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HydroPaws is an Arduino Uno-based pet-water prototype that switches a pump on when a sensor detects a low bowl level. The project, published on Hackster.io on December 25, 2024, is a useful introduction to analog sensing, relay control, and simple closed-loop automation. It is not, however, a validated unattended pet-care appliance: the published design does not document overflow protection, pump runtime limits, electrical isolation, sanitation testing, or long-duration reliability.
What HydroPaws does
HydroPaws follows a simple control loop:
- Sense: an analog water-level sensor measures the bowl.
- Decide: the Arduino compares the reading with a threshold.
- Actuate: a relay switches a DC water pump.
- Repeat: the Arduino checks the sensor again after a delay.
Water-level sensor → Arduino Uno → relay module → water pumpThe project is designed to replenish a bowl when the sensed level is low. It does not measure how much a pet drinks, purify water, send remote alerts, guarantee hydration, or provide veterinary monitoring. Although the project description refers to dispensing based on time and water level, the published sketch performs periodic polling with a one-second delay; it does not implement clock-based scheduling or a real-time clock.
Original components
| Part | Purpose | Important limitation |
|---|---|---|
| Arduino Uno | Reads the sensor and controls the relay | The Uno revision is not specified |
| Water-level sensor | Produces an analog level reading | The sensor type, calibration, and waterproofing are unspecified |
| Relay module | Switches pump power | Relay logic polarity varies between modules |
| DC water pump | Moves water into the bowl | Voltage, current, flow rate, and head height are unspecified |
| Tubing | Carries water | Food-safe material and diameter are unspecified |
| 9V battery or DC supply | Provides power | A rectangular 9V battery may provide poor pump runtime |
| Breadboard and jumper wires | Prototype interconnections | Unsuitable for a permanent wet-area installation |
| Arduino IDE | Uploads code and displays readings | The project does not state an IDE version |
These are the components listed by the original project. Do not assume that any particular pump, sensor, or power supply is the original hardware when the page does not identify a model.
Wiring overview
The published wiring uses the following assignments:
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- Sensor VCC → Arduino 5V
- Sensor GND → Arduino GND
- Sensor signal → analog input A5
- Relay VCC → Arduino 5V
- Relay GND → Arduino GND
- Relay IN → digital pin D3
The pump’s positive supply path is switched through the relay’s COM and NO contacts. The pump’s negative terminal returns to the negative side of its supply. The relay’s NC contact is left unused.
Sensor signal ───────────────→ A5 Arduino D3 ─→ Relay IN
Sensor VCC ──────────────────→ 5V Arduino 5V ─→ Relay VCC
Sensor GND ──────────────────→ GND Arduino GND → Relay GND
Pump supply positive ────────→ COM
Relay NO ────────────────────→ Pump positive
Pump negative ────────────────→ Pump supply negativeThis arrangement is a conceptual redraw, not a substitute for checking the markings on your module. Many relay boards are active-low, meaning a LOW signal energizes the relay; others are active-high. The original sketch assumes active-low behavior because it initializes the relay LOW and uses LOW for “pump on.” Verify the relay with the pump disconnected before connecting the water system.
Power and wet-area precautions
- Match the pump supply voltage to the pump’s rating.
- Size the supply for startup current, not only normal running current.
- Use a separate, appropriately rated pump supply where practical.
- Keep mains voltage completely away from the bowl and pet-accessible area.
- Add a fuse or resettable overcurrent protection.
- Keep the Arduino and relay above the maximum splash and spill line.
- Replace breadboard wiring with secured, insulated connections for a permanent build.
If a transistor or MOSFET replaces the relay, use a correctly rated driver and a flyback diode across a brushed DC pump. That is an improved design choice, not a feature documented in the original HydroPaws project.
Rank #2
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- High-quality: Made of food-grade plastic materials, with all water-contact parts BPA-free. Durable, easy to operate and clean. The water-level window and blue LED light attract pets and make monitoring water levels simple. A convenient switch on the cord lets you easily turn the light on or off.
