# grendell

• grendell commented on thediylife's instructable Simple Arduino Home Energy Meter3 months ago

Hi,Yes the CT does produce an AC voltage. This could be fed to an RMS convertor chip to produce a DC voltage, however the arrangement here is to bias one leg of the CT to 2.5v DC and let the other leg swing either side of 2.5v (but not above 5v or below zero). In this simple setup the "RMS" is assumed to be 0.707x the peak values.

HiCongratulations on a simple introduction to electricitymetering. I too have been looking at various complicated solutions on theinternet but would certainly look to build this as a starting point.As a matter of interest, how close are your results to yourcompany meter over say a month? I would suggest, having compared the resultsfor a while you could always alter the value of the fixed “voltage” (220) up ordown to bring the results closer to each other which would compensate for yourlocal supply voltage and the average power factor for your house.Another thought in regard to the ½ reference divider, couldyou not use another analogue input to read this “fixed” value from time to timeand use that value for the subtraction? Also I am not clear as to what th...see more »HiCongratulations on a simple introduction to electricitymetering. I too have been looking at various complicated solutions on theinternet but would certainly look to build this as a starting point.As a matter of interest, how close are your results to yourcompany meter over say a month? I would suggest, having compared the resultsfor a while you could always alter the value of the fixed “voltage” (220) up ordown to bring the results closer to each other which would compensate for yourlocal supply voltage and the average power factor for your house.Another thought in regard to the ½ reference divider, couldyou not use another analogue input to read this “fixed” value from time to timeand use that value for the subtraction? Also I am not clear as to what the … if(maxCurrent <= 517)…. is needed for- does this correct for no load drift?Finally to be a little pedantic, I think you should not usethe label peakPower as that could be confusing, rather use maxPower. JoergeliI love your display for energy usage. Any chance of an Instructable(in English!) to show how it is done?G

• grendell commented on StephanP1's instructable Ingeniously simple mousetrap3 months ago

I was wondering what the big knife was for at the start of your video!Also, peanut butter I find works well too.G

• I think you are having trouble shooting on a whitebackground because the camera is on auto exposure.Most cameras assume the overall average reflectance of the sceneis 18% of the whitest area. If you shoot a small object on a big white card thecamera will adjust the average brightness down so the white becomes grey as thecamera will under expose.There are several options to correct this. Check if you camerahas Back Light Compensation. If it does see if you can set it to plus 2 ½ stops.This will fool the camera to overexpose which should bring the white back towhite.Another option is to see if your camera has Spot Metering.This masks the cameras metering area to a spot, usually in the centre thisignoring the white background but correctly exposing your item of interest.If you have ...see more »I think you are having trouble shooting on a whitebackground because the camera is on auto exposure.Most cameras assume the overall average reflectance of the sceneis 18% of the whitest area. If you shoot a small object on a big white card thecamera will adjust the average brightness down so the white becomes grey as thecamera will under expose.There are several options to correct this. Check if you camerahas Back Light Compensation. If it does see if you can set it to plus 2 ½ stops.This will fool the camera to overexpose which should bring the white back towhite.Another option is to see if your camera has Spot Metering.This masks the cameras metering area to a spot, usually in the centre thisignoring the white background but correctly exposing your item of interest.If you have no adjustments your camera may be able to lockits exposure by partly pressing the shutter button.You will need a tripod. A good photographicsupplier should be able to sell you an 18% grey card. Hold the bard behind youritem with one hand, partly depress the shutter to lock the exposure (and focus) then remove the grey card and fully press the shutter. then remove the grey card and fully press the shutter.

• Hi there,Many thanks for your time in producing this guide. I am not clear though, will this only send a preset message? I am looking to send at least one vairable number such as " The current temp is" 123 "c" and may be date and time as well. I intend to use a RTC to send the email once a day so could add the date / time to the email.