Chinese Hiland 0-30V/Audioguru PSU build (down the rabbit hole)

Discussion in 'Electronic Projects' started by bushtech, Oct 27, 2017.

  1. bushtech

    bushtech

    Joined:
    Sep 13, 2016
    Messages:
    474
    Likes Received:
    32
    Location:
    Vaalkopdam North West
    bushtech, Oct 27, 2017
    #1
    1. Advertisements

  2. bushtech

    bushtech

    Joined:
    Sep 13, 2016
    Messages:
    474
    Likes Received:
    32
    Location:
    Vaalkopdam North West
    And his parts list:

    Audioguru0-30V Parts List Rev6 Jul 2014.png
     

    Attached Files:

    bushtech, Oct 27, 2017
    #2
    1. Advertisements

  3. bushtech

    bushtech

    Joined:
    Sep 13, 2016
    Messages:
    474
    Likes Received:
    32
    Location:
    Vaalkopdam North West
    Some bits and bobs I've been rounding up:

    bits.jpg

    Want to use the heatsink from a cpu. Just need to temperature control it via the 3 cable connection
    And a nice surge protected power plug
     
    bushtech, Oct 27, 2017
    #3
  4. bushtech

    bushtech

    Joined:
    Sep 13, 2016
    Messages:
    474
    Likes Received:
    32
    Location:
    Vaalkopdam North West
    Probably the first of many questions regarding this build

    I don't want the fan on the heatsink to run continually but I want it to come on when the heatsink gets too hot

    I found this design on electronicshub.org


    PC-Fan-Controller-Circuit.jpg Will this work Ok? Or can it be improved?
     
    bushtech, Oct 27, 2017
    #4
  5. bushtech

    Audioguru

    Joined:
    Sep 24, 2016
    Messages:
    1,557
    Likes Received:
    363
    With a 12V supply that needs a bypass capacitor at the 555 IC as mentioned in the datasheet for an LM555, the maximum output high is 10.5V and the emitter-follower transistor reduces the voltage to the fan to only 9.7V. Will the fan start running with such a low voltage? The transistor should be used as a saturated switch with the fan connected between the positive supply and its collector, then the fan gets about 11.8V.

    I think the cheap Banggood Chinese kit is not made anymore (recently sold at a clearance low price) and the Chinese have a different one (with no regulation or poor regulation) and it has a display.
     
    Audioguru, Oct 27, 2017
    #5
  6. bushtech

    bushtech

    Joined:
    Sep 13, 2016
    Messages:
    474
    Likes Received:
    32
    Location:
    Vaalkopdam North West
    bushtech, Oct 27, 2017
    #6
  7. bushtech

    Audioguru

    Joined:
    Sep 24, 2016
    Messages:
    1,557
    Likes Received:
    363
    The cheap cost of the Banggood Hiland kit has been reduced to a clearance price.
    Who is "Hiland" anyway? I saw the Greek kit (Smart Kits?) about 13 years ago as a project on www.electronics-lab.com .
     
    Audioguru, Oct 27, 2017
    #7
  8. bushtech

    bushtech

    Joined:
    Sep 13, 2016
    Messages:
    474
    Likes Received:
    32
    Location:
    Vaalkopdam North West
    I kept seeing references to Hiland in threads but have never managed to find the source
     
    bushtech, Oct 28, 2017
    #8
  9. bushtech

    bushtech

    Joined:
    Sep 13, 2016
    Messages:
    474
    Likes Received:
    32
    Location:
    Vaalkopdam North West
    My lack of electronics knowledge is very evident here. I have tried to make sense of what Audioguru was saying about the bypass capacitor ( The LM 555 datasheet actually talks about 2 capacitors :confused:) and the fan connected between the positive supply and the 2n222 collector.

    Here is my LTspice recreation with the 2 changes:

    I have no idea how to place things like fans and thermistors in spice so I just plugged something similiar in there.

    Comments/suggestions/ corrections.
     

