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  1. BobK

    Remote Control Circuit with CD4017 - counter decoder

    One thing you should do is clip all the leads on the back of the perfboard. It is too easy for them to short each other now.
  2. BobK

    Using Ardunio and MOSFET to drive 5V to 12V

    The N channel MOSFET cannot be used as a high-side switch as you have it, unless you can supply a voltage to the gate that is higher (by 4 to 10V depending on the device) than the supply voltage. You need to connect one side of the the load to V+, other side of load to drain and source to...
  3. BobK

    how to achieve desired delay time in cmos inverter

    Bob: Why do you answer a question with a question? vead: Why not? Bob
  4. BobK

    help needed for engineering college project

    When someone says what is the minimum resistance needed too ...? I assume he means that any resistance above that will be OK. That makes no sense in the context of the OP. Bob
  5. BobK

    how to achieve desired delay time in cmos inverter

    Are you talking about in fabricating an IC or using existing CMOS logic ICs? Bob
  6. BobK

    Source/sink

    If the analog input is anything like the analog input on a PIC microcontroller, it needs fairly low output impedance from the voltage source. In the PIC this is typically 2.5K. The impedance of your hand will be much higher than this. Did you try the capacitor that Kris suggested. That would...
  7. BobK

    help needed for engineering college project

    Why would there be a minimum resistance? Bob
  8. BobK

    "Eh, I just had it laying around" How to know if it's okay?

    That circuit is to regulate the voltage for the entire car. It is not what you want. What you probably need is a series diode + resistor before the regulator, a zener diode from there to ground, and a large capacitor. But I am not an expert on this. There are others on this forum who know...
  9. BobK

    how to achieve desired delay time in cmos inverter

    Well, modern microprocessors are all CMOS and run at frequencies as high as 4GHz which is a 250 ps clock cycle, so they must have gate delays of well under 215 ps. Bob
  10. BobK

    "Eh, I just had it laying around" How to know if it's okay?

    If you use this with the car running, you need a lot more circuitry to protect from voltage spikes that exist in an automotive system. You may end up blowing out the regulator with this simple circuit. Bob
  11. BobK

    simple radio building

    If you allow both sides of a sine wave through, the average voltage is 0. If you allow only the positive part, the average voltage is > 0 and varies with the amplitude of the sine wave. Bob
  12. BobK

    simple radio building

    Easiest, replace the headphones with a 1K resistor then connect the junction of the collector and the resistor through a capacitor (1uF) to your stereo system through an AUX input. Bob
  13. BobK

    "Eh, I just had it laying around" How to know if it's okay?

    What kind of power supply is feeding it? If it is a battery and it is close to the regulator, you could get by with no cap. A 100uF in parallel with a .22uF would probably be good. Bob
  14. BobK

    "Eh, I just had it laying around" How to know if it's okay?

    If you had to substitute, a larger cap would be better there. The .22u will probably work fine though. If you have 2 of them you can parallel them. All it is doing is providing current quickly if the demand changes. Bob
  15. BobK

    simple radio building

    It is biasing TR2 into the linear region. If you remove it (why would you?) you would get distorted sound as only the positive half of the waveform would come through. Bob
  16. BobK

    Who etches photoresist PCBs?

    Far more accurate that I ever got with toner transfer. I would almost always have broken tracks and could not get nearly as good resolution with toner transfer. This board had no issues at all and all of the tracks and pads were very sharp and clean. Of course the pre-sensitized boards do...
  17. BobK

    Automating my living room/space

    Let me see if I understand what you are trying to do. You have an existing mains light switch, and you want to signal your computer when this switch is flipped. Is that correct? Is the switch also still controlling a light? Bob
  18. BobK

    Voltage regulator.. or Help the noob!

    Nor for a car that is not running. bob
  19. BobK

    Who etches photoresist PCBs?

    I just made my first board with a photo-resist, and it came out great the second time (I did not develop it long enough the first time). See here: https://www.electronicspoint.com/threads/photo-resist-pcb-help.268585/#post-1609340 I bought an exposure kit from MG Chemicals for $55 and it...
  20. BobK

    Op Amp for speaker circuit

    Having speakers rated at higher wattage than the amp is no problem, in fact it is desirable since it means you cannot destroy the speakers. You would not want to regulate the voltage down. All that does is wastes power and limits the power you can get out of the amp. The LM386 is a popular...
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