Measuring frequency using a laser module and LDR sensdor

Hi! :grinning: :grinning: :grinning:

I have a project for detecting insects (Tephritidae fly). Winged insects have pairs of wings in their back which each of them has a different shape and width. Many journals use laser (or infrared transmitters) and light sensors as the receiver for detecting it. How does it work? We'll wait for insects to pass the laser and sensor, then we'll get a value named wingbeat frequency.

My problem is, the LDR module sensor we used (LM393) performances aren't at their peak. The sensors can't detect flickering light (laser module) that has more than 100Hz frequency after calibration (according to the journal the wingbeat frequency is about 197-203Hz). So is there a recommendation for the kind of sensors we could use? Are there new ways to measure flickering light using any kind of sensor? Sorry for bad grammar.

Phototransistors or photodiodes would react hugely faster than LDR. I am no expert so cannot suggest a part number. But hardly recent inventions!

Photodiodes mostly require an amplifier for proper digital signals, but phototransistors should be okay for your purpose.

I built my first cross-beam light barrier for insect photography using a pair of LEDs and BC107 transistors with cap rasped open. Both in tubes for ambient light suppression and in a distance of about half a meter. That was enough to trigger a SN74123 monoflop for taking pictures. So I think that any phototransistor for about the wavelength of your light source will do with a reasonable pullup resistor.

An LED as light source is easier to detect than a laser, for its wider beam.

This topic was automatically closed 180 days after the last reply. New replies are no longer allowed.