    Attached Files:

    bushtech, Oct 28, 2017
    #9
  10. bushtech

    Audioguru

    Joined:
    Sep 24, 2016
    Messages:
    1,557
    Likes Received:
    363
    EEK! Your schematic has lotsa mistakes and is as big as my neighbourhood.
    1) The fan is always connected to +12V and ground so it runs all the time but turns off when the transistor turns on and short circuits the 12V power supply then the transistor releases its magic smoke.
    2) The value of the 100pF capacitor is at least 100 times too small.
    3) The VCC terminal of the 555 is not connected to +12V but is connected in series with a capacitor instead. The capacitor must be connected between VCC and GND.
    4) I should have noticed before that the circuit from Electronics Hu3 is an oscillator that turns the fan on and off over and over with the frequency controlled by the temperature. Instead you want a comparator that turns on the fan when the temperature is hot and keeps it on until the temperature is low enough.
     

    Attached Files:

    Audioguru, Oct 28, 2017
    #10
  11. bushtech

    bushtech

    Joined:
    Sep 13, 2016
    Messages:
    474
    Likes Received:
    32
    Location:
    Vaalkopdam North West
    Thanks for the valuable feedback Audioguru, much appreciated. You can now see that I am a professional magic smoke producer.

    Thinking about your comments you are probably correct. A fan that turns on and off at set temp. points is preferable to one that is constantly revving up and down.

    So I went hunting again: This one looks nice and simple. It just uses a 9V battery for power. Can I shove 12V down it's throat without it spewing my magic smoke?
    https://www.slideshare.net/ZaheerBasha2/temperature-controlled-dc-fan-using-thermistor

    Also they talk about it activating at room temperature. I obviously need it coming on at a teensy weensy bit more than that. Is that where the pot comes in?
     
    bushtech, Oct 28, 2017
    #11
  12. bushtech

    Audioguru

    Joined:
    Sep 24, 2016
    Messages:
    1,557
    Likes Received:
    363
    The circuit from India uses a BC548 transistor that has a maximum allowed collector current of only 100mA and is usually used with a maximum base current of 5mA. The LM358 opamp produces a maximum output of 60mA which will probably destroy the base of the transistor. Therefore a resistor between the output of the opamp and the base of the transistor is needed to limit the base current.

    How much is the stalled current of the fan motor? It is stalled by its inertia when it starts. Probably a transistor with a higher max current rating is needed.

    A comparator usually oscillates when its input voltages are near the switching threshold. Therefore hysteresis is usually used so that the comparator switches abruptly with no oscillation.

    The LM358 has two opamps. The article does not show how to disable the second opamp so that it does not cause interference with this circuit.

    The schematic does not show a pot, instead it shows an arrow in the wrong location.
    And this article full or errors came from a University??
     
    Audioguru, Oct 29, 2017
    #12
    bushtech likes this.
  13. bushtech

    hevans1944 Hop - AC8NS

    Joined:
    Jun 21, 2012
    Messages:
    3,342
    Likes Received:
    1,615
    Location:
    Venice, Florida, USA
    Here is a link to the original Electronics Lab project page, which also contains a link to the website of the Greek Smart Kits, but no indication that the kit is currently available there. Please read all the comments regarding other people's attempts to build this project with varying degrees of success.

    It is quite apparent that most of the "makers" responding with "it doesn't work, please tell me how to fix it" are typical "monkey see, monkey do" hobbyists with little or no understanding of electronics. In reply to one of these "help me" requests, a recent response (2 Feb 2016) was "There are reports that this power supply works. I suggest you to follow the PCB design and not the schematic itself. Please also check all your connections and parts placement." In other words, monkey, ignore the schematic and go by the PCB layout! The original "design" was purportedly published in the the October 1978 issue of Practical Electronics magazine, but I doubt anything would be gained by finding and re-publishing the article here.
     
    hevans1944, Oct 29, 2017
    #13
    bushtech likes this.
  14. bushtech

    bushtech

    Joined:
    Sep 13, 2016
    Messages:
    474
    Likes Received:
    32
    Location:
    Vaalkopdam North West
    Thanks Audioguru. I am stunned. I knew there are lots of dodgy circuits on the internet but I didn't expect one from a university with an assistant professor involved. I looked at the LM358 internal layout but that is way beyond me.I also realised that there could that oscillation problem at the comparator's switching point but I reasoned picking a switching point 20 or 30C above ambient would probably get rid of that problem.

