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  1. BobK

    Simple DC-DC Boost Converter 19.50V(dc) to 20.50V(dc) and 8A for charger.

    164W DC/DC converters are not simple. I don't understand why having the inputs and output on the same side makes the board you show flawed for your usage. Bob
  2. BobK

    Increasing Battery life Question

    This datasheet shows 12000 mAh at 250 mA. It is down to about 10000 at 500mA, which is the highest current the characterize it at. If the drain in 1/2 hour it is probably drawing several amps, but not close to 24, which I doubt that it could ever supply. Using it an application this far away...
  3. BobK

    Increasing Battery life Question

    Alkaline D cells have a capacity of about 12Ah, so, if is lasting only 1/2 an hour, it pulls an outrageous amount of current. So, maybe the submarine batteries Steve suggests are just about right. You say you have a 12V portable source. How much current can it provide? And what capacity? A...
  4. BobK

    24VAC Step-up Transformer

    Okay, we can now see the whole picture. I guessed that you were wiring the LED in series, but now I know why as well (you don't have the connections to wire it in parallel). I would go with @kellys_eye's second suggestion, wire a relay across the switch and use the NC contacts to light a light...
  5. BobK

    Smoothing a charging current for a phone?

    The MPPT controller must be used to charge a battery directly. It puts as much energy into the battery as it can under varying conditions. Once the battery has enough energy to charge the phone, you would hook it up to a buck or boost converter to get 5V to charge the phone. Bob
  6. BobK

    24VAC Step-up Transformer

    Your description does not make any sense. A 20mA LED should have little effect an the voltage to the relay. And how is the length and size of the wire relevant at all? There should be no change to the wiring to the relay. Show us how you wired it. It sounds to me like you wired the LED in...
  7. BobK

    Seeking a voice changer with mic and amplifier in order to communicate with hearing impaired

    Just had a thought. If you have a PC, get the free sound editing program called Audacity. On it, you can record your voice and lower the pitch to determine whether it works. Bob
  8. BobK

    Seeking a voice changer with mic and amplifier in order to communicate with hearing impaired

    Do you know what frequencies he can hear? I am skeptical that lowering the frequency of your voice will help. Can he understand people with unusually low voices? If so, it might help, particularly if your voice is high. Bob
  9. BobK

    Simple moisture meter circuit?

    And I agree completely with you. I have an electric guitar and tried recording it by taking the signal directly out of the guitar, and it sounds awful! I found that electric guitar is recorded through a mic off the speaker of your amp. This sounds like an electric guitar. The waveform...
  10. BobK

    LED forward voltage and brightness

    Less light in a given direction, more light overall. Bob
  11. BobK

    LED forward voltage and brightness

    And be aware that mcd is NOT a measure of how much light an LED outputs and mcd / power is NOT a measure of efficiency. The viewing angle is also necessary to determine these. You might have one LED that is rated at 1000 mcd and another that is rated at 100 mcd. But if the first one as a...
  12. BobK

    Simple moisture meter circuit?

    Actually no. You want your equipment to faithfully reproduce the music the way the artist recorded it. Yes, hard rock / metal uses a lot of distortion purposely. But you do not want to add distortion with your the equipment you are listening on. Bob
  13. BobK

    LED forward voltage and brightness

    Yes, but your eye will barely distinguish the difference between 15 and 20 mA. Bob
  14. BobK

    LED forward voltage and brightness

    The luminous output of an led is roughly proportional to the current. You are right that the current will not be well controlled when the led Vf.is 3.0V and the supply is 3.3V. Bob
  15. BobK

    Capacitance on PIC I/O line

    If you are worried about an input drawing an enormous current and blowing out your signal source, no, this is not a problem. The capacitance is tiny and the current would be drawn for only nanoseconds. The capacitance of the output source would generally supply all the current needed. You do...
  16. BobK

    Make an Oscilloscope?

    You can use the audio jack of your PC as a very low performance scope, good only for audio frequencies and not good for DC since there will be a capacitor on the input. Search the web for this, it is only a few simple parts. And you can get free software to display it. Bob
  17. BobK

    Smoothing a charging current for a phone?

    Phones expect a constant voltage of 4.5 to 5V to charge. The only way to smooth the current is to accumulate the energy somewhere else before charging, like in another battery, which you have rejected. A supercapacitor would be the other option. Charge it until its voltage reaches 5V, then...
  18. BobK

    Unable to get solenoid controlled by Arduino to work anymore

    Actually, it shows the base connected to the solenoid and the emitter or collector connected to Arduino. Cannot tell which since he omitted the arrow to indicate which is the emitter. Bob
  19. BobK

    Make an Oscilloscope?

    A waveform generator creates signals. An oscilloscope displays signals visually. They are not the same thing, and one is not a part of the other. What is it you want to do.? Why did you decide that you needed to make a waveform generator instead of an oscilloscope? Bob
  20. BobK

    Please help: Build for GPS tracker with SOS signalling

    I see three possibilities here, none of which correspond to the story the OP is telling. 1. A simple troll. 2. A criminal of some type misleading us to get help for a tracker to be used for some nefarious pupose. 3. A delusional individual. In all cases, we should stop interacting with him. Bob
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