Jump to content


  • Content Count

  • Joined

  • Last visited

  • Days Won


Everything posted by enl

  1. enl

    4 x 6 cm Projects

    I highly recommend it, if you can justify the cost. It isn't worth cheaping out. I use mine for a variety of things including fitted tool trays (need models for micrometer or planer gauge trays?), machine parts, dinguses for my teaching job, and a slew of other things, including a couple PC boards. It hasn't paid itself off yet in paying work, and I don't think it ever will, for me. I put the money aside over time because I wanted the tool. The learning curve wasn't too bad for me, as I have machining experience and CAD experience, though not much CNC prior to buying the mill. A wooden clo
  2. enl

    4 x 6 cm Projects

    Since the advent of inexpensive one-offs, same for me. But once in a while it is handy to have the capability, especially to prototype a part of a design quickly so the correct design can be sent out in the first place. The main use I have for in-house is in conjunction with me teaching hat. Students mess up a lot, and the rapid turnaround lets them mess up fast and fix it fast.
  3. enl

    4 x 6 cm Projects

    Main reason for messing with CNC is no wait. Photo-resist etching, same thing. The drawbacks to both of these is the mess and the limitation to double-sided boards and no through plating. Sourcing from a commercial shop in China is days to weeks, depending on quantity, complexity, destination, and holidays. Quality of a commercially made board is likely to be higher, and generally has the bells and whistles of solder mask and screenprinting, but when you need it tomorrow, or today, you sometimes even go as far a sharpie and that sludgie bottle of Ferric Chloride that has been sitting i
  4. I recently (within the last year) got rid of several of my templates, including flow chart and logic symbols, because with the youngest of them being 30+ years old, the plastic was starting to get `that smell', as it degraded. You all know the smell.somewhere between stale cheese and decaying animal,along with the white crust on the surface. I can't remember the source of the flowchart template (IBM? Digital? Data General? One of the big ones), but the logic symbol were the green TI and the blue National. I remember getting them at a recruiting fair in the early '80s.
  5. Two wire: rheostat (variable resistor), not a potentiometer. You will need an external resistor to make up a voltage divider. I would suggest uing one that i approximately equal to the full range resistance of the sensor. I can outline the code as: Read sensor using ADC If reading is less than threshold, do whatever you need it to do Not a complicated structure. A starting point for the ADC is http://www.ti.com/lit/ml/slap115/slap115.pdf and http://coder-tronics.com/msp430-adc-tutorial/ There are a lot of others, including a number of university sites (BYU, Cornell) th
  6. First thing would be more detail on the sensor and more detail about what you are trying to do. What do you mean 'control GSM and LCD according to' the sensor? Are you trying to display a fuel level? Are you trying to send an alarm message? To get you started, I'm going to guess the sensor is resistive with float, as they are quite common, or potentiometer with float, but there are other options. If it is, then the easiest way to read it is set up a voltage divider, one end to ground, the other to your processor supply, and the wiper to one of the analog capable inputs, and read the analog
  7. The ULN2003 doesn't require power. It is darlingtons with flyback diodes Whoops. I didn't notice that. If built like as shown, I concur that is another problem. I have grown used to not paying attention to the position on the board in this style of diagram, as they so often do not reflect the actual construction.
  8. Presuming the diagram you attache is correct, you have the LED connected to ground. As the ULN2003 switches the other lead to ground, the LE will not light. You need the anode to f the LED attached to the 3V rail, and a current limit resistor in series with it (maybe 100ohms) Again, the outputs switch to ground, not positive supply.
  9. You will find a lot of projects on this forum, a few mine, many other peoples. I don't keep a heavy online presence, and many of my projects are either done because they need to be done NOW, so I don't really get around to posting anywhere, or, in a few cases, are client work. You'll see a few projects, including one of mine, at http://forum.43oh.com/topic/4511-ended-oct-2013-43oh-halloween-contest/?hl=halloween Another of mine (still on first set of AA after 3 years and as close to dead on time as it started, showing low power) is http://forum.43oh.com/topic/4068-year-clock/ Note tha
  10. There are a number of Arduinos available with various capabilities, speeds, and memory capacities. The 2553 is comparable to the UNO in many respects, with max clock speed of the '2553 matching the UNO, but without the need for the crystal, but half the RAM and half the program memory, and comparable I/O capability. Advantages to the '2553 include lower power and fewer support components required than the ATmega, making it easier to use in your own system without the commercial board. The arduino boards have a broad base of daughterboards relative to the launchpads, but if building
  11. Has anyone used the LDC1612 or LDC1614? I am looking for input, as it looks like it might be what I want for a load cell application with an MSP430G talking to it. The price is right for non-contact sensing, and the specs look good, but not sure if it will do it in the field, so I figured I'd ask for input before diving in.
