Search results

  1. OBW0549

    Seeking Knowledge!!

    I'm sorry for having to be so blunt, but your questions tell me you don't have anywhere NEAR the knowledge needed to do any such thing; you'll just end up blowing your settlement money and have nothing to show for it but a lot of frustration and disappointment. (HINT: You're not going to obtain...
  2. OBW0549

    Capacitor Explosions

    They can make a pretty impressive bang, but I doubt they're powerful enough to do structural damage. I doubt it. But you'll probably need to change your underwear afterward...
  3. OBW0549

    Oscilloscope use

    Don't use the oscilloscope calibration port for ANYTHING other than checking the calibration of your scope and its probes. That's what it's meant for, and ALL it's meant for.
  4. OBW0549

    Inverting op amp attenuator help

    Your problem is caused by the input offset voltage of the opamp. If you look on the data sheets, Vos for the LM324 can be as much as 7 millivolts, and for the TL072 it can be up to 10 millivolts. These will translate to a direct offset error in your output. To fix the problem, use a better...
  5. OBW0549

    Detecting a Signal of varing contant frequency

    The kind of circuit you're looking for is called a "missing pulse detector." Googling on that phrase will bring up numerous designs, such as this one using a 555 timer IC. The values of the timing resistor and capacitor will have to be changed to be appropriate for the pulse frequency coming...
  6. OBW0549

    Wire wrap circuit

    I get most of my wire wrap supplies from Digi-Key: IC Sockets Wire Wrap Wire Wrapping Tools Perf Board Pins for Discrete Components I've also had fairly good luck finding wire wrap stuff on Amazon.com.
  7. OBW0549

    pots in parallel

    Your resistance measurements are exactly as I would expect them to be, given that your pots are all connected in parallel. Why not test your circuit the way you're actually going to be using it: simply connect a 5 volt supply across terminals P1 and P5, and check the voltage between P5 and P2...
  8. OBW0549

    Parallel LEDs - resistor needed?

    If you want to drive LEDs in parallel, it's usually best to put some resistance (enough to drop a hundred mV or so) in series with each LED to make their current consumptions more or less equal; otherwise, unless the LEDs are well matched you will end up with uneven brightness. In that case...
  9. OBW0549

    Pizero or arduino nano?

    I don't know whether Adafruit ships to Belgium but if they do, this board might be an alternative worth considering. Small, lightweight, fairly powerful processor, and with a MicroSD socket built in. It can be programmed through the Arduino IDE, and can interface to a variety of sensors.
  10. OBW0549

    50 euro computer possible or not?

    A small LCD screen with an HDMI driver board (which is what you need for a Raspberry Pi) costs roughly around $100 (or more, depending on size). A small keyboard/mouse combination will probably cost around $25. Keep in mind that the Raspberry Pi Zero is severely limited and is really intended...
  11. OBW0549

    List of CMOS digital devices, CD4xxx

    Motorola called their line "McMOS." I still have my copy of the 1974 edition of the McMOS Handbook, right there on the bookshelf next to my Volume 1, Issue #1 (Sept. 1975) of Byte magazine.
  12. OBW0549

    LM13700 voltage controlled LP filter derivation

    The gain is unity because those two transistors are in the common-collector configuration, a.k.a. an emitter follower. Enter "darlington emitter follower" into Google and you'll get beaucoup stuff.
  13. OBW0549

    LM13700 voltage controlled LP filter derivation

    Just think of the Darlington pair, the 10K resistor connected to the Darlington's emitter, and the negative supply as a unity-gain buffer amplifier: high input impedance, low output impedance, and a gain of 1. It's only there to isolate the capacitor C from whatever load is connected to the...
  14. OBW0549

    Schematic capture software recommendation

    I recommend Eagle. The Express freeware version for non-commercial use would stack up against your list as follows: 1. Check. 2. Check, including creating your own library parts. 3. Check. Netlist export is included. 4. Check. Also available is image export to the clipboard. 5. Check. The...
  15. OBW0549

    Op-amp Current Source Analysis

    No surprise there; with an active device (the instrumentation amplifier) with gain in the feedback loop, this is perfectly normal. I don't see any reason for that; DC-wise, at least, the circuit should work as shown. Check all devices, models and connections. This is usually pretty easy to do...
  16. OBW0549

    Power rail names

    Yup. Just accept the conventions for what they are: conventions. (It's probably a good idea to follow them, too; if someone sees a negative supply voltage labeled "Vdd" their head will probably explode.)
  17. OBW0549

    Power rail names

    No criteria, really, nor any "proper" usage; they are just a commonly-used naming convention that helps us quickly and intuitively determine what kind of voltage, positive or negative, they represent. When I see "Vdd" or "Vcc" I expect a positive supply voltage; and when I see "Vss" or "Vee" I...
  18. OBW0549

    Component Help

    As has been suggested above, you need to do some research and develop a better idea of what you're after; then come back with more specific questions. For starters, here are some links to some light bedtime reading: How to Design a 13.56 MHz Customized Tag Antenna Components of the RFID System...
  19. OBW0549

    ltspice

    Another thing to consider is that when you do a simulation and run into difficulties, with LTSpice you'll be able to post the simulation files here and get help from a large number of other people who use LTSpice; the same may not be true with other simulators that aren't as widely used.
  20. OBW0549

    It's 1890!

    A laser pointer might be a fun thing to take...
Top