Max 1270 Help

gunstarg10

Hi everyone,

I am trying to measure the power consumption of a light 60watt incandescent lightbulb. So far I have a the max 1270 connected to the propeller and a current transformer output connected to the first channel of the ADC. I have modified the code from the obex to get the readings and calculate power. However, I have two issues one is that I am not getting the correct results because it usually reads close to 60watts the first time I run the code but then anytime after that it reads around 70watt. My calculations are to compute the rms since the output of the CT is ac voltage. Second I am having trouble setting a specific number of samples so that if I turn off the light it reads zero. my code should be attached, if anyone can give me any assistance on getting better results I'd appreciate it.

JonnyMac

It seems odd that you'd have the ADC object handle your RMS calculation, and I'm kind of betting that you don't need floating point, either.

I would simplify the ADC object to limit what it does, though I do like the idea of letting it update a hub variable on a schedule of your choice. If you do that, then you can launch a Spin cog like the one shown below that will take that value and automatically update another hub variable. Just an idea:

pri rms(vpntr, rmspntr) | t

  t := cnt                                                      ' synchronize timing
  repeat
    result := 0                                                 ' clear to start
    repeat 16
      result += (long[vpntr] * long[vpntr])                     ' square samples
      waitcnt(t += (clkfreq / 60) >> 4)                         ' 16 samples @ 60H
    result >>= 4                                                ' average squares
    long[rmspntr] := ^^result                                   ' update RMS

gunstarg10

Thanks for the help. I was able to get it working how I needed it, but you posted some good info. Thanks.