    I thought that in the overall scheme of things this is not one of the most difficult or complex problems. So in the Star Wars tradition: This does not compute.

    More research required
     
    bushtech, Oct 29, 2017
    #14
  15. bushtech

    bushtech

    Joined:
    Sep 13, 2016
    Messages:
    474
    Likes Received:
    32
    Location:
    Vaalkopdam North West
    Thanks hevans. Yes, I have always realised and accepted that this could be a troublesome project. But I expect it to to a very educational exercise and so far I am learning a huge amount very quickly, including not trusting professors;)

    I am still slaving away at the LTSpice simulation of this. I have never managed to successfully run a spice simulation and I expect successfully running this simulation is going to be much more difficult than actually building the power supply
     
    bushtech, Oct 29, 2017
    #15
  16. bushtech

    Audioguru

    Joined:
    Sep 24, 2016
    Messages:
    1,557
    Likes Received:
    363
    The fan control uses one of the opamps in the LM358 as a comparator. Comparators always use some hysteresis to avoid oscillation near the switching threshold because the DC gain of an opamp or comparator is 200,000 times or more and at the threshold the load is turned on and draws current which causes the supply voltage to drop a little which causes the reference voltage to also drop which causes the comparator to amplify the little voltage drop a lot which cause the load to turn off then it turns on all over again. Look at the datasheet of a comparator like the LM339 quad to read about their Application Hints discussion of the requirement for hysteresis.
    The professors in India did not read it. Maybe LTspice also did not read it.
     
    Audioguru, Oct 29, 2017
    #16
  17. bushtech

    bushtech

    Joined:
    Sep 13, 2016
    Messages:
    474
    Likes Received:
    32
    Location:
    Vaalkopdam North West
    bushtech, Oct 29, 2017
    #17
  18. bushtech

    hevans1944 Hop - AC8NS

    Joined:
    Jun 21, 2012
    Messages:
    3,342
    Likes Received:
    1,615
    Location:
    Venice, Florida, USA
    Did you not understand @Audioguru's comment that comparators always require hysteresis to avoid oscillation near the switching point? The circuit you posted uses a CA3140 op-amp as a comparator, but it DOES NOT provide any positive feedback that is necessary to implement hysteresis. Do you think you can figure out how to add positive feedback to add hysteresis to the circuit?

    Try to determine how much hysteresis will result from your chosen method of implementation. Ideally, if you know the temperature-versus-resistance characteristic of the thermistor, you should be able to express the hysteresis as the number of degrees of temperature swing required to switch back and forth between fan ON and fan OFF states. So, starting at room temperature or nominally 20C, a rise to 30C will (for example) turn the fan ON. But in order for the fan to turn OFF, the temperature must fall to 25C (for example). A subsequent rise in temperature to 30C will turn the fan ON again.

    Assuming the same thermal energy input to the heat sink that caused the temperature increase is still present, the circuit (with hysteresis) will turn the fan ON and OFF in repeating cycles. The frequency at which the cycles repeat will depend on (1) the amount of heat input to the heat sink, (2) how much heat is removed by the fan when it is ON, and (3) the difference (hysteresis) between the switch fan ON and switch fan OFF temperatures.

    A comparator with hysteresis is really easy to simulate in LTSpice, once you figure out how to add the positive feedback. Be sure you fully understand how and why hysteresis is necessary for successful comparator operation. It is a fundamental concept that you will probably use a LOT as you make progress in this hobby. Hint: because it is positive feedback, a comparator doesn't require a large amount of feedback to obtain a satisfactory amount of hysteresis.
     
    hevans1944, Oct 29, 2017
    #18
    bushtech likes this.
  19. bushtech

    bushtech

    Joined:
    Sep 13, 2016
    Messages:
    474
    Likes Received:
    32
    Location:
    Vaalkopdam North West
    Thanks hevans, apologies if I'm starting to irritate you. This is heady stuff to get my 62 year old brain around. I am going to draw this in spice and see if I can figure this lot out.

