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enl

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  1. Like
    enl got a reaction from ElevenToes in Project Help - Digital Command Control(DCC) Operation Using a timer   
    Looking at the standard on the NMRA site (S-9.1 - http://www.nmra.org/sites/default/files/standards/sandrp/pdf/s-9.1_electrical_standards_2006.pdf), the timing isn't terribly tight.
     
    If I were going to implement this, I'd use a single timerA and deal with the outputs in an  interrupt handler. Let the timer free run in continuous, and use CCR1 to set the interrupt time. Each entry to the interrupt, add the appropriate time to CCR1 and change the state of the output as appropriate. There are a number of ways to sequence the bits. I would probably not do it in the interrupt routine. I would use a semaphore to signal the main loop to prep the next bit, and place the value in a shared volatile.
     
    I would run the timer from MCLK, and pretty much any calibrated speed would be fine for this... the timing is really not that tight (52-64us for each half of a `1' pulse) 8MHz clock is MORE than adequate, and 1MHz might even be OK, though the interrupt latency variability might make it sketchy for a receiver that isn't real tolerant. The `0' bits are so loose that timing for them isn't an issue (95 to 9900us for each half cycle, total less than 12000us) This is a perfect application for software handling of the data. For the 8MHz clock, I would set the timer to divide by 8, so it counts microseconds. Interrupt latency will be less than 3/4us (six processor clocks).
     
    There are a number of standard samples showing the basic idea for using the interrupts this way, such as Example 1 in http://www.ccs.neu.edu/home/noubir/Courses/SWARM/S09/slides/msp430-clocks-timers.pdfor on pages23/24 of https://courses.cs.washington.edu/courses/cse466/11au/calendar/04-Interrupts-posted.pdf
     
    A number of the timer examples in the TI MSP430 documents also use the same model.
  2. Like
    enl got a reaction from Fmilburn in Controlling RGB LED strip with MSP430?   
    You followed up while I was typing.
     
    Using the tip31c will require a different setup to drive it, as they are relatively low current gain. Darlington using a 2n3904 for the first stage will do fine.
     
    Also, you CAN do more than one PWM, even on the most basic MSP430g devices. The 'g2452 has two hardware driven outputs for the single timer_A (each of which can be one more than one pin), for example. Other higher level devices allow more hardware PWM.
     
    That said, using software, you can do as man as you want. Somewhere in the past ( http://forum.43oh.com/topic/4511-ended-oct-2013-43oh-halloween-contest/) I have a project that does 8 PWM for a similar purpose. Not quite the resolution of hardware PWM, but does a dandy job for many things.
     
    edit: typo in part number
  3. Like
    enl got a reaction from RROMANO001 in Who is using MSP430G2553?   
    I will freely admit that I am still a DIP guy. Several reasons: I'v been around a long time so familiarity is a piece; I can see a DIP without the microscope; Most of what I do anymore is personal or for teaching, and being able to pop a 2553 or 2452 or.. into  breadboard with a small cap an a resistor and nothing else, rather than make up a PC board, is a big benefit.
  4. Like
    enl reacted to austen520 in Self-balancing PID robot w/ code + schematic + UART tool   
    I recently completed a final project for an undergrad circuits class, throughout which this forum was a huge help, and so I just wanted to try and give back a little by presenting our code here. The project was, as you may have guessed, a two-wheeled self-balancing robot via a PID controller:

     
    We used an MSP430G2553 with the EXP430G2 launchpad, although the code should of course be applicable to any similar MCU. We also used the apparently popular MPU6050 IMU to produce angle estimates, and a simple H-bridge using TIP-102 transistors for motor control. The schematic that I've attached is a complete reproduction of our setup (including our pin configuration), and can also be found on the github linked to at the bottom of this post.
     
    The files that describe the primary control sequences are main.c, which of course has the setup and main loop, as well as the PID controller code; and StateEstimate.c, which describes how the raw IMU data is combined into a more accurate estimate of the robot's current angle with the ground (we used the so-called "complementary filter" with reasonable success, which just sums a low-passed accelerometer reading with a high-passed gyroscope reading). Furthermore, the parameters for the PID controller are located in Config.h (the parameters currently in the repo are just toy values), and the parameters for the state estimator are located in StateEstimate.h.
     
