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Herman the German

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Posts posted by Herman the German

  1. Hi tags,

    I've never built an automatic fish feeder.

    Fish can easily survive in an aquarium for a period of two months without being fed.

    If you know you're staying out of house for a longer period just feed a bit more for about one month. This allows the fish to put up extra weight which they can use during your absence.

    Additionally you might think about using Guppies to breed fresh food for the others.  ;D

    An easy way for an automatic feeder would be a kind of caroussel with the daily food rations contained in small chambers. Kick the caroussel every 24 or 48 hours with a solenoid and a sprocket similar to the one used in old clocks or hand operated hoists (allows movement in one direction only).


  2. To make a burst of three flashes you will need two timer ICs, one wired as a monostable and the second as an astable MVV.

    Timing must be accurate enough to have the astable put out three pulses until the monstable times out and keeps the astable in reset condition.

    At 80ms pulses and  50% duty cycle the 'on-time' of the monostable must be 400ms, after which the monostable resets the astable.

    Initial triggering is done by taking the TR input of the monostable to ground via a pushbutton. (Pulse must be very short or use a non-retriggerable circuit)

    Check out the timing diagram in the attachment.



  3. Hi stuee,

    you might try this circuit.

    It uses two timer ICs and a decimal counter.

    Function: Timer1 (IC1) generates  the clock frequency of 380Hz for the counter while timer2 (IC2) generates enable pulses for the counter. Since the frequency ratio is not dividable with an integer result the decimal outputs are active pseudo randomly.

    Connecting a low current LED to the diode network you might omit a current limiting resistor if VCC doesn't exceed +9V.

    Using a power LED omit D8 and R5 and connect transistor Q1 (BD139) as shown. For your specified LED use an 82Ohm resistor for current limiting at VCC=+9V.

    I recommend using two independant timer ICs since they might influence each other using a dual timer IC (NE556).




  4. Hi Sukhbinder,

    I guess there is no difference in general purpose rectifier diodes and high efficiency ones.

    The manufacturers might call a general purpose rectifier a "fast rectifier" diode or what so ever.

    Fast recovery diodes can normally stand multiples of the rated current being pulsed. At high switching frequencies this might become important, e.g. driving a stepper motor to it's rpm limits.

    I doubt you can use a high efficiency diode as a fast recovery diode.

    Schottky diodes generally have a lower voltage drop than silicium type rectifier diodes. Used as an "idiot's diode" to prevent false polarity in a circuit they drop the supply voltage by 0.4V. Rectifier diodes do 0.7V.


  5. The circuits won't work with a normal opamp and is meant to use a open collector comparator.

    The following diagrams show one of the problems I stated earlier

    The first two diagrams show the circuit in both conditions. ( I only left the switches in their respective states for clarity). It can be seen from the simulation that LED1 is always on, while LED2 is off in the SET state.

    Next is the circuit that uses another PNP transistor driven from the collector of first PNP. Simulation voltages show the results.

    You need to zoom in otherwise mA looks like nA. (At least on my monitor)

    Hi AN920,

    this has nothing to do with the circuit you are discussing. After having purchased a lousy, but expensive simulation program I'm looking for a better one. Would you kindly give me the name of the one you are using?

    Thank you in advance.

    Kind regards

  6. If you have the means to do so, I would certainly like to see a picture of the guts of this device.

    I don't know how they can claim to save any power with resistive loads like a range, toaster. or light bulb.  Does anybody reckon they are designed to deceive the meter by using an amp or two at peak and feeding it back at higher current near crossover?  If so it is illegal in several countries.

    Hi again today Ldanielrosa,

    I know about this stuff. They sell it in Thailand for a relatively high amount of money (about 32US$). My friend purchased such a thing and he gave me permission to open it. The box was glued together all over for good reasons. Inside there where three capacitors of 0.15MicroFarad/250VAC in parallel, a 470K resistor and a LED. There is no change in the meter plugging or unplugging it. It's just cheating!
    Since the LED consumes electric power too the bill will increase.

  7. I'm not sure how helpful I'll be, but it may help to turn off the caps-lock when posting here.  Also, when was this assigned and how much longer do you have?

    Hi Ldanielrosa,

    he doesn't have anything to type low case letters because he is using a Radio Shack TRS80 (Trash80)  :P
  8. Hi,

    I had the same problem. For differential etching the film must be inverted. I made a normal positive print and used reversing film to make a negative. There is reversing film at the market and it can be exposed like a board with photoresist. That way there were only negligible inaccuracies on the film and I could use it for double sided board. The rinsing water must not be too hot or too cold (just room temperature is OK).

    If your electronic shop doesn't offer that kind of film check at a photo lab.


