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  1. hevans1944

    bma150 with pic18f26k22

    Go this article and read it. It will behoove you to purchase an evaluation board with the accelerometer and the microprocessor already integrated, leaving "just" the software to worry about.
  2. hevans1944

    GPS NMEA, Failover Circuit upgrade attempt.

    Yep, they would. That's why it is called counterfeiting. Big problem with semiconductors sourced from Asia. Not just Rolex watches and Gucci handbags anymore: everything is counterfeited in Asia. Quality varies, but always caveat emptor. Even authorized distributors have been scammed. Only way...
  3. hevans1944

    LEDs in parallel don't consume sum of individual currents??

    Like they really care if the LED brightness matches. And isn't this just a scheme to sell more cheap batteries?
  4. hevans1944

    LEDs in parallel don't consume sum of individual currents??

    NEVER parallel LEDs, matched or not. It just isn't worth wasting time trying to solve the problems that can occur. Connect two or more LEDs in series with appropriate current-limiting resistor if powering from a constant-voltage supply or power them from a constant-current supply.
  5. hevans1944

    impose current ceiling

    Automobile brake and turn-signal lamps have heavy filaments that require substantial current to "light up" unless they are LED lamps. Try some, perhaps two or more in parallel, to see it that works.
  6. hevans1944

    NPN transistor as switch for LED problem

    Absolutely! A transistor is a piece of doped silicon with precisely implanted ions that define where the emitter- base, and base-collector junctions are. If you "toast it" all that stuff melts and fuses together into a single conductive chunk of silicon. Usually. You can also vaporize the...
  7. hevans1944

    NPN transistor as switch for LED problem

    That unspecified NPN transistor is probably toast by now with a 100 Ω resistor connected from base to +12 V... unless it is a 2N3055 power transistor, which would be a bit of overkill for lighting up your typical LED. IIRC, the 2N3055 needs a huge amount of base current to turn on properly and...
  8. hevans1944

    Help With Basic Seven Segment Display Counter Circuit

    The "loop" you see on the diagram represents the package outline, NOT electrical wire, Each resistor is separate and there is one resistor connected between any of the seven outputs of the 74LS47 and the corresponding segment of the 7-segment display. I hope you didn't connect all the resistors...
  9. hevans1944

    impose current ceiling

    Well, relays that short out some panels could work too, but what a waste of good sunshine. I didn't want to mention that there would have to be some extra circuitry associated with the MOSFET switch and Allegro current sensor, for fear of scaring off the OP. Can't design anything now anyway...
  10. hevans1944

    GPS NMEA, Failover Circuit upgrade attempt.

    Has anyone checked for ground loops and common-mode voltages between the serial port on the PC (or a USB-to-serial converter) and the MAX chip? It sounds like something is overloading the MAX inputs, perhaps by a LOT to make it get hot and fail. I just now stumbled onto this thread but it...
  11. hevans1944

    impose current ceiling

    Maybe you could modulate the current with a MOSFET in series with the solar panel. Full current when the MOSFET is on, no current when the MOSFET is off. Vary the pulse width to accommodate the sunshine. Initially, turn the MOSFET on and sense the current with an Allegro current sensor. Start...
  12. hevans1944

    Help With Basic Seven Segment Display Counter Circuit

    Make sure pin 3 (active-low lamp test) on the 74LS47 BCD-to-7-segment decoder is not grounded. Check for logic levels on pins 1, 2, 6, and 7. The only time an "8" should be displayed is if pin 6 is high and pins 1, 2, and 7 are low. A tactile switch does not provide a "clean" transitions for...
  13. hevans1944

    LEDs in parallel don't consume sum of individual currents??

    A perfect example of the GIGO principle: Garbage In, Garbage Out. Failure to consider ALL the parameters affecting experimental results has led more than one person down the primrose path. But to seriously question Kirchoff's Laws requires either some real chutzpah or extreme naivety about how...
  14. hevans1944

    transistor equivalents

    I love it when a solution is simple.
  15. hevans1944

    Automotive coil on plug conversion HELP

    It may be possible, after all the computer manages to figure out when to fire a single coil four times for every two engine revolutions of a four-cylinder four-cycle engine. So, what sensors do you have to work with? You mentioned in your first post that there were three: (1) cam angle, (2)...
  16. hevans1944

    PIC Micro Output I/O

    The output is shorted to common by the lower MOSFET when the output is low. The upper MOSFET in the totem-pole (NOT push-pull) output is turned off when the output is 0. The 10 kΩ "pull up" resistor is in parallel with the upper MOSFET (which is NOT conducting) and therefore provides a small...
  17. hevans1944

    PIC Micro Output I/O

    Go revisit Ohm's Law. What is the resistance to ground at the output when the output is low?
  18. hevans1944

    Designing a Time Delayed Relay

    I think I would try to make a "desoldering" tool with a vacuum port in the center to simultaneously melt the solder on all the pins and pull the Allegro chip off the board. This could be an "interesting" project in its own right, depending on how long the tool has to be and where the heating...
  19. hevans1944

    Automotive coil on plug conversion HELP

    Any luck on adapting your existing distributor cap and rotor with optical or Hall-effect sensors?
  20. hevans1944

    Designing a Time Delayed Relay

    Are both Allegro chips doing this?
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