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Everything posted by enl

  1. migh be the next version....
  2. Did something similar for the classroom I teach in. Clock runs at about 2/3 speed for the first 30 min, then speeds up to about 4/3 speed, with about a 5 minute smooth change in rate. REALLY messes with the students. You thought class seemed to drag before.....
  3. greetings. Do you have any particular plan for your flash controller? I am curious how you plan variable power, as I haven't dealt with that in a long time and only with pure analog.
  4. I see. Schematic helps. You don't have the LED's paralleled with a single limit resistor. You have the LED/limit resistor pairs paralleled. What you did is correct. ANY component will degrade with time/heat/use.... White LEDs degrade fairly quickly due to phosphor aging/burning, like the phosphors on an old CRT-type display, but higher quality ones hold up better.
  5. White LEDs, as all components, vary in quality. Most white LEDs use a phosphor to produce a yellow that mixes with the blue emit by the LED forming whte. Thre are a number of different phosphors used, depending on the exact blue produced by the LED, and the cheaper ones tend to be single phosphor types. Over time, the phosphors may change properties due to heat or just age, even in high quality devices. Running the device cooler (lower peak current and lower average current) will reduce this. Read the data sheet carefully, and be conservative with design to reduce the risk of early failure.
  6. Back in the days of large cards covered with neat rows and columns of DIP IC's, mostly 7400 series and the occasional MSI or LSI (almost 50000 transistors! On one IC!!!), the card looked like little industrial cities when laying on the test bench, full of warehouses and factories. Power supplies were commonly pretty beefy-- my 5V bench supply is an old 30A Delta, with a big crowbar bolted to the outside (from the factory) and remote voltage sense lines-- and a failure could turn that nice clean postcard-picture factory city looking board into 1950's Pittsburgh in an instant. Stunk like crazy,
  7. Forgot two things: Modes: on with occasional blink, fade in fade out, and hard on hard off. Also, used phone crimps for connections (pic attached).... real handy, but only good for a few hundred mA edit: third thing: eyeballs are epoxied in pairs to 12Ga bare wire to hold position. A little black paint and not visible. Used liquid electrical tape (again, black) to coat exposed joints. The crimps are watertight.
  8. Took the challenge. Started monday when I got home from work. Project is spooky eyes for the bushes. 8 channels, each of which will drive approx 3 amps, which is abou 110LEDs from the the 12V LED strip I used. Cut the strip into three LED sections (the minimum for this type), soldered on 300mm lead sets (twisted pair from cat5 cable), and used epocy to ttach the leds to ping pong balls. bent the strip so the LEDs fit flush to the surface. The epoxy provides good coupling, so, before painting, the balls had a good bright red glow. Masked pupils and painted the balls black with the c
  9. enl

    Water Pump

    Stilll don't have enough information. Indoor plants in pots? Outdoor plants like rose bushes? Or heavy shrubs? Large number or only a few? Environvent (dry, moist, warm, cold?) Makes a difference between pints every couple days or gallons several times a day. Also, what is water supply? City water? Well? Pond? If outdoor and more than a maybe a couple of gallons a day, I second (third? forth?) the solenoid valve as best solution. No pressurized water (drawing from a pond or equiv) need to know how much water and more about situation to make a suggestion, as pump sizing is impor
  10. (duplicate post deleted... sorry) allocator_demo.c
  11. I will second pabigot that the big concern is failure to allocate at some point when it is tough to identify. Several reasons this can happen include too much active data for the available memory, memory leak from not freeing un-needed memory, memory leak from poor practice (allocating and than forgetting where the data is, allocating un-necissarily, etc), and leaks from un-anticipated events in event driven/interrupt driven code. The extra code to handle these cases may make it not worth using a general purpose allocator due to both code size and execution speed considerations. I
  12. The penalty of software floating point. The difference in code size suggests to me that the operations are optimized for sppeed, not code size. It is roughly 4 times as many primative operations for adouble multiply as for float, as when doing long multiplication by hand. It goes by the square of the number of digits. (really by n_log_n, but using 16 bit ints as the primative operation, it really doesn't make a difference) If optimized for code size, I would expect only a few percent difference, but a significant time cost to loop and conditional overhead. I do not miss coding FP routines
  13. No question that for most applications, in C or C++ or java, single precision is now the better option. The period from the early '80's to the early 2000's there were good reasons, on a general purpose processor, to use double unless there was a really good reason for single precision (memory usage was the best argument). Even the earliest DSP's handled single precision faster than double, and only hardcore modelling and utility tools are coded in C or C++ (I don't count java.... the floating point is too crippled to do the work where it would matter) where it would be significant for MOST pur
  14. The rule of thumb comes from several places 1) Many general purpose processors (X86, motorola, etc), going back to the mainframe era, share hardware for single and double precision, so the only saving is accessing memory, which may or may not be a saving, depending on the details of the job and details of the memory architecture. The hardware was double prec, so why not use it? In some cases single precision was actually handled a little slower. 2) When I was involved with numerical/scientific computing (lots of integrating systems of differntial equations, etc) the more precision the
  15. If you are trying to raise the output by using a diode on the ground terminal of the regulator, the diode will NOT see load current. Load current is returned to ground independantly of the regulator. The diode will see the quiescent current of the regulator. The LE33C has an ill-specified quiescent current of something less than 0.5mA to 3mA, depending on load (ignoring the inhibit state, where the output is, for practical purposes, floating). This is a pretty wide range (factor of 6) giving a variation of about 50mV for the diode drop (conservatively). The current is low enough that a
  16. It works. Put the filter caps to ground, not the the ref/ground pin of the regulator. As you have it, the filter caps can not source more current than the regulator quiescent current (due to the diode), and when the caps are sourcing, your diode drop will be very unstable, as the diaode current will vary. You may also want a resistor from the output to the anode of the diode, if you use a more modern regulator, or need to tweak the diode current. With the '140 as is, you get about 6mA, and for a small sig diode (like the 1N914) you are in the zone. If needed, select the resistor to provide
  17. enl

    Year clock

    The 'art store' mechanisms seem to be more consistant. Over several years, all I have bought are the same. About 240ohm coil, go back together easily and work well after installing leads, and consistantly drive with 10 to 50ms pulses at 1 to 3V. The full clock may be as good or better for use unmodified (I haven't tried to determine this, but some of the ones I have tried seem to be better build quality. In particular, the Staples clock with 'made in USA' mechanism) but don't have as consistant coil DC resistance, and are much more finicky about drive, and are tougher to get back together with
  18. enl

    Year clock

    (Code is for CCS) Noting that the standard clock runs twelve hour cycles, and that there are 12 months in the year, I thought, "What if I use the hour hand for months? What can I do with this?" The result looks like a clock, uses a standard single phase quartz movement from the art store (cheaper and more consistant than the full clocks from Wally-world or Target, plus, I get the fun of making the face), but the hour hand shows months and the minute and second hands indicate point in month, using the standard Sumerian system, with minute hand being 60ths and the second hand being resid
  19. New to forum, but not new to controllers and computing and doing things the hard way because I can. Started with 8080, Z80, 6502, 8031, and IBM system 360 mainframes, doing software, then hardware and have only recently let myself drift to out-of-date. Wrote an IEEE floating point library for CPM on the 8080 (mumble mumble) years ago, did 44.1KHz ADC for Z80 systems (I stil have fond memories of the alternate register bank and non-memory I/O space), and have been teaching both hardware design and software for (mumble) decades. Used an original Basic Stamp as an ignition control for a bike
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