Recent content by flippineck

  1. flippineck

    LM394 National Semiconductor 'supermatch' NPN pair

    I might try using some form of op-amp to handle the sense resistor, and maybe use a dedicated multiplier chip. I found something along those lines in an old ETI edition.. https://www.worldradiohistory.com/UK/Electronics-Today-UK/90s/Electronics-Today-1998-No-13.pdf#page=26 Page 26
  2. flippineck

    LM394 National Semiconductor 'supermatch' NPN pair

    Noticed I've got my power supply connected the other way round to yours, I'll have another look at the way I've been thinking the transposition from AC operation to a DC circuit. Wonder if this is the root of my incorrect transistor biasing too. LT2940 - Common-mode range 4-80V is pretty...
  3. flippineck

    LM394 National Semiconductor 'supermatch' NPN pair

    Tried again to look at the original National Semiconductor circuit diagram and convert it to a 'snapshot' at the most negative point of the AC cycle: https://tinyurl.com/yocn73bh It really would seem that those base-collector junctions are forward biased. I've had this circuit behave a bunch...
  4. flippineck

    LM394 National Semiconductor 'supermatch' NPN pair

    Hmm.. ok I can see that now.. It's because, that's how I interpreted fig. 12 in Delta Prime's link I thought I was extrapolating from a circuit intended for mains AC, to a DC version. I figured if 'neutral' (0V) was the top rail, and 'hot' was the bottom rail, and "the circuit measures power...
  5. flippineck

    LM394 National Semiconductor 'supermatch' NPN pair

    Thanks Delta Prime. Figures 12 & 13 & associated discussion looks very useful! It will take me a while to digest. My circuit is intended for 0-40V DC @ 0-8A, to measure Watts produced by Trinasolar TSM-230C05 panels which have a rated Pmax of 230W. I'm hoping to try using the BCM847BS and a...
  6. flippineck

    LM394 National Semiconductor 'supermatch' NPN pair

    No problems on the practical side, it's the theory and maths side I struggle with more.
  7. flippineck

    LM394 National Semiconductor 'supermatch' NPN pair

    I've ordered a BCM847BS & a board to solder it to.. will give it a try!
  8. flippineck

    LM394 National Semiconductor 'supermatch' NPN pair

    LM394 datasheet https://www.farnell.com/datasheets/25507.pdf I have a simplish circuit which seems to be a long tailed pair made from an LM394 driving a galvanometer, to give an indication of circuit power. Although the occasional LM394 does appear on eBay it seems to be obsolete and expensive...
  9. flippineck

    Automatic DC supply selection?

    Interesting patent https://patents.google.com/patent/US6847249B1/en The inventor Fig 1 looks like a solution, if built for a small hysteresis and no overlap of states?
  10. flippineck

    Automatic DC supply selection?

    Because of the placement of the 2 banks, they never have direct line of sight to the sun at the same time. At noon precisely, the sun is at 90 degrees to both sets, and a significant time delay passes whilst the roof overhang's shadow transfers from the West to the East walls, engulfing both...
  11. flippineck

    Automatic DC supply selection?

    I've already blown up one controller by not watching the power input carefully, don't want to do it again! Thanks for the warning Would it be worth looking at a 100V varistor in parallel with the final input and a 5A fuse in series?
  12. flippineck

    Automatic DC supply selection?

    I have a solar array (4 x 80W panels in series) on the East facing wall of my house, and a matching array on the West facing wall. In the brightest summer sun I get about 5A at 80V. My controller has a maximum input rating of 100V/500W and it feeds a couple of 12V lead-acid leisure batteries...
  13. flippineck

    Solar panel equal/unequal siting

    Am I understanding correctly then, that the shaded panel (if one's on the west wall and one's on the east wall with both in series) will act as a low resistance and not seriously hinder the power coming through from the panel in direct sunlight? Sounds good.. With the weather in the UK being...
  14. flippineck

    Solar panel equal/unequal siting

    I have an off-the-shelf MPPT solar charging regulator connected to a 12V lead acid battery, and two solar panels. The panels are advertised to have 'built-in blocking diodes'. I could mount both panels side by side on an east facing wall, both panels side by side on a west facing wall, or one...
  15. flippineck

    Cat collar

    Yes I found plenty of battery powered and USB rechargeable ones, even tritium powered ones online. Catching each of our 10 cats once a day every day to change / charge collars would be too much to keep up with though, and the tritium ones are too expensive. We have cats that would almost be...
See more
Top