[TriEmbed] Raspberry Pi & Object Detection

[Scott Hall]

Sounds like you are building the basics for an HO hump yard -- at least the club
members at NRVMRRC would love to see the demonstration.  (Combine it with an
auto-decoupler and push-and-shove moves and you're almost there).  They're in
the process of building a new yard module for the club layout.  (you'll need to
detect a modulated reflected signal from a barcode on each car)

There was an article in last month's Circuit Cellar or Elektor magazine about
using an IR LED as a photosensor.  The author also compared and contrasted
phototransistors, LED's, photodiodes and photosensitive resisters as sensors.

Basically you need to bias the LED, and amplify the result through a high-gain
op amp.  Then a second-stage op amp uses a comparator to give you your detection
signal (to a straight digital input).  Alternately you can use a separate ADC
chip and read the analog samples from the first stage to detect beginning and
end of an object.

Give me a couple of days to dig up the article for you.

On 10/07/2013 03:55 PM, Grawburg wrote:
> I'm working on a project to demonstrate how a basic conveyor system can separate
> different size objects by using some HO train cars and electric turn-out switches.
>
> The intention is to have a detector, either a visible light photocell arrangment using
> LEDs or an infrared LED emitter/receiver.  The turn-out switch will be isolated from
> the Pi with a relay.
>
> I know the photocell will give me a basic ON-OFF (high-low), but what does the IR
> LED give?  I will have a timer loop in my Python code that instructs the switch to remain
> in the diverted position for x-seconds and then return to the default position.
>
>
> Brian Grawburg
> Wilson 
>

-- 
Scott G. Hall
Raleigh, NC, USA
ScottGHall1 at GMail.Com

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mail.triembed.org/pipermail/triembed_triembed.org/attachments/20131013/020d18d8/attachment.htm>