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  1. (*steve*)

    Light therapy device

    Using a constant 17.3mA current source (which varied from 17.29mA to 17.34mA during the test) I tested 56 LEDs (A small sample, but enough to give an indicative estimate. These were cheap while LEDs, no guarantee that they are part of the same batch. The graph of voltage vs count is shown here...
  2. (*steve*)

    Setting up idiot led's...

    I'm doing that to bias the bases at a constant voltage above the ground. Assume no current is flowing, Vbe of both transistors is about 0.65V and the bases are at 1.3V, so the voltage across R5 is 0.65V (and the current is therefore 6.5mA. If everything is nicely balanced, the current...
  3. (*steve*)

    Setting up idiot led's...

    The circuit given above requires a voltage drop of at least 0.6V. If this is a problem (and it might be more so for a 12V system than a 24V system), then a circuit like this requires 0.1V (or less) to be dropped across the resistor.
  4. (*steve*)

    Tool-activated vacuum

    I guess because it needs to be after the power switch for the saw. Otherwise the vacuum will be powered whenever the saw is powered. And you might as well just power them from the same outlet -- no relay required at all.
  5. (*steve*)

    Tool-activated vacuum

    Google "green power board" They typically have one or two outlets which turn on the others when power is drawn. You'll need to check that these can switch your load safely, but they're a ready-made option that doesn't require fooling with mains voltages. Incidentally, that instructable seems...
  6. (*steve*)

    Light therapy device

    Yeah, that's possible. They have a fairly wide tolerance, and require a minimum voltage to achieve their stated current, but the variation in current between devices would not be hugely significant. The question is whether you can get these in the current that you require, and their price...
  7. (*steve*)

    Light therapy device

    My current limiting will not know what batch they're from. It will, however, know what a constant current is.
  8. (*steve*)

    PWM Controller

    The 1N4148 used to protect the transistor is a small signal diode and is probably not the best option. I'd use a 1N4001. The diode would probably fail short circuit which would then take out the transistor, followed by the 555 (U1). You've said the motor still works in some respects, so the...
  9. (*steve*)

    PWM Controller

    Just the 555, but wait until I have another look... (Just in case there's something else)
  10. (*steve*)

    Inverter Output Transformer Saturation

    You should possibly study the voltages in series resonant circuits. You may want to stay away from resonance, but even still, there will be effects.
  11. (*steve*)

    Light therapy device

    Whilst this is true to some extent (as it is true of resistors, capacitors, and transistors, and any other component), the problem with the array as shown is that the resistor drops only a very small fraction of the total voltage (0.27V). Assuming a range of forward voltages which are randomly...
  12. (*steve*)

    Can anyone explain this

    It looks to me as though there is an error in the diagram. P is connected to NOT Q.
  13. (*steve*)

    Inverter Output Transformer Saturation

    It's quite possible for it to have -70V on one side and +70 on the other.
  14. (*steve*)

    Wireless Power transmission using Atmega .... pls help!!!

    What's the reason for the specific type of cap?
  15. (*steve*)

    Inverter Output Transformer Saturation

    Not the dreaded KelvinHertz!
  16. (*steve*)

    Inverter Output Transformer Saturation

    If the total time your H bridge remains in one state does not equal the total time in the other state over some large number of cycles, then there will be a net DC voltage across the transformer and a net DC current. Yes, a cap would improve things, but the voltage rating would be significantly...
  17. (*steve*)

    Light therapy device

    It's not a physical reason, and there's no magic in them having 4 pins.
  18. (*steve*)

    PWM Controller

    One major problem is that your 10k pot can cause the discharge pin to be connected directly to Vcc. When the transistor in the 555 turns on to discharge the capacitor it immediately gets destroyed. The 555 datasheet (or at least some of them) will suggest a minimum resistance between Vcc and...
  19. (*steve*)

    Ultra Caps .. Super Caps

    Capacitors and batteries both have some of their critical properties determined by surface area. Fractal surfaces will benefit both. Both battery and capacitor technologies (I think) will be unimaginably different if some of this research can find its way to market.
  20. (*steve*)

    Light therapy device

    It's really just a matter of looking at the devices available and checking out their datasheets. LEDs are available in many packages. Some packages are designed to be mounted on heatsinks and are typically capable of much higher power. Remember that there power rating you'll see in the...
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