Sensing small voltage changes

[Gaussx123]

The voltage signal from my radio receiver changes from 0.15V when switch is off to 0.3V when its on. I want to operate a 5V relay which switches on and off along with this switch. How can this be achieved?

 

[Torben]

The voltage signal from my radio receiver changes from 0.15V when switch is off to 0.3V when its on. I want to operate a 5V relay which switches on and off along with this switch. How can this be achieved?

Hi Gauss, and welcome to the forum.

Which voltage signal? Is this a clean on-off signal (it doesn't sound like it) or is it the output on e a headphone or line out?


Torben

 

[Gaussx123]

Thanx. No its the signal from my FUTABA radio receiver on my plane. Its actually the landing gear switch. It is a PWM signal with the pulsewidth changing from 1ms to 2ms when I operate the switch. But I also noticed that the voltage across the signal and the ground leads changes the way I have mentioned. I want to use the voltage change directly instead of change in pulsewidth.

 

[Torben]

Thanx. No its the signal from my FUTABA radio receiver on my plane. Its actually the landing gear switch. It is a PWM signal with the pulsewidth changing from 1ms to 2ms when I operate the switch. But I also noticed that the voltage across the signal and the ground leads changes the way I have mentioned. I want to use the voltage change directly instead of change in pulsewidth.

Is that voltage measured with a DMM? If so you are probably just seeing the average voltages as the PWM's duty cycle goes up.

It is probably possible to trigger just on the average voltage change, but I think it would be easier just to use the PWM output as it's intended to be used.


Torben

 

[Gaussx123]

Ya I tried to do that, I asked my professor and he gave me this circuit. I got an IC 7413 for the schmitt trigger but it is a 4-input device and I am not able to figure out how to use it. I have attached the document here. Also he has mentioned that I may have to use a flip flop but hasn't mentioned which one to use. Can you help me?

 

[ericgibbs]

Ya I tried to do that, I asked my professor and he gave me this circuit. I got an IC 7413 for the schmitt trigger but it is a 4-input device and I am not able to figure out how to use it. I have attached the document here. Also he has mentioned that I may have to use a flip flop but hasn't mentioned which one to use. Can you help me?

hi,
Look at this option.

EDIT: dwg edited to make clearer.

 

[Gaussx123]

I am a bit confused now..Are the 4013 and HEF4013 u have indicated the same or are they different? And what are the components that you have indicated in blue and what are their values? Also what's this one shot and what is the input to the one shot implementation circuit given in Page 3 of the file I have attached. Can anyone give the whole circuit in one piece..Also help me in using IC7413 because it has 4 inputs..

 

[ericgibbs]

I am a bit confused now..Are the 4013 and HEF4013 u have indicated the same or are they different? And what are the components that you have indicated in blue and what are their values? Also what's this one shot and what is the input to the one shot implementation circuit given in Page 3 of the file I have attached. Can anyone give the whole circuit in one piece..Also help me in using IC7413 because it has 4 inputs..

hi,
A HEF4013 type 'D' flip flop has two identical FF's in the same plastic body.

The Res and Cap are the monostable timing components.

A one shot is a monostable.

A 7413 ic is a quad dual input Schmitt NAND gate, why did you ask for a 'D' type FF.??