AVR-Chat

OWEN-A wrote:

> Thank you for the suggestion Ralph, the application is for the sudden loss
> of coolant from an engine, detecting the presence or absence of coolant in
> the top tank of a radiator for this the stainless steel probe works well and
> is very robust, an earlier system used a pressure switch to detect loss of
> pressure but this was not reliable.
> The pressure sensor you suggest would work but may not be able to withstand
> the vibration and heat which was the case with the pressure switch.
> I was thinking that an avr may be able to perform a simular function to the
> LM1830 by generating a pulse train on one pin and coupling this to the probe
> with a capacitor and using the inbuilt comparator. I was wondering if anyone
> had tried this.
> 
> Thanking you.
> Owen.    

On a car, you could use a missing pulse detector with a 556, one half to 
generate the pulse the other to detect the missing pulse, when the 
collant is up to level, it will miss pulses due to being shorted to 
ground, but when it goes low, after a short delay, the pulse is sensed 
and the output of the second half will swing, and can be used to turn on 
a led / buzzer.

Could do the same with an AVR eg Tiny15 (just remember to put a resistor 
in series with the output and sense on the radiator side of the resistor 
(470R or there about should over ride the leakage current)

Regards,

Kat.

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