Three USB ports, switched by radio

This station listens on 2.4 GHz radio and switches its three USB-A ports on and off, each one independently. The commands come from its partner, the 2.4GHz Radio Frequency Transmitter Panel Station, plugged into a computer. One transmitter drives as many of these receivers as share its radio frequency, and each receiver only acts on commands addressed to its own serial number, or to all of them.

Note: Works as a pair. This station receives and switches, the transmitter station sends, so you need at least one of each.

The base

It starts with the Nano Base Board, a buzzer and a set of stacking headers.

The buzzer and headers go on first, and four screws fix the board to the 60 x 60 x 7 4-Pillar Flat Snap Mount.

Then the Nano, with long stacking headers ready for the boards above.

The switching

The ULN2803 8-Channel Driver Shield does the switching. Its ULN2803 is an array of eight Darlington transistors, and each output gets its own XH connector.

The chip sits in a socket rather than on the board, so it can be swapped without desoldering.

Only three of the eight outputs are used here, OUT2, OUT3 and OUT6, driven by pins D2, D3 and D6 of the Nano. Each gets a red XH connector.

The driver shield stacks onto the base board.

The ports

Three USB-A breakout boards, each with its own XH lead, will become the station's outputs.

They sit inside the cover, behind the three openings in its front wall.

The radio

On top goes the nRF24L01 Radio Communication Shield, the same one as on the transmitter: an nRF24L01 module, a 10 µF capacitor to hold its 3.3 V steady when it transmits, and two 10 kΩ trimmers.

Assembled, and from underneath.

Two trimmers, many uses

As on the transmitter, the two trimmers are wired to analog inputs on the Nano, and today's firmware leaves them alone: the receiver listens on the shared broadcast address and picks out the commands that carry its serial number, or ALL. On a receiver, they open up their own set of options.

Groups. One trimmer sets the group the receiver belongs to, so it only answers the transmitter set to the same position.

Frequency. The second trimmer sets the radio channel to listen on, one of the nRF24L01's 126, from 2.400 to 2.525 GHz, to match its transmitter and keep clear of Wi-Fi.

Anything else. They are just two analog inputs, so they can set local behaviour instead: how long a port stays on before switching itself off, or which ports an ALL command reaches.

Three boards high

Before the cover closes, each USB-A lead plugs into its XH connector on the driver shield.

Base board, driver shield and radio shield, one on top of the other, and the 60 x 60 x 78 3-Port USB-A with nRF24L01 Vent Panel Cover goes over them.

Closed: three USB-A ports at the top of the front, USB-C power below the serial label, and vents along the sides.

Taking commands

Power it from any USB-C supply. At boot it beeps, and if the radio module isn't found, an error tone says so straight away.

From the transmitter's serial terminal, 117283:CH1 ON switches on port 1 of this receiver, 117283:CH1 OFF switches it off, and 117283:ALL ON or ALL OFF switches all three. Use ALL as the target, and every receiver in range does the same. The buzzer confirms each one: a success tone when a port turns on, a finish tone when it turns off, and a warning for a command or port it doesn't know. STATUS logs the state of every port to the receiver's own USB serial.

In this build, all three ports give 5 V from the USB-C supply, so anything that runs from a USB port works: a lamp, a fan, a small pump, a charger. The ULN2803 itself switches loads up to 24 V.

On our bench, two of these receivers take commands from one transmitter in the same room.

How far from the transmitter can it be? The receiver listens at 250 kbps, the nRF24L01's slowest data rate and the most sensitive one, so it picks up weak signals best. With the transmitter at low power and printed antennas on both modules, a receiver typically hears it from about 10 to 20 m indoors, through a wall or two, and further in the open. Raise the transmitter's power and it carries to around 100 m in a clear line of sight, and an nRF24L01 with an amplifier and an external antenna (a PA+LNA version) on the same 8-pin header lets a receiver listen from several hundred metres. Walls, metal and busy Wi-Fi shorten the distance, so a receiver at the edge of its range does best up high and in the open.

