Re: Hypatia 3.0

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katsmeow said...

Thank you for that. But that's over $200 for a Pi plus hat plus power plus case plus fan/heatsinks and one lan port for each set of three relays, and no parport connection! Then it's still not remotely operated, i would still need to goto the cellar to check the Pi readout, at which point i don't need the Pi plus keybd plus lcd screen down there to check the water level down there.

How is it that OE can check the status of which buttons i press on this keybd without spending $200 to build a separate computer with 8 GB of ram on a new linux computer running Python?

In 1984 i had two 19" 3U rack boxes full of cards hooked to a C64, but i cannot run a cussed thing from any wintel computer i have.


The computer (especially Windows computers) became an appliance 20-30 years ago.

First reason: computers are too expensive to let them anywhere near "danger". Electricity is dangerous. Two more reasons: people are stupid, and manufacturers hate to get lots of fried computers returned for "warranty repairs". Another reason: not very many people want to do things like this, so there's no incentive to get UL approval for something that you'll only sell occasionally. And most people who do buy stuff like this have to meet requirements of the NEC.

You can buy industrial controllers which meet code and are UL approved. This gets expensive fast:

If you aren't afraid to DIY, look at the Arduino Leonardo - 20 digital I/O,( 7 can do PWM for motor speed control or light dimming) and 7 analog inputs. $16 at Amazon. This can send text to your computer as if it was a HID keyboard, so you could read the status of the various ports, and whatever text you wanted to your Eu program, e.g. value of one or more inputs...etc. Of course these inputs are limited to 5 volts. So you're going to need to design sensors that won't fry stuff with higher voltages.

Bi-directional*may* be possible - read as if it was a keyboard, and write to ports on the Leonardo, but it's probably easier to use a second Leonardo or other Arduino along with optical-isolated relays to do the output handling.

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