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Posts posted by MP

  1. Hi

    I want to build a Big, High quality Loud Speaker But I do not Know how to choose a high quality speaker for it.
    I mean How can I determine if a speaker is good or not?

    Choose it by model? (JVC, Pioneer, ...)
    choosing by magnet?
    choosing by diaphragm meterial?


    ThanX in advance

    The specifications of the speaker are part of it. However, the design of the box is also very important. Also, it must work well with the signal you are putting into it. All of this is calculated into the design by the system professional. You might want to start from a kit as Sasi has mentioned. Otherwise, you should spend considerable time researching this subject. There are tutorials and books that can help you. Kits are a great hands-on tutorial, and many kits will give you a lot of background data that tells you how the specifications were calculated.

  2. RF,
    I don't think you can print out your finished board with ExpressPCB. The manufacturer gives it away so that you will send them the file and pay them for boards. No one else can read their files.
    You can get a free copy of Eagle on the links section of this site. It will work much better for you. You can print the files to use for etching a board or send them to any board house, etc. With ExpressPCB, you are stuck with using their services.


  3. Yes, fatman would give you some flexibility. Also, you mentioned programming. I was wondering if you knew that microcontrollers can be programmed with basic. The PIC can use PicBasic and AVR microcontrollers have Bascom AVR. Even if you do not use it for the heart of your project, it makes for a nice LCD interface, etc.
    What are you using for a keyboard? I did not notice if you mentioned this.


  4. This topic has been moved to Circuit/General Requests.
    This topic was removed from the Projects Q/A forum. The Projects Q/A forum is reserved for discussion regarding projects in our Projects section. To see these projects, click on the blue button near the top of the page titled "Projects".

    To continue with this subject, click on the following link:

  5. Hi Rf,
    These are exactly what I meant. You will need a VCO for each note of the chord that will be played at once. a low pass filter, high pass, and band pass will be very helpful for fine tuning the instrument that you want to simulate. Then you will run the filtered VCO(s) through the envelope filter which will change the attack and decay of the note. This is what is known as the envelope of the sound. The envelope determines whether it sounds like a piano, flute, oboe, etc. You can attach any and all of these modules together as needed. The keyboard part is just switches allowing higher or lower voltages, depending upon which key is pressed.
    Let me know if you need more information. I can probably come up with some patch diagrams as well. What sounds are you going to have come from this instrument?


  6. Pic needs 4 clock cycles per instruction. AVR completes one instruction per clock cycle.
    I have no idea what you are talking about with bitwise chips, comparisons, and having problems extracting a bit at a time with a micro. Never had such problems with a micro. Are you refering to CRC error checking? Not required, but a good idea to check to make sure your transmitted data is ok. You didn't say RS232 was a requirement. Why not use I2C protocol?


  7. sounds like you are trying to re-invent basic vcos and voltage controls, but going in the wrong direction.

    Reptilian: Just look up PAIA electronics and look for schematics for their old synthesizer modules. They used very few parts and had much more capability than what you can get out of a 555. Primarily, you want to look for the 2720 series modules such as 2720-x where x is a number which denotes the model such as VCO, VCA, ADSR, etc. All are controlled by a simple voltage control input and all are connected to each other permanently or by patch cords. They also had a more advance series which were the 4700 series modules.

    If you can't find information on any of this, please let me know. I am sure I can come up with examples with a little digging into my archives.


  8. Handcannon,
    Here is what I meant with the diode.
    The pots are for the proper adjustment of the circuit. You should start with them in the center position. Usually, the designer will add a fixed resistor in series so that full adjustment will not allow a direct short. You can calculate how much current draw will be required by using the ohm's law formulas. Calculate high and low resistance requirements, which means the span of which you will adjust the pot. You do not want this to exceed the rating of the regulator. If it does, you can add the addition of a series resistor to limit current. It is easier to do this after a regulator than to do so with full battery power. Otherwise, a lot of current is dissipated in the series resistor, requiring a high watt rating.