    The two biggest frustrations we faced when developing the project was successfully communicating with the MPU6050 over I2C (included in the github is the i2c device library, separately available at http://www.i2cdevlib.com),and getting useful information sent over a UART connection. So, I hope that by releasing this code we can make those tasks at least a little bit smoother for people tackling the same problems. The code is set up, by default, to use pins 1.1 and 1.2 for UART communication over the hardware serial interface. The MSP430 will send the angle estimate and PID control signal over UART, which can be captured and saved as a CSV, or even displayed in an OpenGL gui, using the supplied serialReader.py python utility (instructions are in the repository README). Using the supplied C code as a template, sending and receiving arbitrary data for post-processing should hopefully be trivial. UART is configured in main.c, and the functions for sending data over the connection are located in hwuart.c.
     
    Link to github: https://github.com/austensatterlee/robotbuddy
     
    Anyway, I hope this is helpful or at least interesting to some of you. I'd be happy to answer any questions about how we got this working, or receive any criticisms from more knowledgeable members!

  5. Like
    enl got a reaction from BruteForce in Blinking LED in a random interval   
    Deeper issues:
     
    The structure you have is actually fine if you want a SINGLE blink per input. Change the inner 'while's to 'if's.
     
    If you want repetitive blinking, with the inputs changing the state, the structure you have isn't really ideal, but can be used.What you might try is adding an additional condition to each of the inner while loops, similar to this:
    while (incomingByte =='1' && Serial.available()==0) This will cause the inner loop to end when another input is available, so that the outer loop can read it.
     
     
     
    A better overall structure for the code could be selected, as well, but I will avoid that for the moment.
  6. Like
    enl got a reaction from vinicius.jlantunes in Horowitz and Hill 3rd ed   
    There was a tremendous thump on my porch. The cat spun out hard, regained traction, and headed for under the couch. I opened the door to see the postman walking away and a large box sitting there. I opened it. A gold colored book. The third. has arrived. The cat reappeared, tail fur puffed out more than I have ever seen, sniffed the book, and promptly began dismemberment of the box.
     
    Then began the odyssey: reading the thing
     
    I have only done a partial look through at this time. It will take time. There are a LOT of changes. Much more a new book than a new edition, in many ways.
     
    Highlights:
     
    additional appendices and additions to the old ones. For example, a short intro to Spice. Nice for the students. It is correct, unlike many, many of the online tutorials. A short addition to the o'scope section for digital scopes.
     
    A decent (yes, this I read all of) chapter on microcontrollers. Not detail heavy. A good overview of use, architectures, some examples, a brief comparison guide. Pro: this now in the book. Con: not much to it. It is made up for by updates in the other digital electronics chapters. I will vote overall win, as WAY too broad an area, with too many options that change quickly, for much detail in a long-life, comprehensive text.
     
    New chapter on PLD's that looks good.
     
    Lots of updates to analog chapters.
     
    Missing is the section on construction techniques (unless it was blended into the main text somewhere). That was one of the parts I most often directed students to, as there really haven't been significant changes over the years. (protoboard, PC board, wire wrap, etc, though there have been changes in how frequently each is used with the dominance of surface mount components and easier PC board production compared to 20 years ago)
     
     
     
    Overall review/summary: it was worth the money to update. I have used 1st and 2nd ed.s since they came out as references for all of those things I don't use often, reference tables for part selection, and as references for students to look through. I would still recommend this to a student, in fact more than the outdated 2nd ed, with the caveat that this is NOT a barebones introduction to electricity. It has the target audience (advertising notwithstanding) of a student that has a basic understanding of DC circuits, math at the level of trig (or intro calculus), and basic physics concepts from an intro E&M  course.
  7. Like
    enl got a reaction from vinicius.jlantunes in Horowitz and Hill 3rd ed   
    I have, to this time, done close review through ch2. I have submit two errata (not bad for first print). There are about a dozen alreadty listed on the H&H site
     
    I have been quite happy with the changes overall, in particular to ch2 (bipolar transistor). I will update as I continue close reading, and would encourage any other that have the text to add their to this.
     
