WHITE LED triggering a LIGHT DETECTOR

Comments & issues
Post Reply
9000cse
Phidgetly
Posts: 22
Joined: Sat Nov 02, 2013 7:50 am
Location: Southampton, UK
Contact:

WHITE LED triggering a LIGHT DETECTOR

Post by 9000cse »

I have a question. Regarding WHITE LED triggering a LIGHT DETECTOR. which connects to a Phidget 1012, then to computer running windows 10, 64 bit. The problem. This only triggers under slow conditions. Works perfectly. However. Under higher speed, nothing. Its some sort of timing issue, i THINK. but not sure where. There's nothing I can see, to adjust that timing value. suggestions please. The distance between LED and DETECTION, is 4mm. Please see photos for on/off state.
Many thanks
Attachments
20210921_105745.jpg
20210921_105737.jpg
20210921_105730.jpg
20210921_105717.jpg
User avatar
mparadis
Site Admin
Posts: 959
Joined: Fri Oct 28, 2011 12:17 pm
Contact:

Re: WHITE LED triggering a LIGHT DETECTOR

Post by mparadis »

How fast is the LED flashing when this problem occurs? The 1012 is specified for a minium of 4ms pulse length on the high and 16ms on the low side, so if the light is on for less than 4ms, it won't trigger. There's also a possibility that the light sensor you're using has a minimum trigger length and it's not activating for the same reason.

You may want to try wiring the digital input directly to the LEDs circuit so you don't have to worry about the light at all. If you're doing this for isolation purposes, you might have better results with a dedicated opto-isolator IC rather than using an LED and light sensor.
9000cse
Phidgetly
Posts: 22
Joined: Sat Nov 02, 2013 7:50 am
Location: Southampton, UK
Contact:

Re: WHITE LED triggering a LIGHT DETECTOR

Post by 9000cse »

Hi. Thanks for getting back to me.
The LED is on permanently, and works fine at slow passes. The flag that breaks the beam is appx. 20mm long.
I think your idea of an opto-isolator IC is a sound one. So may go down that route. But what would make the opto-isolator IC count a pass. I'm very basic at this.
Its the slot cars flag that breaks the beam. And gives a time on how long it takes to travel a 3mtr circle. As I say. Works fine under slow speed, but up that speed, and it does not trigger the 1012.
Many thanks
User avatar
mparadis
Site Admin
Posts: 959
Joined: Fri Oct 28, 2011 12:17 pm
Contact:

Re: WHITE LED triggering a LIGHT DETECTOR

Post by mparadis »

The opto-isolator suggestion was based on my incorrect assumption that the LED was being turned on and off by a circuit, so it won't work in this case.

You might have better results with a infrared proximity sensor like the PRX2300 or 3525, but it'd be hard to know if it could work at high speeds without testing it first.
9000cse
Phidgetly
Posts: 22
Joined: Sat Nov 02, 2013 7:50 am
Location: Southampton, UK
Contact:

Re: WHITE LED triggering a LIGHT DETECTOR

Post by 9000cse »

Hi thanks for getting back to me.
PRX2300 looks ideal. I'll check spec and try.
Andy, cheers
Post Reply

Who is online

Users browsing this forum: No registered users and 26 guests