[chbot] Fwd: Raspberry Pi etc.

Charles Manning cdhmanning at gmail.com
Tue Aug 17 09:06:23 BST 2021

Due to the hazards of playing with anything AC, consider other options:
How about a Hall Effect sensor and a spinning magnet on the pump? Or a
spinning disc, LED and photo sensor.

If I was going to be actually measuring power then I'd probably use a
YoctoWatt. These are isolated power meters with both USB connectivity or
can also log into built in flash. Very useful items for various logging.

On Tue, Aug 17, 2021 at 7:30 PM Starr Moffatt <zl3custarr at gmail.com> wrote:

> Hi All,
> Thank you for including me as a member.
> I was the person that asked for help regards using the Raspberry Pi for
> logging electrical data.
> As I thought I might be chatting only to a few people, rather than the
> whole group, I did not have anything prepared.
> Thank you for the suggestions. As mentioned it was too much for me to
> remember everything so please also inform me using this list. (Or use my
> email address  zl3custarr at gmail.com )
> Please see below more info.
> 17 AUGUST 2012
> The idea for this came about at my brothers place where it was thought
> that maybe due to an “unseen” water leak the water pump would be
> operating at “regular” intervals and therefore consuming electricity.
> For this to be checked the best place to monitor the pump circuit is at
> the switchboard.
> A clip on a.c. current sensor would be the best option for detecting
> when the pump was operating.
> For this to be logged, the current sensor could drive a 4N26 opto
> isolator along with a storage capacitor arrangement on its output, to
> provide a constant signal to the Raspberry Pi’s input while the current
> was flowing to the pump. Note this would not provide a value of current,
> instead just the indication that the pump was on or off.
> The Pi would be required to log this on/off state, at regular intervals,
> say 1 minute, along with a time/date stamp. Therefore the Pi would need
> to populate a suitable spread sheet with this data.
> Mark, I think you had some suggestions on this so I would appreciate you
> written comments.
> Peter Harris suggested I look at Openenergy Monitor which I have done
> and I have found a suitable circuit for the current sensor arrangement.
> Thank you.
> Another idea that I am looking at is to be able to check the times that
> a water heating circuit is enabled. This would only need a 230V coil
> relay with a NO contact connected between a Pi supply and one of its
> inputs. This would also require another column to be populated in the
> spread sheet.
> In the future:
> I am also thinking that it may be of use to record the values of current
> and voltage. Again a spreadsheet would be needed which could also have
> columns for power and, using integration, kWh. I guess an Arduino would
> be simpler as it has built in A to D conversion, however as I already
> have the Pi I will persevere with it at this stage. Just looking at the
> drawing for the current sensor for the Arduino;
> https://learn.openenergymonitor.org/electricity-monitoring/ct-sensors/files/Arduino_AC_current_input_A.png
> it looks as if the software determines the peak value and from there
> calculate the RMS value. I assume the voltage RMS value will also be
> calculated using the peak value as well. I have heard that the scan rate
> of the Pi is slower than the Arduino so I wonder if this would have a
> bearing  on the Pi’s ability to determine the peak value.
> Cheers,
> Starr Moffatt
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