    There is some elaboration vs 2nd ed for switching with transistors, in particular a Schmidt trigger application, as well as a few new things appropriate for low voltage (3v) drive. They open with transistor as a switch, whereas previous editions opened with (linear) current amplifier. A little change in the pure analog side with an emphasis on current source that, to me, fits well with how I have approached things for years. In prior editions, they began with the emitter follower (a good approach when leading to the common emitter amp), but they now break it down into two conceptual pieces explicitly: current source and resistor to convert current to potential.
  8. Like
    enl got a reaction from bluehash in Measuring frequency from TSL235R LIGHT-TO-FREQUENCY CONVERTER using a TIVA Launchpad   
    There are several ways, and which way depends on the accuracy you need in the result and how frequently you need the result.
     
    For example, if you only need the light value every few seconds, using a counter to count the output pulses for 1sec gives you the frequency directly.
     
    If you need the light value 10 time per second, counting for 1/10s, and multiply by ten
     
    If you need the value on demand, quickly, then you can use a timer to measure the length of a single, or small number, of pulses (get the period, which is 1/f), and take a reciprocal to get frequency.
     
    The longer you can measure, the more precise the result, since the measurement will be done by counting pulses, and the count will always be +/-1 or +/-2 (depending on synchronization conditions). The net result of this is that at HIGH intensity, with HIGH frequency, best precision is by counting cycles from the sensor, the longer the better. At LOW light, with LOW frequency output, the best precision is timing the cycle from the sensor.
     
    For example: If you are interested in low light for photographic exposure, you would time the length of the pulse using a timer and capture mode. The output of the sensor goes to a capture input, the timer is configured (details depend on the application and language/programming package used) and the number of timer timer clocks  is counted and stored in the appropriate CCR automatically. This is automated in many libraries. For example, there may be a function such as "pulseIn" in the Arduino toolset to time the length of a pulse. Sometimes quite precisely, sometimes less so.
     
    For example: for high light levels, you can set the timer to cycle at, say 1/10th second. The output of the sensor again goes to an appropriate timer/counter input. Clear a counter at the beginning of the cycle, and read it at the end of the cycle. Again, this is a common process, so it is pretty well automated and many libraries provide a tool to do most of the heavy lifting for you.
  9. Like
    enl got a reaction from spirilis in Cheap solar battery + wireless IoT node   
    Solar cells have a pretty high output impedance, compared to a battery. The open circuit voltage can be a good bit higher than the design (loaded) voltage.
     
    In your application, the battery is acting to stabilize and regulate. With the battery, you get an equilibrium that is set by the battery charging rate/charge state/terminal potential/temperature relationship. This provides regulation in a manner similar to how the battery in a car or motorcycle stabilize and regulates (exactly how depends on whether the system is a generator or alternator, the regulator type-mechanical or electronic- and other things as well). Brighter sun, where the open terminal voltage of the PV cell would be higher, the battery draws a greater charging current, keeping the voltage down, with the current determined by the difference between the open circuit voltage, the battery voltage, and the effective internal resistance of the battery and the PV cell at the operating conditions.  When the battery is near full charge, the current drops, and the terminal potential goes up, leading to your need to load the PV cell to keep it down.
     
    More to it, but this is about the limit of my knowledge these days. When I was fresh out of school and in the semiconductor lab (I hate the suits) this was one of the things being played with there, but that was several generations ago. I remember something about source resistance being a function of carrier mobility, incident light flux, current density, and......
     
    This is why both battery charging systems and solar conversion systems are a specialty that should be left to the specialists for critical tasks.
  10. Like
    enl got a reaction from dubnet in Cheap solar battery + wireless IoT node   
    Solar cells have a pretty high output impedance, compared to a battery. The open circuit voltage can be a good bit higher than the design (loaded) voltage.
     