    Sorry audioguru. This forum is for discussion of projects on this site. I have moved your google find to the proper forum, Project Design/Ideas. If handcannon wants to dump this project and use that one, it is in that forum under "Auto Dimmer".



  9. I doubt this graduating student is having a problem building the simple amplifier circuit for the stethoscope. As AN920 has mentioned, the tasks needed can easily be performed by a micro. Bynes needs to decide which one and which language, for further assistance.


  10. MP,

    What rating for the pots do you recommend for R3 and R4 to be able to set them at zero ohms in the car battery circuit when S1 is closed?

    As I said, I recommend the use of a regulator, ante.

    I am sure the author never expected anyone to put a pot in the zero ohm positon, which of course, is a direct short. Aaron Cake admits that he is not an engineer. It is just a circuit that worked for him. I do not know what he used for pots.

    Handcannon: Use a voltage regulator. Even on a voltage regulator, a pot in the zero ohm position is a direct short. However, you can overcome this by connecting a 1N4004 or similar diode across the input and output pins of the regulator in a reverse position to protect the circuitry from shorts. Let me know if you need more explanation of this.

    Unlike others in this forum, I am trying to help you find a solution instead of useless grumblings about the circuit. Hope it helps get you there.

  11. I haven't been following this thread, but yes, a microcontroller could be programmed to give you the sounds you need. Each output pin could give you a different voice. You should understand, however, that a 555 and micro will both give you a pulse or square wave without additional hardware to make it into a sine wave. Not sure if that is a problem for you or not. If you need a sine wave, you would be better off building a simple VCO for synthesizer.
    Here is a sound chip that is actually PIC based and might be a better choice for you than to learn programming a PIC:

    A link to the data sheet is also on this page. This company also has other sound chips.
    Hope this is helpful to you.


  12. The link to this project is here:

    What is the rating on the pots you have used? In a car circuit, you must use high watt rated pots or you will have the problem you are discussing. These pots are limiting voltage to a car battery. Since this circuit only causes relays to go on and off, a simple fix would be to add a voltage regulator to the circuit before the battery. This would limit the available current to this part of the circuit.

    To all:
    Please note that many of the projects in our projects section have come from various places on the Internet. There is no guarantee from this site that any of them work...thus we have this forum for Projects Q/A where we discuss how to make them work.


  13. You could get a lot of good tutorial information by searching the web for Vellum kits. This is a brand name. They always put a very nice soldering tutorial in the beginning of their projects. B1 is Battery #1, R1 is resistor #1, C1 is Capacitor #1, U1 is IC#1 (or Integrated Circuit #1), the numbers behind them are model numbers, values, or part numbers that you would use.

    You can make your own pc board or just try the circuit on a breadboard to start. You can use the generic perf board and run wires between all the parts. You will not have much current, so small gauge wire is fine. You might even want to invest in a "Wire Wrap" tool. This is a nice little tool that will help you connect the parts with a very fine wire that it spools around the leads of the components you want to connect.

    Hope that gets you started.


  14. It all depends upon your level in electronics. It would be a good project to learn. It will certainly give you soldering practice and experience with schematics.
    What problems are you having with the parts lists in the schematics?


  15. Ben,
    You probably have oxidation on the copper strips on the board. This is easy to overcome. Go to your local electronics store and get a small bottle of liquid solder flux or a solder flux pen. Put a liberal amount of flux on all surfaces that you want the solder to adhere to before applying heat. You should succeed with a nice even flowing solder joint that flows perfect on all parts. Flux is one of the best things you will ever encounter in the world of soldering. Use a little isopropyl alcohol to clean the flux from your board when finished. If you do not clean the flux off the board after you are finished, dirt will stick to it and after some time, you could end up with a short between pads or components. Thus cleanliness is important.
    I hope these pointers help you.


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