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  1. BobK

    Amps higher than voltage possible?

    We won't even mention negative resistance devices :eek: Bob
  2. BobK

    Hold 5v Line

    Okay. A resistor / capacitor circuit followed by a comparator would do what you want. Set the comparator at 2.5V and output 5V whenever it is higher and 0V when it is lower. And choose the resistor and cap so that it takes 2 seconds to charge / discharge to 2.5V. If it is driving a relay...
  3. BobK

    Amps higher than voltage possible?

    You are forgetting that the resistance can be less than 1! Bob
  4. BobK

    Toner transfer testing

    Hmm. My process with glossy magazine paper and a laminator would only get me 10 mil and that was iffy, I would have to redo most boards several times. I now use positive photo process which still does not get me to 6 mil, though the results are more consistent. Bob
  5. BobK

    Small Audio Amp

    You can find class D amps, there is a very common one that is 3W and runs off 5V on Ebay, it costs only a couple of bucks. As for speakers, I don't know. MadisoundSpeakerStore.com is a good source for raw drivers and info on building speakers. I went there and tried to search for efficient...
  6. BobK

    LED Setup

    Did you put 5V directly to the base? That would be a bad idea, it must go to through a resistor. How about supplying a schematic and showing us what you have tried. Bob
  7. BobK

    Buffered High Speed ADC for embedded oscilloscope

    There are fast buffered ADC chips out there that would do what you need (at least the capture portion of it). I don't remember who makes them, but if you search at Mouser or DIgi-key, I am sure you can find one. Bob
  8. BobK

    UV Sterilization Light

    Always good to hear that our advice has resulted in success. Bob
  9. BobK

    Hold 5v Line

    Basically you can do this, but at the expense of having a several second delay in every intended state change. Is that OK in your application? In other words, is it OK if the relay does not respond for several seconds after the micro directs it to be on, and similar on turn off? Bob
  10. BobK

    Android Mirror on PC Using MicroController

    What experience do you have? I have been doing electronics for 47 years and would not even think of trying to build that. Edit: You would be using a lot more than a microcontroller. A microcontroller cannot handle data at anywhere near that rate. Bob
  11. BobK

    Small Audio Amp

    For highest efficiency with battery operation, you will want a class D amplifier. These will use half the power of a standard (class AB) at the same power level, meaning the same batteries will last twice as long. You should also look for efficient speakers. There are speakers out there that...
  12. BobK

    Some questions for my Container Overheat Indicator

    Using a fuse across the mains supply is never a good idea. I would put it in series with the mains supply. Bob
  13. BobK

    Which battery is suitable?

    mA is a measure of current. This is an instantaneous value that changes with the load. mAH is a measure of how much current can be supplied for 1 hour. This is a measure of battery capacity. Theoretically, a battery that has 1000mAH can supply 1A (1000mA) for 1 Hour or 100mA for 10 hours...
  14. BobK

    Android Mirror on PC Using MicroController

    Does your PC monitor have an HDMI input? Do you have a WIFI router? If the answer to these questions is yes, get an Amazon FireStick and you will have everything you need! I use this setup to mirror my tablet display on my TV, and it works beautifully. Edit: Trying to DIY, not as likely. Bob
  15. BobK

    Wish me luck

    My workplace (Intel in Hudson Massachusetts) is shutting down the FAB facility (I am not affected because I am engineering unrelated to the FAB.) So they are selling off some equipment at ridiculous prices. They will put the names of all who bid on the items in a hat and pull out the winner...
  16. BobK

    Toner transfer testing

    Yes, if those are 6 mil it is better than I was able to get. Please describe your process. Bob
  17. BobK

    Ground lift

    Well, ground effect gives you extra lift when you get close to the ground when landing an airplane, but I don't think that is what the OP wants. Bob
  18. BobK

    Which battery is suitable?

    Hmm. Are you sure it is only 4.5W? That should be no problem. 4.5W at 12V is 375mA. An rechargeable AA cell has 2000mAH so it would run up to 5 hours (realistically 3-4). It would take 10 of them to make 12V (rechargeables are 1.2V.) Lithium batteries such as 18650s can be found with up to...
  19. BobK

    design score broad for a game

    Nope. A PNP transistor is turned on when the base is about 0.6V less then the emitter, opposite of an NPN. Since the emitter is at 12V, any voltage less than 11.4V will have the transistor on. Putting 5V on it (through a resistor of course) will have it on. Personally, I would have stuck...
  20. BobK

    design score broad for a game

    Which one? the first diagram is correct, the second one is not. You have reversed the emitter and collector. And, once you have turned it back around, you cannot drive this switching transistor directly from the microprocessor because it takes 12V to turn it off. You need a level shifter...
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