  9. Thank you :)

    Making a PCB with EAGLE is just as fast as an eye twinkle. Type "board;". Don't forget the colon. Eagle will ask you a silly question: "The board does not exist. Create from schematic?" Click OK and you'll have a board instantaneously. All components are placed beside a standard board of 160X100mm.

    Delete the "dimension" lines first because they are not drawn accurately. They don't meet at XY 000. Chose layer "dimension" and width 0 and draw a new 'box'. If you are using the light version don't exceed 160X100mm or near it. Use grid size 1/20 inch (1.27mm), 'grid on - dots' for close results.

    If you want to route the power lines manually omit them in the schematic first, since they will be air wires on the layout.

    After having drawn the new box group all parts and move them onto the 'board' using the right mouse button.

    After that you can move each part, rotate it and make the board according to your plans.

    Using the autorouter is sometimes not desirable. You might wish to use it. However it tends to 'surround' itself. If you aren't satisfied with the routing just type "ripup;" and you'll get back all your air wires.

    If you have any more questions concerning EAGLE just let me know via e-mail. I have more than 15 years of experience with EAGLE and can give you useful advice.


  10. Hi Herman,
    The CD4047 was used because it is an oscillator IC that has a digital divider so its outputs are a perfect square-wave, and it has two opposing outputs (one is inverted).

    Hi audioguru,

    well, a CD4047 will do the required job. I just thought of the 100Hz cycle it produces internally to be divided by two. It is kind of hard to achieve a stable 50Hz cycle anyway. Higher frequencies are easier and using the appropriate output and just one transistor for inverter will result in the desired function.

    I used a 4060 for accurate timing with outputs of 400, 200, and 100Hz and it worked as accurate as a stopwatch.
  11. Analog devices offers a new two-axis accelerometer chip. It can sense angles up to 0,1degrees accuracy in both X and Y direction.

    The name of the circuit is ADIS16201. There will just be a small problem using it. It does not have pins, but a so called "Land Grid Array" LGA-package meaning the solder pads are just underneath the device to save room for more parts on the board.

  12. You might also use Eagle light. Look up CadSoft.de and download version 4.12. There are no restrictions on parts or functions. The only restriction is the maximum board size of 160X100mm.

    However it is free and includes a fairly good autorouter as well.


  13. Hi Herman,
    Nobody was disrespecful to me:
    "Texas Instruments and Fairchild recommend a minimum of 10k ohms for the capacitor in a CD4047 oscillator, then an inexpensive high accuracy capacitor can be used? Thank-you for pointing it out, Audioguru".

    I get thanks like this all the time.

    Hi audioguru,

    I just saw it that way. Why not take a CD4060? That one can use an Rt > 1K and Rs about 10XRt. Of course, it has an odd outputs (compared with the CD4047),  but can be compensated by setting the correct clock frequency.

    Inverter frequencies should be near the nominal main frequency. I tolerate +/- 1Hz. As pointed out before a crystal oscillator will do best and for extra accuracy the crystal can be pulled slightly with a 40pF adjustable capacitor.

  14. Walid,
    Perhaps you have misunderstood the conversation. No one has been disrespectful to audioguru. However, you might not know that audioguru is not an R&D Engineer. In fact, he is not an Engineer. He mentioned in another forum that he did not complete his Engineering course.
    In regards to being disrespectful, I find it disrespectful to say someone looks unusual when discussing their knowledge or capabilities. It is an insulting statement. Ones appearance has nothing to do with ones Electronic knowledge or capability.


    Hi MP,

    I suppose that you know what you are talking about after having been engineer for more than 30 years. I read every argument in this topic and I think that some of your words chosen are very close to disrespect. It is not important to be an engineer. It is important what you do and how you do it. In my special field I was just a technician concerning aerodynamics and air flow, but I had an engineer for breakfast every day. They just talked high tones not knowing their jobs properly.

    So please have the kindness not to get PERSONAL in any discussion. To me it appeared like a declaration of war! Since I was soldier for more than 23 years I know something about that "topic" too and I'm proud of having killed 255 communists who wanted my butt but lost the competition.

    Just live in peace with audioguru to make me happy.
    Herman the German
  15. :o The most simple way is just dumping your PCB into irontrichloride in a flat bowl.
    Etching accelerates with a little mechanic help. This can be done by causing the liquid to make small waves on the surface. Advantage: You can see the progress and take out the PCB early enough to prevent under-etching. Disadvantage: You have to do this for about 30 minutes.

    2. Use a container high enough not to spill the chemical stuff. Then use a rotary type aquarium pump and a spray bar (Poke little holes into a plastic hose) and spray equally over the entire board. Either oscillate the board or rotate the plastic hose at moderate speed to cover the sprayed area all over your board. That works faster than the above described method.


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