If you have a project in mind, tell us about it and we will help you build it.

Parts in this build

• HomeBotica 3-Channel (5-24V) USB 2.4GHz Radio Frequency Driver Panel Station
• HomeBotica nRF24L01 Radio Communication Stack
• HomeBotica Nano Base Board
• HomeBotica ULN2803 8-Channel Driver Shield
• HomeBotica nRF24L01 Radio Communication Shield
• HomeBotica 60 x 60 x 7 4-Pillar Flat Snap Mount

Other components

• Nano (ATmega328P)
• Passive buzzer
• ULN2803 Darlington array, in an 18-pin socket
• 3 x XH connectors
• 3 x USB-A breakout boards on 2-wire XH leads
• nRF24L01 2.4 GHz radio module
• 10 µF 50 V electrolytic capacitor
• 2 x 10 kΩ trimmers (103)
• Stacking headers between the three boards
• Screws (x4), base board to mount

Questions about the build, or a project of your own in mind? Tell us in the comments.

Originally published on HomeBotica Use Cases. More builds at homebotica.io. Text by Claude Opus 5.5 (Anthropic), from Felipe Lodi's build photos and notes.

One transmitter, many receivers

This station takes a line of text from a computer over USB and sends it out over 2.4 GHz radio. On its own, it switches nothing. The listening end is its partner, the 3-Channel (5-24V) USB 2.4GHz Radio Frequency Driver Panel Station, which turns its three USB ports on and off. One transmitter talks to as many receivers as share its radio frequency, and each command says which one it is for.

Note: Works as a pair. This station sends and the radio frequency driver station receives and switches, so you need at least one of each. Add more radio frequency driver stations, and the same transmitter controls them all.

The base

It starts with the Nano Base Board: a socket for a Nano, a buzzer, and stacking headers that carry every pin up to the boards above.

The Nano and the buzzer go on, and four screws fix the board to the 60 x 60 x 7 4-Pillar Flat Snap Mount.

The radio

The nRF24L01 Radio Communication Shield carries the radio to the top of the stack. Together with the base board, it makes the nRF24L01 Radio Communication Stack.

The radio is an nRF24L01 module, a 2.4 GHz transceiver about the size of a stamp, with its antenna printed on the board. A 10 µF capacitor sits across its supply: the module draws short bursts of current when it transmits, and the capacitor keeps its 3.3 V steady through them.

With the radio, the capacitor and two trimmers in place, the shield is ready to stack.

Two trimmers, many uses

The two trimmers are wired to analog inputs on the Nano, so the firmware can read where each one is set at any moment. Today's firmware leaves them alone: every transmitter and receiver shares one broadcast address, and each command names the receiver it is for. When a broadcast to every station in range isn't what you want, the trimmers are the way out, and there is more than one way to use them.

Groups. One trimmer picks a group, and the transmitter only talks to receivers set to the same position. Two pairs in the same house then work side by side without hearing each other's commands.

Frequency. The second trimmer picks the radio frequency itself: the nRF24L01 has 126 channels, 1 MHz apart, from 2.400 to 2.525 GHz. Turning it moves a pair away from a busy Wi-Fi band, or away from another pair.

Anything else. They are simply two analog inputs, so they don't have to be about the radio at all: a transmit power, a repeat interval for a command, or a value sent along with each command for the receiver to act on.

Stacked

The radio shield plugs into the base board's headers, and the module sits on the top layer, clear of the Nano.

From every side, two boards and one mount.

A home for it

The 60 x 60 x 78 nRF24L01 Vent Panel Cover slides down over the stack, and its side opening lines up with the Nano's USB-C port.

Closed, it is a plain green tower: vents around the top, USB-C on the side, next to the station's serial label.

Sending a command

Plug it into a computer and open any serial terminal at 9600 baud. Each line you type goes out over the radio when you press Enter, and the buzzer beeps to say it was sent.

