Hello,
I want to connect to arduino (5V) a rain sensor (tiping bucket with reed switch) and an anemometer.
I have seen that in some schemes they use protection diodes type TVS at the input of the sensors. In one case the diodes are 250mA/100V
Are these values critical?
TVS diode protection on inputs...
curro92:
Are these values critical?
Not particularly, but you are using them to try and protect the input pin from voltages over 5v (or under GND), so slapping some TVS diodes which start 'protecting' at 100v is not the best choice.
Something like this would be a lot better choice:
ESD Suppressors / TVS Diodes TVS AXIAL 9.4V 400W
The important parameter is: Working Voltage: 9.4 V, which you want to be above 5v (in this case)
(there are devices with working voltages closer to 5v, but not in stock at Mouser)
Yours,
TonyWilk
P.S. The diagram you show is not complete, there needs to be some pullup for the reed switch and a bit of isolation for the input pin. Ideally you also need a bidirectional TVS diode to protect the supply rails (for when those input TVS diodes do their thing and conduct a voltage spike... it has to go somewhere!)
e.g. Diagram:
