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  1. gorgon

    first pcb stebs - sallen key filter

    Sure, I totally agree, most of my comments reflects on what was done, I did not analyze the layout in itself. Since this is a relative simple layout, rearranging components would do wonders with the ease of routing. Size and choice of components would also make things more easy. I have one...
  2. gorgon

    first pcb stebs - sallen key filter

    We normally do 4 layers at work. The inner power and ground layers are good for noise reduction, and since we are in Europe, all commercial electronics need CE marking, and testing. Routing signals on the outer layers will also make small changes and prototype reworking possible without too...
  3. gorgon

    first pcb stebs - sallen key filter

    steve: My question was triggered by the fact that there already was 2 or 3 paths running on the bottom layer. It could of course just be a planned jumper for a single layer PCB, I've seen that before, hence my question. TOK ;)
  4. gorgon

    first pcb stebs - sallen key filter

    If you layout for a 2-layer PCB, why not use both layers? You should also resize your vias, don't use square pads. Have you run the DRC for this layout? (Design Rule Check) From what I can see you have some shorts, or too close paths. I know, it's not easy to get everything correct the...
  5. gorgon

    Digital Pot setup

    At last a schematic of the logic solution. You need a +5V regulated supply for this. With a light sprinkle of decoupling capacitors, like 100nF. The 68k resistor may need adjustment to get the frequency you want. It's depending on the hysteresis in the hc132. TOK ;)
  6. gorgon

    DC power supply from AC through bridge rectifier

    Normally the mains voltage will fluctuate a bit over the day/load, I would guess as much as +/-10%. Distance from the nearest distribution transformer will also count. To get a stable 6V output from the power you'll need a regulator after the rectifier/capacitor bank. Most linear regulators...
  7. gorgon

    Current meter is burning out microcontrollers

    You say that the board measure the current by itself, do you know how this is done, in the circuit? Normally this will be over a small defined resistor? When you connect the DVM are you extending the power leads? Have you got any HF equipment close by, antenna, radio, induction heater...
  8. gorgon

    Digital Pot setup

    I've done a predesign and come up with a solution using 2x 4017, 2x 4013, and a 74hc132, for both channels(up/down). I need to redraw it and I'll post it tomorrow evening. For this you can use both the AD5228 and the buttons you posted above. Depending on the supply voltage I would think you can...
  9. gorgon

    Digital Pot setup

    Sure, but due to all the flak around this, I just wanted to be certain that the solution was wanted. It does take some time to do it, and I had the impression that simple logic was off into the woods. More like, if you can't do it with a microcontroller it's not worth doing. BTW I was...
  10. gorgon

    Digital Pot setup

    You need to take a closer look at the datasheet. The 600ms is the wait time to start the autoscan, not to debounce. Debounce time is listed as 10ms. So any push time more than the debounce time will advance the counter, no problem to advance 6 times for each push. Did a closer check on the...
  11. gorgon

    Digital Pot setup

    The simplest way I could think of, would be to make a small circuit that puts out 6 pulses for each button press. You'll need 2 of them, one for each button, up and down. When you push the button, you'll advance the counter in the potmeter 6 counts instead of 1, and pressing 5 or 6 times max...
  12. gorgon

    Current meter is burning out microcontrollers

    Well, a DVM in current mode is in fact a direct short, or shunt as it is called. Connected wrongly will make a great shortcircuit. I suppose the DVM is battery operated too? No other test equipment connected at the same time, like PC or scope? BTW why can you only use this on battery...
  13. gorgon

    Digital Pot setup

    You don't need to wait for the autoscan to start, just push repeatedly on the button and it will count much faster. As far as I can see the debounce is 10ms. I can't see any reason to complicate the design with a microcotroller. If you need fewer steps, you could use a 4bit binary up down...
  14. gorgon

    Current meter is burning out microcontrollers

    I've been reading through the postings and I can't understand why you don't post a schematic of the circuit you are asking about. That said, if your circuit is working alone, a couple of the things that could go wrong when you add a DVM is that you short one or several outputs from the micro, or...
  15. gorgon

    Digital Pot setup

    The components you have collected looks good. From what you have shown, the only item missing is a stable 5V supply for the pot and the 0-5V input. You need to take some care with decoupling this supply, to reduce the noise from the motor controller. To make the box waterproof should be no...
  16. gorgon

    p16f877a programming

    Needs are a good start, but if you want any answers, you need to give us more technical data for this. Most serial data is voltages of some sort, you need to specify if they are digital or analogue, frequency /format, schematic of the PIC with LCD and so on... TOK ;)
  17. gorgon

    I have a problems with K-Map minimization

    Karnaugh maps is the graphical, and practical tool between a truth table and the logic expressions resulting from it. The result is eventually the discrete logic gates you will need to process the signals to the get result in the truth table. TOK ;)
  18. gorgon

    I have a problems with K-Map minimization

    Have you got the equations or the truth table of the signals in question? I also wonder about all the '-' squares, are they 'don't care' or what? If this is the case I would think that an inverse solution is what the professor is seeking. You have far less '0's than '1's in the diagram. But...
  19. gorgon

    2:1 ratio step down transformer question from newbie

    Just a thought, why did the old motor die, could something in the mechanics load it too much and make it burrn out? TOK ;)
  20. gorgon

    Alarm clock

    In Norway we have this saying, 'to shot sparrows with a cannon'. This project idea has a flavor of that in it. If you know IT, you should know that running Linux require a certain hardware level, and this level is rather advanced in our sandbox. To solder chips of that complexity for a...
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