U720 modem updating

Posted by / 14-Feb-2020 15:05

I calculated resistors values for this circuit using online calculators on Random Science Tools and Calculators site to turn on fan when temperature is more than 30 degrees C and turn it off if T below 27 degrees C.

Heater respectively turns on if T is below about 3 degrees C and turns off when it rises more than 7 degrees C.

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My father lives in the village where no broadband connection is available.

To completely secure the nuts in the base I used small amount of cyanacrylate momentary glue.

To protect internal space from humidity, ventilation holes are made in the places that are safe from water sprays, but everything else should be securely insulated.

Comparator forms inverting and non-inverting Schmitt triggers.

I started with a search of the case that will be able to accommodate all required components.

But I found that cases in stores either hermetically sealed (which is unacceptable in my design because of airflow is required to cool components) or does not provide adequate protection from harsh conditions and mostly expensive (appropriate sizes starts at around US equivalent for the IP55 rated box).

Thus I decided to go with own case design and manufacturing.

First of all I made plastic sheet bender out of nichrome wire strained between two long screws secured in the wood plank and 12V/10A power supply with alligator clips.

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