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"Simple Water Level Indicator"

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SunnyRulz

New Member
hi...!!
i am in my 3rd semester of Electrical Telecomm. Engineering...!!
Studying electronics-1...!!
A circuit i found on thre net is attached...!!
It uses transistor "BC548"...in my city this transtitor is not available...!!
I have got "C945" transistor...but the circuit is not working...instead the LED remains on ie. no effect of water level...!!
please help...what alterartions are required...??
 

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ericgibbs

Well-Known Member
Most Helpful Member
hi...!!
i am in my 3rd semester of Electrical Telecomm. Engineering...!!
Studying electronics-1...!!
A circuit i found on thre net is attached...!!
It uses transistor "BC548"...in my city this transtitor is not available...!!
I have got "C945" transistor...but the circuit is not working...instead the LED remains on ie. no effect of water level...!!
please help...what alterartions are required...??

hi,
Check the polarity of the battery and are BC548 and C945 the same npn/pnp.???

EDIT:
Do you have datasheet for the C945.?
 
Last edited:

ericgibbs

Well-Known Member
Most Helpful Member
Both are npn...!!

You say all the LEDs are lit when there is no water.?

I was concerned that you may have read the +9V text near the battery as +V to the left terminal.!


The other point, is the pinout of the C945. check it, in case its different to the BC
 
Last edited:

SunnyRulz

New Member
You say all the LEDs are lit when there is no water.?

I was concerned that you may have read the +9V text near the battery as +V to the left terminal.!


The other point, is the pinout of the C945. check it, in case its different to the BC
no...i have connected the battery as shown in the circuit diagram...ie. +ve terminal in to the water reservoir and to the led and -ve to the emitter...!
 

SunnyRulz

New Member
You say all the LEDs are lit when there is no water.?

I was concerned that you may have read the +9V text near the battery as +V to the left terminal.!


The other point, is the pinout of the C945. check it, in case its different to the BC

and the pin configuration is also different...!!
C945 has base at terminal 3,collector at 2 and emitter at 1...also catered for this too...!!
no result...!!
One of my senior said that resistance values and battery may also effect...??
 

Boncuk

New Member
Bottom view of BC548 from left to right: EBC, bottom view of 2SC945: BCE.

Also water has a relatively high resistance. Depending on the quality it is between several 100K to 10MΩ.

Even if the circuit works for some time it will quit sooner or later due to electrolytic effects using DC.

Boncuk
 

ericgibbs

Well-Known Member
Most Helpful Member
and the pin configuration is also different...!!
C945 has base at terminal 3,collector at 2 and emitter at 1...also catered for this too...!!
no result...!!
One of my senior said that resistance values and battery may also effect...??

In your opening post you say: .instead the LED remains on ie. no effect of water level...!!

In that case you have wired the circuit incorrectly or blown the transistors C to E s/c..!

I did ask.
You say all the LEDs are lit when there is no water.?
 
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