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Fluidlever indicator

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TheSwede73

New Member
Hi!

I need some assistance with a new project, just bought a campingtrailer and of course i want it to be filled with electronics :)
So i need a fluidlevel-indicator, just a simple one, showing the level with Led's.

Wires placed in the tanks, lighting up led's as the level rises or sinks, no fancy electronic sensors this time just the basic, as simple as possible..

I saw one somewhere just using transistors, resistors and led's i think, and when water shorts the wires its indicated by led's.

It should be pretty easy to make, but i need some guidande.

Thanks!!:)
 

ericgibbs

Well-Known Member
Most Helpful Member
Hi!

I need some assistance with a new project, just bought a campingtrailer and of course i want it to be filled with electronics :)
So i need a fluidlevel-indicator, just a simple one, showing the level with Led's.

Wires placed in the tanks, lighting up led's as the level rises or sinks, no fancy electronic sensors this time just the basic, as simple as possible..

I saw one somewhere just using transistors, resistors and led's i think, and when water shorts the wires its indicated by led's.

It should be pretty easy to make, but i need some guidande.

Thanks!!:)
hi.
There are a number of water level detectors on the web.
I Googled water level-indicator

Water-level Indicator - RED - Page95
 

Bob Scott

New Member
Junk yards must be full of wrecks with fuel level sending units inside the fuel tanks. Marinas have them for boats. Hmm?
 

Boncuk

New Member
Don't use DC for sensing! (Electrolytic destruction) Sooner or later your circuit will be ready for the junkyard, too.

Boncuk
 

jbeng

Member
I've used this circuit before... You can add (pretty much) as many channels as you want, mine had 10. It uses a probe arrangement like the circuit Eric posted, but unlike that one, the circuit gives a bar graph display not a moving dot.
If you put an n.o. pushbutton switch in the +12v supply line, electrolytic action like Boncuk mentioned is minimized and battery current is only consumed when the button is pushed. Each led uses about 5mA when it's on but that would be if you ran it on 12 volts. I used a 9v battery, so the current was less. You can use any n-channel MOSFET that is the right size for the load, I used BSS123 in a SOT-3 package as the design was SMD. I would also recommend a suitable fuse in the supply line as well.

Jeff
 

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TheSwede73

New Member
Thanks!

i just dont know what all the components in the picture are... im a total newbie with doing electronics without a ready made kit :)
Please decribe it as you would to a child..haha :)

Thanks again!
 

jbeng

Member
In each channel, there's two resistors, an LED and an N-channel MOSFET. The 2K res limits current thru the LED and the MOSFET. The 1M pulls the MOSFET gate to ground when no water is between the probe and probe common, keeping it turned off. When water is between the probe and probe common, the resistance of the water forms a voltage divider with the 1M. The water's resistance is (most likely) quite a bit lower than 1M, so the gate voltage goes high enough to turn the MOSFET on and current flows thru the LED.

Jeff
 
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jbeng

Member
1M = 1 megohm (1,000,000 ohm) resistor.

I've also used a single channel version of this circuit (with a larger FET) to act as a "overfull" monitor for a basement sump. It has already prevented my brother's basement from getting flooded due a malfunction of the float switch on the pump. Ten bucks well spent.

Jeff
 
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