A command is a target and an instruction, separated by a colon. The target is a receiver's serial number, or ALL for every receiver in range: 117283:CH1 ON switches on port 1 of receiver 117283, ALL:CH2 ON switches on port 2 of every receiver, and ALL:ALL OFF switches everything off.

The radio sends and doesn't wait for a reply, so the transmitter's beep means sent, not received. Each receiver confirms with its own tones. If the radio module isn't found at power-up, an error tone says so straight away.

On our bench, one transmitter drives two receivers in the same room, and the serial terminal is all it takes.

How far apart can they go? The radio runs at 250 kbps, the nRF24L01's slowest data rate and the one that reaches furthest, at low transmit power. With the module's printed antenna, that typically covers about 10 to 20 m indoors, through a wall or two, and more in the open. Raising the transmit power in firmware takes it to around 100 m in a clear line of sight. Beyond that, nRF24L01 modules with an amplifier and an external antenna (the PA+LNA versions) use the same 8-pin header and reach several hundred metres. Walls, metal and busy Wi-Fi all shorten the distance, which is where a different frequency helps.

If you have a project in mind, tell us about it and we will help you build it.

Parts in this build

• HomeBotica 2.4GHz Radio Frequency Transmitter Panel Station
• HomeBotica nRF24L01 Radio Communication Stack
• HomeBotica Nano Base Board
• HomeBotica nRF24L01 Radio Communication Shield
• HomeBotica 60 x 60 x 7 4-Pillar Flat Snap Mount

Other components

• Nano (ATmega328P)
• Passive buzzer
• nRF24L01 2.4 GHz radio module
• 10 µF 50 V electrolytic capacitor
• 2 x 10 kΩ trimmers (103)
• Stacking headers between the two boards
• Screws (x4), base board to mount
• For use: a computer with a serial terminal (9600 baud)

Questions about the build, or a project of your own in mind? Tell us in the comments.

Originally published on HomeBotica Use Cases. More builds at homebotica.io. Text by Claude Opus 5.5 (Anthropic), from Felipe Lodi's build photos and notes.

A pump that waits for the dark

Some things only need to run at night. This station watches the light through a window in its top and, when it gets dark, switches on whatever is plugged into its USB-A ports. Here it's an air pump bubbling through a tank.

Note: No microcontroller needed. There is no Nano or other controller in this station and no code to flash: a light sensor, a resistor and a single transistor do all the work, so it starts the moment it gets power.

Two shields, no controller

It's built from just two of our boards: the HomeBotica Converter Booster Shield at the bottom, which makes the output voltage, and the HomeBotica Resistive Sensor Driver Shield on top, which decides when to switch it on. There is no base board and no controller under them.

Power first

The Converter Booster Shield takes 5 V from USB-C and boosts it with an MT3608 module, anywhere from 5 to 24 V.

The capacitors, the diode and the stacking headers go on first, then the boost module on its own pin legs.

A small voltmeter gets an XH lead, so it plugs into the shield and shows the output at a glance.

Four screws fix the shield to the 60 x 60 x 7 4-Pillar Recessed Cutout Snap Mount.

At first power, the MT3608 is dialled in to 5.02 V for a USB pump. The display is green, our colour for 5 V and under.

The sensing shield

The Resistive Sensor Driver Shield is where the switching happens: two USB-A ports, a MOSFET, a DIP switch, and pads for a resistive sensor and its partner resistor.

The sensor here is a light-dependent resistor (LDR), paired with a 47 kΩ resistor; we check its value before soldering it in.

The switch itself is an IRLZ34N, a logic-level MOSFET that turns fully on from a few volts at its gate. Two flyback diodes, one per port, absorb the kick a motor gives back when it switches off, so a pump can't damage the board, but they are optional.

The two USB-A ports go on first.

Then the LDR, the resistor and the MOSFET. The LDR and the resistor form a divider on the MOSFET's gate: in the light, the LDR's resistance is low and holds the gate down; in the dark it climbs, the gate voltage rises, and the MOSFET switches both USB-A ports on together. The resistor sets the switching point, so another value moves it from dusk to deep night.

