Hello all,
from a -12vdc to +12vdc voltage signal, I would like to be able to detect only the positive signal. example I want an LED to light up when there input signal is +.
would a comparator LM339 be suitable for this application?
there is only one input signal and It would need to be referenced with ground. instead of two different voltages .
question(s):
--> for the supply voltage on the comparator do i need to have vcc and vdd +5v (for example) and -5V? or just +5v to ground?
-->does it matter if the input signal (the signal i need to analyse) is greater than the supply voltage?
--> i read on the datasheet that each of the 4 open colector transistors sink up to 15 ma, could i just drive the LED + limiting resistor right from vcc, instead of using an outside transistor to drive it.
i have an 2n2222a in case i do need an outside transistor.
--> i read here on other posts that a pullup resistor is nedded,
--> i believe i read on the data sheet that voltages less than -0.3V should not be applied, is this only for differential between two different voltages or it is also for what i want to do?
--> in multisim i tried to simulate the circuit and it worked, when i supply a + signal i would see the LED on, the utput current was possitive, and viceversa with the - voltage the output current was negative and the transistor wouldnt turn on.The only thing I found weird was the fact that as i would increase the supply voltage more positive the output sinking current would go up up to .1A, and as expected when i soldered and tested the circuit, i messed up the LM339
I had the input voltage as my Vcc and Vdd was ground reference.
ANy help will be super apreciated.
from a -12vdc to +12vdc voltage signal, I would like to be able to detect only the positive signal. example I want an LED to light up when there input signal is +.
would a comparator LM339 be suitable for this application?
there is only one input signal and It would need to be referenced with ground. instead of two different voltages .
question(s):
--> for the supply voltage on the comparator do i need to have vcc and vdd +5v (for example) and -5V? or just +5v to ground?
-->does it matter if the input signal (the signal i need to analyse) is greater than the supply voltage?
--> i read on the datasheet that each of the 4 open colector transistors sink up to 15 ma, could i just drive the LED + limiting resistor right from vcc, instead of using an outside transistor to drive it.
i have an 2n2222a in case i do need an outside transistor.
--> i read here on other posts that a pullup resistor is nedded,
--> i believe i read on the data sheet that voltages less than -0.3V should not be applied, is this only for differential between two different voltages or it is also for what i want to do?
--> in multisim i tried to simulate the circuit and it worked, when i supply a + signal i would see the LED on, the utput current was possitive, and viceversa with the - voltage the output current was negative and the transistor wouldnt turn on.The only thing I found weird was the fact that as i would increase the supply voltage more positive the output sinking current would go up up to .1A, and as expected when i soldered and tested the circuit, i messed up the LM339
I had the input voltage as my Vcc and Vdd was ground reference.
ANy help will be super apreciated.