WHITE LED triggering a LIGHT DETECTOR

[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

[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]

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

[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]

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