to make it work. > > You are suggesting I need more components, i.e. at least add an optoisolator > into the mix. > > > > How many popcorn makers have you been through on this project? :-) > > LOL. Two have died from natural causes. I fried the heater on the third by > running without a fan. > > > the heater might just be overheating a little bit each time, gradually > weakening itself until it breaks. > > Yes, that sounds like a great theory as well. The wire on the coil breaks, > close to where the windings start. It may be due to the number of heat and > cool cycles it goes though. > > >Also bear in mind that your $30-or-so popcorn popper simply isn't built > for longevity. > > Yes. It's supposed to last 12 months of popcorn usage. For most units it's > probably rare to be used many times in a 12 month period. > > The system I design needs to be reasonably easy to swap out the failed > parts, which so far seems to be the heating element. > > Thanks > > Craig > _______________________________________________ > 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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