    OK, slapped my brain into gear (no alcohol involved) and I think I now get the oscillation problem I am going to get around the bottom threshold.

    But it burns me that I keep on finding circuits designed by people who know a helluva lot more about electronics than yours truly. Why have they not implemented hysteresis.:mad:

    "A comparator with hysteresis is really easy to simulate in LTSpice" heh, we shall see. If I just manage to find the component I am looking for in spice it's a major milestone for me
     
    bushtech, Oct 29, 2017
    #19
  20. bushtech

    hevans1944 Hop - AC8NS

    Joined:
    Jun 21, 2012
    Messages:
    3,342
    Likes Received:
    1,615
    Location:
    Venice, Florida, USA
    Not irritated at all, as you seem interested in actually learning about electronics, instead of just blindly copying what other people have done.

    Learning about feedback was a hugely complicated effort for me in the 1960s because I didn't yet have either the math background or an understanding of the circuit theory I needed, nor a suitable instructor/mentor who could explain the concepts clearly. Negative feedback was the hardest because, in trying to analyze what was going on, I seemed to always be "chasing my tail" like a dog, instead of making any progress. By contrast, I thought positive feedback was literally a snap: the output was either on or it was off and positive feedback made sure that once it began to change from one state to the other it continued on that path without hesitation or oscillation in between. I did think this odd at first, since I "knew" that oscillation required positive feedback. But I digress (as per usual)...

    I am not a big fan of LTSpice simulation (or any other computer simulation) over hands-on experimentation with real components to learn electronics. A couple of 9V batteries and a 741-type op-amp, along with a handful of assorted resistor values and a cheap digital muiltimeter, will teach you pretty quickly what is going on with feedback, both positive and negative. Take careful notes of what you are doing so you can keep track of your learning progress. Here is a common-sense definition of feedback: applying a sample of the output back to the input to effect a desired response. With op-amps, you can take a portion of the output and apply that portion to either the inverting or non-inverting inputs, or both. Depending on exactly how you do this, the result can be either positive feedback or negative feedback.

    There are several simplifying assumptions you can make about op-amps that will greatly speed circuit analysis, at the minor expense of some quantitative inaccuracy in the results. Once you have mastered elementary circuit analysis and design, you can use Spice programs to simulate circuits to "better" accuracy, but the results will be no better than the models used by the Spice program.

    You will have to think about what the following simplifying assumptions mean in terms of their effect on circuit operation and analysis.

    First, assume an op-amp has infinite differential gain for signals applied between the inverting and non-inverting inputs, that it's output can swing either positive or negative to any voltage, and that its output can supply any current to any load. Next, assume it can do this at any frequency without loss of response, that there is infinite impedance between the inverting and non-inverting inputs, and that if the same signal is applied simultaneously to both inputs (a common-mode signal input), there will be no change in output. This last property is called common-mode rejection. The ratio of output change to common-mode input change is called the common mode rejection ratio or CMRR and is a very desirable property of real op-amps, often being on the order of 100 db or more with careful design and construction.

    The first assumption, infinite gain, means there must be zero differential voltage between the inverting and non-inverting terminals for any finite output. Why? Because any differential voltage, multiplied by infinite gain, results in infinite output voltage... not a practical outcome for real op-amps. For circuits with negative feedback, it is the feedback that forces the differential input voltage towards zero. For circuits with positive feedback, it is the power supply rails that determine how far the output voltage can actually swing, and that in turn affects the differential input voltage, which is not necessarily zero with positive feedback. In any case, we only pretend that the output can swing to plus or minus infinity voltage and then see what the consequences of the pretense would be in a real op-amp circuit.

    Infinite impedance between the inverting and non-inverting inputs means zero current flows between those two inputs, so the only currents you need to be concerned with for circuit analysis are the currents through external components. No current enters or leaves the two op-amp input terminals. The ability of the output to provide any current to any load means you don't have to worry about the output voltage depending on output current or load resistance either, a fine if unrealistic convenience. Real op-amps have outputs that DO depend on their output current and the load resistance, but you can ignore that for purposes of a simplified circuit analysis.

