Water Level Sensor Circuit

In summary, the circuit should work, but it doesn't because the input to the 7407 hex buffer is logic 1, which will lead to its output as logic 1 also. The solution is to add a 270ohm resistor from the LED anode to the 5V supply, so that the output will be +5V regardless of input logic.
  • #1
cyeokpeng
69
0
Hi,

Theoertically, this circuit should work, because when water reaches the probe sensor (Level n), it will have a finite conductance and the input to the 7407 hex buffer will register as logic 1. This will lead to its output as logic 1 also, and since 7407 uses positive logic convenetion, this will mean H voltage, and will light up the LED. But I test it out on breadboard, and it doesn't work. I have checked and checked the connections again, but they are all correct.

Is there anything wrong with the design?
 

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  • #2
i tried to d/L your circuit but did not see a circuit, i must be doing something wrong , it opened in wordpad ??
maybe if you post it as a jpg i could see it..
 
  • #3
It is a Microsoft Word document, needs MSWord to open it.

Anyway, the diagram is drawn using MSword. I cannot upload the original circuit diagram drawn using Circuitmaker becuase it is too big in size and resolution for this forum to allow.
 
  • #4
A quick look at the datasheet reveals that the 7407 is an Open Collector device, so it won't quite work right in your circuit.

Keep the circuit as it is, but try adding a 270ohm resistor from the LED anode to the 5V supply. Should work then.
 
  • #5
Sorry, just to ask, what do you mean by open collector device?

If I connect the LED anode to the +5V supply, wouldn't it always light up regardless of whether the input logic is 1 or 0?
 
  • #6
An open collector device is not capable of driving its output high. It's only capable of driving its output low.

If you connect a resistor to +5V -- called a "pull-up" resistor -- the output will then be +5V as long as the chip is not pulling it low.

- Warren
 
  • #7
Thanks, it finally worked.

The trick is to find the correct value of the pull down resistor at the input pin. I decide to use 7404 hex NOT gate, suince it is in abundance. Only if the correct value of the pull down resistor (4.7kohms) at the input will switch between 0.9V (Logic 0) when no water AND 1.3V (Logic 1) when there is water. Of course at the output pin, I use a 3.3kohms pull down resistor and the anode of the LED directly connected to +5V supply to drive the LED.

A quick check using the multimeter revealed

No water: output voltage = 3.54V
so the voltage difference between +5V supply and 3.54V is
not enough to drive the LED.
Water present: output voltage = 2.46V
so the voltage difference between +5V supply and 2.46V is
able drive the LED.

The forward conducting voltage for most normal green LEDs = 2.1V

Again Thanks you very much Chroot and delta!
 
  • #8
need help for simple water level circuit

hello all...i have a little problem now...i hope you all can help me out from this troublesome...if some of you here can give me a water level circuit diagram...i really appreciate it very much...10q..
 
  • #9
cyeokpeng, could you put your finished circuit after you put the 7404 hex NOT gate in, on the site please
 
  • #10
hi buddies
just i want to ask

i know that water breaks at 1.23 V to oxygen and hydrogen and what you wrote in the diagram is 5 V , so i am asking if this water level will affect water and could break it or how it works i am just confused ?
 

1. What is a water level sensor circuit?

A water level sensor circuit is a type of electronic circuit that is used to detect and measure the level of water in a container or tank. It typically consists of a sensor, a control unit, and an output display or alarm.

2. How does a water level sensor circuit work?

A water level sensor circuit works by using a sensor, such as a float switch or a conductive probe, to detect changes in the water level. The sensor sends a signal to the control unit, which then processes the signal and triggers an output, such as turning on a pump or sounding an alarm.

3. What are the applications of a water level sensor circuit?

A water level sensor circuit has many applications, including in industrial processes, agriculture, and household utilities. Some examples include monitoring water levels in tanks and reservoirs, controlling water levels in irrigation systems, and detecting leaks in plumbing systems.

4. How accurate is a water level sensor circuit?

The accuracy of a water level sensor circuit depends on several factors, such as the type of sensor used, the calibration of the circuit, and the environmental conditions. Generally, most water level sensor circuits have a high level of accuracy, with some models capable of detecting water levels to within a few millimeters.

5. Are there different types of water level sensor circuits?

Yes, there are different types of water level sensor circuits based on the type of sensor used, the technology used, and the intended application. Some common types include float switches, ultrasonic sensors, and capacitive sensors. Each type has its own advantages and limitations, so it is important to choose the right type for your specific needs.

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