Best Way to Protect 12V 6A Water Pump Sensors: MOSFET vs Inrush Current Limiter?

Hello!

Here I am working on a system that involves a few electrical components controlling and driving a DC 12v Water pump (max current 6amps). My desire is for a capacitive water level sensor to kick on the pump when a specific level of water is detected, and alternately shut off the pump when the water level is too low. Furthermore, an integrated water flow reed switch shuts off the pump when no flow is registered on a parallel piping system.

My realization is that the inrush current (and operation current) of the pump burns out both the capacitive sensor and the reed switch. To combat the operation (and inrush) current of the pump, I have discovered two possible solutions: Inrush Current Limiters (ICL) or MOSFET.

Questions:

1) Which of these solutions is simplest and least expensive to implement?
2) Are there other solutions that I should investigate?
3) As far as the rating of MOSFETs and ICLs go, would I have to purchase different MOSFETs/ICLs to protect the different individual components (sensor and switch)?
4) And lastly, if I've supplied enough information, which MOSFET/ICL would I need?

 

Links and tech data of the components I am using: 

Pump 

Amp draw: 3.6A (max 6A)
Voltage: 12vdc

Capacitive water level sensor 

Rated operational current (I_e): Continuous ≤ 50 mA
No-load supply current (I_o): ≤ 10 mA
Voltage: 10-30vdc

Flow Switch  

Current: 0.08A
Working Voltage: 12-130vdc

I am not married to any of the components, however, I am content with the operation of the flojet pump. I hope the dilemma is clear enough - any help would be much appreciated.

Best

A wiring diagram would help. The sensors should not be carrying the motor current
so I don't see how they can be be damaged by the inrush current, which probably results in a momentary drop in voltage in the system. Turn off may be a problem, so put a reverse biased diode directly across the motor. Simplest approach is probably relays if you need to switch a higher current from low current sensors, they are cheap, robust, and simple to wire up,
cheers,
Richard

Thank you Richard! I am working on the wiring diagram now - using the relay solution. Either an SSR or electromagnetic relay is what I am searching for. However, I am unsure on how to select the appropriate relay.

If the pump draws up to 6A at 12vdc, would a 10A 3-30vDC relay work? Electronics are fascinating to me, yet I often find myself confused... Thank you once again for the help!

Get relays contacts rated for an inductive load (motor), which is normally specified in the data sheets (surge rating), the turn on current can be five to ten times the running current. The coil parameters need to fall within the current and voltages that the sensors run at,
cheers,
Richard

I understand - thank you Richard!


Quick question regarding the coil parameters... If the voltage is 12v DC and the *current is 80mA* of the sensors, but the relay's coil parameters *trigger current is 50mA*, would this jeopardize the relay? I am having a difficult time trying to find an appropriate relay with a trigger current of 80mA.

The coil will only draw the current it needs, look at the coil resistance, if the coil rating is 12V DC, then at the same time it will either have a current draw at that voltage, or a resistance value, so current = voltage/resistance. As long as the current drawn is less than the current that the sensor can supply(which will be specified as a maximum current), then you are OK. Normally you use the lowest current relay coil(highest resistance) you can find, since it reduces power consumption for the whole system,
cheers,
Richard