- Two flow designs: The Veken Pet Fountain has 2 modes: flower waterfall (faucet drinking) and the gentle fountain. The water streaming down the petals of the flower on the fountain will draw your pets attention and encourage animals to drink more often.
- 5 stages filtration system: In addition to circulating water to help keep it fresh, the 5-stage filtration system combines multi-layer filter media, coconut shell activated carbon, and a composite scale inhibitor to improve taste and reduce impurities.
- Ultra-quiet pump: This water fountain uses an ultra-quiet, low-energy pump designed for long-term use. To maintain smooth operation, clean the pump and replace filters every 1-2 weeks. Always keep water in the fountain when running to avoid damaging the pump.
What the published Arduino sketch does
The original code reads A5, prints the value at 9600 baud, and uses 300 as its stated threshold:
Do these 3 things before closing this tab:
1Fix the driver behind crashes, sound loss and screen glitches2Clear out junk files and repair common Windows errors3Scan for outdated or missing drivers - takes under a minuteconst int relayPin = 3;
const int waterLevelPin = A5;
int waterLevelThreshold = 300;
int waterLevel;
void setup() {
pinMode(relayPin, OUTPUT);
digitalWrite(relayPin, LOW);
Serial.begin(9600);
}
void loop() {
waterLevel = analogRead(waterLevelPin);
Serial.print("Water Level: ");
Serial.println(waterLevel);
if (waterLevel == 0) {
Serial.println("No water detected!");
Serial.println("Pump ON");
digitalWrite(relayPin, LOW);
} else if (waterLevel > waterLevelThreshold) {
Serial.println("Water is High");
Serial.println("Pump OFF");
digitalWrite(relayPin, HIGH);
} else if (waterLevel < waterLevelThreshold) {
Serial.println("Water is Low");
digitalWrite(relayPin, LOW);
Serial.println("Pump ON");
}
delay(1000);
}A reading below 300 turns the pump on, while a reading above 300 turns it off. A reading exactly equal to 300 matches none of the three conditional branches, so the relay simply retains its previous state.
The value 300 is not universal. Sensor readings depend on the sensor, bowl material, water chemistry, mounting position, wiring, and supply voltage. Record actual readings with the bowl empty, at the desired low level, and at the desired full level before choosing a threshold.
Rank #3
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Why the original control logic needs improvement
- No hysteresis: readings around 300 can make the relay switch repeatedly.
- No runtime limit: a failed sensor, empty reservoir, disconnected tube, or stuck relay could leave the pump running.
- Unsafe zero handling: zero may mean an empty bowl, disconnected sensor, broken wire, or failed sensor. The original code turns the pump on in every case.
- No filtering: a single noisy reading changes the pump state.
- No cooldown: frequent starts can increase relay and pump wear.
- No overflow sensor: a blocked outlet or incorrect level reading could flood the bowl.
- No source-reservoir sensor: bowl level alone cannot confirm that the pump has water available.
- No watchdog or restart strategy: a crash or brownout is not handled explicitly.
Calibrate before connecting the pump
- Upload the original sketch with the pump disconnected.
- Open the Arduino IDE Serial Monitor and select 9600 baud.
- Record readings with the sensor dry, submerged at the intended low level, and submerged at the intended full level.
- Repeat measurements several times and note how much they fluctuate.
- Choose thresholds from the measured installation rather than assuming 300 will work.
A better design uses separate thresholds: one to start filling and a higher one to stop. This gap is called hysteresis and prevents rapid switching near the boundary.
