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  1. (*steve*)

    Light therapy device

    It refers to lumens per watt, not the percentage of power converted to light. Look at the specs for the cheapest IR LEDs on mouser it digikey or some other site that provides datasheets. Check out their efficiency. Your LEDs are probably no better than them. I really don't know if a wide or...
  2. (*steve*)

    PWM Controller

    Can you post a diagram of the circuit you're using. The are several possibilities, that the circuit is wrong, that you've built it wrong, that noise from the motor is disrupting the 555, out that you've damaged the 555 out other components (possibly from spikes from the motor). We may have to...
  3. (*steve*)

    How do I terminate the wires for this Android device?

    Just because the device allows a variable input voltage, it didn't mean you must use a power supply capable of providing a variable output. A fixed output power supply somewhere in the range of valid voltages (probably near the middle than either extreme) would be best. 24V, and 2A would...
  4. (*steve*)

    Power Dissipation Across A Transistor In Cutoff

    The off voltage refers to the maximum voltage where the transistor is guaranteed to be off (the definition of off should be in the datasheet somewhere, but you can probably assume cutoff). At voltages between the off and the on voltage it will go through the active region, however the exact...
  5. (*steve*)

    Power Dissipation Across A Transistor In Cutoff

    The on voltage and the off voltage. We've been through this before.
  6. (*steve*)

    How do I terminate the wires for this Android device?

    Be very, very, very careful you don't connect the power up backwards.
  7. (*steve*)

    Types of capacitors

    You want to look for 105C rated, low ESR, electrolytic (aluminium) capacitor.
  8. (*steve*)

    Light therapy device

    They say that the Vf is typically 1.2V and that at 20mA (when the total power available is 1.2 x 0.02 = 0.024W) and under these circumstances the IR output power is 0.02W. That means 0.02/0.024 = 83.333% of the input power is converted to IR. I'm not convinced. It's higher than the...
  9. (*steve*)

    Ultra Caps .. Super Caps

    Wow, you must be pretty far north. I have friends in Mission Beach who got plenty of rain. (I think they got theirs days before it crossed the coast though) I've been through a cyclone close to that size. It's not an awful lot of fun (and I was in a house built like a concrete bunker)
  10. (*steve*)

    Light therapy device

    I'm not sure I trust those specs. They suggest a conversion efficiency greater than 80%
  11. (*steve*)

    Light therapy device

    Ok, what is their forward voltage and what current is this (20mW output) quoted for?
  12. (*steve*)

    Need parts suggestions for a computer fan type air circ system

    Larger fans are typically quieter than small fans because for a given air flow they spin slower
  13. (*steve*)

    Light therapy device

    There is a significant difference between the power consumed by a LED and the energy emitted from it. The energy conversion efficiency of LEDs ranges from 4% to 50%. If your LEDs are 25% efficient in converting electrical energy to light, then if they're operating at 1.5V and 20mA (30mW) they...
  14. (*steve*)

    Ultra Caps .. Super Caps

    How's the "beautiful one day, perfect the next" weather around the great barrier reef at the moment?
  15. (*steve*)

    Ultra Caps .. Super Caps

    Oh, and post some pictures of your actual board
  16. (*steve*)

    Ultra Caps .. Super Caps

    That's what we're trying to find out: 1) Do some caps discharge faster than others when NOT connected to the board? 2) Is there some unexplained low resistance across some of the capacitor connections? For each of the places where the capacitors connect, check the resistance with the probes...
  17. (*steve*)

    Hello All

    Remember the paper tape option on ASR-33 teletypes?
  18. (*steve*)

    Ultra Caps .. Super Caps

    No, check the resistance of the board where the cap connects, not the cap! Also, try charging up the caps and disconnecting them. See if any discharge faster than the others over a period of 24 hours or so.
  19. (*steve*)

    Ultra Caps .. Super Caps

    You need to ask a question. But not in someone else's thread
  20. (*steve*)

    Ultra Caps .. Super Caps

    Let's assume that the 200F cap discharges from 2.7V to 1V in 24 hours and that the leakage current is constant. I = c dv/dt = 200 x 1.7 / 86440 = Approx 4mA I presume you've swapped the caps around to check is not the capacitors. If not, I'd remove the carrots and read the resistance with a...
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