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  1. CDRIVE

    Amplitude Modulation using Op Amp.

    You're FET has no negative gate bias. You need a source resistor to bias the FET in its linear region. As it stands, your FET is will not transfer the positive excursions on the gate to the Drain. Oops! Never mind. I didn't see the neg bias input. Must rethink... Chris
  2. CDRIVE

    Rectifier circuit fails when capped.

    Good point. The bottom view of the board seems to show groups of three diodes in parallel per leg but that makes no sense either because then I would expect a total of twelve. :confused: Chris
  3. CDRIVE

    Rectifier circuit fails when capped.

    I'd prefer caps rated >=50V but when wiring the caps in series you must provide a voltage divider by placing a resistor in parallel with each cap. A 10KΩ to should do it. Chris Edit: After re-thinking this the resistors may have to be lower than this. The larger the caps are the lower the...
  4. CDRIVE

    MOTOR SPEED CONTROL

    This seems to be a fairly honest assessment.. http://www.zen22142.zen.co.uk/Prac/winscope.htm Chris
  5. CDRIVE

    MOTOR SPEED CONTROL

    Winscope has a bandwidth of about 20Hz to 20KHz. A 20KHz square wave will look more like a sine wave. Be aware that the vertical scale is not calibrated. It can't see a DC level either. As PC based scopes go the USB versions are far Superior but aren't free. Chris
  6. CDRIVE

    MOTOR SPEED CONTROL

    Arg, when you post code copy it from your Picaxe editor and paste it between Code Tags. Doing so will keep it formatted.;) Chris
  7. CDRIVE

    I (a newb) would like to design a small & simple GPS tracking system for my 2 cats

    What you're describing is opposite of his system. He holds the receiver while the cat carries the transmitter. That said, yours might be a better system. Condition the cat to know that relief from the annoyance is simply a matter of not going any further. This is similar to the way electric...
  8. CDRIVE

    I (a newb) would like to design a small & simple GPS tracking system for my 2 cats

    Can't add anything to the GPS issue that hasn't been said but I'd like to say that's a very pretty kitty. ;)
  9. CDRIVE

    Valve (tube) amplifier schematic help

    This fact alone makes it nearly miraculous that the WW2 'Proximity Fuse' actually worked! :cool: The guys that designed and built the prototypes were mostly Hams of the era and they (in my opinion) were geniuses! ;) Chris
  10. CDRIVE

    Valve (tube) amplifier schematic help

    Think of it more like a solid state replacement for an electromechanical relay. This is all well and good but the study of electronics begins with basic electron theory and a solid understanding of Ohms Law. Everything else is built upon these. Besides, this is the 'Electronic Projects'...
  11. CDRIVE

    Valve (tube) amplifier schematic help

    I didn't say anything about "automatic". I think we've reached a point in this thread that you should be pointed here.. https://www.electronicspoint.com/electronics-tutorials-f101.html Doing otherwise could find this thread active in 2020! :rolleyes: Chris
  12. CDRIVE

    Valve (tube) amplifier schematic help

    MOSFETs are primarily used for switching because they have a very narrow linear region. JFETs are preferred for amplifier applications. Their operation closely mimics a vacuum tube and have a broad linear region. Chris
  13. CDRIVE

    Valve (tube) amplifier schematic help

    In addition to what Kris said it won't make much sense with a 9V B+ either.. Chris
  14. CDRIVE

    Digital Pot setup

    Yes Gorgon, good point. I replaced the Diode with a 30V Zener and added a 10 Ohm resistor for current limiting. Justin, Zeners drop their rated voltage in their regulating direction and drop .7V in their reverse direction. So, as Gorgon said, this circuit should limit the + voltage to the...
  15. CDRIVE

    Easter engine problem

    The TIP127 is a Power Darlington. Its characteristics are not similar to a 2N3906 in any way, except for being a PNP. Perhaps you missed it but I stated previously that this is a novelty circuit. With a large cap and low current motor it will do very minor work. It's not even the starting...
  16. CDRIVE

    Valve (tube) amplifier schematic help

    I believe this to be a modern incarnation that began with logic blocks and the way they're drawn separately, despite the fact that they're all contained in a single chip. I also believe that the advent of Spice modeling had a hand in this. Back in the day dual triodes were never drawn like this...
  17. CDRIVE

    VHF booster

    They didn't coin it the "Iron Curtain" for no reason. ;) RF design is a field unto itself. If you want a fascinating topic, read up on "Transmission Line Theory & Design" in the ITT "Reference Manual For Radio Engineers". It's the RF Bible! By the way, the broadband amp in the PDF uses a...
  18. CDRIVE

    Easter engine problem

    Wingnut, my motor model had a resistance of 62.5 Ohms. Your DMM isn't going to catch this short pulse. Also note that the author's photo indicated an unloaded motor with a piece of tape on the armature shaft so he could see it move. Also, and as I said before, I think this circuit is best...
  19. CDRIVE

    VHF booster

    Here's a direct link.. http://www.datasheetcatalog.org/datasheet/motorola/MPF102.pdf Chris
  20. CDRIVE

    VHF booster

    Since Dave sent you some MPF102's here's some links of tuned RF amplifier designs. You would have to recalculate the resonant circuits for the frequency your using. http://radiofrequencyamplifier.blogspot.com/2012/02/6m-rf-preamp-using-mpf102.html...
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