Search results

Search Forums New Posts
  1. BobK

    input 4 bit analog to USB output?

    Yes, it looks like about the cheapest way you could start ARM development without soldering! Bob
  2. BobK

    input 4 bit analog to USB output?

    shadowdog, From what I can tell, I don't think the teensy does what you are asking for. It could be programmed to do it, but this is up to you. The gpio board that I linked is already programmed to do what you are asking for. bob
  3. BobK

    Is Differential Amplifier badly inaccurate?

    Each op amp has a specification of the allowed range of common mode. If you stay within this, they work as advertised. I don't see any problem with your circuit, as long as the voltage across the sensing resitor is between 0 and 0.5V, the output should be that difference * 18. Have you tried...
  4. BobK

    input 4 bit analog to USB output?

    Somebody must have made a product that does that. Oh, they did! http://numato.com/8-channel-usb-gpio-module There are many others, but this one was the cheapest I found. Bob
  5. BobK

    how to charge 3.2v 15.6ah cell pack

    Hi Hunterstow, welcome to the forum. Can you send me a link to the LED you are using? 1000 lm at 3V and 700ma would be the most efficient LED I have ever heard of. Bob
  6. BobK

    My free energy generator

    No, don't you guys get it! One motor is the motor and the other is a generator. The generator produces the power to run the motor AND and the LED AND the motor turns the generator! This will change everything! Short ALL energy stocks now! Bob
  7. BobK

    Wind Generator

    Your calculation is a little off: A 160 degree cone at 8ft high will light a 46ft circle. So in a room much smaller than that, most of the light is going to be on the walls, not on your working surface. A 60 degree will light a 4.7 foot circle. So a 2 foot grid of 60 degree lights would work...
  8. BobK

    Wind Generator

    Well, the calculator should be correct, IF the luminious intensity is the same over the entire angle, which it most likely is not even close to. By my thinking, a 160 degree angle is not really desirable for ceiling lighting. A lot of the light would be hitting the upper parts of the walls...
  9. BobK

    is this chirping from the electrical wiring?

    Congratulations! We all were pretty certain that it was a smoke alarm. We were wrong. Bob
  10. BobK

    Wind Generator

    If it really is 160 degrees. then it can't be anything like 16000 mcd over that angle. From the calculator here: http://led.linear1.org/lumen.wiz That would be 83 lumens, which is impossibly high in a 20ma white LED. Okay, the calculator does say beware of wide angle LEDs. So the 16000...
  11. BobK

    Could this circuit work?

    Yes. Simply delete the circuit and make a new one. In all seriousness, that circuit is pretty much useless. You could eliminate most of the components and it would do the same thing, turn on an LED with a switch. Bob
  12. BobK

    Wind Generator

    I am not saying either way, I am just saying that the specs are not correct. I suspect that the angle is really 60 degrees rather than 160, which would also be more normal and actually more useful. Bob
  13. BobK

    Curcuit design help needed, help.........

    You do realize that that is illegal, right? (And probably not as simple as you think.) Bob
  14. BobK

    Wind Generator

    Those specs cannot possibly be correct: I get (worst case: 3.4V 20ma 160 degrees) 83 lumens for .068 Watts or 1280 lumens / W. The best LEDs do about 200 lumens per watt. Bob
  15. BobK

    Buck Converter Calculations - Halp!

    Kris, I think Raven was suggesting that he just use a constant current supply and no buck converter. This should work, although I would question how well it would work when the capacitor was near zero. But it will waste a lot of power by lowering the output voltage with a resitive (or...
  16. BobK

    Potential divider problem

    Very nice explanation Steve, I learned something new. Bob
  17. BobK

    Buck Converter Calculations - Halp!

    Hi Luni, Here is a circuit I designed for a constant current LED booklight. This circuit is designed to provide 30ma across the LED and actually was able to do so as the 9V battery ran down all the way to 4V. For 5A you would need to beef up the power components, (inductor, mosfet and...
  18. BobK

    rechargeable batteries, odd size

    NiCad are also better at large current draws than NIMH. I learned this when I tried to replace batteries for my drill / driver with NIMH. Even though the voltage was the same and capacity was higher, the NIMH were anemic. I had to go back to NiCad. Bob
  19. BobK

    Buck Converter Calculations - Halp!

    First of all, you need a P-channel MOSFET in that circuit. Then I think you can just drive the gate from the '555. You don't need the 2200uF since it is just going to be in parallel with your supercap. Basically think of it not as a voltage regulator, think of it as loading up some current...
  20. BobK

    BJT Ramp?

    I don't see how the output voltage can not change with changing input. The gain and offset voltage could be off due to the tolerance of the resistors, but it should still behave liinearly over the entire input range. What is the load on the op amp output? It should be no more than 1K. To...
Top