Hi! everyone...I am designing an automatic water level controller using digital Ic's like 7408,7432,7404. I dip a wire +vcc(8V) in water and voltage come out from water at the inputs of Ic's are 4V approx. I have connected a pull down resistor of 1K with Ic pin but my Ic does not picking this voltage level. can you tell me how to determine the proper value of pull down resistor.???its urgent...........plzzzzzzzzzzzzzz

 

The conductivity of clean water is fairly low so you will probably need some circuitry between the water your TTL logic.
Something like this:

 

The conductivity of clean water is fairly low so you will probably need some circuitry between the water your TTL logic.
Something like this:
View attachment 111236

thanks. can i use 2n3904 instead of 2n2222A

 

Yes, almost any NPN transistor will do.
If your electrodes in the water are very small and the water is very clean, that circuit may not work and you will need a darlington transistor to get it to work.

 

Try a high impedance input, 2N7000.
Max.

 

The conductivity of clean water is fairly low so you will probably need some circuitry between the water your TTL logic.
Something like this:
View attachment 111236

the circuit that you have attached provides output LOW when water sensor dips. but i need HIGH output when sensor dips. can i use this this circuit in common collector configuration.???

 

You can use your 7404 to invert the signal at Q1 collector from low to high...

 

You can use your 7404 to invert the signal at Q1 collector from low to high...

thank u so much. i used this circuit in common collector configuration and its working well....thanks again

 

Hi everyone! I want to drive a 5V circuit from sensor voltage 2V. plz help me to find the solution...thanks

 

Hi everyone! I want to drive a 5V circuit from sensor voltage 2V. plz help me to find the solution...thanks

You haven't provided enough information to even begin to help you find a solution.

What kind of sensor is it? Can we see a spec sheet?

What are you going to do with the 5 volts once you get it? Actuate a relay? Drive a motor? Provide an input signal to an Arduino input pin? Light an LED? How much current must the output source (or sink, or both)?

Is the 2 volt input signal a digital signal? Or an analog signal? If digital, what are the logic levels? 0 volts and 2 volts?

If analog, what is the input signal voltage range? 0 to 2 volts? Or some other voltage to 2 volts? How do you want the input range mapped to the output range? How accurate must it be?

The people here need to know all these things if they are to help you.

 

You haven't provided enough information to even begin to help you find a solution.

What kind of sensor is it? Can we see a spec sheet?

What are you going to do with the 5 volts once you get it? Actuate a relay? Drive a motor? Provide an input signal to an Arduino input pin? Light an LED? How much current must the output source (or sink, or both)?

Is the 2 volt input signal a digital signal? Or an analog signal? If digital, what are the logic levels? 0 volts and 2 volts?

If analog, what is the input signal voltage range? 0 to 2 volts? Or some other voltage to 2 volts? How do you want the input range mapped to the output range? How accurate must it be?

The people here need to know all these things if they are to help you.

thanks. Actually i want to drive 7404 hex inverter IC from sensor voltages (DC 2V).

 

Do you already have a 5V supply for the 7404?

 

thanks. Actually i want to drive 7404 hex inverter IC from sensor voltages (DC 2V).

What is the max amperage of the sensor output?

Are you driving only from the sensor "output" or do you want to supply 2V power to the sensor and use that same 2V power supply to feed a chip that boosts voltage up to 5V?

 

hi ali,
Is this for the water level sensor probe voltage as discussed in your earlier thread.?
E

 

What is the max amperage of the sensor output?

Are you driving only from the sensor "output" or do you want to supply 2V power to the sensor and use that same 2V power supply to feed a chip that boosts voltage up to 5V?

yup..i am directly driving the TTL from 2V

 

hi ali,
Is this for the water level sensor probe voltage as discussed in your earlier thread.?
E

yes you are absolutely right eric. i am talking about water level sensor probe. actually i have dip a 7 volt wire in water tank. but as water is a poor conductor so maximum voltages are being dropd across water and just 1.8~2V are coming from sensors. so i want to drive TTL to control the motor. but these 2V are not able to trigger the TTL

 

Do you have any reason to start another thread, but it has the same problem with the previous one?
Pull down resistor for coupling of water level sensor with 7408

If there is no any good reason then I will merge this thread to the previous one.

I saw two of your threads, but I still can't get the info for the sensor, do you have any info or link for it?

Why do you want to use the TTL(7404, 7408,7432) for this application, can you use other ic?

Could you draw a block diagram and label all the function and voltage?

 

so i want to drive TTL to control the motor. but these 2V are not able to trigger the TTL

hi ali,
TTL technology is not the best choice for your sensor, consider using high impedance input logic, such as CMOS.
A HEF4049 CMOS inverter would be a good choice.
Use caution when handling, avoid risk of static discharge damage of the 4049.
If you need guidance, please ask.

E

 

hi ali,
TTL technology is not the best choice for your sensor, consider using high impedance input logic, such as CMOS.
A HEF4049 CMOS inverter would be a good choice.
Use caution when handling, avoid risk of static discharge damage of the 4049.
If you need guidance, please ask.

E

thanks eric....your suggestion is valuable but the problem is that i have made hardware of my project so now a large change in circuit is impossible so therefor i m trying to play with this circuit. plz see the attached file. thanks

 

So what happened to "thank u so much. i used this circuit in common collector configuration and its working well....thanks again"?