Voltage comparator and led binker with lm393 :-)

[voidptr]

hi

so i need to detect a slow dropping voltage and at a level stating to blink a led alarm

so i found a voltage comparator with hysteresis who i can adjust to my needs, now i still have one comparator left and i also found a nice led blinker that works fine on it own ...
so basically i want to start the blinker when the voltage comparator output go high .

my question is how to link the 2 circuits together, i kind of noob with all this

comparator



oscillator



circuits from this awesome page
**broken link removed**

 

[MikeMl]

The oscillator for the blinker is fine. If you want to detect a dropping voltage (such as a discharging battery), you can use a comparator, but the comparator has to compare the dropping voltage to a Reference voltage. The circuit you linked does not have a reference per say; a pot off a power supply does not a https://en.wikipedia.org/wiki/Voltage_reference make...

You need device that makes an absolute reference voltage such a Zener, an IC voltage reference like an LM431, or the ones listed here.

Here is my favorite "light a LED when a battery is discharged to xxx Volts" circuit.
Discussion here. If you want the LED to blink, buy a blinking LED

 

[ccurtis]

hi
my question is how to link the 2 circuits together, i kind of noob with all this

Hi there. Connect the cathode of a diode to the output of the Comparator stage and the anode of that diode to the - input of the comparator in the Oscillator stage. When the output of the Comparator stage is high the diode is reverse biased and the Oscillator stage operates. When the output of the Comparator stage is low, the diode is forward biased, preventing the capacitor in the Oscillator stage from charging above ≈0.6 volts and forcing the LED off. It's a good idea to add a 220 ohm resistor in series with the diode to limit the capacitor discharge current.

 

[voidptr]

Well after few thought about that, here what I did

The first comparator circuit work really fine, my reference come from a stabilized 5V, I don't really need great precision, so a voltage divider is fine.
Right now I'm using pots so I can adjust thing after each cycle of detection...
The comparator output drive a blinking led, for the moment it is much more simpler than with my oscillating second circuit
(those lead blink fast tho, 2 or 3 Hz)

Now I might planing another thing, the lm393 has 2 comparators, so I might build 2 levels of threshold, something like a warning, and a near power failure warning...

Thank for your comments, it is cool to explore few ideas