    In your application, the battery is acting to stabilize and regulate. With the battery, you get an equilibrium that is set by the battery charging rate/charge state/terminal potential/temperature relationship. This provides regulation in a manner similar to how the battery in a car or motorcycle stabilize and regulates (exactly how depends on whether the system is a generator or alternator, the regulator type-mechanical or electronic- and other things as well). Brighter sun, where the open terminal voltage of the PV cell would be higher, the battery draws a greater charging current, keeping the voltage down, with the current determined by the difference between the open circuit voltage, the battery voltage, and the effective internal resistance of the battery and the PV cell at the operating conditions.  When the battery is near full charge, the current drops, and the terminal potential goes up, leading to your need to load the PV cell to keep it down.
     
    More to it, but this is about the limit of my knowledge these days. When I was fresh out of school and in the semiconductor lab (I hate the suits) this was one of the things being played with there, but that was several generations ago. I remember something about source resistance being a function of carrier mobility, incident light flux, current density, and......
     
    This is why both battery charging systems and solar conversion systems are a specialty that should be left to the specialists for critical tasks.
  11. Like
    enl got a reaction from abecedarian in 220DC dropout   
    As a side note: I grab supplies from desktop computers on a regular basis. Modern ones generally provide 12V@5 to 15A (or more), as well as 5V@10A (or more) and 3.3V@10A (or more). They are often free from machines that have some other failure, such as hard drive, or so full of dust as to overheat the processor to failure.
  12. Like
    enl got a reaction from spirilis in 220DC dropout   
    As a side note: I grab supplies from desktop computers on a regular basis. Modern ones generally provide 12V@5 to 15A (or more), as well as 5V@10A (or more) and 3.3V@10A (or more). They are often free from machines that have some other failure, such as hard drive, or so full of dust as to overheat the processor to failure.
  13. Like
    enl got a reaction from tripwire in 220DC dropout   
    There are a bunch of issues here. I'll address a couple.
     
    First is the issue of isolation: In general, it is a good idea to isolate derived low voltage from the high voltage source
     
    Second is regulation: if the target required reasonably well regulated voltage, then some means is needed to ensure he regulation
     
    These lead to the commonly applied options (there are others, but they really shouldn't be implemented by someone that isn't quite conversant with power supply design and safety): Transformer voltage conversion and isolation, followed by regulation.
     
     
    The two traditional methods (over the last 50 years) are to use a transformer to reduce the potential, filter with a capacitor, then use either a linear or a switching regulator to produce the output voltage. Today, there are integrated switching solutions that make this the preferable method for currents greater than maybe half an amp. TI, National, Maxim, and pretty much every other manufacturer of power supply IC's have reference designs for such applications, and these should be implemented directly for reliable service.
     
    Rectification at high voltage (220V, in your case) will produce high, unisolated, voltage (300VDC or more in your case) that requires an experienced designer to safely deal with. DO NOT DO THIS. If you need to ask the question, you are 1) not ready to handle this, and 2) smart enough to realize that you are not yet ready to handle this. Good for asking. There are solutions for HV rectification (and many commercial supplies use them)  but they require good understanding of switching supply design to implement with proper isolation for safety.
     
     
    If I was going to make a recommendation, I would say transformer to 12VAC to 24VAC, rectify and filter (producing about 15 to 17VDC for 12v V or 30 to 34VAC for 24V transformer,with some ripple with the appropriate filter cap) and use a switching reg running at 100KHz or so. I am a few years out of date on this so don't know what the best choice today is. There are several TI options, as well as from other manufacturers. The last time I dealt with this was about 6 years ago, and the design was roughly 500W, converting -38VDC to +12VDC. Used a National 5pin switcher, which required a hand wound toroidal. Design was close to reference design from the data sheet. The topology you are looking for is a buck converter. These can be very efficient, even with low voltage drop, and provide very high current outputs.
     
    I would NOT recommend that you do this without more experience, but if I needed to do this without a transformer, I would use one of the available buck converter IC's designed for high voltage input. They are available, but come with some real risks for damage to equipment or personal injury/death if not imlemented correctly.
     
    EDIT: elaboration last two paragraphs
  14. Like
    enl got a reaction from roadrunner84 in 220DC dropout   
    There are a bunch of issues here. I'll address a couple.
     
