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  1. PhilHornby

    Photo Voltaic - Immersion heater power diverter - SAFETY WARNING!

    Had a dummy run with the immersion heater connected today. Despite being crudely laid-out on prototyping boards and the CT being connected using an old headphone extension, it works a treat! (This is still Jeremy's code and circuit) For the first time since I moved into this house, today we...
  2. PhilHornby

    Photo Voltaic - Immersion heater power diverter - SAFETY WARNING!

    I found some more insight at Open Energy Monitor, which I'm going to have to study, because it seems quite nuanced... ROFL - When I read this in the datasheet :- I wondered what magic this was and how it worked (since it did). Turns out I just dropped lucky when I wired it into circuit :whistle:
  3. PhilHornby

    Photo Voltaic - Immersion heater power diverter - SAFETY WARNING!

    With the 'correct' Burden resistors (2x4R7) - calibrated at 2KW - I got a 'reading' (stopwatch timing!) of about 12.5W, for a 9.7W LED bulb (my plug-in power meter said 9.8W). Now 9.7W is probably far too low to be considered useful and it was still an answer of the right order of magnitude...
  4. PhilHornby

    Photo Voltaic - Immersion heater power diverter - SAFETY WARNING!

    It seems that Jeremy may have done just that! (The AD7755 spec. actually says :- "The CT turns ratio and burden resistor are selected to give a peak differential voltage of ±470mV at maximum load"). I measure 41mV rms @ ~2KW which equates to ~23KW max. load. (I'm moderately surprised that the...
  5. PhilHornby

    Photo Voltaic - Immersion heater power diverter - SAFETY WARNING!

    If I re-introduce the 100K resistor and set the preset to give ~121mV rms @ the V2 Channel, I get a "CF" frequency of 100Hz for a 1KW load, with 2x4R7 Burden resistors. In other words, I've successfully built the circuit as specified and got it working to spec. :) (given my ineptitude for all...
  6. PhilHornby

    Multiple readadc10 commands in a row

    I've just remembered what you said ... I've just powered up my AD7755 for the first time, with a load attached - no Picaxe yet, just the 'scope. I was somewhat perplexed to see that the CF signal is only 18uS wide (not 80). Checking the datasheet and Jeremy's code, this is indeed correct for...
  7. PhilHornby

    Photo Voltaic - Immersion heater power diverter - SAFETY WARNING!

    OK, I see what I was doing wrong :oops: ... Moving swiftly on ... To get a voltage in that region, I've had to swap the 100K resistor in Jeremy's design to circa 33K. (36K would probably do it, but I don't seem to have one). I claim to be using the same transformer as Jeremy - but a decade has...
  8. PhilHornby

    Photo Voltaic - Immersion heater power diverter - SAFETY WARNING!

    This application seems to have exposed a huge gap in my knowledge :rolleyes: I thought I knew what a differential signal was, but what on earth is a "differential voltage signal, referenced to a common mode (usually AGND)" ? I thought that the whole point of differential signals, was that...
  9. PhilHornby

    Hacking RS-232 communications between my Altair 8800 and a PC app

    Maybe this: https://freeserialanalyzer.com/ along with https://freevirtualserialports.com/
  10. PhilHornby

    Hacking RS-232 communications between my Altair 8800 and a PC app

    You used to be able to buy a device to do this, "back-in-the-day"; it was dedicated piece of hardware, called a Datascope. It had a screen, keyboard and plug-in analysers and cost £many. The modern equivalent is something like this (and is still not cheap). For a DIY approach, you're going to...
  11. PhilHornby

    Photo Voltaic - Immersion heater power diverter - SAFETY WARNING!

    Indeed... This web site points out that Current Transformers should never be left open-circuit, in the same way that Voltage Transformers should never be short-circuited. Apparently, many tens of kilovolts are available to catch you unwares. Who would have thought these things had that trick up...
  12. PhilHornby

    Photo Voltaic - Immersion heater power diverter - SAFETY WARNING!

    Thanks for that. I wanted to try and build the circuit exactly as shown (since apparently it works). Maybe I'll have to go through more than one iteration :unsure: I tried to obtain the same parts as Jeremy used, but the current transformer caused a bit of confusion. Jeremy specified a...
  13. PhilHornby

    Multiple readadc10 commands in a row

    https://www.ipo.gov.uk/p-ipsum/Document/ApplicationNumber/GB1718943.2/fc4fa766-0537-43a3-b984-68109980573e/GB2562550-20181121-Publication%20document.pdf So have I understood it correctly - it uses the Current Transformer (without the 'burden resistor') to charge up a local power supply, then...
  14. PhilHornby

    Multiple readadc10 commands in a row

    I had been thinking along the same lines - and for the same reasons (Oil boiler connected to Immersion Heater circuit), but in the end, I bit-the-bullet and managed to rewire the Boiler onto a lighting circuit. No one need ever find out... While hot water heating is not going to necessarily...
  15. PhilHornby

    Photo Voltaic - Immersion heater power diverter - SAFETY WARNING!

    AD7755 Application Note AD7755 Evaluation board documentation I have a few queries about the hardware design, if anyone can help ... In the circuit above, the modified burden for the Current Transformer is shown as: I was slightly bemused, as to why there are 4x10R resistors, rather than...
  16. PhilHornby

    Multiple readadc10 commands in a row

    I don't know how you are getting on, but @Jeremy's hardware documentation was a little sparse, so I've been having a few issues trying to build a practical board. I found some documentation relating to a now obsolete AD7755 Evaluation Board, which answered some of them. It's a shame I can't...
  17. PhilHornby

    20M2 Mobile Robot

    The "Wayback Machine" has archived some of the referenced material - in case @erco can't find it ... Part 1 Part 2 Part 3 Part 4 (Be patient - the web site is quite sluggish!)
  18. PhilHornby

    Are >= and <= valid?

    They're in the PDF version of the manual ...
  19. PhilHornby

    Multiple readadc10 commands in a row

    I was wondering (not knowing a great deal about three phase and its metering) ... If you could arrange for the Solar PV Inverter and the Immersion Heater to be on the same phase, couldn't you just go with the circuit as specified by Jeremy? [just monitoring a single phase] A supplemental...
  20. PhilHornby

    Multiple readadc10 commands in a row

    There is an "Application Note" for the AD7755, here: https://www.analog.com/media/en/technical-documentation/application-notes/an559.pdf
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