[TriEmbed] Coffee roaster sanity check

Brian triembed at undecidedgames.net
Tue Jan 7 10:50:29 CST 2020


Shane,

Did you get a chance to take a look at the photos of the disassembled 
coffee maker that Craig put in his Google Drive?  The easiest-to-access 
feed of power to the fan motor is *AC*, not DC -- there is a discrete 
bridge rectifier soldered directly to the motor terminals.

I think a simpler, easier approach would be to use an optocoupled triac 
on the AC "upstream" of the bridge rectifier.  Then there is no need to 
get in between the bridge rectifier and the motor (which would be 
something of a headache).

My $0.02,
-Brian

On 1/2/20 4:55 PM, Shane Trent via TriEmbed wrote:
> Craig,
> 
> 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).
> 
> image.png
> https://electronics.stackexchange.com/questions/67663/criteria-behind-selecting-pwm-frequency-for-speed-control-of-a-dc-motor 
> 
> 
> Shane
> 
> 
> On Thu, Jan 2, 2020 at 8:10 AM Craig Cook via TriEmbed 
> <triembed at triembed.org <mailto:triembed at triembed.org>> wrote:
> 
>      > The 4N25 is a common choice but is rated for use up to only 30
>     volts while the HCPL-181 looks to be around the same price and is
>     rated for up to 80 volts.
> 
>     Oh, I am actually using one of these
>     https://cdn.sparkfun.com/datasheets/Components/General/FQP30N06L.pdf
>     (32A, 60V). I was lazy doing to schema diagram. It's been updated
>     again now. I think I have the diode in the correct place and direction.
> 
>     Thanks
> 
>     Craig
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> 
> 
> -- 
> photo 		
> *Shane D Trent*
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