    First is the issue of isolation: In general, it is a good idea to isolate derived low voltage from the high voltage source
     
    Second is regulation: if the target required reasonably well regulated voltage, then some means is needed to ensure he regulation
     
    These lead to the commonly applied options (there are others, but they really shouldn't be implemented by someone that isn't quite conversant with power supply design and safety): Transformer voltage conversion and isolation, followed by regulation.
     
     
    The two traditional methods (over the last 50 years) are to use a transformer to reduce the potential, filter with a capacitor, then use either a linear or a switching regulator to produce the output voltage. Today, there are integrated switching solutions that make this the preferable method for currents greater than maybe half an amp. TI, National, Maxim, and pretty much every other manufacturer of power supply IC's have reference designs for such applications, and these should be implemented directly for reliable service.
     
    Rectification at high voltage (220V, in your case) will produce high, unisolated, voltage (300VDC or more in your case) that requires an experienced designer to safely deal with. DO NOT DO THIS. If you need to ask the question, you are 1) not ready to handle this, and 2) smart enough to realize that you are not yet ready to handle this. Good for asking. There are solutions for HV rectification (and many commercial supplies use them)  but they require good understanding of switching supply design to implement with proper isolation for safety.
     
     
    If I was going to make a recommendation, I would say transformer to 12VAC to 24VAC, rectify and filter (producing about 15 to 17VDC for 12v V or 30 to 34VAC for 24V transformer,with some ripple with the appropriate filter cap) and use a switching reg running at 100KHz or so. I am a few years out of date on this so don't know what the best choice today is. There are several TI options, as well as from other manufacturers. The last time I dealt with this was about 6 years ago, and the design was roughly 500W, converting -38VDC to +12VDC. Used a National 5pin switcher, which required a hand wound toroidal. Design was close to reference design from the data sheet. The topology you are looking for is a buck converter. These can be very efficient, even with low voltage drop, and provide very high current outputs.
     
    I would NOT recommend that you do this without more experience, but if I needed to do this without a transformer, I would use one of the available buck converter IC's designed for high voltage input. They are available, but come with some real risks for damage to equipment or personal injury/death if not imlemented correctly.
     
    EDIT: elaboration last two paragraphs
  15. Like
    enl got a reaction from chicken in Horowitz and Hill 3rd ed   
    There was a tremendous thump on my porch. The cat spun out hard, regained traction, and headed for under the couch. I opened the door to see the postman walking away and a large box sitting there. I opened it. A gold colored book. The third. has arrived. The cat reappeared, tail fur puffed out more than I have ever seen, sniffed the book, and promptly began dismemberment of the box.
     
    Then began the odyssey: reading the thing
     
    I have only done a partial look through at this time. It will take time. There are a LOT of changes. Much more a new book than a new edition, in many ways.
     
    Highlights:
     
    additional appendices and additions to the old ones. For example, a short intro to Spice. Nice for the students. It is correct, unlike many, many of the online tutorials. A short addition to the o'scope section for digital scopes.
     
    A decent (yes, this I read all of) chapter on microcontrollers. Not detail heavy. A good overview of use, architectures, some examples, a brief comparison guide. Pro: this now in the book. Con: not much to it. It is made up for by updates in the other digital electronics chapters. I will vote overall win, as WAY too broad an area, with too many options that change quickly, for much detail in a long-life, comprehensive text.
     
    New chapter on PLD's that looks good.
     
    Lots of updates to analog chapters.
     
    Missing is the section on construction techniques (unless it was blended into the main text somewhere). That was one of the parts I most often directed students to, as there really haven't been significant changes over the years. (protoboard, PC board, wire wrap, etc, though there have been changes in how frequently each is used with the dominance of surface mount components and easier PC board production compared to 20 years ago)
     
     
     
    Overall review/summary: it was worth the money to update. I have used 1st and 2nd ed.s since they came out as references for all of those things I don't use often, reference tables for part selection, and as references for students to look through. I would still recommend this to a student, in fact more than the outdated 2nd ed, with the caveat that this is NOT a barebones introduction to electricity. It has the target audience (advertising notwithstanding) of a student that has a basic understanding of DC circuits, math at the level of trig (or intro calculus), and basic physics concepts from an intro E&M  course.
  16. Like
    enl got a reaction from bluehash in Horowitz and Hill 3rd ed   
    There was a tremendous thump on my porch. The cat spun out hard, regained traction, and headed for under the couch. I opened the door to see the postman walking away and a large box sitting there. I opened it. A gold colored book. The third. has arrived. The cat reappeared, tail fur puffed out more than I have ever seen, sniffed the book, and promptly began dismemberment of the box.
     
