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  1. Arouse1973

    18650 stays @ 4.15 volts

    You should avoid charging them higher than 4.2 Volts. At 4.15 Volts they are pretty much charged, the charging current at 4.15 Volts is going to be quite low. Adam
  2. Arouse1973

    Transistor hfe

    Ok, no rush.... we can then put a plan together to try and understand whats going on. Cheers Adam
  3. Arouse1973

    Transistor hfe

    I like this sort of thing, I have never seen any thread closed for too many threads, If people are getting bored and they don't want to help you then they can go and ..... well I can't say what I want to say :) This sort of issue is so valuable for people wanting to learn electronics. This is...
  4. Arouse1973

    Transistor hfe

    Why do you keep saying final post, the whole point of this forum is to try and help people. I think we do a pretty damm good job bearing in mind we are in different parts of the world. With a strange fault like this it can take quite a while to understand and solve. You will get an output with...
  5. Arouse1973

    Transistor hfe

    Edit: After this I placed a 1K resistor in the common line and it did the same thing. This is possibly due to the internal 5.1V Zener lifting the nominal 12 Volts on the output up to 17 Volts.
  6. Arouse1973

    Transistor hfe

    Here is something that might be of interest. I simulated approx. your circuit, see below. Everything works fine with 100R and with the circuit drawing 4.5 Amps. Now what's interesting is if I disconnect the common from the V Reg. Guess what voltage I get on the output. Yep 17 Volts. It only does...
  7. Arouse1973

    Need to build an interface between an audiometer and a set of LED lights

    Amy, the files look like they are for LT Spice. This is the simulator a lot of us use on here and we have a few experts that know it very well. You can download a copy from Linear Technology for free. You can then copy the files into the relevant folder and away you go... Adam
  8. Arouse1973

    Need to build an interface between an audiometer and a set of LED lights

  9. Arouse1973

    Need to build an interface between an audiometer and a set of LED lights

    This is just an example to show you how it works, it's not your circuit. I'll draw you yours the best I can. The bottom end of R2 (connected to the IC) basically gets connected to your common point through the IC, it limits the current for the LED otherwise a standard LED would be destroyed. It...
  10. Arouse1973

    Need to build an interface between an audiometer and a set of LED lights

  11. Arouse1973

    Need to build an interface between an audiometer and a set of LED lights

    Don't feel stupid, we all have to start somewhere. I just wish this forum was around when I started 20 years ago. Adam
  12. Arouse1973

    Need to build an interface between an audiometer and a set of LED lights

    The beauty of an open collector means you can control another device which maybe on a completely different voltage. Because it's open it doesn't have any reference to the supply voltage that's controlling the drive of that transistor. Does that make sense? Do you want me to do a drawing? Adam
  13. Arouse1973

    Need to build an interface between an audiometer and a set of LED lights

    Alec did you get your LM3914 spice model working? Might be good to upload it if you can.. Thanks Adam
  14. Arouse1973

    Need to build an interface between an audiometer and a set of LED lights

    The regulator will work, you don't need any resistors before or after. If accuracy is important for the 1V ref... you could look at a 1.024 V reference IC. You can get 1 Volt versions but they are not as common and quite expensive. Adam
  15. Arouse1973

    Need to build an interface between an audiometer and a set of LED lights

    Because the output of the LM3914 is open collector (Comparator) then you could potentially run the IC from a lower voltage. Adam
  16. Arouse1973

    Can You Paint a Circuit Board?

    No after reflow / bath. It's low temperature so it won't melt any solder.
  17. Arouse1973

    Should I design my PSU for 230Vac/+-10%?

    The UK and Europe were harmonised a few years a go and now all of western Europe is classified as 230V only the tolerances are different 240V +6% -10% for the UK and 220V -6% +10% for Europe. No one is actually generating 230V. That's the EU for ya. Adam
  18. Arouse1973

    Need to build an interface between an audiometer and a set of LED lights

    Ok, it’s generally good practice to include a current limiting resistor to the base of a BJT that’s operating in common emitter mode. All though not always necessary it’s good practice to always think first base “Resistor!” Do I need one? In this case I think we need one. If you look at the...
  19. Arouse1973

    Need to build an interface between an audiometer and a set of LED lights

    Yes that should work Amy. Now you also need to have a think about some resistors to protect the base/emitter junction from over current. Also a pull-up resistor will be required from the base terminal to the + V supply terminal (emitter), this ensures the transistor is off when it should be...
  20. Arouse1973

    Need to build an interface between an audiometer and a set of LED lights

    Oh that must be what bar-graph and dot mode is then ;).
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