Post Your Answer Discard By clicking “Post Your Answer”, you acknowledge that you have read our updated terms of service , privacy policy and cookie policy , and that your continued use of the website is subject to these policies. So, how if I want my infrared sensor to detect black colour surface? Is it to reduce noise? Otherwise, I think I have added everything as you said, and as given. Now, are you still using a 10K pullup resistor? Sign up using Facebook.

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The relay is a standard Bosch automotive relay.

Also, are you saying that I could eliminate the NPN alltogether by upgrading the comparator?? Quick Links Categories Recent Discussions.

Working with the Comparator Circuit | ermicroblog

Therefore by applying the upper and lower threshold formula, we could get the hysteresis voltage as follow:. LM based 4-bit voltage indicator – click picture for full size. Oct 2, 5, 1, You will also see a Lm3339 relay on the left that is always supplying the fuel pump enhancer a 12V input.

Another option, which takes better advantage of the comparator’s open-collector output would be to use a PNP e. Of course this depends on what load you are driving as well. An easy way to do this is with a comparator like an LM and some sort of a voltage reference. The output of the comparator goes to ground with a minimum current of only 6mA.


Help configuring NPN Amp switch for 12V Relay

PS what is a snubber? Also–“Audioguru”can you recommend a different Comparator that may better handle this current? AND now I can with confidence take voltage readings and figure the current: By your description, you’re using an NTC thermistor.

KyranF 5, 8 As you could see from the video this circuit is working nicely. Automotive or not, that is what you need to know to select the proper device to drive it.

So the “referance” voltage should relya higher than lets say 3. So I am asking this question on here. NTE parts are very expensive replacements for real parts. Let us know how things work out.

That is where I am having problems configuring this NPN into the schematic. Substituting the R1 R3 R1 parallel R3 inside this equation we will get this following formula:.

Articles Top Articles Search resources. I already upvoted, but it would be great if you could reay where the k value for the hysteresis resistor comes from. The non-inverting input relah designed to use the 1. The power supply for the circuit A is isolated from B power supply meaning it does not power B from which the two input wires come from.


Comparator Circuits Examples Tutorial

Tommy, Before you go to all that trouble, take kjennejohn’s advice and replace the 10K pullup on the comparator with something smaller. I could easily do this with a microcontroller, but this seems relau just too simple of a project to waste one on.

I am only working off the “output” signal from the main computer going to the fuel pump computer. Say turn off a blower motor in a green house felay the sun goes down. I just measured the coil and it reads 90 ohms.

The series resistor is not required. Otherwise, depending on things like the output current and temperature, may cause the transistor to go into conduction prematurely.