[tog] Help with a circuit

Chris Hancock chs2048 at gmail.com
Fri Apr 26 13:43:07 CEST 2019

The sensor output is definitely linear with pressure? Why avoid digital
components? ; a single microcontroller is more adaptable and can replace a
complexity of discrete components; are you looking for low space usage, low
complexity, or low component count?

Should there be a delay in the led lighting if pressure changes are quick
(or sensor output is noisy)? Aka, how responsive does it need to be.

Should the led latch, or at least persist a little once lit (so it can be
seen if change is quick)?

I believe zener diodes are discretes that will trigger on a fixed voltage
threshold, but i think they latch to some degree (as in a lower voltage is
needed to close them than open them).

As for the difference between the circuits, maybe an op amp?


On Fri, 26 Apr 2019, 11:44 Stephen Church via tog, <tog at lists.tog.ie> wrote:

> Ok so heres a puzzle.
> I have two pressure sensors , they have a limear output that increases
> voltage from 0-4.5v depending on the pressure of the liquid theyre
> monitoring. I want to (in as analog a capacity as possible, no arduino
> etc... as simple a circuit as I can , have it that if the pressure
> difference between them is say greater than 10% that they trigger an output
> to an LED , im alright with that difference being variable , the pressure
> of the liquid may change at any point and thats fine as long as theyre
> roughly the same between sensors but it means I cant use a circuit that has
> an absolute threshold for either sensor.
> --------------------------------------------
> Stephen Church
> Director
> Stephen at IMESIreland.com
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