Does a diode delay the signal?

Using Arduino General Electronics
1

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?

2

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

3

billroy:
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.

4

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)

5

Works perfectly. Thanks!

6

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.

7