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  1. BobK

    Audio Standards

    This might be helpful: http://en.wikipedia.org/wiki/Line_level Bob
  2. BobK

    Recharging a car battery

    Actually, if you use a bridge rectifier, the motor can spin in either direction. Bob
  3. BobK

    SMT Mounting

    SMT soldering is not as difficult as it looks. There are many good tutorials on the web. You need a good magnifier and I reccommend paste solder and a syringe to apply it (you can buy it that way). Bob
  4. BobK

    Transistor Mosfet pairs to drive LED cube layers

    Bad idea. You are going to waste a lot of power in your resistors if you use a 12V supply to light that many LEDs. Find a logic level mosfet than can be fully turned on with 5Vand stick with the 5V supply. Bob
  5. BobK

    Logic gate

    Yes, but you need a transistor as well. Bob
  6. BobK

    PIC interrupt routine help

    nepow, But what you describe is done just as well by a call. An interrupt has no advantage if it is always triggered from the same spot in the program, which seems to be the end of your ADC read. If I understand it, your program is something like this: <initialization> main_loop...
  7. BobK

    Flashing 5watt led?

    Yep, the are already solderd to an aluminum "star" which provides some heat-sinking, and slots so that they can be bolted to a more massive heat-sink. Bob
  8. BobK

    resistor question on 'aircasting' project

    Unless you are doing SMT. Bob
  9. BobK

    You would think Boeing would know better

    Well, that is a relief. But I still wonder about what they have done wrong with the LI Ion batteries. My guess is that it is actaully a software problem. Here is why. The batteries have a problem if you charge or discharge them too fast. Charging is a no-brainer -- you can limit the...
  10. BobK

    Wanted$$: Super simple 8 input & 8 output select

    Believe it or not, I was actually considering offering to do this for free, as a demonstration on the forum of what is needed to agree on a specification and get a project done. People come here with unrealistic expectations of what it takes for a project like this. This one is actually...
  11. BobK

    Automatic bicycle hub gear changer using servo

    I think you should go for a torque converter. Bob
  12. BobK

    Wanted$$: Super simple 8 input & 8 output select

    Try to write a really good specification, that might inspire more interest. The problem is, from what you have said so far, I expect it would take hours of back and forth just to clarify what should actually happen. And $100 / x hours is not much per hour when x > 2. Bob
  13. BobK

    You would think Boeing would know better

    Yep. Bob
  14. BobK

    Circuit board for flashlight - need help

    3 x 1.2V = 3.6V which is close enough to 3.5V, so I think the batteries can drive this bulb directly. Bob
  15. BobK

    simplest portable battery charger

    You can trickle charge them at 0.05C, but that will take about 24 hours to charge. Otherswise you really need a smart charger. (0.05C means 0.05 x the capacity in maH, so if capacity is 800maH, charge rate will be 40ma) Bob p.s. the solar cells from a calculator will probably not...
  16. BobK

    You would think Boeing would know better

    Lithium Batteries Central to Boeing's 787 Woes It's not like there has not been any press about the dangers of Li Ion batteries... You would think Boeing would have the expertise and motivation to handle them correctly, but apparently not. Bob
  17. BobK

    Flashing 5watt led?

    My tip would be to buy one on a star. These can then be bolted to a heat sink. Bob
  18. BobK

    simplest portable battery charger

    1. There is no such thing as a 1.5V lithium ion battery. 2. If you think tinkering with lithium ion batties is something for amateurs to do, read up on the problems with the Boeing 787: http://abcnews.go.com/Politics/wireStory/emergency-faa-grounds-boeing-787s-18234982 3. Your batteries...
  19. BobK

    Raspberry Pi

    Did it come with any specifications? The current requirement should be listed. Bob
  20. BobK

    automatic switch

    I suppose, if the current requirements are not that big, you could use a resistor to mimick the load and after the voltage across it remained stable for some time interval, switch it out and the real load in. Then you could switch back if the voltage across the real load drops. But again, way...
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