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  1. hevans1944

    help in finding best micro controller

    Sounds ambitious if you are building a single rotor helicopter. OTOH if its a quad-copter, there are control packages available that make it almost a no-brainer to build a flyable platform. You will need to experiment with various air screws (propellers or ducted fans) to determine how much...
  2. hevans1944

    Potential Divider: Unexpected Voltage Readings

    Yup, I agree with @Martaine2005. The input resistance of the meter is loading the 10 Megohm divider, effectively decreasing the ohmic value of whichever resistor it is measuring across. One simple solution to this "loading problem" is to make a balanced potentiometric bridge measurement of the...
  3. hevans1944

    help in finding best micro controller

    The 40 mA no-load current requirement is too large for a micro controller to directly run your motor. The actual current under load will be higher. You will need some sort of interface circuit between the micro controller and the motor. Please tell us what you want to do with this motor so we...
  4. hevans1944

    sleep mode help!

    I am pretty new at programming PIC microcontrollers, too. But this year I programmed a PIC12F206 to go to sleep and wake up from either a button-push or a watchdog timer expiring. It spends most of its time asleep, drawing an average of less then 10 μA current. So, assuming your security system...
  5. hevans1944

    Bracelet That Pings A Nearby Ring [Help]

    You should think along the lines of a Fitbit Flex bracelet, but with a Bluetooth transceiver inside each bracelet. This is not an easy task, but it is doable. Power the bracelets from rechargeable Li-ion batteries. It would be barely possible to "reverse engineer" a Fitbit bracelet to retain the...
  6. hevans1944

    Psychic amplification apparatus - calculating inductance??

    Horns? I gotta shave those off every day!:cool: I would love to check in on Bambie from time to time, but (1) my next door neighbor doesn't have a hot wife and (2) my hot wife would kill me if I ever tried something like that.:D Being a handsome devil does have its perils.
  7. hevans1944

    Psychic amplification apparatus - calculating inductance??

    Hmmm. I had one, but I think I left it hooked up to my parapathetic inductor, which has since vanished somewhere in time. If it turns up (or down) I will let you know ASAP.
  8. hevans1944

    Psychic amplification apparatus - calculating inductance??

    @Martaine2005 knew you were going to say that!
  9. hevans1944

    Understanding the Transistor Amplifier

    I have never adequately documented any project the way I thought it should be done: provide enough information to allow it to be reproduced and maintained. Ideally, this documentation would include a theory of operation section explaining how the project works, a set of schematics and/or wiring...
  10. hevans1944

    LED Periodic Table with Arduino Mega

    Even if each LED draws only 20 to 30 mA, you should probably still use a transistor driver, like a 2N3904, on the latch outputs to control the LED. If you can, draw up some schematics and post them here for us to make comments and/or suggestions. If you do all the logic in CMOS you will minimize...
  11. hevans1944

    LED Periodic Table with Arduino Mega

    That sounds like a very ambitious project... but doable! You need to break the problem up into specific tasks and then determine how you will accomplish those tasks. For starters, consider the LEDs in the periodic table display. Each of some 118 LEDs must be individually and independently...
  12. hevans1944

    Understanding the Transistor Amplifier

    Using a transistor as a linear amplifier, instead of using it as a switch, takes you into the wonderful realm of analog circuit design. I suggest you go to the library and check out some texts that will guide you. One of my favorites now (it wasn't written yet when I started my career) is the...
  13. hevans1944

    sleep mode help!

    A search of the microchip.com website did not return any results for a "pic16f268a" microcontroller. Are you sure you provided the correct part number? Is it possible you are using the pic16f628a microcontroller? If so, please download the datasheet from the microchip.com website and read...
  14. hevans1944

    Psychic amplification apparatus - calculating inductance??

    Chris beat me to it. I think perhaps the 100 Ω resistors and 22 nF capacitors do a decent job of keeping RF out of the power rail. The schematic shows the inductors as being variable by means of a movable core. That, in conjunction with the varactor diode capacitances, strongly implies the...
  15. hevans1944

    Psychic amplification apparatus - calculating inductance??

    More accurately, a variable gain tuned radio frequency amplifier. The essential components of psi telepathy are a "transmitter" and a "receiver" consisting of cognitive living organisms. In the case of other psi phenomenon, such as remote viewing, precognition and telekinesis, the "transmitter"...
  16. hevans1944

    Help with comparison of DMM's.

    You should buy the best multimeter you can afford. You will be using this meter for the rest of your career. Fluke is a good reliable brand, but I have had good success using B&K Precision multimeters. The B&K series is updated often, so a meter you purchase today may not be available in a year...
  17. hevans1944

    Rotary sensor with logic output, kind of...

    You can couple the pulse train to a peak detector through a diode connected to a "reservoir" capacitor with a "bleeder" resistor in parallel to discharge the capacitor when the pulses stop. When pulses are present, the "reservoir" capacitor charges up and you can use this as a signal to hold a...
  18. hevans1944

    Do I need resistors with my transistor?

    If you intended to upload a schematic diagram or image, try again. It didn't work.
  19. hevans1944

    Rotary sensor with logic output, kind of...

    You have to care about speed! What if the axle is rotating one revolution per day? Do you want the relay to activate and stay activated once each day? How will you determine when the axle is not rotating? If you have something that generates pulses when the axle is rotating, you can use those...
  20. hevans1944

    How do I figure out these resistors?

    The 555 has a "totem-pole" output. See attached PDF. The output on pin 3 is either pulled up toward Vcc or pulled down toward ground. You can use just about any value resistor in the range of 1 kΩ to 10 kΩ to provide base current for the transistor that is switching the inductor on and off. The...
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