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  1. BobK

    Circuitry design

    Ja, wir sprechen kein Deutsch hier. Bob
  2. BobK

    90 day countdown timer

    If you don't want to dive head first into micro development, a PICAXE is a good choice. It needs only a serial port (or USB to serial converter) to program and the software is free and it is programmed in a BASIC like language. There are several forum members here who have experience with them...
  3. BobK

    90 day countdown timer

    Are you set up with tools to program any particular type? Bob
  4. BobK

    diode for collapsing magnetic field

    This discussion has been going on for weeks now. Did you ever try the diode(s)? Bob
  5. BobK

    90 day countdown timer

    What is your experience with microcontrollers? Bob
  6. BobK

    2 pin flasher

    I suppose a JFET + resistor across R3 with the gate driven by a comparator on the current sense. Bob
  7. BobK

    Building a miniature 'Warm Box'....need advice

    In a closed box, a resistor, a light bulb, nichrome wire, or a heating element will all produce the same amount of heat per Watt i.e. 1 Watt of heat for each 1 Watt of electrical power. All of the power is going into heat. The amount of power needed to maintain a temperature will depend on...
  8. BobK

    Remote control

    If you already have a remote for it, your best bet is to just put it in a box with a big button, and connect that button the one one on the remote. Bob
  9. BobK

    Stuck with LCD Display and Black Blocks

    When I have used LCDs, the init sequence was much more complicated than one command, but that might be due to using the 4-bit instead of 8-bit interface. If i recall, you also have to wait a good long time after powering up before issuing a command, something like 10ms. Bob
  10. BobK

    MOTOR CONTROL /Satellite Control

    Half steps if it is bipolar. Bob
  11. BobK

    Matching Wattage

    However, the voltage must match. What was the voltage spec for the panels? bob
  12. BobK

    Stuck with LCD Display and Black Blocks

    Just putting the data on the D lines does not initialize the LCD. You have to set all of the three control pins as follows: RS - connected to ground to send a command. RW - connected to ground to write E - must be strobed to issue the command (i.e. low to high then low again). If you...
  13. BobK

    BJT Ramp?

    Confirmed. Be aware that you need a 5V regulated supply, otherwise the voltage output will vary with the supply voltage. You can use a different (regulated) supply voltage, but you will have to change the divider that is setting the voltage on the +_input so that it is set to 1.5V. If you...
  14. BobK

    Raising 1.5v DC to 5+v DC using LM358?

    Yep, a look at the datasheet shows minimum startup voltage as typ: 1.1 max 1.8. So it is not guaranteed to start on 1.5V, though it typically will. Bob
  15. BobK

    6.5 minute speech timer, Please help

    Or you could use a microcontroller, 3 LEDs 3 resistors and that's it. And you could then have multiple programs for different length timings etc. Bob
  16. BobK

    Sallen-Key Filter problem

    Yep, that was done on LTSPICE. It took me about 10 minutes. I love my LTSPICE! Bob
  17. BobK

    Sallen-Key Filter problem

    The problem taking the output through a 10n capacitor! This makes a high pass filter. What is the load? If you are driving a speaker, the capacitor should be more like 1000uF. Here is my simulation of your circuit with a 100Hz square wave going in, and simply measuring the output of the...
  18. BobK

    BJT Ramp?

    By the way, I designed this circuit on paper and it worked in simulation exactly as designed with no twiddling necessary. That is the beauty of op amps. They behave like an ideal mathematical amplifier when used within their limits. If you want to progress in electronics, learning op amps is...
  19. BobK

    BJT Ramp?

    Then it is time to learn! The opamp circuit is this simple (see attachment) The blue line is the input ramp from 2.0V to 2.5V. The green line is the output from 1.0V to 0.5V. To do this this accurately with transistors, you would essentially be inventing the opamp. Edited to add: The...
  20. BobK

    Help me figure out these pin assignments?

    On the other hand, the Arduino output is probably not capable of sourcing much more current than the segments can take. But that is not a reason to omit the resistor. Bob
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