  12. Shouldn't need to constantly adjust. Unless you expect major changes in operating conditions (supply voltage, temperature) during operation, you should only need to check the calibration at startup. Stability of the oscillator is sufficient for the serial clock if conditions don't change. You can do both serial and BPM with the DCO, but I would use the crystal for BPM (using a TimerA) and DCO for serial, myself. A couple percent variation is OK for serial if the DCO drifts a little, and the crystal is much, much more than fine for the BPM, and much more stable.
  13. Your error calc isn't correct. At 676,46 counts nominal and 676 counts actual, the error is at most half of (1/676)*100, which is 0,0014*100, or 0,14%, for a max error of 0,07% (this matches your calculation). At 121,2bpm, the error will be much less, as the actual rate with a count of 676 is 121,18. You will have a 0,1% worst case error at a freq of roughly 180bpm. At your 121bpm range, you have an accuracy of approximately +/-0.1bpm. If you need more accurate than this, you can jitter the count in a manner analogous to the way the DCO clock and the clock divider for the serial module do.
  14. This device will not directly drive a high freq crystal, but there are a number of options as an external source can be used for internal timing: a) Use an external oscillator or clock generator module. Benefit: a programmable module will give you exactly the frequency you want (within error limit) Drawback: additional components calibrate the SCO to the 32KHz crystal. This will remain stable for a reasonable time, and the recalibration can be done periodically if needed. The DCO is rated at about 6% over the operating range of the device, but is quite stable over moderate term as lon
  15. No idea why the pins are swapped. If I were to make a guess, the G series software came before the hardware UART, and the way the hardware modules worked out ended up with exchanging the pins. I doubt it has anything to do with making sure the user knows what they are working with. More likely it has to do with parallel development between the software side and hardware side, and the use of standard macro cells and compatibility with previous devices for port assignment and hardware blocks, but that is only a guess.
  16. The dedicated hardware pins, on the processors that have a hardware UART, such as the 2553, are swapped from the pins used by the software serial on the non-hardware UART devices. One position is for use with hardware UART *or* software serial that uses the same Tx and Rx as the hardware UART. The other position is for use with the TI software serial Tx and Rx. Why are they different? I don't know.
  17. Saelig: http://www.saelig.com/category/CW.htm?utm_source=2015+Cyber+Week+Pre-Order+%28A%29&utm_campaign=Cyber+Week+Pre-Order+Event++%28A%29&utm_medium=email
  18. My first thought would be to agree about the use of volatile. External variables should be treated as volatile by default, but not all compilers do. My next thought would be that a reset is being done before you are looking at the values. Can you watch the vlue during operation?
  19. What he said about soldering the crystal. I would also suggest using paste rather than wire solder form. Then you can hold the component down with a dental pick or a toothpick while heating with your iron. This reduces the risk of moving it, as tape won't hold it against a twitch with the iron tip. I would not use a different crystal if you want reliable operation. Well, ok, maybe I would, but I don't recommend it unless you have all of the data for the crystal you use. Don't forget that the board and lead capacitance was designed into the LP for the supplied crystal, and you will need to
  20. For your application, I'd definitely agree to go with non-latching. Latching relays are the cats meow for cases where the time between switching is relatively long and persistent state is needed without power, such as power fail tolerance or very low power battery operations. This is why they are seen in thermostats, where low power is key, but not in motor controls, where you want it to drop to the off state on power loss, so the motor doesn't start right up when power is restored.
  21. Better than my first experience with the 0603 by hand. To the extent that I do anything this size by hand (not much as I am too shakey and my eyes are shot), I use a solder paste rather than wire. Holds the component in place, easier to get the appropriate quantity, and leaves my other hand free to hold the component down with a dental pick so I don't displace it. I would definitely suggest getting several small tips, both points and chisel end. If you want to experiment with tip shape, file an old tip to the shape you want to try. It won't last too long once filed, as the core alloy-- usu
  22. Depending on the application, you might try a latching relay instead. In a low power ap, you can't beat them, but there are a few drawbacks, such as they do not drop out on power loss like a standard relay. Even in a non-low power ap, not needing to power the coil continuously is a nice feature. If you haven't seen a latching relay, among other places you see them is in electronic thermostats.
  23. @@Fmilburn Very nice. That is a costume that he will look back upon in 50 years and remember fondly.
  24. Q4 is going to see greater than 20Vgs, and may fail. Generally not a lot of leeway in these ratings. I wouldn't even count on a long life if you are running at just below 20V, as even small transients beyond 20V can damage the FET. As for the two BJT's, I don't see any particular issue with Q2 until the gate of Q4 fails, as there shouldn't be dissipation greater than about 225mW while switching for Q2 at 30V supply (15mA*15V), and a few mW when full on. That shouldn't be sufficient to lead to heating issues. Once the gate fails for Q4, though, there is indeterminate current limiting for th
  25. Now I miss tim horton's. Been a good while for me. (I didn't live in an igloo when I lived north of the border, but I did enjoy more than my share of tim hortons and poutine, as well as all of the television choices available in any US city, in addition to CBC and a few others not available in the US)
  • Create New...