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  1. (*steve*)

    impose current ceiling

    The R is the decimal point, so it's 0.22 ohms. The formula is approximately I = 0.7/R (or R = 0.7/I). So the power dissipated in the sense resistor is approximately 0.7I. To keep things cool, choose a resistor about twice the value of the power dissipated. In this case that would be 5W. A...
  2. (*steve*)

    Lamp: Will it burn my house down and kill me?

    Are you referring to the "China Export" marking?
  3. (*steve*)

    Special Led Chip Array With Step Down Converters.

    Also don't short things out and what do you want to do with the LEDs?
  4. (*steve*)

    Special Led Chip Array With Step Down Converters.

    You don't actually tell us what happened?!?! I recommend you adjust the output voltage of the buck regulator. reducing it will make the fans run slower (which may be what you're after -- again you don't really say). Don't touch the current control on the regulator -- leave it turned up.
  5. (*steve*)

    impose current ceiling

    For some reason I was thinking a grid connect inverter with several hundred volts at 10A or more when I was writing that. The insulation requirements in your case are far less stringent :-) It would be worth trying a modified version of this circuit: Except do it with beefier transistors...
  6. (*steve*)

    Please explain circuit

    Actually he's right. "Johnson counters are a variation of standard ring counters, with the inverted output of the last stage fed back to the input of the first stage. They are also known as twisted ring counters. An n-stage Johnson counter yields a count sequence of length 2n, so it may be...
  7. (*steve*)

    Dr Who's K9 circuit help...

    This is going to be written off the top of my head. Expect syntax errors! const int numLeds = 12; // there are 12 LEDs cons int numOn = 4; // we want 4 of them to be on at any one time // if the LEDS are not on pins 1 thru 12, change them here int LEDS[numLeds] = {1, 2, 3, 4, 5, 6, 7, 8, 9...
  8. (*steve*)

    impose current ceiling

    The main concern is that 50% of the power coming from your panels could be converted to heat. That's a lot of heat. Even worse, if the output is shorted, 100% will be converted to heat. Whilst the characteristics of solar panels are such that you'd be very unlikely to hit the sweet spot to...
  9. (*steve*)

    Please explain circuit

    In this case, it's done in an interesting way that would appear (on the surface) to be reliable. Is there a possibility of getting into a metastable state? Is it possible to get 2 clock pulses before the output goes low? I agree with your other concerns.
  10. (*steve*)

    Please explain circuit

    If the lock is open, pressing any key other than one of the combination keys will immediately lock it. Even without wear on the operational buttons you can determine what key is part of the combination.
  11. (*steve*)

    Please explain circuit

    The weakness of that if you find the lock open frequently, you can determine the buttons that are part of the password. From here it's just a matter of trying all the combinations until you find the right one.
  12. (*steve*)

    Capacitors

    In theory there is no limit to the magnitude of the current you can draw from any capacitor. The capacitance asking with the voltage across it when you start week tell you how long you can draw that current as the voltage drops to zero. Practically there is a limit to the current due to...
  13. (*steve*)

    About Proteus

    Ckt? Cricket?
  14. (*steve*)

    Resistors or not?

    Those panels work fine at 12V at a particular temperature, on a particular day, when the phase of the moon is right. At other times and in other conditions they will either draw less current (besides being a little dim this is no problem) our more current (which is a problem). Technically...
  15. (*steve*)

    I lost my solder point on board! What I do?

    There are many forms of poor technique that can allow this to happen. The general solution is to find where that pad was connected and use a short length of very fine wire to connect the pin to where it should be connected. It is possible the pad was not connected anywhere. A description of...
  16. (*steve*)

    Dr Who's K9 circuit help...

    I'll try to write something for you. If I don't post something in a couple of days, post again to remind me.
  17. (*steve*)

    Wireless Inductive Coil - How does the transistor make it work ?

    Google "blocking oscillator" for any number of examples and explanations.
  18. (*steve*)

    Wanted: Solder Reflow Oven/Toaster Machine

    My oven is very well insulated, has some very powerful additional elements and has a fan to move the hot air around. I have no problems in maintaining a very good profile everywhere in the oven. The only exception is in the cool down part of the cycle. Another colleague of mine has a similar...
  19. (*steve*)

    Wanted: Solder Reflow Oven/Toaster Machine

    It's what I use
  20. (*steve*)

    Wanted: Solder Reflow Oven/Toaster Machine

    There are plenty of kits out there, and done prebuilt options are also available. Watch out for the cheap Chinese reflow ovens. They're horrible. Try googling for controleo.
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