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  1. KrisBlueNZ

    auto restart in the event of a power failure

    GreenGiant, I think you need to reconsider your attitude to safety. Where there is a risk of injury or death, one should simply banish any thoughts along the lines of "that couldn't happen", any attempt to justify one's failure to consider any particular possibility, and any sense that the job...
  2. KrisBlueNZ

    Latching Relay Logic Help

    Hi again jdkru and sorry for the slow reply. There's not enough information for me to fully understand how the seat works. Specifically, I think the seat heater probably has two separate heating elements, which are connected to the battery supply in different ways for low and high heating...
  3. KrisBlueNZ

    SMPS's with cascoded opto feedback

    I strongly suspect that whoever wrote the data sheet had simply not realised that it was meaningless to describe a two-terminal optocoupler transistor as operating in common emitter or emitter follower topology, and that the usual differences between those topologies do not apply. Whether...
  4. KrisBlueNZ

    SMPS's with cascoded opto feedback

    Sounds fair enough.
  5. KrisBlueNZ

    Need help to write a program to control AD9834 DDS using PIC16F877A micro controller

    Hello and welcome to Electronics Point. Contributors on these forums are happy to help by answering questions, but no one here will write your program for you. If you want that kind of service, I suggest you try http://www.freelancer.com. If you make an effort yourself and have trouble, we...
  6. KrisBlueNZ

    Possible Project??

    Normally, ceramic capacitors are used for decoupling. Axial or radial doesn't really matter. 50V rating is good.
  7. KrisBlueNZ

    auto on and of to over-ride a manual switch

    You should be able to find a small switching converter that will produce 24V from your mains supply. It doesn't need to be very big. A rated output current of 100 mA would be enough, which is 2.4 watts. You should be able to find something small and relatively cheap.
  8. KrisBlueNZ

    Crock Pot modification

    I guess you're talking about cooking food... I've watched so much Breaking Bad that when I hear the word "cook", I think of something else :-) Any other Breaking Bad fans here? (Since we're already somewhat off-topic.)
  9. KrisBlueNZ

    Phillips 3055 scope problem

    I can't see how burning up a resistor in the vertical input section could affect the screen in that way. My guess is that the halo effect has always happened when you turn the brightness up very high like in that second picture. You probably just never noticed it before because you weren't...
  10. KrisBlueNZ

    Possible Project??

    Corrections to schematic of post #23 as identified by KJ6EAD. Thanks KJ6EAD :-)
  11. KrisBlueNZ

    Possible Project??

    Well, here's my suggestion. It's very similar to the previous design but all of the test resistances are fed from 1k resistors, and the two low-resistance ones have their voltages amplified by low-offset op-amps. I'm really not sure if this is a good design or not. Specifically I'm concerned...
  12. KrisBlueNZ

    capacitive commutation of thyristor

    You didn't answer all my questions so I'm not sure whether this will help. Connecting a load in the cathode path of an SCR is not normal. Normally, the cathode is connected to the 0V (negative) rail of the circuit, and the load is connected between a positive voltage and the anode. I am going...
  13. KrisBlueNZ

    Possible Project??

    It would help me if you could tell me the maximum and minimum acceptable values (either as ± percentages or actual resistances) for the four resistances. If you don't know exactly, can you estimate the furthest from the nominal resistance that you think you will ever need to accommodate.
  14. KrisBlueNZ

    Possible Project??

    There's a problem with the 1 ohm and 5 ohm measurements. If you use a series resistor of 1 ohm and a test resistance of 1 ohm, for a total of 2 ohms, across a 9V battery will draw 4.5 amps! That is more than ten times the amount of current that a 9V battery can supply, even for a few seconds...
  15. KrisBlueNZ

    Crock Pot modification

    It would be useful to know the voltage across it, at different temperatures. You can measure this at the board, so you can leave the device in contact with the pan. You'll need to do this with the unit powered, and parts of the board are live, so I suggest soldering some wires onto the board and...
  16. KrisBlueNZ

    BOSS DS-1 Pedal

    Make sure you use transistors that are specifically flagged as low-noise for Q1~3. Does anyone know whether transistor noise gets worse with age with modern devices? If it does, that would be a good reason to buy new parts.
  17. KrisBlueNZ

    auto on and of to over-ride a manual switch

    That's great! You're welcome :-)
  18. KrisBlueNZ

    BOSS DS-1 Pedal

    2SC2240-GR (Q1,2,3) is a low-noise NPN with the standard Japanese pinout (E,C,B from left to right looking at the flat side with the pins downwards). Current gain for the -GR version is 200~400, although that's only significant for Q2. If you want to keep the same pinout, your options are...
  19. KrisBlueNZ

    Latching Relay Logic Help

    Do you mean a centre-off switch? You can push it one way for HI, and the other way for LOW, and it's spring-loaded so it returns to the centre position, right? I'd agree with that. The relay may be part of the circuit that controls the power to the heater elements, but it can't be the whole...
  20. KrisBlueNZ

    TDA2009 Bridge Amplifier Problem

    The PCB looks OK to me as well. I would also avoid the long track under the IC if your PCB doesn't have a solder mask, because of the risk of a solder short to it. Check carefully for solder bridges (you can scrub the underside with a toothbrush and isopropyl alcohol). If that doesn't fix it...
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