A safer example control strategy
The following is an editorial improvement, not the original HydroPaws source code. It assumes an active-low relay and still requires calibration:
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const int relayPin = 3;
const int waterLevelPin = A5;
const int pumpOnThreshold = 250;
const int pumpOffThreshold = 400;
const unsigned long maxPumpRunMs = 10000;
const unsigned long cooldownMs = 30000;
bool pumpRunning = false;
unsigned long pumpStartedAt = 0;
unsigned long lastPumpStoppedAt = 0;
void setPump(bool on) {
// Verify this polarity on your relay module.
digitalWrite(relayPin, on ? LOW : HIGH);
pumpRunning = on;
if (on) pumpStartedAt = millis();
else lastPumpStoppedAt = millis();
}
void setup() {
pinMode(relayPin, OUTPUT);
setPump(false);
Serial.begin(9600);
}
void loop() {
int level = analogRead(waterLevelPin);
bool invalid = (level <= 1 || level >= 1022);
if (invalid) {
setPump(false);
Serial.println("Sensor reading invalid; pump stopped.");
delay(1000);
return;
}
if (pumpRunning && millis() - pumpStartedAt >= maxPumpRunMs) {
setPump(false);
Serial.println("Maximum pump runtime reached.");
}
if (!pumpRunning && level < pumpOnThreshold &&
millis() - lastPumpStoppedAt >= cooldownMs) {
setPump(true);
Serial.println("Pump ON");
}
if (pumpRunning && level > pumpOffThreshold) {
setPump(false);
Serial.println("Pump OFF");
}
delay(250);
}This example adds hysteresis, invalid-reading shutdown, a maximum pump runtime, and a cooldown. A production design should also add independent protection against overflow and an empty source reservoir. For pet safety, ambiguous conditions should stop the pump rather than keep it running.
Rank #4
- Award-winning product: Veken is proud to be a 2023 Category Winner of the Pet Innovation Awards, an honor given to only the most forward-thinking products within the rapidly expanding Pet industry.
- High-quality: Made of food-grade materials, with all water-contact parts BPA-free. Durable, easy to operate and clean. The water-level window and blue LED light attract pets and make monitoring water levels simple. A convenient switch on the cord lets you easily turn the light on or off.
- Two flow designs: The Veken Pet Fountain has 2 modes: flower waterfall (faucet drinking) and the gentle fountain. The water streaming down the petals of the flower on the fountain will draw your pets attention and encourage animals to drink more often.
- 5 stages filtration system: In addition to circulating water to help keep it fresh, the 5-stage filtration system combines multi-layer filter media, coconut shell activated carbon, and a composite scale inhibitor to improve taste and reduce impurities.
- Ultra-quiet pump: This water fountain uses an ultra-quiet, low-energy pump designed for long-term use. To maintain smooth operation, clean the pump and replace filters every 1-2 weeks. Always keep water in the fountain when running to avoid damaging the pump.
Build and test sequence
- Confirm the pump’s rated voltage, running current, startup current, flow rate, and maximum head height.
- Choose tubing that fits securely and is suitable for contact with drinking water.
- Mount the sensor firmly at the intended bowl level.
- Bench-test the sensor and record readings.
- Test the relay with the pump disconnected, then verify which logic level means ON.
- Connect the pump through COM and NO, keeping its power wiring separate from signal wiring.
- Secure the reservoir, bowl, tubing, and pump so a pet cannot tip or chew them.
- Test with the pet absent: low level, full level, blocked tubing, empty reservoir, disconnected sensor, and power interruption.
- Disconnect power immediately if the bowl overflows or the pump runs unexpectedly.
- Enclose the electronics only after the circuit passes bench testing.
- Introduce the pet under supervision and keep a conventional backup bowl available.
