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  1. Alec_t

    PIC16F877, 250Hz PWM

    Can you explain that?
  2. Alec_t

    Need to build an interface between an audiometer and a set of LED lights

    The LED-drive outputs of the 3914 are, as stated above, open collector, but they are configured as controlled constant-current sinks.
  3. Alec_t

    Amber Beacon Repair and Modification

    I think the 'NPN' is more likely to be a logic-level N-channel MOSFET, given the appearance of that LED array. The array looks quite current-hungry. Whatever that IC is, you could replace it with a 555 and re-route the connections appropriately. As for why the circuit fried, it could be that the...
  4. Alec_t

    Need help to getting started

    Do you have a good grounding in Ohm's Law and Kirchoff's Laws? When it comes to choosing components, download their datasheets and study those. They will tell you such things as the maximum current or voltage that a component can withstand.
  5. Alec_t

    PIC16F877, 250Hz PWM

    :confused: I make that a 200uS period (5kHz) with a 25% duty cycle. Or does the "1 in 50uS" and "0 in 150uS" relate to the pulse rise and fall times, respectively?
  6. Alec_t

    Trying to Attach Momentary Push Buttons (Rocker-Type) to a circuit board with Silicone Buttons.???

    Once the wires are soldered, anchor them in place physically, e.g. with some kind of clamp, or hot glue etc, so that vibration doesn't fracture the joints.
  7. Alec_t

    Optocoupler delay off MOSFET solenoid

    Welcome to EP! If I've understood your intention correctly I think you should connect the emitter to the +ve end of the cap instead of to ground, and disconnect the collector from the +ve end of the cap. You might need to reduce either the cap value or the 1meg value.
  8. Alec_t

    Assorted Gubbins on toy tank

    Precautions include not trying to drive heavy-current loads directly with Arduino outputs, and ensuring that any relay coil, motor or similar inductive load has a catching diode across it to suppress back-emf voltage spikes.
  9. Alec_t

    LED Circuit Help

    Welcome to EP! Let's do the math. Assuming you can persuade USB3 to give you 900mA, that's a power output of 5V * 0.9A = 4.5W. Each LED requires 2.9V * 0.7A = 2.03W, so 3 LEDs would need 3 * 2.03W = 6.09W. So clearly those LEDs are too power-hungry.
  10. Alec_t

    Assorted Gubbins on toy tank

    Apart from the amp's dreadful distortion, that 8Ω speaker will kill the battery in no time (that's if the LEDs don't kill it first) ;).
  11. Alec_t

    Novice designing circuits

    Have you considered the Intellectual Property aspects of this? It looks as though you would be incorporating existing things which might be already patented/registered.
  12. Alec_t

    Genie/Astable help

    I know nothing of the Genie's capabilities, but virtually every modern MCU/processor made should find 1kHz a doddle ....providing, of course, it has been properly programmed.
  13. Alec_t

    Clean square waves using a 555 timer?

    Try a 10k or less resistor as a load from pin 3 to ground.
  14. Alec_t

    Where Can I Buy a 100w Resistor?

    I doubt that bit of circuitry is much to do with actually charging the battery. It looks more like just an indicator-LED driver. With only 18V as the supply, there's no way a 1k or 10k resistor should pop.
  15. Alec_t

    Electric load controller high voltage capacitor

    Here's my sim for the cap current when the IGBT (I cheated with a FET) is switched at 10kHz 5% duty cycle. RMS current is nearly 6A, with >30A peaks.
  16. Alec_t

    Limiting inrush current without power loss?

    You could try an 'inrush-limiting varistor'.
  17. Alec_t

    Trap Door Project: DC BATTERY BACKUP for 12VDC Linear Actuator

    The battery will quickly die from being overcharged.
  18. Alec_t

    Where Can I Buy a 100w Resistor?

    That's a helluva wattage! How many Ohms? What are the charger and battery specs? Plenty of 100W resistors on sale, such as these.
  19. Alec_t

    Genie/Astable help

    Show us how you have them interfaced. Welcome to EP!
  20. Alec_t

    Gate driver datasheet for IGBT

    Are we still talking about C7 in your post #20 schematic?
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