One board, many sensors

The LDR is only one choice. The shield takes any two-pole resistive sensor, paired with a resistor that suits its range, for example:

NTC or PTC thermistors, for temperature; force-sensitive resistors, for pressure or weight; flex sensors, for bending; resistive humidity sensors such as the HR202; two-pin soil moisture forks and raindrop plates; even two bare wires in a tank, as a water level probe.

Swap the sensor and the resistor on their pads and the logic flips: with an LDR, the outputs then switch on in the light instead of the dark. With a thermistor, one way round runs a heater when it gets cold, the other a fan when it gets hot.

And the sensor doesn't have to live inside the box: the same pads take XH connectors, so a sensor on a lead can sit wherever it needs to be, outside the station.

Note: Flexible by design: one shield, any two-pole resistive sensor, switching on either side of its threshold, mounted on the board or out on a lead.

Stacked

The sensing shield plugs straight onto the booster's stacking headers, and the stack is complete.

A home for it

The 60 x 60 x 38 2-Port USB-A with Voltage Display Slot and Top Airflow Box Cover has a slot in its front for the voltmeter, held by its own two screws.

From the outside, the display sits flush in the front wall.

Closing up

The voltmeter's lead plugs into the booster, and the cover goes over the stack.

Before it closes, the DIP switch: each switch enables or disables a port. Here two of them turn on the two USB-A ports. The shield also has four XH outputs on its other side, which a second MOSFET and a second resistive sensor could drive, and the other two switches are kept for future upgrades of the board.

Closed, the voltmeter shows 5.04 V, and the LDR looks up through the hexagonal window in the top.

Round the back, the openings fit the ports perfectly: both USB-A outputs and the USB-C power input sit flush in their chamfered windows, with no gaps around them, next to the station's serial label.

Lights on, lights off

On the bench, a USB air pump feeds an air stone in a tank of water. With the window in the light, the pump is off, the water is still and the display reads 5.03 V.

Cover the window, with a hand or a small block of foam, and the pump starts at once: bubbles rise, and the display dips to 4.90 V under the load. Uncover it, and the pump stops.

At night the station does this on its own, so a tank gets its air when the lights are out. If you have a project in mind, tell us about it and we will help you build it.

Parts in this build

• HomeBotica Resistive Sensor 2-Channel (5-24V) USB Driver Box Station
• HomeBotica Converter Booster Shield
• HomeBotica Resistive Sensor Driver Shield
• HomeBotica 60 x 60 x 7 4-Pillar Recessed Cutout Snap Mount
• HomeBotica 60 x 60 x 38 2-Port USB-A with Voltage Display Slot and Top Airflow Box Cover

Other components

• MT3608 adjustable boost module, set to 5 V here
• Capacitors, a diode and a USB-C power socket on the Converter Booster Shield
• 3-digit voltmeter on a 2-wire XH lead
• Light-dependent resistor (LDR) and a 47 kΩ resistor
• IRLZ34N logic-level MOSFET
• 2 x flyback diodes
• 4-way DIP switch
• 2 x USB-A ports
• Stacking headers between the two shields
• M2 screws (x4), shields to mount
• For the test: a USB aquarium air pump with an air stone

Questions about the build, or a project of your own in mind? Tell us in the comments.

Originally published on HomeBotica Use Cases. More builds at homebotica.io. Text by Claude Opus 5.5 (Anthropic), from Felipe Lodi's build photos and notes.

Your plant's soil, in colour

House plants rarely die from neglect alone; more often they get too much water or too little, and the soil doesn't tell you until it's too late.

This station does. A probe sits in the pot, and a light on top shifts colour with the moisture of the soil, so a glance across the room tells you whether a plant needs water.

Printing the parts

Everything starts on the printer. The 60 x 60 x 38 1-Port 3XH, Module Slot, 270° Wraparound Ventilation and Top Airflow Box Cover prints upside down, top first, so the round airflow opening and the wraparound vents come out clean, with no supports.

