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Topic: Home Energy Monitoring via flashing LED on Meter (Read 5 times) previous topic - next topic


i think it might be a good idea to pull down the other 5 inputs...
because: a floating input wastes power...  :)

good luck for ur test...


i think it might be a good idea to pull down the other 5 inputs...
because: a floating input wastes power...  :)

Thanks for the advise.

I take it that pulling it down means connecting a resister to GND?

If so how do I calculate the correct value for a resister to GND?

Should I be looking at the datasheet for this type of Information? I am a newbee and want to learn so if you can point me to a web site that would be great, even just letting me know a 10K resister etc would.



i would connect it with very low resistance...
is "pull down" wrong for that?
i mean "short" to ground (but just the _inputs_)...  ;)


I tried it with the TSOP4136 too, on a Itron CL200 meter in the USA.   It never worked well and consistently.  I thought it was a noise issue too.

After some trial and error, I discovered that the TSOP4136 is totally unsuitable this purpose.  It detects modulated signals, and I am not even sure that my electric meter was outputting modulated signals.    Their technical specs for the meter don't mention anything about it.

On a hunch, I tried just an simple infrared detector from Sparkfun, SEN-00241 https://www.sparkfun.com/products/241  That did the trick.  Now I detect the pulses extremely reliably, to every single watt-hour to be able to predict when the meter will flip over to the next kWh digit.   The only possible issue is that the sensor is certainly sensitive to ambient illumination, so I have to shield it.  The ambient infrared tends to pull the signal low, so to get a clear HIGH and LOW signal, I route it through a comparator, comparing it against a reference voltage of about 3.5 V (arrived at by trial and error).   I don't have a scope to verify the purity of my signal, but I was able to measure the pulse width to be consistenly 10.025+/- 8 milliseconds.


If you have a LED that produces visible light, then an infrared sensor that captures invisible light (different wavelength) is hardly an optimal solution.

As others have already mentioned, TSOPs are common in decoding infrared remote controller signals, which use high frequency carrier signal (such 36kHz, 52kHz or something like that), and modulate this when keys of the remote controller are pressed. Definitely not optimal for calculating pulses of a visible light LED.

A simple LDR sensor, light dependent resistor, easily does the trick. If you connect it to Arduino, you don't need any fancy extra components. Just sample that sensor fast enough and do all the signal processing with software. This method allows logging and plotting the actual signal, and tuning your algorithm for it.

I've written quite a detailed series of articles about exactly this use case at SensorBay.com. These should be very helpful for you and others who are building the same thing - even if you decide to use your own HW method.

HW: http://www.sensorbay.com/2012/11/project-1-home-energy-monitor-with.html
SW: http://www.sensorbay.com/2012/12/project-1-home-energy-monitor-with.html
Data: http://www.sensorbay.com/2013/01/project-1-home-energy-monitor-with.html

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