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  1. 47gandalf

    A Transistor Book

    I found "Transistor Circuit Design" by Laurence G. Cowles extremely helpful. There are numerous copies available on Amazon at very low cost. I did not find it on Prentice Hall web site so it may be out of print.
  2. 47gandalf

    Z-axis Thermal Expansion of FR4

    So are you trying to find out what the change in THICKNESS will be for this board over a temperature range? If so, your data indicates a thermal coefficient of expansion of 0.045 inches per inch per degree Celsius (assumed temperature scale as you didn't state), or 0.045 millimeters per...
  3. 47gandalf

    Current Source/Sink Notation

    Well since you asked, underling99, please stand corrected. In electrical engineering academia the direction of current flow is always that of positive carriers, even when the physical units are negatively charged elecrons. My professors always pointed out that it's strictly a matter of...
  4. 47gandalf

    Toll gate coin reader

    And some machines check the image on the coin too. To prevent using Canadian or Mexican coins for example. There are more tests but magnetism, size, and density are the most common. [upsidedown]
  5. 47gandalf

    TATTLE TAPE DETECTION

    If the strips can be detected optically, I'd try using both a magnetic detector and an optical detector with their two outputs correlated. In other words, the optical section would tell you that there is a tape strip present, and the absence of output from the magnetic detector would tell you...
  6. 47gandalf

    Decoupling Capacitor value on a dc supply

    One additional input. If your RF frequency is high, you might make the last capactitor a dipped silver-mica type. They remain capacitive at very high frequencies, but the maximum C value is not very high. [upsidedown]
  7. 47gandalf

    Can I get some help to make an automatic light-dimmer

    Or get the module from a junked BMW. They have this function on the dome light and the light on the mirror behind the sun visors. [upsidedown]
  8. 47gandalf

    Measurement of time delay between the out puts of two opto sensors.

    All of these techniques are pretty dependent on knowing what kind of delay we're measuring. Is that picoseconds or kilocenturies? And of course what kind of accuracy is required.[upsidedown]
  9. 47gandalf

    Cleaning PCB for Conformal Coating

    And for a really simple, cheap-and-dirty approach that is surprisingly effective try this. Put the boards in a dishwasher and wash them with ordinary dishwashing soap. This will solvate many types of contaminants, but does not bring the issues that organic solvents do as others have pointed...
  10. 47gandalf

    water level...

    Yet another way is to shoot an ultrasonic wave down the container and measure the time delay for the reflected wave off the surface. As you can see from the replies, there are many ways to do this so more specific help would require more information about your application, specification, and...
  11. 47gandalf

    db9 contact resistance

    ...contacts, but cost less. When you have cabling or connections that lead to a signal passing through multiple contacts with high current, the I*R losses can add up suprisingly. And when you add this resistance to the model of your circuit, it can affect things like the corner frequency of...
  12. 47gandalf

    AC source with a FET

    ...control the current source, or adjust/calibrate it, or just have a fixed-current source with the value determined by component tolerances? And how *about* is your need for 1 mA? I mean, what tolerance is acceptable? Also, what "symmetrical characteristics" of a FET are you...
  13. 47gandalf

    Efficient Analysis of Schematic Electronic Circuits

    In addition to experience, there's another parameter that makes a big difference. That is what used to be called "Drafting". I mean that the schematic can be made easier or harder to understand by the artistic presentation, or design of the schematic. It's a picture after all...
  14. 47gandalf

    PCB Layout

    Excuse me for answering in inches instead of millimeters. I don't think that .037" drill and .055" OD on the via is large. Depending on the components you're using. I've used that drill size for the legs of through hole components for years. And as a rule the via OD wants to...
  15. 47gandalf

    Solenoid Parameters

    Rather than design your own solenoid, why not look at LVDT (linear variable differential transformer) approaches? You would buy the LVDT from a vendor and couple its movable core to the unit whose vibration you want to sense. When the core moves with respect to the solenoid winding an output...
  16. 47gandalf

    rear stop/tail light from led's

    And if you still want to do it yourself, I offer this suggestion: Why not create the brightness difference by pulsing the LEDs with differing frequencies for STOP and TAIL functions. As long as both frequencies are not too low, the human eye will never notice that they are not constantly on...
  17. 47gandalf

    Frequency "Limit" Relay

    If cheap (inexpensive) is what you want, I agree that any-old-micro can do this. I'd look at the MSP430 or PIC12 family since they are under a dollar at quantity one. Assign one pin of the processor to drive the relay, one to input the frequency signal, and write a very short program to...
  18. 47gandalf

    Switch Debounce

    Please note that the MC14490 is now a product of ON Semiconductor. The Motorola web site thinks MC14490 is a serial to parallel converter. The debounce circuit sounds like a winner. I'm going to get the ON data sheet and look to use this part. Thanks for bringing it up.
  19. 47gandalf

    Microcontroller choice

    You have not yet given enough information to make a clear choice of processor. For example, in the ADC and DAC circuits, how many bits of precision do you need? How many bits of accuracy? How many samples per second must each handle? Processor programming language? Estimated program size...
  20. 47gandalf

    Anyone tried to use Compact Flash in an embedded system?

    I've used compact flash as system component just as you are. And for many of the same reasons. We did have to write drivers for one use we made of it. In another place we had a Windows-like embedded OS to interface with it. Still needed drivers, but the vendor had already written and...

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