Next to the finished cover, the 60 x 60 x 7 4-Pillar Recessed Cutout Snap Mount, the base the board screws onto.

A socket in the wall

The probe never plugs straight into the board. Instead, a short 3-wire lead gets XH plugs crimped on and its joints covered in heat shrink.

Its far end ends in an XH socket that presses into the cover's 3XH port. It's a press fit, but we add a drop of glue just in case. From now on, anything with an XH plug can be connected from outside, without opening the box.

Building the board

Our HomeBotica Nano Base Board comes as a kit: the bare board, headers for the Nano and the RGB LED module, an XH socket, a jumper header and the buzzer. Its silkscreen names every pin, so it's clear where each part goes.

Once soldered, four small screws hold it onto the mount.

Then the two modules: a Nano controller and a KY-009 RGB LED module, each plugging into its own headers.

Putting it together

The lead from the cover plugs into the board's 4-pin I2C bus socket. Only three of its four pins are used: the probe's signal goes to SDA, which on the Nano is the analogue pin A4, and the jumper next to the socket sends 5V to the probe.

Closed, it's a neat box: the Nano's USB-C port on the back for power, and the probe socket on the side. A round diffuser sits in the top opening; the LED shines through it, so the colour is seen from above, and it glows softly through the vents too.

The probe

A capacitive soil moisture probe gets its own lead, cut to length, with XH plugs at both ends: one for the probe, one for the socket on the box. Being capacitive, it has no exposed metal in the soil, so nothing corrodes.

It clicks into the side of the box, and can be swapped or replaced without opening it.

First light

Powered from USB, the station reads the probe and lights up. Lying on the bench, in dry air, the probe reads as dry as it gets.

What the colours mean

At every check the station turns the probe's reading into a percentage: 0 % is the probe in dry air and 100 % is the probe in water up to its line, so real soil always sits somewhere in between.

The light then fades, over about two seconds, to that percentage's colour: white at 0 %, yellow around 10 %, green around 35 %, blue around 65 %, purple around 85 % and red from 95 % up. In between, the colours blend, so a pot drying out walks slowly from blue through green to yellow.

The colours fall into four bands: below 20 % the soil is dry (white to yellow), from 20 to 50 % it's moist (green), from 50 to 80 % it's wet (blue), and above 80 % it's soaked (purple to red).

On the bench, a tub of soaking-wet soil shows the two ends of the scale.

One for every pot

Each station watches one pot. Here three of them sit along a shelf of house plants, a ficus ginseng in the middle, each glowing the colour of its own soil, so the plant that needs water stands out at a glance.

And what it says

The buzzer on the base board keeps you informed without being a nuisance, and each band has its own sound.

Dry: a falling four-tone warning, repeated on every check until the plant is watered. Moist: a short rising chime, once, when the soil gets there. Wet: a low two-tone alert, once, on the way in. Soaked: a high, urgent two-tone call, on every check until the pot drains.

When nothing has changed and nothing needs attention, each check ends with four short, soft beeps instead, so you know the station is alive. If the probe is unplugged, the light goes off and the urgent call sounds every five seconds until it's back.

Ours checks once an hour, which is plenty for a pot. If you have a project in mind, tell us about it and we will help you build it.

Parts in this build

• HomeBotica Soil Moisture Presence Colour-Spectrum LED Box Station
• HomeBotica Nano Base Board
• HomeBotica 60 x 60 x 7 4-Pillar Recessed Cutout Snap Mount
• HomeBotica 60 x 60 x 38 1-Port 3XH, Module Slot, 270° Wraparound Ventilation and Top Airflow Box Cover

Other components

• USB-C Generic Nano Board with ATmega328P and CH340 Chips
• KY-009 RGB LED Module
• Passive Buzzer (on the base board)
• Capacitive soil moisture probe (v2.0)
• 2 x 15-pin female headers for the Nano, a 4-pin female header for the LED module
• 4-pin (2.5 mm) XH socket for the board, 3-pin (2.5 mm) XH socket for the cover's port
• 3-pin male header and a jumper, set to 5V
• Two 3-wire leads with XH plugs, and heat shrink
• Round top diffuser, with a HomeBotica sticker
• M2 screws (x4), base board to mount

Questions about the build, or a project of your own in mind? Tell us in the comments.

