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  1. hevans1944

    Newbie Question......Suitable power supply

    Apparently you did not go down the thought pattern far enough. The device you purchased is not authorized for unlicensed use in the United States. The 433 MHz ISM band is restricted to Region 1, which includes Africa, Europe, and Russia. The USA, the Americas, Greenland and some eastern Pacific...
  2. hevans1944

    Electronic supply, help.

    You have a business plan? That would surely include lining up suppliers, not wasting our time here.
  3. hevans1944

    Microcontroller controlled by pushbutton for LED flashlight

    No, but I'm not looking for the shortest interval available. The 135 ms interval is with the WDT prescaler set to 1:8 division ratio. I believe it will go down to about 18 ms with 1:1 division ratio, but 135 ms is as close as I can get to the 100 ms originally desired. Even longer periods would...
  4. hevans1944

    Small Inductance meter

    The LC301 with Kelvin probes is your "best bet" for measuring nano-henry inductors in SMD packages. At what frequencies are these nano-henry components being used? A ten nano-henry inductor has a reactance of 0.06 ohms at one megahertz. None of these LCR meters even attempts to measure...
  5. hevans1944

    Microcontroller controlled by pushbutton for LED flashlight

    Most of my problems had to do with initializing memory variables just once instead of after every reset occurred. I finally got a clue on this when I belatedly realized everything I needed to know was coded into the bits of the STATUS register. Once I was able to distinguish the different modes...
  6. hevans1944

    Microcontroller controlled by pushbutton for LED flashlight

    Well, it just keeps on getting better... I re-discovered recently that, whenever the PIC awakes from sleep, it sets a bunch of bits in various registers to logic "1" state. Included in the list is the 4-bit TRIS register associated with the I/O ports, and the OPTION register and CMCON0 register...
  7. hevans1944

    Got room for a resistor? :D

    Hmm. Better make sure it's gotta a heat sink: 7500 A at 0.075 V is 562.6 W being dissipated across 10 μΩ. I presume you adjust the calibration of this thing with a small flat file, maybe looking for 75 μV at 7.5 A?.
  8. hevans1944

    Small Inductance meter

    You want to measure nanohenry values for 0603 SMD? Why even bother to try? Why should the inductance value have changed since manufacture? It will not be easy to measure SMD inductors with a few tens of nanohenrys inductance. The task is virtually impossible "in-circuit," and almost impossible...
  9. hevans1944

    Hey, have you seen one of these?

    Could it be an ancient Schering bridge? (In pretty damn good condition it appears!)
  10. hevans1944

    Need help with design issues - resistor questions

    That is a valid concern and I don't have an answer. Best bet would be not to exceed the maximum voltage that can be safely applied, whether PWM or not. Just to be safe. Or try it out on just one peltier plate at low duty cycle and 48 V to see if it "smokes" it. That sounds like a good plan. You...
  11. hevans1944

    books

    WTF? Free as in stolen? The "Art of Electronics" is copyrighted material.
  12. hevans1944

    5 Ways to Harness Free Energy

    What a COS the link points to. The author claims "Each cell will produce about 1.3 to 1.8 volts depending in the concentration of bleaching powder in the cell. The current flowing will be about 300mA to 600mA in each cell." Then he goes on to say this: "Hence, 10 such cells in series will give...
  13. hevans1944

    More efficient LDR "dark" switch?

    Yes, I picked up an LM317 at Radio Shack a few weeks (months?) ago, along with the 5 V 7805 3-pin series regulator. I've been using a 9 V DC "brick" rated at 300 mA but most of its current capacity is being used to light an LED to remind me that it is on. The LM317 is not a low-drop-out (LDO)...
  14. hevans1944

    Need help with design issues - resistor questions

    Peltier coolers are wonderful toys. The model you are using can be safely connected directly to the 12 V DC electrical system of an automobile without the need for any "current limiting" resistors. However, since are using a 48 V DC electrical system, you must be careful that each Peltier device...
  15. hevans1944

    How to toggle on/off via Power Line?

    The X10 modules ARE the proof of concept: they send and receive high-frequency control signals, carried on the power lines as signal conductors while at the same time those same conductors provide power to the loads. What part of this do you not understand? What wheel are you trying to re-invent?
  16. hevans1944

    biasing this op amp

    Ah hah! An old-school analog designer! With a musical inclination too. I love it. Well, sometimes the choices we make up front have long-term unforeseen consequences down stream... but that doesn't mean the choices were wrong. Perhaps just unfortunate or inconvenient with the benefit of 20-20...
  17. hevans1944

    biasing this op amp

    Yikes! I would certainly investigate another solution at that price and minimum order quantity. Perhaps we could help you find other solutions if you would tell us what you are trying to do, rather than you providing your proposal of how to do it. There is usually more than one solution to any...
  18. hevans1944

    Opamp Power Supply

    Traditionally, op-amps were bi-polar devices, early op-amps operating with ±100 V DC outputs provided by vacuum tube electronics. Later solid-state op-amps settled on ±15 V DC power supplies to produce ±10 V DC outputs. As "head room" improved, power supplies were reduced to ±12 V DC for the...
  19. hevans1944

    biasing this op amp

    Of course it out of the question with the circuit and components you have. It is what it is. You could try to substitute an op-amp with rail-to-rail output capability. Google is your friend. Maybe the attached file will help.
  20. hevans1944

    biasing this op amp

    So, you connected two 4.7 kΩ resistors in series across your 9 V battery, and are using their common junction as your "virtual ground?" If so, that is what you measure your output with respect to, the junction of those two resistors. You should be able to get the TL082 outputs to swing ±3 V or...
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