lm393 module

[paule999]

Is there a reason why an lm393 photodiode module is specified / preferred over an photoresitor module? I've struggled a bit with photodiodes as sensors for leds (mainly with setting thresholds correctly) but directly replacing the diode on the module with a ldr (5506) has (for me) made things much easier / reliable with added bonus that the flat ldr face sits closer to the meters led requiring a far less bulky / elaborate light proof housing etc.

I assumed from the warning in the hardware section that ldr modules are not correct but I'm struggling atm to figure out why a photodiode module would be better? Am i missing something?

[marcosscriven]

Did you get an answer elsewhere? I'm curious as well.

[paule999]

No I'm still wondering / hoping for input from someone with greater knowledge than myself! I never asked the question elsewhere.

From what I've noticed / observed though... it works perfectly... at the end of the day the led pulses are detected without fail, the lm393 comparator is doing its job and sends D0 high just the same as if a photodiode was being used for led pulse detection... esphome / HA glow knows no different, its only looking for the rising edge on whatever pin is used and counts it as 1/1000 kwh or whatever is set in software...

[klaasnicolaas]

I recommend using a photodiode module primarily due to its rapid response time and precise detection capabilities, which are essential for accurately capturing the brief LED pulses emitted by energy meters.

Photodiodes offer a linear and swift reaction to changes in light intensity, making them suitable for this application. However, they can saturate under strong ambient light, potentially obscuring the desired signal.

LDRs, while more straightforward to implement and capable of being positioned closer to the meter's LED, have slower response times and are also affected by ambient light, which can lead to less accurate readings in environments with fluctuating light conditions.

So you can use an LDR for the Home Assistant Glow. Make sure the sensor is well shielded from external light sources to maintain measurement accuracy.

./Klaas

[paule999]

Thank you Klass, I did wonder about response times but after so much trouble with the photodiode modules I had I thought it was worth a try. After 3 weeks uptime the LDR version I cobbled together is still working great (and far more reliable than the photodiode version I started with) that's unlikely to be the same for everyone though so best sticking to your original instructions 👍