    Then began the odyssey: reading the thing
     
    I have only done a partial look through at this time. It will take time. There are a LOT of changes. Much more a new book than a new edition, in many ways.
     
    Highlights:
     
    additional appendices and additions to the old ones. For example, a short intro to Spice. Nice for the students. It is correct, unlike many, many of the online tutorials. A short addition to the o'scope section for digital scopes.
     
    A decent (yes, this I read all of) chapter on microcontrollers. Not detail heavy. A good overview of use, architectures, some examples, a brief comparison guide. Pro: this now in the book. Con: not much to it. It is made up for by updates in the other digital electronics chapters. I will vote overall win, as WAY too broad an area, with too many options that change quickly, for much detail in a long-life, comprehensive text.
     
    New chapter on PLD's that looks good.
     
    Lots of updates to analog chapters.
     
    Missing is the section on construction techniques (unless it was blended into the main text somewhere). That was one of the parts I most often directed students to, as there really haven't been significant changes over the years. (protoboard, PC board, wire wrap, etc, though there have been changes in how frequently each is used with the dominance of surface mount components and easier PC board production compared to 20 years ago)
     
     
     
    Overall review/summary: it was worth the money to update. I have used 1st and 2nd ed.s since they came out as references for all of those things I don't use often, reference tables for part selection, and as references for students to look through. I would still recommend this to a student, in fact more than the outdated 2nd ed, with the caveat that this is NOT a barebones introduction to electricity. It has the target audience (advertising notwithstanding) of a student that has a basic understanding of DC circuits, math at the level of trig (or intro calculus), and basic physics concepts from an intro E&M  course.
  17. Like
    enl got a reaction from abecedarian in Horowitz and Hill 3rd ed   
    There was a tremendous thump on my porch. The cat spun out hard, regained traction, and headed for under the couch. I opened the door to see the postman walking away and a large box sitting there. I opened it. A gold colored book. The third. has arrived. The cat reappeared, tail fur puffed out more than I have ever seen, sniffed the book, and promptly began dismemberment of the box.
     
    Then began the odyssey: reading the thing
     
    I have only done a partial look through at this time. It will take time. There are a LOT of changes. Much more a new book than a new edition, in many ways.
     
    Highlights:
     
    additional appendices and additions to the old ones. For example, a short intro to Spice. Nice for the students. It is correct, unlike many, many of the online tutorials. A short addition to the o'scope section for digital scopes.
     
    A decent (yes, this I read all of) chapter on microcontrollers. Not detail heavy. A good overview of use, architectures, some examples, a brief comparison guide. Pro: this now in the book. Con: not much to it. It is made up for by updates in the other digital electronics chapters. I will vote overall win, as WAY too broad an area, with too many options that change quickly, for much detail in a long-life, comprehensive text.
     
    New chapter on PLD's that looks good.
     
    Lots of updates to analog chapters.
     
    Missing is the section on construction techniques (unless it was blended into the main text somewhere). That was one of the parts I most often directed students to, as there really haven't been significant changes over the years. (protoboard, PC board, wire wrap, etc, though there have been changes in how frequently each is used with the dominance of surface mount components and easier PC board production compared to 20 years ago)
     
     
     
    Overall review/summary: it was worth the money to update. I have used 1st and 2nd ed.s since they came out as references for all of those things I don't use often, reference tables for part selection, and as references for students to look through. I would still recommend this to a student, in fact more than the outdated 2nd ed, with the caveat that this is NOT a barebones introduction to electricity. It has the target audience (advertising notwithstanding) of a student that has a basic understanding of DC circuits, math at the level of trig (or intro calculus), and basic physics concepts from an intro E&M  course.
  18. Like
    enl got a reaction from Rickta59 in Horowitz and Hill 3rd ed   
    There was a tremendous thump on my porch. The cat spun out hard, regained traction, and headed for under the couch. I opened the door to see the postman walking away and a large box sitting there. I opened it. A gold colored book. The third. has arrived. The cat reappeared, tail fur puffed out more than I have ever seen, sniffed the book, and promptly began dismemberment of the box.
     
