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  1. BobK

    Can I use a NiMH battery in a NiCad charger?

    Inductors do come in that kind of package, complete with color code. The one in the picture read 470, which matches the 470uH inductor in the schematic. Bob
  2. BobK

    Sine PWM program

    I am not following your calculations. To divide the half-cycle into 32 parts, you get a PWM frequency of 120 * 32 = 3840 Hz. With an 8 MHz clock, you get resolution of one part in 8M / 3840 = 2083 or about 11 bits. Which is actually more than the 10 bit resolution PICs have for their PWM...
  3. BobK

    Can I use a NiMH battery in a NiCad charger?

    There is no such thing as a 1.2V white LED, they are in the range of 3 to 3.6V typically. The chip includes a boost converter to up the voltage to drive the LED. That is why there is an inductor. Bob
  4. BobK

    Can I use a NiMH battery in a NiCad charger?

    Okay. Do you plan to use the entire circuit, and just replace the battery? Because a 1.2V battery will not run and LED without a boost converter. Bob
  5. BobK

    Can I use a NiMH battery in a NiCad charger?

    In that case, why do you need a larger battery? Bob
  6. BobK

    simple amplifier for LME49710

    As I told you before, that part cannot power speakers. It is not a matter of quality, it just cannot do it. If you read the datasheet, it is designed to power loads down to 600 Ohms. A speaker is 8 Ohms. And about size: the part I linked to is tiny, about 1/4 in square, and requires only...
  7. BobK

    How can I scale amperage?

    Here are a some of MOSFETs that meet your needs. You simply need to keep narrowing the search...
  8. BobK

    How can I scale amperage?

    Actually, the current the specify when specifying Vgs(th) IS the load current. It is just at a level that is not useful, it is the level where it is just starting to turn on. This would be an important parameter if you were using the MOSFET in the linear region (partially on), which is almost...
  9. BobK

    Can I use a NiMH battery in a NiCad charger?

    This is just a trickle charge at the max rate that the solar cell can provide, which is probably not much. So, yes, you could charge a NiMH battery the same way. A larger capacity battery might takes days to charge though. Bob
  10. BobK

    How can I scale amperage?

    Deleted, had suggested an N channel device. Bob
  11. BobK

    How can I scale amperage?

    You are completely misunderstanding the Vgs. The datasheet will have a parameter Vgs threshold. This is the voltage at which the MOSFET just starts to turn on, and is totally useless in picking a device. The current you see is the source to drain current at Vgs threshold. 250uA is not...
  12. BobK

    Low voltage sine wave output

    You are right it is hard to find a single supply 5MHz op amp that will operate at 9V. Here is one that would work. http://www.digikey.com/product-detail/en/TLE2142CP/296-10464-5-ND/380986 Bob
  13. BobK

    Sine PWM program

    I am not at Atmel user, so I can't help you with the actual program. Bob
  14. BobK

    How can I control a DC 12V motor

    N channel MOSFETS are less expensive and more widely available than P channel. You put the N channel MOSFET between the motor and ground. You also want to look for a logic level MOSFET so that it can be switched on completely with 5V out of your PICAXE. Typical MOFSETS need about 10V to...
  15. BobK

    How can I scale amperage?

    No, the resistor from ROUT needs to go to V+ so the chip thinks it is driving an LED. The gate can be connected to ROUT directly. And the IRF9530 is not a logic level MOSFET. It will not turn on enough at 5V to use in this circuit. Bob
  16. BobK

    How can I control a DC 12V motor

    If you want to control it from a picaxe you should not need an external controller. The picaxe is capable of producing the PWM signal. All you need is an approriate MOSFET to switch the motor. Bob
  17. BobK

    Help powering a small Delta fan with a wall wart

    A device takes only as much current as it needs. If the voltage is right, and the power supply can delive at least the required current, you are safe. That is why plugging a 25W lamp into a wall socket than can provide 15A (1800W) does not blow out the light bulb. Bob
  18. BobK

    How can I scale amperage?

    Great, now we are getting somewhere! It is an interesting chip for stringing together RGB LEDS, but of course, has the 18.5mA limitation. To drive higher power LEDs while still using this chip to control the PWM generation, you would just replace the R, G, and B LEDs with resistors and...
  19. BobK

    How can I scale amperage?

    Also, how may of these are you stringing together? Bob
  20. BobK

    How can I scale amperage?

    Okay, I have read the datasheet, not easy since the writer apparently does not speak English. So this is an RBG LED controller that is controlled by a non-standard serial inteface and it runs the LEDs (or LED strings up to 12V) at a constant current when on. It varies the duty cycle to get...
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