Common failures
| Symptom | Likely causes | Recovery |
|---|---|---|
| Pump never starts | Wrong relay polarity, incorrect pin, poor supply, failed pump | Test the relay and pump separately; verify wiring and supply ratings |
| Pump runs continuously | Reversed threshold behavior, disconnected sensor, wrong active level | Print raw readings, stop the pump, and verify sensor and relay logic |
| Bowl overflows | Bad sensor position, siphoning, blocked outlet, stuck relay | Disconnect pump power and add an independent physical overflow limit |
| Reading stays at zero | Broken signal wire, incorrect sensor, poor sensor placement | Check continuity and voltage; do not assume zero means safe to pump |
| Relay chatters | Noise around threshold or weak supply | Add hysteresis, filtering, and a cooldown |
| Arduino resets | Pump startup noise, inadequate supply, loose wiring | Separate supplies where practical and improve grounding and suppression |
| Water turns cloudy or slimy | Stagnation, contamination, unsuitable materials, inadequate cleaning | Stop using the system, clean it, and provide fresh water |
Cleaning and pet-safety considerations
Water circulation does not automatically make water clean, and the Arduino project does not document filtration, sterilization, water-quality testing, or a sanitation schedule. Inspect the bowl, reservoir, tubing, pump, and sensor regularly; clean them according to the materials and pump manufacturer’s instructions; and replace any part that becomes cracked, slimy, corroded, or difficult to clean.
Keep cables inaccessible to chewing pets, use a stable bowl, keep electronics above splash level, and never make HydroPaws the sole water source until it has demonstrated reliable operation under supervised testing. If the pump stops, the reservoir empties, or the controller reports an invalid reading, provide fresh water manually.
Component choices and trade-offs
| Choice | Advantage | Trade-off |
|---|---|---|
| Resistive level sensor | Cheap and simple | Can corrode, drift, or foul during continuous contact |
| Float switch | Simple threshold behavior | Mechanical wear and mounting requirements |
| Non-contact sensor | Less exposure to water | Higher cost and sensitivity to bowl geometry |
| Relay | Easy to understand and provides load switching | Mechanical wear, clicking, and contact arcing |
| MOSFET driver | Quiet and efficient for DC pumps | Requires correct component selection and suppression |
| 9V battery | Portable | Often a poor choice for pump runtime and startup current |
| Breadboard | Fast prototyping | Vulnerable to moisture, vibration, and loose connections |
Is HydroPaws right for you?
HydroPaws is a good educational project if your goal is to learn analog inputs, threshold control, relays, pumps, and fault handling. It can also serve as a supervised proof of concept.
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- The Fresh Water They Deserve: 4-layer filtration removes fur, heavy metals, and odors. The cat water fountain stainless steel tray is non-toxic and hygienic. For best performance, we recommend using PETLIBRO official replacement filters designed specifically for this fountain.
- Designed for Pets: Choose continuous or timed water flow modes in the Cat Fountains for Drinking app based on your pet's needs. Stainless steel cat water fountain's anti-knockover design can stand up to curious paws and frisky drinkers. Whisper-quiet operation of pet water fountain means you can even put it where you sleep.
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It is a poor fit if a pet must depend on it as the only water source while you are away, if the device will be installed outdoors without a suitable enclosure, or if you need certified safety, remote alerts, consumption tracking, or filtration. A manual bowl is simpler; a commercial fountain is easier to deploy; a float-valve waterer may reduce electronics; and an ESP32-based redesign could add connectivity, but each option introduces its own maintenance and failure modes.
Do not confuse the Arduino project with commercial HydroPaws products
Several unrelated products use the HydroPaws name, including commercial fountains at tryhydropaws.com, a portable dispenser at hydropaws.store, and a fountain listing at Zanvon. The available sources do not establish that these products share the Arduino project’s design, maker, company, or hardware. Their filtration, safety, guarantee, and health-related statements should not be transferred to the DIY build.
The Bottom Line
Bottom line: HydroPaws is a clear and approachable Arduino automation prototype, but the published version should be treated as a supervised educational build—not as a completely unattended or veterinary-grade hydration system. Add calibration, hysteresis, runtime limits, fault detection, overflow protection, secure enclosure and wiring, reliable power, and a backup water source before considering regular pet use.
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