Pas Home / Home ventilation with RPiSoC

1 Sep 2014

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I will use the RPiSoC to control and catch the status of my home ventilation system. Integrate with OpenHAB and my humidity sensor, when i take my shower humidity sensor detect the humidity increase and automatically start the ventilation. I suck in electronics I'm going to need your help.

The plan

The timer

I open the current control and check component.

Its seems simple enough:

4 wire 12v, GND, LED Control, SW (Switch),

LM2901DG Chip (From spec 'Designed for use in level detection')

3 LED

Push button

100uf 63v 85°C (Capacitor)

The signal

With the Tektronix oscilloscope i check what happen in SW and LED wire.

SW wire, have continuous 5v DC and when i press control button its drope near 0v and when i release it return to 5v. When signal is reduce to 0v for about 1 second or more the main control unit detect it and start ventilation and switch between each timer state.

What is the name of this transition? Do you know some tutorial links to reproduce this with RPiSoC ?

The LED wire have his voltage between 0v to 10v. Each value indicate a state. Measure voltage between 0v to 5v with RPiSoC its seem very easy with analog port and this sample code https://github.com/EmbeditElectronics/psoc_2_pi/blob/master/API_Python_v_1_1/SAR_ADC_voltmeter.py

But how measure voltage with range 0v-10v? Use a Voltage Dividers? Do you know a good tutorial?

Top Comments

kipe over 10 years ago in reply to verrverr +1

Hey. Try with larger resistors, so the affect on the existing circuit won't be that much. Something like 1M and 470k might work...

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hlipka over 10 years ago

What you measure for the switch looks like a normal input with a pull-up resistors. You should be able to control that with a transistor (or a small relay if you want to have isolation).
Are the switches on the panel mechanical?
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verrverr over 10 years ago in reply to hlipka

Hi thank for your help, for the pull-up resistor if I understand if a use a relay I just need to link the gnd and switch wire using the relay for a small duration?
The current push button on the switch have a 100uf capacitor on the vcc side, do I also have to use one?
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hlipka over 10 years ago in reply to verrverr

Yes. No. A relay can alway replace a button, just connect it in parallel. And if there is already a cap (though I'm not sure what its used for), you should not add another one.
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hlipka over 10 years ago in reply to verrverr

Yes. No. A relay can alway replace a button, just connect it in parallel. And if there is already a cap (though I'm not sure what its used for), you should not add another one.
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