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Topic: Does a diode delay the signal? (Read 431 times) previous topic - next topic

marian42

Hi,

I have a project with two ultrasonic distance sensors.
Each has a trigger and echo pin. The trigger pin is pulsed and the Arduino measures the time until the echo pin goes HIGH.

Since I dont measure both at the same time, I only need to know if echo1 or echo2 is HIGH.
I assume connecting two to one pin will shortcut them if one is HIGH and the other is LOW.
So I put two diodes between them to prevent that. This delayes the echo signal so I cant calculate the distance anymore.

Is there a way to get the two inputs on one pin without buying additional hardware?

billroy

Combining two inputs on one pin in this way is very creative but unlikely to get you what you want.

Can you explain why it is a problem to code for echo returns on the two separate inputs?

-br

marian42

Can you explain why it is a problem to code for echo returns on the two separate inputs?

Its not a problem, I was just wondering if I could save pins.

MarkT

google for "wired OR" and "wired AND" gates...  With diode logic you will need a pull up or pull down resistor as
appropriate (this probably explains your impression of a delay)
[ I won't respond to messages, use the forum please ]


oric_dan

Diodes such as 1N4148,1N914 are very fast, and won't delay signals as slow as those here. However,
if the R is missing from the wired-OR diode ckt, then the diodes are not really turning on. Try
R = 4.7K or 10K.

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