It looks like your transistor is not being turned on hard enough. We don’ need no steenkin’ transistor! Sign up using Facebook. When you look closely to the comparator symbol, some of you will recognize it as the Op-Amp Operational Amplifier symbol, so what make this comparator differ from its big brother; Op-Amps is designed to accept the analog signal and outputting the analog signal while the comparator only outputting the digital signal; although the ordinary Op-Amp could be used as the comparator such as the popular National Semiconductor LM quad Op-Amps, but the real comparator is designed to have a faster switching time comparing to the multipurpose Op-Amps. Welcome to our site! Now the 3rd function is the pump enhancer. The of course getting enough “amp” output to trigger the relay.

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By clicking “Post Your Answer”, you acknowledge that you have read our updated terms of servicellm339 policy and cookie policyand that your continued use of the website is subject to these policies. If you could help me with the schematics, it will be a mercy on me, Waiting for your help Cheers Dear.

Use say a 4.

lm “open collector” question — Parallax Forums

It does the same thing as Fig. Until that moment the output is low, so that. The type of capacitor is important but is not discussed on the brief datasheet from Relayy. Your first circuit won’t work. How to trigger a relay and LED when a certain threshold of 0. I’ve updated my answer. It provides hysteresis to the comparator, making it less susceptible to oscillation near the threshold point.


Working with the Comparator Circuit | ermicroblog

The 8K2 in the base of the power transistor will only give a base current of 1. As the resistance of R2 decreases in daylight Vref is higher than Vin thus the comparator id off. If so, what is a recommended value for that?

My circuit is near identical to this one: Do you want the 5V to trigger the relay, or the 2. Comments 19 Comments sorted by Date Added Votes. Post Edited Beau Schwabe Parallax: You will want to add the l339 that were suggested earlier such as the snubber, flyback diode, voltage divider and pull-up resistor on the output of the LM since it is open-collector.

Now, the question is, what value of R5 do we need if we want V to change by 0. Consult the LMN datasheet – there should be example circuits there that will help. An easy way to do this is with a lm3339 like an LM and some sort of a voltage reference. Now I know why I may have needed the Amp.

I have a bc transistor-what are disadvantage of using that-if any instead of a mosfet? Hi, currently I am using LM comparator to supply digital logic signal from IR sensor to my mcu…according to the principle of rslay, when the inverting input is greater than the non-inverting input, the output of the comparator will be low and vice versa…but the results that I obtianed is not really precise.


Help configuring NPN Amp switch for 12V Relay

This is not quite activated as yet, but it is fully “armed”. The output of the comparator probably won’t be able to drive a relay check the current requirement of the relay, and the output drive of the comparator.

Note that the schematic is for a comparator with push-pull output. This will impact the reference divider and hysteresis component value selections.

The non-inverting input is designed to use the 1. You could read more about LFR on this following articles:. Therefore using this formula, we could calculate the frequency of l3m39 LED blinker circuit above as follow: KyranF So the hysteresis makes it accurate to millivolts range or about 0.

I just looked at the datasheet more closely and it’s flippin terrible.

lm339 “open collector” question…

The main engine management, and the secondary Fuel Pump computer. To participate you need to register. There’s no reason that a single 2N shouldn’t be able to sink enough current to turn on your relay.

Otherwise, I think I have added everything as you said, and as given.