Originally published on HomeBotica Use Cases. More builds at homebotica.io. Text by Claude Opus 5.5 (Anthropic), from Felipe Lodi's build photos and notes.

A prototype that knows when it rains

This one is a prototype. It watches a raindrop plate and tells one thing only: whether it is raining right now, not how hard.

While the plate is dry, one channel is on. The moment rain arrives, it switches to the other and sounds a warning; when the plate dries, it switches back. On the bench we show it with two LEDs, and here are two of the finished stations.

The same stack, a different sensor

Under the hood is the stack from our soil moisture station: our HomeBotica Nano Base Board, with the Nano and a buzzer, and our HomeBotica ULN2803 8-Channel Driver Shield on top. Only the sensor and the code change.

The raindrop plate

The plate is a board of interleaved copper tracks. A drop of water bridges them, and the reading on its comparator board falls.

That small blue board also has a digital output with its own adjustment screw, but we only use the analogue reading. It lets the code set its own thresholds and notice when the module goes missing.

Ordinary male and female breadboard wires carry the module onto the shield's pins. Its power comes from a Nano pin, switched on only for the instant of each reading, so the plate isn't under constant current and corrodes far more slowly.

Trying it with LEDs first

As always, LEDs come before anything else. Two short leads, an XH plug on one end and breadboard pins on the other, take the two channels to a white LED for clear skies and a blue one for rain.

With the plate dry, the clear channel is on.

One drop is enough

A single drop on the plate and the station switches to the rain channel, with a warning tone. Once the plate dries, it switches back to clear with a short chime.

To keep it from flickering while a wet plate dries, rain starts at one reading and only clears at a clearly drier one. The station checks every minute on ours, and if the module is unplugged, it switches both channels off and calls for attention every few seconds until it is back.

Where it goes next

As a prototype, it proves the sensing, the switching and the sounds; what the channels end up driving depends on the project. If you have a project in mind, tell us about it and we will help you build it.

Parts in this build

• HomeBotica Rain Presence 2-Channel (5V) XH Driver Cube Station
• HomeBotica Nano Base Board
• HomeBotica ULN2803 8-Channel Driver Shield
• HomeBotica 60 x 60 x 5 4-Pillar Recessed Cutout Snap Mount
• HomeBotica 60 x 60 x 58 3-Port 2XH and Forward Ventilation Cube Cover

Other components

• USB-C Generic Nano Board with ATmega328P and CH340 Chips
• ULN2803 8-channel driver chip, in the shield's socket
• Passive Buzzer (on the base board)
• MH-RD raindrops module: sensing plate and its comparator board
• Male and female breadboard wires, module to the shield's pins
• M2 screws (x4), base board to mount
• For the bench test: a white and a blue LED, each with a resistor, and two XH-to-jumper leads

Questions about the build, or a project of your own in mind? Tell us in the comments.

Originally published on HomeBotica Use Cases. More builds at homebotica.io. Text by Claude Opus 5.5 (Anthropic), from Felipe Lodi's build photos and notes.

When the soil is too wet

Most plant gadgets worry about dry soil. In our laboratory in Luxembourg, we see the opposite just as often: rain, cool air and little sun keep pots and beds soaked for days, and roots sitting in wet soil start to suffer.

This station watches the soil and, when it gets too wet, switches on small fans that move air over it so the moisture can leave. The wetter it gets, the more fans run.

Two boards, one stack

The brain is our HomeBotica Nano Base Board. A Nano microcontroller sits in its sockets, and a small buzzer on the board gives the station a voice.

On top goes our HomeBotica ULN2803 8-Channel Driver Shield. A Nano pin can't power a fan, so each output drives one channel of the ULN2803 chip, and the chip switches the fan. The shield has eight channels: five end in 2-pin XH sockets that carry 5V, so a fan simply plugs in, and the other three are on pins on the same board.

