Search results

Search Forums New Posts
  1. BobK

    LED light: 120V and 25watts vs 12Volts and 25 watts: whats the difference?

    Power and energy are one of my pet peeves. It seems that every time I read an article about a new power plant or solar farm, they state it's output is megawatts per year. People just can't get their head around the fact that Watts is not a unit of energy. If they can't understand that...
  2. BobK

    Maximum value of Potentiometer.

    You seem to have some misconceptions about the role a potentiometer plays in an audio amplifier. The maximum output of the amplifier is determined by: 1. The supply voltage and the maximum voltage swing of the output stage. 2. The impedance of the speaker. 3. The efficiency of the speaker...
  3. BobK

    LED light: 120V and 25watts vs 12Volts and 25 watts: whats the difference?

    There is nothing pedantic about it at all. It was a clear mistake that I wanted to correct so less knowledgeable people would not be misled. Bob
  4. BobK

    LED light: 120V and 25watts vs 12Volts and 25 watts: whats the difference?

    Damn, I looked that up and got the wrong answer. Actually, it is 746. Bob
  5. BobK

    LED light: 120V and 25watts vs 12Volts and 25 watts: whats the difference?

    I have a lot of energy too. Let's calculate it: 67Kg times c^2 = 67 x (3 x 10^8)^2 = 6.03 x 10^18 Joules. Since a Joule is a Watt * Second, an 735 Watts is a horsepower. My energy is equivalent to: 8.2 x 10^15 HP * seconds. Since there are 60 * 60 * 24 * 365 seconds in a year...
  6. BobK

    What is a capacitor?

    One way to understand it is that it is like a battery that does not have that much capacity but it can take a charge and release it in a very short time, depending on the circuit, anywhere from multiple seconds to billions of times per second. If you put a constant current into a capacitor, the...
  7. BobK

    Smartphone interfacing with Audio Amplifier and External Speakers.

    We have a little Bose bluetooth speaker that travels around the house with us, wherever we want to listen. Surprisingly good sound out of a 6" x 9" or so box. Also used to bring it to the gym, where we practised ballroom dance in their exercise class room when it was not it use. Then the gym...
  8. BobK

    Touchscreen Digital mini calculator integration in Fountain pen.

    External buttons and screen? That sounds like ... wait for it, here it comes ... a calculator! Just where does the fountain pen come in? Bob
  9. BobK

    Smartphone interfacing with Audio Amplifier and External Speakers.

    Or, you could go with bluetooth and eliminate the cables, and be able to walk around and use the smartphone while it was also putting out the audio. Bob
  10. BobK

    LED light: 120V and 25watts vs 12Volts and 25 watts: whats the difference?

    Energy is not measured in Watts. Change "energy" to "power" in the above post. Bob
  11. BobK

    Bistable relay as monostable - why 2 transistors ?

    Silly me, I did not look at the cicuit but assumed from title that it was a monostable multivibrator he was talking about. So my previous post is not relevant. Bob
  12. BobK

    Bistable relay as monostable - why 2 transistors ?

    The two transistor circuit gives you positive feedback, which makes the transitions fast and sharp. A single trasistor with a charging capacitor would turn on and off slowly. Bob
  13. BobK

    Formula for Magnetic field at a distance

    Look up dipole field on google. Bob
  14. BobK

    Mosfet gate voltage

    I am sorry, my vision is really bad, I am having trouble seeing your very simple circuit. Bob
  15. BobK

    Boost converter

    You do not have a design for a battery charger, as I have stated before an Harald just stated. As an alternative to Harald’s suggestion, you could implement a battery charger by controlling the boost converter via both current and voltage feedback processed by a mocrocontroller. A practical...
  16. BobK

    Boost converter

    You can’t. If you need 1.5A at something over 12V, you will need about 4 times that at 3.7V. And that is average, the peak current will be higher since it must supply all the power in 73% of the time. Bob
  17. BobK

    Add LEDs to main power line

    Presumably, there is a low voltage power supply inside, run the LED off a low DC voltage. Bob
  18. BobK

    Boost converter

    No, in a real circuit you would need to cotrol the charging current. That cannot be done with a voltage source, as you see in your similation. Bob Ringing of the LC circuit. Bob
  19. BobK

    Help with designing a relay with adjustable hysteresis

    There is no problem with measuring the power supply voltage as long as it is high enough to power the comparator and the voltage reference. The difficulty is that you want it to work starting at 0V. I think a circuit could be designed to do this. A MOSFET with a gate threshold above the min...
  20. BobK

    I need help with capacitors...

    And the answer is still no. A 2.7V capacitor does not act like a 10V capacitor. You cannot put 10V on the 2.7V capacitor just because there is a 10V capacitor in parallel. You can make a 10V 100F capacitor by putting 4 400F 2.7V capacitors in series, but you need extra circuitry to ensure...
Top