Digital Stealth Care · ventilation
Grow room ventilation
Ventilation is the first thing a grow room asks for: fresh air in, hot and wet air out, and air moving past the canopy. This is how Digital Stealth Care runs the fans first and the appliances second, and what the fans do if the brain stops.
4
wired fan channels on the hub: an intake for each tent, a room exhaust and an outside exhaust
35 °C
tent temperature at which the hub runs the outside exhaust and both intakes flat out, whatever the brain is doing
3 min
without a valid tent temperature before the hub drops to a gentle, outdoors-biased airflow
Fans before appliances
Air exchange first, then the appliances
A room that is too hot or too wet usually needs its air changed before it needs a dehumidifier or a heater. The hub's firmware works that way: the fans run all the time, and the appliances sit above them.
The intake fans for each tent and the shared exhaust chase VPD and temperature under the control strategy you choose in Settings, and the priority tent wins the shared exhaust when both tents need it. The exhaust to outside works harder as the tent runs above its temperature target, and harder again when humidity runs well over the top of its band.
The dehumidifier, humidifier, heater and heat mat are on a ladder of their own, with waits and rests so they do not chatter. They are the second response, not the first.
The fans and the appliances also stay out of each other's way. While the heater or the humidifier is running, the hub holds the outside exhaust at a low floor and lets recirculation carry the air, so the heat or the moisture stays in the tent. A humidity overflow overrides that and extracts anyway.
The rung order and the waits are in the guide: the climate ladder, failsafe and reality gates. For what the appliances do, see humidity controllers for grow rooms.
The air path
Intake, exhaust, pressure and mixing
Four things decide where the air goes. All four are set in Settings › Climate, and the Climate desk shows them.
01
Intake and exhaust
Each tent has its own intake and its own targets. One room exhaust and one outside exhaust serve both tents. Fresh air comes in through the intakes and leaves through the exhausts.
02
Negative pressure
Each tent has a pressure regime: negative, neutral or positive. An intake budget sets how much the intakes may run relative to the exhaust. Settings › Climate › Pressure says which regime a value asks for. Positive pressure bypasses the carbon filter, so check the regime before you change it.
03
Recirculation
A recirculation fan moves air past the canopy. In the hub's automatic mode it never drops to nothing, and it runs faster as humidity climbs above the band.
04
Air-mixing pulse
For a tall tent with a warm top and a cool floor, a periodic burst of recirculation mixes the layers. The Climate desk prints it as Air-mixing pulse, and Settings › Climate calls the switch De-stratification pulse, with its period, length and level.
A humidifier can ride the intake path or not, depending on your ducting. The Climate desk prints that as Humidifier air routing, and Settings › Climate calls the switch Humidifier intake routing.
The air path card on the Climate desk draws intake, tent, room and exhaust with the flow, and shows the measured net flow. The rows are explained on Settings › Climate.
Fan speed
Hub fans have a speed, plug fans have a switch
How much DSC can do with a fan depends on how it is wired.
Fans on the hub's channels
The hub drives its four fan channels with 1 kHz PWM, through converter modules that turn the PWM signal into 0 to 10 V, so each fan has a speed and not just on and off. The hub sets those speeds from its own sensors, all the time. On the Climate desk each of these fans has a slider on the Fan duty % card, live only while you have taken the fans over (the header then shows FANS: YOURS). Press Hand back and the hub carries on.
The hub build guide covers the channels, the modules and metering every output before the first flash.
A fan on a smart plug
A fan on a smart plug gets an on and off switch on the Fan duty % card, and the switch asks first. The brain cannot set its speed. That suits a clip fan or a circulation fan you already own. For an inline exhaust fan, a speed control matters, so it belongs on a hub channel.
A known fan that nothing reads or controls shows an assumed duty and a sentence saying so, not a control. The supported devices page lists the fans and plugs DSC recognises.
Failsafe
What the fans do when the brain stops
The brain is the Raspberry Pi that runs the dashboard, the plans and the logs. If it stops, the hub keeps running its wired fans and dimmed lamps from its own sensors and its own clock, inside its hard limits.
| When | What the hub does |
|---|---|
| Tent temperature reaches 35 °C (clears below 34 °C) | The outside exhaust and both intakes run at 100 %, the room exhaust is off and the lamp is off. The hub stops asking for heat and humidity. |
| No valid tent temperature for 3 minutes | The outside exhaust runs at 40 % and the other three fans at 25 %. The hub stops asking for heat and humidity. |
Those two limits are in the hub's firmware and apply whether or not the brain is running. Between them, the hub keeps ventilating the tent from its own temperature and humidity sensors.
A fan on a Tuya or Zigbee plug holds its last state when the brain stops, because there is no hub cut-out behind it. That is another reason to put the fans that matter on the hub.
A kit with no hub has none of this: no wired fans, no 35 °C limit and no sensor-fault mode. We do not recommend running a room that way for the long term.
The full detail is in when the brain stops: the hub and the plugs. What runs today and what is coming is on the status page.
Ventilation is half of climate
Once the air moves, hold the humidity
The other half of a grow room is humidity and VPD. We wrote up how DSC holds them in humidity controllers for grow rooms, and the free VPD calculator turns a temperature and humidity reading into the number growers steer by.
Every alpha build is free, this one included, and yours to keep. No account, no subscription, no licence check. Keep the image and you keep the software.