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# Water Pump (R385)

The R385 is a 6 V to 12 V DC diaphragm pump that self-primes, lifts water 3 m and moves 1 to 3 litres a minute for plant-watering projects.

Source page: https://www.tinkered.ai/components/water-pump

## In short

The R385 is a small DC diaphragm pump that runs from 6 V to 12 V, draws 0.5 A to 0.7 A under load and moves 1 to 3 L/min, with a 2 m suction lift and a 3 m head (Kitronik 2567 R385 pump product page). It is a brushed motor, so never wire it to a GPIO pin: power it from its own 6 V to 12 V supply and switch its negative lead with a logic-level MOSFET such as the IRLZ44N, with a 1N4007 flyback diode across the pump terminals and the supply ground tied to the microcontroller ground.

The R385 is the pump most Arduino and ESP32 irrigation builds use: a brushed DC motor driving a small diaphragm, with a barbed inlet and outlet for 6 mm silicone tube. Because it is a diaphragm pump it is self-priming: it can pull water up a dry suction line, up to a 2 m lift, and push it to a 3 m head (Kitronik 2567 product page). That lets the pump sit beside a tank instead of inside it, unlike a submersible pump.

Kitronik rates it at 6 V to 12 V DC, 0.5 A to 0.7 A under load and 1 to 3 L/min, with liquid up to 80 °C and a 2500 hour service life. Flow and pressure both rise with the applied voltage, so a PWM duty cycle on the switching transistor gives a simple flow control. The positive terminal is marked in red on the pump body (Kitronik 2567 product page).

Electrically the R385 is an inductive motor load. A microcontroller pin can supply a few tens of milliamps at most, so the pump always sits behind a driver: a logic-level N-channel MOSFET (IRLZ44N), an NPN power transistor, a motor driver or a relay. A flyback diode across the terminals absorbs the voltage spike the motor winding produces every time the switch opens. The pump also moves air, though far more loudly than it moves water.

## Agent rules

Follow these when you wire this part or write code for it.

- Do: Never drive from a GPIO: switch it with a MOSFET (logic-level, e.g. IRLZ44N, best for PWM) or a transistor/relay.
- Do: MOSFET needs a gate series resistor + a 10k gate pull-down; a floating gate switches randomly.
- Do: Flyback diode (1N4007) across the pump terminals: cathode to VCC, anode to GND (the drain/collector side). Back-EMF destroys the switch without it.
- Do: External supply (6-12V): the board's regulator can't source ~0.7A. Share the ground: external-PSU GND ↔ MCU GND is the one link between domains.
- Do: Drive with analogWrite for flow control, or plain on/off.
- Never: No bare pump straight to a pin, no missing flyback, no powering it from the board's 5V/3V3, no floating MOSFET gate.

## Pinout

| Pin | Function | Type |
| --- | --- | --- |
| VCC | Positive (+) | passive |
| GND | Negative (-) | passive |

## Wiring

| Water Pump (R385) | Connect to | Note |
| --- | --- | --- |
| GND | IRLZ44N MOSFET D |  |
| VCC | 9V Battery VCC | Pump + from the EXTERNAL supply |
| VCC | 1N4007 Diode cathode | Flyback |
| GND | 1N4007 Diode anode |  |

## Specifications

| Spec | Value | Source |
| --- | --- | --- |
| Supply voltage | 6 V to 12 V DC | Kitronik 2567 R385 water pump product page |
| Current under load | 0.5 A to 0.7 A | Kitronik 2567 R385 water pump product page |
| Flow rate | 1 to 3 L/min (rises with voltage) | Kitronik 2567 R385 water pump product page |
| Maximum suction lift | 2 m | Kitronik 2567 R385 water pump product page |
| Maximum head | 3 m | Kitronik 2567 R385 water pump product page |
| Liquid temperature | Up to 80 °C | Kitronik 2567 R385 water pump product page |
| Service life | 2500 hours | Kitronik 2567 R385 water pump product page |
| Tube | 6 mm inside, 8.5 mm outside diameter | Kitronik 2567 R385 water pump product page |
| Polarity | Positive terminal marked red | Kitronik 2567 R385 water pump product page |
| Weight | 35 g | Tinkered component registry |

