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  1. (*steve*)

    Marx Generator

    You will need something which goes from high to low impedance is around 12V. A spark gap is unlikely to work because the points would have to be extremely close to each other. You could (maybe) use opto-isolated triac drivers. You would manually trigger them by applying the appropriate current...
  2. (*steve*)

    RF Circuit Battery Efficiency

    Also be aware that building it on a breadboard may cause some problems. Fingers crossed.
  3. (*steve*)

    Critter Zapper

    Design a circuit that will generate about 300V and use this to charge a capacitor (say a couple of uF). The boost circuit need only run when the capacitor voltage is (say) < 250V (so it doesn't run all the time). Now, 300V across a 10uF is pretty nasty. I doubt it will kill anything of...
  4. (*steve*)

    0-5V to -24-24V using an opamp?

    You're right. The second time I looked at this I assumed the voltage source on the left was your input, sorry.
  5. (*steve*)

    How do you fix IBM Selectric II right hand margin stop

    Look for the button/lever that controls the carriage release. Maybe it's stuck in the release position.
  6. (*steve*)

    0-5V to -24-24V using an opamp?

    R3 and R4 are unnecessary. Just calculate R1 and R2 for a gain of 24/5.
  7. (*steve*)

    Replacing Large PCB Pin-Headers/Eurocard?

    A picture would help, but a vacuum desoldering station will probably do what you want.
  8. (*steve*)

    0-5V to -24-24V using an opamp?

    Aside from the fact that this is a very high voltage power supply voltage for an op-amp, your calculations are essentially correct. I guess you could make a high voltage op-amp from discrete components, or add a high voltage output stage to a normal op-amp. The next issue is that you have...
  9. (*steve*)

    Marx Generator

    As long as the spark gaps will arc over at 12V... If it worked perfectly, your circuit would generate a pulse at 36V. Not really impressive. The "low voltage" input to most Marx generators is in the order of thousands of volts. Check out Wikipedia for more information (or this).
  10. (*steve*)

    Using An Oscilloscope

    Does this device have a transformer in it which is connected to the mains input? If so, and assuming the transformer don't have a huge fault, the circuit is probably already isolated. Be aware though, that if the designer tied a power supply rail to ground, then you are limited in what you can...
  11. (*steve*)

    Woo-Woo Electrical R of a plant leaf vs. human thought

    Their "test" has a huge number of red flags. Firstly it is not blinded at all. Everyone knows when "evil thoughts" are being directed at the plant, and then they go looking for reaction. Secondly, we don't know what their criteria for success was. If they were directing evil thoughts every...
  12. (*steve*)

    Woo-Woo Electrical R of a plant leaf vs. human thought

    Having just read the resistance of some things with a sensitive meter, I can either confirm that the V vs I characteristics of semiconductor junctions are affected by my thoughts, OR a plethora of things including the electric field around my body, electrical noise, and random fluctuations.
  13. (*steve*)

    Phone's car charger

    You charge your car with that? Just kidding. I expect that your phone is attempting to draw a higher current from the charger than it can supply. Is the other charger exactly the same type?
  14. (*steve*)

    How to check 5 pf or 1.5 pf disc capacitor

    Without the schematic it's not possible to know if they can be tested in circuit (and it also depends on the failure mode). If you have to remove them to test them, it may be faster just to replace them.
  15. (*steve*)

    Component to cut off current to parts of low power circuit

    Another option, if you are using voltage regulator to generate the 3v3 rail, is to find regulators with an enable pin and have a separate regulator for each section of circuitry you want to power up and down. Be aware that even without power the devices may continue to draw power and operate...
  16. (*steve*)

    I thought I'd measure the leakage current of a few caps

    My plan is to see what happens over a couple of days (or however long it takes to stabilize). Some people have done this inadvertently and claim it had no detrimental long term effects.
  17. (*steve*)

    Electric circuit VS Economy

    There is an obvious similarity. Measures which can be converted to scalar values and for which there are domain rules which mean that they are equal, all use the same "scalar equal" function. So you may have found that both economics and electronics use the same definition of basic...
  18. (*steve*)

    NE555, LM7805, and MC34063

    Bushtech, that doesn't look quite right. The three resistors go from Vcc to gnd.
  19. (*steve*)

    NE555, LM7805, and MC34063

    The 7805 can probably be replaced by a zener, a resistor, and a transistor. The 555 can be used to do so many things that weed have to see the circuit to comment. The 34063 is a switchmode regulator? Again, show us the circuit and consider whether you can use a linear regulator. Mind you...
  20. (*steve*)

    I thought I'd measure the leakage current of a few caps

    OK, so a quick clean of both caps by spraying some isopropyl alcohol on them... Let's look a the 3n3 cap first. The leakage current halved to 4.5pA (reflecting an increase in resistance to about 2.8TΩ So how much better is the polystyrene cap? It now measures 0.2x10-7A. That's a massive...
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