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  1. (*steve*)

    How To Detect When A Line Goes Low

    There are a couple of problems. You need a reverse biased diode across the relay coil to protect the 555 from a high voltage spike as the relay is turned off. The protection circuit can probably be a 10 ohm resistor followed by a 9V zener diode and a 100uF capacitor. A voltage regulator is not...
  2. (*steve*)

    Light therapy device

    Just correcting an error. With batteries, you'd probably want 15 (not 10) AA cells in series. If you run it from a plugpack, you could probably get away with something rated for 24V at 500mA or more (go for 1A). A simple linear current regulator (one for each string) would probably be fine...
  3. (*steve*)

    which part of code show kernel

    Here you go. (10 seconds from reading the question to googling, to posting the link.)
  4. (*steve*)

    which part of code show kernel

    I would say that loosely, it's a combination of user code and a scheduler. There is no OS.
  5. (*steve*)

    Light therapy device

    Well, you could try a TSHG5510-ND from Digikey. It has a wide angle, emits 55mW at 100mA at a Vf between 1.5V and 1.7V. the peak emission is at 830nm. These are about $1.50 each and would be good for about 1cm^2. You would require 20 of them with a total input power of around 3.2W. Because...
  6. (*steve*)

    12v Bicycle Generator Drive By Idler Pulley

    That's not entirely surprising. Many common DC-DC converter chips have maximum input voltages significantly lower than this. The LM2576HVT-ADJ has a max input voltage of 57V -- there will be many others. Frankly, the DC-DC converter seems simpler. If you're worried about what happens when...
  7. (*steve*)

    value of learning vs value of meter

    Firstly, a chip is a component. Secondly, look in eBay for "mega328 capacitance". These go up to 100,000uF.
  8. (*steve*)

    Light therapy device

    Well, 50mW/cm2 over 20cm2 is 1W. Given the approx radiant efficiency of IR LEDs appears to be in the order of 10%, you need 10W of LEDs. You can do that with less than a car battery :-) (my earlier estimate was for about 200cm2) I would suggest that people may be designing things like this...
  9. (*steve*)

    Light therapy device

    What you should be looking for is a high power IR led with a relatively wide beam width. A 10W IR LED will probably produce 1W of IR. Placed in a hexagonal pattern about 3.5cm between centres, and used at a distance such that the beam covers at least a 4cm diameter circle (2cotθ where θ is the...
  10. (*steve*)

    Light therapy device

    Oh, and these LEDs would require a heatsink to draw the heat away from them. I would probably go for an aluminum cored PCB mounted on a heatsink.
  11. (*steve*)

    Light therapy device

    First look at the permissable pulse capability graph. It shows current vs duty cycle. In your case you want a duty cycle of 1 (it's also pretty simply the lowest current shown). That's 0.5A. Helpfully they also give you a graph of Vf vs If. But beware that this is only a typical figure...
  12. (*steve*)

    Light therapy device

    Thermal runaway can occur at any initial forward current. Try measuring the Vf of LEDs with a 6 1/2 digit multimeter from a constant current source. You will see it drop continually for some time. The Vf stops falling when the temperature of the die stops rising. This is the point at which...
  13. (*steve*)

    Light therapy device

    Yeah that sounds about right
  14. (*steve*)

    Computer fan doesn't spin

    Sometimes you can lubricate the fan to get a bit more life from it. It's never a long term fix, but may work until you get a new one. The bearing is often visible under the sticker (that you have removed) -- and yeah I can see it.
  15. (*steve*)

    I need a voltage follower with >= 1Amp output for experiments

    The problem is that you are asking about stuff that requires more knowledge to understand than that which you have. Your complaint about one of my replies is somewhat ironic considering it was an exasperated response to you not recognizing what was an example of that which you initially...
  16. (*steve*)

    Light therapy device

    This is because most IR LEDs are used to send pulses of IR, they are typically not used the way you want to. At 20mA you'll get something between 3 and 4 mW of radiant energy.
  17. (*steve*)

    Converting 110v Trafo To 220v Version

    It is generally possible to use a 110 to 220 volt transformer the other way around. You do need to be VERY careful. I have a variable autotransformer that I use to check these things first.
  18. (*steve*)

    transistors, and capacitors

    It is nothing like it. I recommend you learn some basics about electronics. Please don't make baseless statements like this. The is a small but real chance that someone might read what you say and think it has some basis in fact. At least this post is not in response to someone else. I...
  19. (*steve*)

    Pure Capacitor Circuit Help

    Apart from any initial step (assuming initial conditions other than all zeros), the voltage applied is AC. The simulation should handle that without infinities.
  20. (*steve*)

    Zener diodes not working

    In my case, no. And you can imagine how much use it gets now.
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