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  1. (*steve*)

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

    I'm using a Keithley 610B electrometer. There circuit is very simple, it's just the battery, a diode, a resistor, and the cap under test in series with the electrometer in its current measurement mode.
  2. (*steve*)

    Issue in BLDC motor

    I wasn't referring to the length of the leads, but the number of degrees the magnetic field leads the rotor position. With or without feedback, these motors are simply three phase synchronous AC motors. (Sure there are differences in the windings and the shape of the driving waveform, but the...
  3. (*steve*)

    Issue in BLDC motor

    Presumably the drive to the motor leads the position by some calculated amount. I guess that if you reduced this lead, you would reduce speed and maybe increase torque.
  4. (*steve*)

    problems with HMC253

    Try placing some sort of load on the outputs. This is probably crosstalk and may appear much attenuated when driving something other than an open circuit.
  5. (*steve*)

    RF Circuit Battery Efficiency

    In general, a calculation like that gives you the minimum value for the inductor. Too small an inductor is generally worse than too large a value. For the diode, choose a Schottky diode rated at more than the maximum output current, and more than the maximum input voltage. The current through...
  6. (*steve*)

    Back to back AAA cell whim, bad idea?

    Yeah, at worst the batteries are in parallel. As long as both batteries have a similar voltage, the circuit should not see anything that would damage it. However, if the device uses the centre tap between the cells, some part of the circuit will have a negative voltage applied to it. On that...
  7. (*steve*)

    RF Circuit Battery Efficiency

    Imagine you want 3.3V at 100mA. You have a battery which is currently reading as 6.6V. A linear regulator would have as it's input 6.6V at 100mA, and the excess energy would be expended as heat. This regulator would be 50% efficient at best. As the difference between the input and output...
  8. (*steve*)

    Inverters connected

    Any islanding is a requirement on grid tie inverters to (pretty specifically) stop them from doing what you want them to in this case.
  9. (*steve*)

    Inverters connected

    Ahh, so set up one inverter to produce mains voltage, then try to use a grid-tie inverter to boost it's output. The anti-islanding will almost certainly detect that you're not connected to the real mains and shut down. I believe one of the things that anti-islanding does is check the impedance...
  10. (*steve*)

    Inverters connected

    What do you mean "connect two inverters together"?
  11. (*steve*)

    Antique Automotive Resistors

    You want me to close this thread, don't you?
  12. (*steve*)

    Antique Automotive Resistors

    What!?!?!?
  13. (*steve*)

    Advice before buying an Inverter

    Not the outer diameter, the diameter of the copper inside the insulation.
  14. (*steve*)

    Replacing Large PCB Pin-Headers/Eurocard?

    I agree 100% If you don't want to keep the part your removing intact, cutting the leads and pulling them out one by one is a better option. It may not be as showy as turning the board over and the part falling out, but it is likely to be faster, especially for things with thick, rigid pins...
  15. (*steve*)

    Advice before buying an Inverter

    Yeah, 16 feet because you either need to run 2 wires, or rely on the uncertain resistance through the chassis of the vehicle. Here is where I got the wire size/resistance stuff. 2x28/0.30 means 2 wires, each made up of 28 strands of 0.3mm diameter wire. That works out to be close to 14awg...
  16. (*steve*)

    Advice before buying an Inverter

    40A would be a minimum. Let's look at 10awg wire. It can carry up to 50A, and has a resistance of about 3.4 ohms per 1000ft. You have a run of 16 feet. That's a resistance of 0.0544 ohms, which at 12.5A will drop 0.7V. (5% loss) Going up to 8awg wire. It has a resistance of 2.2 ohms per...
  17. (*steve*)

    Replacing Large PCB Pin-Headers/Eurocard?

    I use the type where you heat the joint up, pull a trigger, and a vacuum pump sucks out all of the solder. The closer the fit of the wire in the hole, the harder it is. It is still very possible to damage the board, and even with the best technique there's always a couple of joints that have...
  18. (*steve*)

    Advice before buying an Inverter

    Use the thickest cable you can reasonably use. Something rated for 4 to 5 times the current you expect should be sufficient. At low voltage and high current losses add up very quickly. Use the same rating of fuse (30A)
  19. (*steve*)

    Replacing Large PCB Pin-Headers/Eurocard?

    Vacuum soldering works like this: Heat up the joint and suck out the solder. Move to the next pin. When all pins have been desoldered, turn the board over and the part falls out. Of course it isn't always this easy, but doing things like desoldering 64 pin chips is pretty easy. Cutting the...
  20. (*steve*)

    How do you fix IBM Selectric II right hand margin stop

    Have you read this page?
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