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Capacitative water level sensor help please

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Wolstan Dixie

New Member
I have bought a Chinese contactless water level sensor. The only documentation is attached:






It works very well - the LED comes on correctly, but I want it to control a motorised valve. Presumably I need to connect a relay to Pin 2. I would appreciate help on how to do this.

Thanks,

Wolstan Dixie
 

alec_t

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Most Helpful Member
Welcome to ETO.
The usual guessing game with Chenglish datasheets :). What is the difference between 'working voltage' and 'exterior working voltage'? My guess is that the device needs a 5V supply (Vcc) but has an open drain/collector output which can withstand up to 24V (Vdd).
Depending on the valve properties you may be able to use a MOSFET to control it (rather than a current-hungry relay).
What control input characteristics does the valve have?
What supply voltage does the valve need?
Does the device output go low when water is present or absent?
 

Wolstan Dixie

New Member
Thanks for this - alas my electronic skills are limited to assembling Veleman kits. I'm glad you are puzzled, I was too - I thought it was just me!
I am using a nominal 12vdc 500mA supply. With no water the output on pin 2 is high (+13v), with water, low (0v).
I don't yet have a motorised valve, I was assuming that once I got it to operate a relay I could do anything I wanted - actually for a start just to ring a bell.
The great advantage of this module should be that as it is contactless it won't suffer corrosion, or need special drillings - it can just be glued to the outside of the plastic tank.
 

alec_t

Well-Known Member
Most Helpful Member
The spec says maximum 30mA drive, which is perhaps marginal for a heavy-duty relay coil (but no problem for a SSR - solid state relay). Without knowing the peak current draw of the valve it's difficult to advise whether a mechanical relay or solid-state switching is the better choice.
 

Pommie

Well-Known Member
Most Helpful Member
I note that the current is for a low signal only, maybe suggesting an open collector type output.

Mike
 

AnalogKid

Well-Known Member
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Hard to speculate about a switch or driver without knowing *something* about what you are switching or driving.

What are the power requirements of the motorized valve?
What power supply voltages do you have available for both the sensor and the valve?

ak
 

Wolstan Dixie

New Member
As I explained, the motorised valve is stage two - let's assume for simplicity I just want to operate a relay - one I have to hand cannibalised from a 9V circuit is marked

SRU-12VDC-SD-C
15A 125AC |10A 240VDC
10A 28VDC| 10A 28VDC

I can buy any suitable power supply, though for convenience it would be neater to use the one powering the sensor - 12VDC 500mA.

A sketch circuit diagram would be most appreciated.
 

AnalogKid

Well-Known Member
Most Helpful Member
The 30 mA output current (assumed sinking low) is enough to turn on a small PNP power transistor like a TIP30 or TIP32 with a 1 K base resistor. The transistor can drive a relay coil that has one end tied to GND by pulling the other end up to +12 V.

ak
 
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