    Op-amps are often used as comparators, either because of ignorance or convenience. There are integrated circuits especially designed to function as highly accurate comparators with fast response times, avoiding most of the limitations in performance imposed by using an op-amp (basically a linear analog component) as a comparator (basically a digital component). Be aware that some comparators have open-collector (or open-drain) outputs, so the output state that occurs when the non-inverting input is more positive than the inverting input means the output is really "off" and must be pulled "high" with a resistor connected to the positive supply rail. Read the datasheet carefully to determine how the comparator output responds to signals applied to its inputs.

    In your example CA3140 op-amp, used in your post #17 as a comparator here, try adding a one meg-ohm resistor from the output on pin 6 to the non-inverting input on pin 3 to add some hysteresis. So, how much hysteresis does this add? Consider two states, output high and output low. Calculate the voltage at pin 3 for each of these states. The difference in the two voltages is the hysteresis and is a measure of how much the thermistor-derived voltage on pin 2 must change to produce an alternating change in output states. If you know the temperature-versus-resistance characteristics of the thermistor, you can relate this voltage change to a temperature change and hence a temperature hysteresis.

    I suggest that you actually breadboard this circuit, using whatever op-amp you have on hand, and substituting a variable resistance for the NTC thermistor. Use your multimeter to investigate the hysteresis effect. You can leave out the transistor and relay if you want, connecting an LED with a current-limiting resistor directly to the output of the op-amp to provide a visual indication of the "on" and "off" states as you vary the resistance of the "simulated" NTC thermistor. Make careful notes of the voltage at pin 2 which causes the circuit to change states, and whether the voltage was increasing or decreasing when the state transition occurs. Try changing the one meg-ohm positive feedback resistor to higher and lower values to see what effect its value has on the switching point voltages. Try changing the set-point potentiometer connected to the other op-amp input to see what effect different settings have on the switching point voltages. After "playing" with this for an hour or so, you should have a pretty good idea of how hysteresis works.

    Why do you assume those people "know a helluva lot more than yours truly?" Last time I looked, there was absolutely NO qualification required to post ANYTHING on the Internet. The typical Instructables post is an excellent demonstration: although some are pretty good, some are plain awful, and many of them are full of errors and unwarranted assumptions. Most people have no idea what hysteresis is or how to use it.

    If you want to learn about hysteresis, do some research that involves reading material from several different reliable sources so you can compare opinions and explanations. Basic circuit analysis texts may be of some help. Google is your friend, but trust nothing until you have verified its truth either from personal experiment or corroboration by other sources. Then hold fast and don't fall for spurious claims that deny what you have already learned to be true. This process takes many years to master, but it is never too late to learn.

    Hysteresis is not always intentional. For example, it is the bane of position control systems (servo-mechanisms) where it causes positioning errors that depend on the approach direction. Expensive procedures, such as anti-backlash gear mechanisms, are often required to minimize it.

    Hysteresis is unavoidable, and sometimes even desirable, in some applications. Most magnetic circuits exhibit magnetic hysteresis, and the effect is sometimes exploited for purposes of heating: a hollow magnetic susceptor (typically made of nickel or a ferrous alloy) is placed in the work coil of an induction heater, where it will quickly become incandescent through induced eddy current losses and magnetic hysteresis losses as it heats the work object inside, indirectly, by infrared radiation.

    OTOH, high-quality power transformers use grain-oriented silicon steel to minimize hysteresis losses in the magnetic circuit. They must still use insulated laminated cores to minimize eddy-current losses, or use an insulated spiral tape core over which the windings are placed. A well-made transformer will have an efficiency of close of 100%, meaning almost no losses. There aren't too many other things made by man that can claim such good efficiency, although three-phase induction motors come close.

    Please let me know if any of the above helped you, or whether it went flying over your head like a flaming meteor. Maybe I should have included some circuit diagrams...

    Hop
     
    hevans1944, Oct 30, 2017
    #20
    twister and bushtech like this.
    1. Advertisements

Ask a Question

Want to reply to this thread or ask your own question?

You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.