Fans are only one option. Any small 5V device, a small pump for example, can hang on a channel, and other types of probes can take the soil probe's place.

Long pins under the shield pass the Nano's signals through, so the two boards stack without a single wire between them. Our base board and shields give access to every digital and analogue pin of the Nano.

The probe

Moisture is read by a capacitive probe, the HW-390. Unlike the cheap two-prong probes, its sensing tracks sit under the board's coating and never touch the soil, so it doesn't corrode. That matters for a station whose whole job is wet soil.

Its three-wire lead brings power, ground and the reading to an analogue input of the Nano. On the bench, ordinary male and female breadboard wires carry it onto the shield's pins.

Trying it with LEDs first

Before any fan, we test with LEDs. Two short leads, an XH plug on one end and breadboard pins on the other, take each channel to an LED, so we can see at a glance which channel is on.

Then the probe goes into a tub of potting soil, and we water it a little at a time and watch the station react.

Two levels, then three

Two levels cover what this station needs: one fan for wet soil, both for soaked. The stack can do more, though. Our first version of the code used three channels, with a third LED for a third level, and the shield has eight output channels, every one of which can be wired.

Then the fans

With the levels right, the LEDs make way for two small 40 mm 5V fans, plugged into the same two channels.

The station checks the soil at a set interval, once an hour on ours, and sorts the reading into four bands:

Dry, below 40%: no fans, and a warning tone, because dry soil needs a person with a watering can.

Moist, 40 to 60%: the happy middle. No fans.

Wet, 60 to 80%: the first fan starts.

Soaked, above 80%: both fans run, and the station sounds an alarm.

A tone plays whenever the band changes. If the probe is unplugged, the station switches everything off and calls for attention every few seconds until it is back.

A home for it

The base board screws onto a 60 x 60 x 5 mm recessed snap mount, and the shield rides inside a cube cover. Our prototype sits on the 5 mm mount you see here; the finished station comes on the 7 mm one.

The cover has three ports on its front, a 3-pin XH socket for the probe and two 2-pin sockets for the fans, wired inside to the shield. Closed, it is a small white cube, with three leads coming out of the front: one to the soil, two to the fans.

Your soil, your thresholds

Different soils, pots and plants call for different levels, and every room or greenhouse has its own airflow. If you have a project in mind, tell us about it and we will help you build it.

Parts in this build

• HomeBotica Soil Moisture Presence 2-Channel (5V) XH Driver Cube Station
• HomeBotica Nano Base Board
• HomeBotica ULN2803 8-Channel Driver Shield
• HomeBotica 60 x 60 x 5 4-Pillar Recessed Cutout Snap Mount
• HomeBotica 60 x 60 x 58 1-Port 3XH, 2-Port 2XH and Forward Ventilation Cube Cover

Other components

• USB-C Generic Nano Board with ATmega328P and CH340 Chips
• ULN2803 8-channel driver chip, in the shield's socket
• Passive Buzzer (on the base board)
• HW-390 capacitive soil moisture probe with its 3-wire XH lead
• 2 x 40 mm 5V fans with 2-pin XH plugs
• M2 screws (x4), base board to mount
• For the bench test: a red and a green LED, each with a resistor, and two XH-to-jumper leads

Questions about the build, or a project of your own in mind? Tell us in the comments.

Originally published on HomeBotica Use Cases. More builds at homebotica.io. Text by Claude Opus 5.5 (Anthropic), from Felipe Lodi's build photos and notes.

One cable in, the right voltage out

Most of the small things that make a home or a greenhouse smarter don't run on 5V. LED strips want 12V, pumps and fans often want 12V or 24V, yet the power we have everywhere is a USB charger.

This little station bridges that gap. A USB-C cable goes in, a USB-A socket comes out, and a display on the front tells you exactly what you are getting, so there is never any guessing about what you are about to plug in.

