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Postby Dave » Tue Jan 17, 2017 5:34 pm

bowen73 wrote:ok, getting a little closer...

the laser triggeris giving out .06v according to the tester, so thats why it appears to be triggering constantly. when it triggers it sends a 12v signal.

so what wouldbe the next step?? i was thinking a 12v relay so it wont allow it to pass the .06v as a non triggered current the maybe a resistor to set it down to 5v from 12v once the relay has triggered??

any idea which relay/resistor i would need?


You'll need to look into setting up a little pull-down-resistor to hold the voltage at 0V when its not triggered. - http://playground.arduino.cc/CommonTopi ... wnResistor

Look into a voltage divider to convert that 12v down to 3v3, do not use 5v, that will damage your Pi as well! - https://learn.sparkfun.com/tutorials/voltage-dividers

If you've already put 12v onto one of the GPIO pins of the Pi, I wouldn't be surprised if you've damaged that pin, and if not others.

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Postby bowen73 » Tue Jan 17, 2017 8:14 pm

Dave wrote:
bowen73 wrote:ok, getting a little closer...

the laser triggeris giving out .06v according to the tester, so thats why it appears to be triggering constantly. when it triggers it sends a 12v signal.

so what wouldbe the next step?? i was thinking a 12v relay so it wont allow it to pass the .06v as a non triggered current the maybe a resistor to set it down to 5v from 12v once the relay has triggered??

any idea which relay/resistor i would need?


You'll need to look into setting up a little pull-down-resistor to hold the voltage at 0V when its not triggered. - http://playground.arduino.cc/CommonTopi ... wnResistor

Look into a voltage divider to convert that 12v down to 3v3, do not use 5v, that will damage your Pi as well! - https://learn.sparkfun.com/tutorials/voltage-dividers

If you've already put 12v onto one of the GPIO pins of the Pi, I wouldn't be surprised if you've damaged that pin, and if not others.


Brilliant thanks, i'll take a look at them.

lady luck may have been on my side though...i connected a PIR up to the pi just to make sure everything else was ok, and it works:-) there is roughly about a 20sec delay from when it finishes recording to when i can trigger it again. i dont think its the pir as when the laser was connected it ran the videa around the same amount of time. but i'll look into that once i get the voltage stopped and reduced.when triggered.

i thought the pi3 was 3.3 to 5v? but if i try get it down to 3.3 then at least i'm playing safe :-)

cheers

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Postby Dave » Wed Jan 18, 2017 9:31 am

You can draw 5v from the 5V pins on the GPIO of the Pi, but when you want to use the GPIO's as INPUTs (so you are supplying voltage to the pin) they are limited to 3v3.

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Postby bowen73 » Thu Jan 19, 2017 4:01 pm

that works perfectly now, im all relay'd up, thanks. :-)

the next bit is, now i have that triggered and recording, how can i have it send a signal to another pi over the network that once triggered then other pi starts to record something like 30 seconds after the trigger?

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Postby BMS Doug » Fri Jan 20, 2017 10:38 am

bowen73 wrote:how can i have it send a signal to another pi over the network that once triggered then other pi starts to record something like 30 seconds after the trigger?


I've seen MQTT recommended in the past, lightweight topic subscription package

Install broker and client onto one Pi and client onto the other one.

https://learn.adafruit.com/diy-esp8266-home-security-with-lua-and-mqtt/configuring-mqtt-on-the-raspberry-pi

apparently this debian version of Mosquito is better than the default Raspbian package.
http://mosquitto.org/2013/01/mosquitto-debian-repository/

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