    Then began the odyssey: reading the thing
     
    I have only done a partial look through at this time. It will take time. There are a LOT of changes. Much more a new book than a new edition, in many ways.
     
    Highlights:
     
    additional appendices and additions to the old ones. For example, a short intro to Spice. Nice for the students. It is correct, unlike many, many of the online tutorials. A short addition to the o'scope section for digital scopes.
     
    A decent (yes, this I read all of) chapter on microcontrollers. Not detail heavy. A good overview of use, architectures, some examples, a brief comparison guide. Pro: this now in the book. Con: not much to it. It is made up for by updates in the other digital electronics chapters. I will vote overall win, as WAY too broad an area, with too many options that change quickly, for much detail in a long-life, comprehensive text.
     
    New chapter on PLD's that looks good.
     
    Lots of updates to analog chapters.
     
    Missing is the section on construction techniques (unless it was blended into the main text somewhere). That was one of the parts I most often directed students to, as there really haven't been significant changes over the years. (protoboard, PC board, wire wrap, etc, though there have been changes in how frequently each is used with the dominance of surface mount components and easier PC board production compared to 20 years ago)
     
     
     
    Overall review/summary: it was worth the money to update. I have used 1st and 2nd ed.s since they came out as references for all of those things I don't use often, reference tables for part selection, and as references for students to look through. I would still recommend this to a student, in fact more than the outdated 2nd ed, with the caveat that this is NOT a barebones introduction to electricity. It has the target audience (advertising notwithstanding) of a student that has a basic understanding of DC circuits, math at the level of trig (or intro calculus), and basic physics concepts from an intro E&M  course.
  19. Like
    enl got a reaction from abecedarian in Silicon Labs EFM8 microcontroller. Free if you poll.   
    8051 (and derivatives) will not die as long as a) there are applications for it 2) it is cheap iii) there are legacy applications where there is no reason to replace it/recode -..) manufacturers keep upgrading the peripherals to meet new needs
     
    That said, I haven't touched one in maybe 20 years. Or a PIC for a good 10.... I wasn't a great PIC fan when they hit the market, and still am not. Both architectures serve a purpose, and have done so for quite a few years, tho.
  20. Like
    enl reacted to abecedarian in Silicon Labs EFM8 microcontroller. Free if you poll.   
    It's funny how 8051 just doesn't want to die. >shrug<

  21. Like
    enl reacted to bluehash in Silicon Labs EFM8 microcontroller. Free if you poll.   
    Webinar registration link.
     
  22. Like
    enl got a reaction from bluehash in Driving 3V relays using MSP430G2553   
    First, DO NOT directly drive it with the microcontroller without knowing more. The output of the microcontroller (any microcontroller, not just MSP430) can be damaged driving the inductive load and current demand of the relay coil if not done properly.
     
    That said, it is tough to give details without having the part number for the relay, so I will give some generalities:
     
    The recommended way to drive the relay is to use a transistor (an npn bipolar is traditional) as a switch to ground, and use a diode across the coil to shunt the inductive kickback when shut off. Directly driving is likely to damage or destroy the microcontroller, sooner or later, even with a protection diode. Not a guarantee, but, again, without part data, I would lean that way.
     
    A six pin SPDT relay could be the same as a five pin, with one unused or a redundant connection (often the common for the switch), or could be a double coil. Need to know what the model is. A double coil is generally a unipolar latching type: trigger one coil to latch to the NO position, the other to release to the NC position. Gotta look at the data sheet to see if coil current polarity matters. Some do, some don't.
  23. Like
    enl got a reaction from jbanik in Driving 3V relays using MSP430G2553   
    First, DO NOT directly drive it with the microcontroller without knowing more. The output of the microcontroller (any microcontroller, not just MSP430) can be damaged driving the inductive load and current demand of the relay coil if not done properly.
     
