EVGRAY Archive

Re: Ron's Aqua Chi

Database ID: 113552
2019-06-20T17:08:34-07:00
onielsen2000 <[email protected]>

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Hi Ron,

LM338t http://www.ti.com/lit/ds/symlink/lm338.pdf has a thermal resistance from junction to ambient of 22.9 K/W. This gives a temperature increase of about 23 degrees Celsius per Watt dissipated. Thus dissipating 5W will increase its temperature by 115K. (207 degrees Fahrenheit) That's 1A with 5V voltage drop. Use a heat sink to drastically reduce the thermal resistance to the ambient.

Alternatively use a switched mode power supply as this kind doesn't have to dissipate the excess voltage with current flow into heat.

Regards
Ole


 

---In [email protected], <iron1of1@...> wrote :

 Hi all,
 

 Here is link for a couple of photos of my progress. I have it setup and making bubbles (water for the tomatoes) The LM338t gets red hot dropping much voltage so IC is off the board and on a big heat sink on back of case now.
 

 https://photos.app.goo.gl/Rs6BDcMZzprXwNj98 https://photos.app.goo.gl/Rs6BDcMZzprXwNj98

 

 Ron

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