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  1. BobK

    Light Bulbs in the house keep Burning Out

    This is odd because my experience with LED bulbs is that they appear brighter than the equivalent wattage they claim. Perhaps your voltage is high which is causing incandescent bulbs to glow brighter than they would be, and shortening their lives. Bob
  2. BobK

    Supercapacitor Based 5 minutes Fast USB Charger

    Read the OP again, he is not talking about charging the phone in 5 minutes, he is talking about charging the supercap in 5 min. Bob
  3. BobK

    Ideas for a school experiment?

    Wireless charging is a hot topic today. Bob
  4. BobK

    Why do my leds blink on this power supply?

    I think it was "working" because the current was limited by what you power supply could provide. Once you upped the voltage and current capability of the power supply, the flaw was revealed. And yes, the picture does show them in series. Something must have shorted to blow out your LEDs. Bob
  5. BobK

    Why do my leds blink on this power supply?

    Arghh! I am sorry that you lost your LEDs, but I did not advise you to do the calculation and do what you did. The 317 circuit for a constant current driver does not involve the input voltage, so I don't know why you needed to change anything based on the input voltage. How did you wire it...
  6. BobK

    Why do my leds blink on this power supply?

    Did you ever notice that you can plug a 7W (58mA) night light into the same socket that you plug a 1500W (12.5A) heater? Plugging something into a power supply that can supply more current than needed is not a problem. The device will use only the current that it needs, your power supply...
  7. BobK

    New to Electronics, having trouble understanding Infrared.

    Actually this does not look ambiguous to me. It is stated that the preamble is 10100 and the timing sequence shows the bits in that order, so it is high bit first. Bob
  8. BobK

    side: better simulators?...

    Hmm. I have always been able to get it to work with oscillator circuits. Perhaps the circuit really does behave that way, have your tried it on circuits that actually work when built? Bob
  9. BobK

    Help with Making Alarm with Snooze

    Yes, just throw all the parts in the blender and see what comes out :) I assume you mean not that you want to build a clock (the parts list is not sufficient for that), but just a standalone device that you can energize after your alarm goes off to give you the delayed alarm. Is that correct...
  10. BobK

    Wanting to build a rectifier circuit for my lawnmower.

    Yes, that is expected. The capacitor will charge to the peak of the AC wave with will be 12V * sqrt(2) minus the diode drops. Bob
  11. BobK

    side: better simulators?...

    I can answer one part of your problem. When using LTSPICE with oscillators you need to go to the "Edit simulation cmd" dialog and check the box "Start external DC supply voltages at 0V" and / or "Skip initial operating solution". These will prevent it from finding a stable solution and get...
  12. BobK

    Is there any internal resistor for the digital I/O of my device?

    You do not send current to an input. You place a voltage on the input and it draws whatever current it wants. In this case, the linked specs indicate that it will draw 8mA at 24V. So your 24V signal must be capable of delivering 8mA. There is no need for a resistor to limit current. Bob
  13. BobK

    2 12v ac transformers to make one 24v ac transformers

    Just to make it more explicit. Connect the primary windings in parallel and the secondary in series. You will either get 24V or near 0V. If you do not get 24V reverse the leads on one of the secondaries. Bob
  14. BobK

    Combining notebook (laptop) chargers for more POWER ?

    Yes, as long as you size the resistors correctly. Use P = I^2 R Then use resistors that have twice that power rating. Bob
  15. BobK

    Embedded Software Architecture

    1. All unused ports should be either: a) Set to output and left unconnected on the board. b) Set to input and pulled either high or low on the board. Never set to an input an leave floating. 2. Generally, one would do all initialization before starting interrupts. 3. That...
  16. BobK

    connect 24 V digital signal to a microcontroller

    You can make this using a voltage divider. The inputs on 18F PICs are either TTL or Schmitt trigger. For TTL inputs: Low: < 0.8V High: > 2.0V For Schmitt trigger inputs (with Vdd = 5V): Low < 1V High > 4V So, if you are using a TTL input, use a divider of 1/7 Low = 0 to 0.71 High =...
  17. BobK

    Combining notebook (laptop) chargers for more POWER ?

    Diodes are used to make the higher voltage supply give all the power. Resistors are used to share power more equally. Neither will guarantee equal sharing, but resistors will do a better job of it. Bob
  18. BobK

    Bipolar Stepper Troubleshooting need help.....

    How fast are you trying to spin the motors? The voltage required to operate steppers depends on the speed they are running at. Try slowing it way down, say a few step per second and see what it does. Bob
  19. BobK

    Need help building a laser diode driver

    You seem to be under the impression that you can control voltage and current separately, you cannot. A constant current driver adjusts the voltage to whatever causes the desired current. That is all there is to it. You choose the current, and the driver chooses the voltage. Bob
  20. BobK

    Embedded Software Architecture

    Explain what you mean by a "software architecture". Bob
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