Beide Seiten der vorigen RevisionVorhergehende ÜberarbeitungNächste Überarbeitung | Vorhergehende Überarbeitung |
hardware:venta_connected [2018/10/14 00:09] – reinhold | hardware:venta_connected [2018/10/28 19:37] (aktuell) – [section 5] reinhold |
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==== 3.1 Power supply: Step-down converter from 24V to 3.3V ==== | ==== 3.1 Power supply: Step-down converter from 24V to 3.3V ==== |
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The Venta LW45 humidified is powered by an external 24V AC power supply, which should be string enough to also power the microcontroller on my board. We simply use the VCC line of the 10-pin IDC ribbon cable and convert the 24V to the required 3.3V of the microcontroller. | The Venta LW45 humidifier is powered by an external 24V AC power supply, which should be strong enough to also power the microcontroller on my board. We simply use the VCC line of the 10-pin IDC ribbon cable and convert the 24V to the required 3.3V of the microcontroller. |
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Initially, I tried a normal LN7805 voltage regulator, but that heated up too much, especially considering that the WiFi-PCB would be placed inside the humidifier inside the plastic enclosure with very little air flow. Instead, I'm using a 24V to 3.3V step-down converter to provide the 3.3V VCC to my own board. | Initially, I tried a normal LN7805 voltage regulator, but that heated up too much, especially considering that the WiFi-PCB would be placed inside the humidifier's plastic enclosure with very little air flow. Instead, I'm using a 24V to 3.3V step-down converter to provide the 3.3V VCC to my own board. |
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I do not, however, separate my own circuit with optocouplers from the Venta's circuit. This means that there is some chance that e.g. a broken comparator on my board might cause 24V to be fed into the microcontroller. That is a risk I'm willing to take, as in this case I'd rather replace the whole board anyway rather than trying to track down which device is fried. | I do not, however, separate my own circuit with optocouplers from the Venta's circuit. This means that there is some chance that e.g. a broken comparator on my board might cause 24V to be fed into the microcontroller. That is a risk I'm willing to take, as in this case I'd rather replace the whole board anyway rather than trying to track down which device is fried. |
{{ :hardware:venta_lw45:venta_lw45_openhab_sitemap.png?direct&400 |}} | {{ :hardware:venta_lw45:venta_lw45_openhab_sitemap.png?direct&400 |}} |
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In my floorplan SVG, the humidifier looks like this can can be controlled by a simple click on the on/off icons or the level numbers: | In my floorplan SVG, the humidifier looks like this and can be controlled by a simple click on the on/off icons or the level numbers: |
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{{ :hardware:venta_lw45:venta_lw45_openhab_floorplan.png?direct&400 |}} | {{ :hardware:venta_lw45:venta_lw45_openhab_floorplan.png?direct&400 |}} |
* Board (NOT tested, routing also not optimized): {{ :hardware:venta_lw45:arduino:ventaconnected_arduino_v0.01_2017-12-11.brd |}} | * Board (NOT tested, routing also not optimized): {{ :hardware:venta_lw45:arduino:ventaconnected_arduino_v0.01_2017-12-11.brd |}} |
* MySensors arduino sketch: {{ :hardware:venta_lw45:arduino:mysensors_ventaconnected.ino |}} | * MySensors arduino sketch: {{ :hardware:venta_lw45:arduino:mysensors_ventaconnected.ino |}} |
* Pictures: {{:hardware:venta_lw45:arduino:venta_lw45_mysensors_00_breadboard.jpg?direct&200|}}{{:hardware:venta_lw45:arduino:venta_lw45_mysensors_02_breadboard.jpg?direct&200|}}{{:hardware:venta_lw45:arduino:venta_lw45_mysensors_03_prototype.jpg?direct&200|}} | * Pictures: {{:hardware:venta_lw45:arduino:venta_lw45_mysensors_00_breadboard.jpg?direct&100|}}{{:hardware:venta_lw45:arduino:venta_lw45_mysensors_02_breadboard.jpg?direct&200|}}{{:hardware:venta_lw45:arduino:venta_lw45_mysensors_03_prototype.jpg?direct&200|}} |
(In the last picture one can see the error LED dimly lit, which is caused by the use of a voltage divider rather than the LM339/393 comparator...) | (In the last picture one can see the error LED dimly lit, which is caused by the use of a voltage divider rather than the LM339/393 comparator...) |