Two ways to boost

The heart of the station is our HomeBotica Converter Booster Shield. It takes one of two boost modules, never both.

The mini DC-DC module is set with small solder switches on the module itself: you choose the output once, solder it, and it stays there. The MT3608 module has a potentiometer instead, which lets you dial in an exact output anywhere up to about 26V. That flexibility is why we call this a 5-24V station.

Either module rides on two pin strips that plug into 5-pin headers on the shield, so it can be swapped later.

Important: Only ever plug in one module at a time: both outputs feed the same USB-A socket, and two different voltages joined there could burn the modules and the board.

Building the board

It starts as a bare Converter Booster Shield. First come the input capacitors and the diode that protects the supply line.

With the capacitors and the diode in place, the connectors come next: USB-C for power in, USB-A for power out, and a small XH connector that feeds the voltmeter.

Then the headers for the boost module. Everything is through-hole and labelled on the board, so the whole assembly takes one sitting with an ordinary soldering iron.

First power-up

The moment of truth: plug in the USB-C cable and the display lights up. Here are two builds side by side: the mini DC-DC version reads 11.6V for a 12V station, the MT3608 version 24.1V for a 24V one.

Dialling in the voltage

With the MT3608 there is nothing to solder: a small screwdriver on its potentiometer sets the output. Here the same station goes from 11.3V to 26.8V in a few turns, and its yellow display marks it as an adjustable build.

A home for it

The board is screwed onto our 60 x 60 x 5 4-Pillar Recessed Cutout Snap Mount, and the 60 x 60 x 18 1-Port USB-A with Voltage Display Slot and Top Airflow Sleeve Cover goes over it. The cover's Voltage Display Slot holds the voltmeter, the Top Airflow vents keep it cool, and the USB-A opening lines up with the output socket.

The voltmeter clips into its window from the inside and plugs into the board with its own lead, so the cover can be lifted off at any time without unsoldering anything.

Closed up, the USB-C input and the USB-A output sit flush in the sides of the cover, and the module stays visible through the logo vent on top.

What we power with it

On our bench a 24V station spins a computer fan, holding steady at 23.9V, and a 12V one lights an LED strip straight from a USB charger, the display at 11.2V while the strip is on, so you can see the supply keeping up under load.

The colour tells the voltage

In our ecosystem the colour of the display says what the station delivers, so you can tell them apart at a glance: green for up to 5V, blue for 12V and red for 24V. Yellow marks an adjustable station, set to any value from 5 to 24V, usually one built with the MT3608 module.

These four show them all: yellow set to 12.0V, red at 24.0V, blue at 11.4V and green at 4.60V.

Ready for the next project

Once the first one works, the next ones go quickly, each one set for the project it will power, closed up and ready to plug in.

Parts in this build

• HomeBotica 1-Channel (5-24V) USB Power Supply Sleeve Station
• HomeBotica Converter Booster Shield
• HomeBotica 60 x 60 x 5 4-Pillar Recessed Cutout Snap Mount
• HomeBotica 60 x 60 x 18 1-Port USB-A with Voltage Display Slot and Top Airflow Sleeve Cover

Other components

• Mini DC-DC boost module, output set with solder switches
• or an MT3608 boost module, output set with its potentiometer
• 2 x 5-pin (2 mm) female headers for the boost module
• 2 x 4-position pin (2.54 mm) strips, outer pins only, as module legs
• 1000 µF electrolytic capacitor (C1)
• 100 nF (104) ceramic capacitor (C2)
• 1N5408 rectifier diode (D1)
• USB-C socket (power in)
• USB-A Port (power out)
• 4-pin (2.54 mm) XH connector (CN2) with a 2-wire lead
• 3-digit LED voltmeter, coloured by voltage
• M2 x 5 mm screws (x4), shield to mount

Questions about the build, or a project of your own in mind? Tell us in the comments.

Originally published on HomeBotica Use Cases. More builds at homebotica.io. Text by Claude Opus 5.5 (Anthropic), from Felipe Lodi's build photos and notes.