## Circuit notes

- Power the pump from a separate 6 V to 12 V supply able to deliver at least 0.7 A, the top of its rated load current (Kitronik 2567 product page). A board's 5 V or 3.3 V pin and its USB port cannot carry that.
- Switch the pump on its negative lead with a logic-level N-channel MOSFET (IRLZ44N): drain to the pump's negative terminal, source to ground, the gate driven from a GPIO through a 220 Ω resistor with a 10 kΩ pull-down from gate to ground so the pump stays off while the board boots.
- Put a 1N4007 flyback diode across the pump terminals, cathode to the positive terminal (supply side), anode to the negative terminal (MOSFET drain). Without it the winding's turn-off spike can destroy the MOSFET.
- Join the pump supply's ground to the microcontroller's ground. That single link is what lets the gate signal switch the MOSFET.
- Use analogWrite() on the gate for flow control, since flow rises with voltage (Kitronik 2567 product page), or drive the pin HIGH and LOW for simple on/off watering.
- Keep the electronics above and away from the water line, and run the suction tube to the bottom of the reservoir so the pump does not run dry once the level drops.

## Common mistakes

- **Wiring the pump straight to a GPIO pin.** The pump draws 0.5 A to 0.7 A under load (Kitronik 2567 product page), far beyond any microcontroller pin. It either fails to start or damages the pin. Always switch it through a MOSFET, transistor, motor driver or relay.
- **Leaving out the flyback diode.** Every time the switch opens, the motor winding produces a voltage spike well above the supply. A 1N4007 across the pump terminals, cathode to positive, clamps it. Without the diode the MOSFET or transistor fails after some cycles.
- **Powering it from the board's 5 V pin.** An Arduino's 5 V rail and USB port are not sized for a 0.7 A motor with a high start-up surge. The board browns out and resets as the pump starts. Use a separate 6 V to 12 V supply and share only its ground.
- **Forgetting the common ground.** If the pump supply's ground is not tied to the microcontroller's ground, the gate voltage has no reference and the MOSFET never switches on reliably. Connect the two grounds.
- **Using a non-logic-level MOSFET.** A standard MOSFET such as the IRF520 or IRFZ44N barely turns on at 5 V and not at all at 3.3 V, so the pump runs weakly and the MOSFET heats up. Choose a logic-level part such as the IRLZ44N.

## Questions

### How do I connect an R385 water pump to an Arduino?

Power the pump from a 6 V to 12 V supply, its rated range (Kitronik 2567 product page), and switch its negative lead with an IRLZ44N MOSFET whose gate goes to a PWM pin through 220 Ω, with 10 kΩ from gate to ground. Add a 1N4007 across the pump terminals, cathode to positive, and join the supply ground to the Arduino ground.

### Can I run the R385 pump from an ESP32 or other 3.3 V board?

Yes, through a logic-level MOSFET that switches fully at 3.3 V on its gate, such as the IRLZ44N. The pump itself still needs its own 6 V to 12 V supply and 0.5 A to 0.7 A (Kitronik 2567 product page); only the gate signal comes from the 3.3 V GPIO, and the grounds are shared.

### How much current does the R385 pump draw?

Kitronik rates it at 0.5 A to 0.7 A under load (2567 product page). Size the supply and the switching transistor for at least that, with headroom for the start-up surge every brushed motor draws.

### Why does my Arduino reset when the pump starts?

The pump is drawing its start-up current from the same supply as the board, and the voltage dips below what the regulator needs. Give the pump its own 6 V to 12 V supply, keep only the grounds joined, and fit the 1N4007 flyback diode across the pump.

### Can the R385 lift water from a tank below it?

Yes. It is a self-priming diaphragm pump with a 2 m maximum suction lift and a 3 m maximum head (Kitronik 2567 product page), so it can sit beside or above the reservoir with its inlet tube reaching the bottom.

### How do I control the flow rate of the R385?

Flow rises with the applied voltage, from about 1 L/min toward 3 L/min across its 6 V to 12 V range (Kitronik 2567 product page). Drive the MOSFET gate with analogWrite() to lower the average voltage, or time how long the pump runs to dose a fixed volume.

## Related parts

- [L298N Motor Driver](https://www.tinkered.ai/components/l298n-stepper-driver.md): drives it
- [5V Relay](https://www.tinkered.ai/components/relay-5v.md): switches it
- [IRLZ44N MOSFET](https://www.tinkered.ai/components/mosfet-irlz44n.md): switches it
- [9V Battery](https://www.tinkered.ai/components/battery-9v.md): wired with it in its circuit
- [220Ω Resistor](https://www.tinkered.ai/components/resistor-220.md): wired with it in its circuit
- [10kΩ Resistor](https://www.tinkered.ai/components/resistor-10k.md): wired with it in its circuit

## Try it

Tinkered can design a circuit with the Water Pump (R385), draw its schematic and check it. Free to start at https://www.tinkered.ai.