rperreta
Posts: 2
Joined: Sun Apr 22, 2018 10:45 pm

GPIO's

Sun Apr 22, 2018 10:49 pm

Hi all,

I need to do a quick continuity test. I want to ground wires to quickly close then open immediately. What GPIO's can I trigger using C/Python to do this?

Ex: I have lets say an LED with power connected and the ground wire is open. I want to trigger from the app a quick close and open like 1 or 2 ms interval. Any help would be greatly appreciated..

Kind regards,

Rich.

nios2
Posts: 37
Joined: Mon Mar 12, 2018 3:22 am

Re: GPIO's

Mon Apr 23, 2018 9:22 am

In terms of switching speed I think that all of the GPIOs have around the same same response time. If you blinked an LED for 1-2 ms I doubt that the human eye would sense such a short duration.

When you say that one end of the LED is open, do you mean floating. i.e. not connected to either high or low? Configuring a GPIO pin as an input and switching off both pull-up and pull down would give this high impedance effect. Then switching the GPIO to output driving low would illuminate the LED (with the anode at logic high and the cathode on the GPIO pin (plus the current limiting resistor).

Are you able to describe your application in a little more detail?

hippy
Posts: 2866
Joined: Fri Sep 09, 2011 10:34 pm
Location: UK

Re: GPIO's

Mon Apr 23, 2018 1:07 pm

nios2 wrote:
Mon Apr 23, 2018 9:22 am
If you blinked an LED for 1-2 ms I doubt that the human eye would sense such a short duration.
You might be quite surprised though brightness does come into it. Flashing a LED off for a short duration is harder to detect than being flashed on because of persistence of vision.

boyoh
Posts: 1123
Joined: Fri Nov 23, 2012 3:30 pm
Location: Selby. North Yorkshire .UK

Re: GPIO's

Mon Apr 23, 2018 7:35 pm

rperreta wrote:
Sun Apr 22, 2018 10:49 pm
Hi all,

I need to do a quick continuity test. I want to ground wires to quickly close then open immediately. What GPIO's can I trigger using C/Python to do this?

Ex: I have lets say an LED with power connected and the ground wire is open. I want to trigger from the app a quick close and open like 1 or 2 ms interval. Any help would be greatly appreciated..

Kind regards,

Rich.
BOYOH
Testing the flashing of a LED for very short period , you have to take in to account
that there is no after glow with a LED. If there was there would be no Optic Fiber
signals, .You could use a LDR to sense the very short flash,and record It.

Regards BoyOh
BoyOh ( Selby, North Yorkshire.UK)
Some Times Right Some Times Wrong

rperreta
Posts: 2
Joined: Sun Apr 22, 2018 10:45 pm

Re: GPIO's

Mon Apr 30, 2018 9:06 pm

Sorry for the confusion... I used an LED as an example... What I'm trying to do is use the GPIO's to trigger a switch close/open. Here's what I want to do.

GND [ / ] GND (Open)
GND [ -- ] GND (Closed) 2 -3 ms
GND [ / ] GND Open

I basically want to simulate touching two wires together to create almost like a trigger effect then return to open state.

Hope this clears is up a little...

thanks
-Rich

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