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pzw

Member Since: September 30, 2010

Country: United States

  • News - The Moment of Truth | last year

    A few things which I learned over the years;

    • When you get a complex PCB manufactured pay for the e-testing! It will save you a lot of headaches and time…

    • During the first power up, use a current controlled power supply, set it to the right Voltage, but to 0.00A. Switch it on, and slowly increase the current limiter… Does it go over the expected current in no time, while the Voltage remains very low, just stop, and check why… (Reversed diode / shorts etc)

    • Use polyfuses where possible!

    • In case of higher voltages/currents use the “light bulb method”. Put a incandescent light bulb in series with your power input. If the bulb starts glowing, most likely there is something (very) wrong… Incandescent bulbs have a very low resistance at room temperature, which will increase considerably when they are burning at nominal power…

    • In case there is an issue with the project, use all your senses… If you smell electrical death, then most likely you will see it too… However using your fingers as “temperature probes” might locate the issue before it is too late…

  • News - According to Pete | about 3 years ago

    The virtual ground is created because in a circuit where the opamp is used in a feedback setup, the opamp “tries” to keep the potentials at the + and - input equal. (That is the simple explanation). So if the + input is grounded (via a resistor) automatically the other one will get a similar potential (ground).
    Since the input impedance of the inputs is high, you can say that there will be no current flow into the opamp. So if a resistor is used between the + input and ground, the potential at both sides of the resistors will be equal.
    Opamps are interesting devices… It is very difficult to put it “all” in 20 mins of video… (i.e. what happens when you drive the + and - with the same voltage/signal…)
    But I think the basics have been covered in it.
    (A reference for basic designs: http://www.physics.unlv.edu/~bill/PHYS483/op-amps.pdf )

  • News - According to Pete | about 3 years ago

    To be more precise, a buffer has a voltage gain of 1, not of zero ;-).
    And the + and - inputs are not coupled internally. The virtual ground is created by the feedback. If you remove the feedback, the virtual ground is gone.
    Also the gain bandwidth product is something to keep in mind during designing. If you want to amplify 100µV with an opamp to 10V (wouldn’t advise doing so without using a low noise opamp) it requires an amplification of 100,000x . If your signal has a bandwidth of 1000Hz,you need a pretty decent opamp to achieve it!

  • Tutorial - Soldering 101 | about 3 years ago

    For leaded solder use approx 340C and for lead free solder use approx 370C .<br /> But remember that the lead free solder comes in many different alloys, so it is possible that the 370C is too low or too high…<br /> <br /> Tip: Clean your soldering iron tip with a piece of paper, not with a wet sponge. It saved a lot of tips over the years. (The water in the sponge accelerates the oxidation of the tip)

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