Search results

Search Forums New Posts
  1. BobK

    16bit pipelined serial parallel multiplier schematic diagram?

    Gee, I designed one of those just a couple of days ago, but I seem to have lost the schematic. I guess you will just have to search the web for it. Bob
  2. BobK

    Led flashlight question

    The word "torch" used by you Brits always amuses me. Here in the US, a torch is what the towns people are carrying when they storm my mentor (Dr. Frankenstein)'s castle. Bob
  3. BobK

    parallel led array

    It looks like it should work. Bob
  4. BobK

    Sensor interface, OP AMP, -500mV +500 mV to 0-5 V amplifier

    Good comments from GPG. I assumed that since the sensor output -0.5 to 0.5V it was already amplified by an op amp, but apparently not. So a buffer amplifier is required before the summing (or differencing) amp. One more thing, though: Even a rail-to-rail amp will not allow the input to go...
  5. BobK

    Sensor interface, OP AMP, -500mV +500 mV to 0-5 V amplifier

    Adam's circuit works, but it is overly complicated and requires a floating supply of 0.5V. An op amp can sum 2 signals and multiply by a constant all at once. This is done by a summing amplifier. Here is the summing amplifier configuration: The gain of a non-inverting amp is (1 + Rf / Rg)...
  6. BobK

    parallel led array

    If it is for a DC brushed motor (2 wires), possibly. This would be a PWM controller, which will turn the LEDs on and off rapidly, with the brightness depending on what percent of the time it is on. But, be warned, that if you have epileptic ghosts, it might induce seizures. And I would not...
  7. BobK

    Replacing triple a batteries

    The other solution is to get a 3V wall wart. No assembly required, just connecting 2 wires to the battery holder. Bob
  8. BobK

    Replacing triple a batteries

    Be careful Martin, there might well be different models, some of which run off USB and others off batteries. To the OP: The correct way to do this is to use a 3V regulator between the 5V USB port and the headphones. It is a fairly simple circuit. Do you have any experience with building...
  9. BobK

    parallel led array

    2.3Ω for 3 in series. But I would not run that at the full 1400 mA because the battery will start out at 8.2V and you would get 1900mA through them. Also additional heat sinking is required if you run them at full current. I would use a 3.3Ω to get about 1A, And, by the way, they are not 3W...
  10. BobK

    Powering a mobile FM transmitter

    And you have a license for broadcasting in the FM band at 7W? Bob
  11. BobK

    SUPERCAPACITORS

    Just for comparison 12 D cells would have more energy: D cell: 1.5V 12AH = 18 WH x 12 = 216 WH Bob
  12. BobK

    parallel led array

    Where did you get 2A? If you put 2A through either of the LEDs you mentioned you will toast them. Bob
  13. BobK

    Using seven segment displays with LED bar display drivers

    What an odd task. Sort of like "Build a car with and internal combustion engine, but it must be drawn by a horse". Bob
  14. BobK

    Voltage when using USB Splitter

    Because a USB hub connects multiple clients to one host. He wants to connect one client to multiple hosts. Edited to add: Actually to a host port and a charging port. Bob
  15. BobK

    What resistors should I use to reduce power from 120v outlet

    You really need to tell us what you are powering, what are its voltage and current specifications. Resistors are rarely the best way to reduce power. Bob
  16. BobK

    parallel led array

    A 1.8Ω resistor would give you about 1A. Bob
  17. BobK

    parallel led array

    Just for comparison, two cells giving 7.4V and 4 LEDs in series, using 5.6V will give you 76% efficiency. This should be fine. Just calculate the resistor as I have shown you in previous posts. Bob
  18. BobK

    What resistors should I use to reduce power from 120v outlet

    Stop! Now! Drop those resistors and walk away! You cannot use resistors to reduce line voltage for electronics. What you are doing is dangerous, could kill you or someone else. If you want to power an Arduino, you need to use a low voltage power supply. Cell phone chargers are cheap and...
  19. BobK

    parallel led array

    You will set the current for whatever the forward current of the LEDs is. You have shown 2 different specs, the first one indicated 1400mA and the second one 1050mA. That is what you want for the current. You set the voltage output to a little above the expected voltage, in this case, maybe...
  20. BobK

    parallel led array

    No, you don't want to set the output voltage, you want to set the output current. The 1.4V is nominal, it will vary from one LED to another. If you happened to have 3 LEDs that ran a little low, setting the voltage to 4,.2V will overdrive them. Most of the cheap DC to DC converters out there...
Top