    That said, it is tough to give details without having the part number for the relay, so I will give some generalities:
     
    The recommended way to drive the relay is to use a transistor (an npn bipolar is traditional) as a switch to ground, and use a diode across the coil to shunt the inductive kickback when shut off. Directly driving is likely to damage or destroy the microcontroller, sooner or later, even with a protection diode. Not a guarantee, but, again, without part data, I would lean that way.
     
    A six pin SPDT relay could be the same as a five pin, with one unused or a redundant connection (often the common for the switch), or could be a double coil. Need to know what the model is. A double coil is generally a unipolar latching type: trigger one coil to latch to the NO position, the other to release to the NC position. Gotta look at the data sheet to see if coil current polarity matters. Some do, some don't.
  24. Like
    enl got a reaction from dubnet in Cheap solar battery + wireless IoT node   
    The options are 1) a complete sealed setup, using the appropriate sealed penetration connectors, capable of holding against the pressure inside and out due to temp changes, 2) run the containment at a slight positive pressure,  3) ensure that moisture can get out before condensing, OR 4) pot that sucker up
     
    I have been involved in option 1 a couple of times, and it is expensive to do well. An ammo can is a decent containment, as long as the gasket is good and the temp changes arn't too great. It will breathe under great enough temp change.
     
    Option 2 is what communications providers often use on trunk lines. They may pressurize with nitrogen and seal it, or use a compressor and air drier. The second of these is why you see some of the little green lights on the boxes on telephone poles. Those are small compressor/driers, and pressure monitors. They alarm if pressure can't be maintained, and provide a small volume of dry air to make up miniscule leaks. I don't know what the pressure is, but I would guess a few inches of water (24 inches of water is about 1PSI; 1 inch of water is about 2mmHg, or about 2.6millibar. Residential gas is about 10 inches in the US)
     
    Option 3 I have used a number of times. Enough ventilation is needed low and high that temperature changes will induce air to move, the electronics are protected from direct impingement, but will follow temp changes fairly quickly so as to not get condensation, and the electronics want to be the warmest thing in the containment. One technique I have used a double roof model: slight overhang with vent at the top, open bottom, like a small garden shed, and the electronics in a box inside with bottom vents, but no top vents. Drip loops on wires entering are a must. Direct solar exposure to the containment is a no-no, as that is asking for after a rain, at the most humid time, the electronics lagging behind the dew point and inducing condensation.
     
    Option 4 is common in automotive and ruggedized gear. Pot it solid. Gotta do it right so moisture can't get in where leads enter the potting. Can be done with wax, silicone, some petro-based rubbers and plastics, or many other materials. The antique auto guys still use pitch for some things, both for insulation and moisture protection. Goes in hot, so moisture is removed and can't get back.
     
    One other option, used by the tool and gun guys, is not appropriate here, due to practical requirements: a small heater. Raises the dew point to prevent condensation, but takes a bit of power as well as running the electronics hotter than needed.
     
    I would use option 3 or 4. Even a low power device, in a small enclosure, running at a few milliwatts, will produce enough heat to keep the containment a degree or two above ambient. As long as no liquid can blow in, and the space around it is generally below the dew point, there isn't an issue, as the electronics will usually be at or above the temp of the surround except during the most extreme rises.
  25. Like
    enl got a reaction from spirilis in Cheap solar battery + wireless IoT node   
    One other point: Many materials we think of as 'waterproof' are not. Many common polymers, such as styrene plastics and polyethylene films, will allow water molecules to diffuse through, over time leading to issues even without an actual leak. This isn't a short term issue, such as when using Saran wrap to keep leftovers fresh, but over longer periods, it is an issue. Tupperware, plastic boxes sealed with gaskets, etc, are not good long term environmental protection on their own for this reason.
     
    Not my specialty, by a long shot, but some of the jobs I have been involved with got me educated enough to know my ignorance. It is AMAZING what is done on oceangoing vessels to protect electronics, and what isn't.
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