MP

Sure, 10.7 MHZ is a size used for IF, but micros also use various size Crystals for specific purposes. A 10.7 MHZ Resonator (or Crystal) will give you almost 3% less error in RS232 data transmission at 57600 baud than a 10 Mhz Resonator (or Crystal). I don't know what OP purchased since I am not clairvoyant, but I would be surprised if it did not work for this purpose. Even a digital gate based clock will work for a micro. MP

PICs can run hot with no current limiting. Since this program is sending out a pulse and not a steady DC voltage, there is no danger to the PIC. It will just run warmer at certain duty cycles. Personally, I like to use resistors on the output pins of microcontrollers. I am just saying that the "no resistor" version will work. MP

Actually, that is not so. What he has is also used for microcontrollers. They are perfect for this application and much cheaper than a crystal. Just ground the middle pin and either of the outside pins can be connected to either of the clock pins on the micro. I have a drawer full of these for this application. I never use a crystal for a micro project, except for specific conditions where I need it. Resonators are commonly used instead of crystals. They take up less space on the pc board since you do not need the capacitors. It also sometimes eliminates routing problems on a pc board. ...of course, mine are much smaller than Hotwaterwizard's resonators ;D MP

Here is a calculator: http://daycounter.com/Calculators/SkinEffect/Skin-Effect-Calculator.phtml MP

Although 10K is a bit more than I would use, either way is fine since the source is a PIC. The project is ok as is. MP

Your circuit is a standard level converter, but the resistor values are high for connection to micro. Try 10K instead of 100K and 3K3 instead of 4K7. Also, the PC should be connected to the 10K and the micro should be connected to the pin marked TTL. Note that this is a one way communication from the PC to the micro. MP

The second power source that you posted a link uses the same circuit as our project here: http://www.electronics-lab.com/projects/power/010/index.html Might as well just build it rather than buy it. I f you just want to jump in, either of these would be good starters. The breadboard is ok, too. It is nice to have one with banana jacks so you don't have loose power supply wires ready to pop out of a breadboard and short things out. MP

Here is an interesting project done at cornell university: http://instruct1.cit.cornell.edu/courses/ee476/FinalProjects/s2006/XL76_SL362/XL76%20SL362/index.html MP

sundar, The filter that was posted by audioguru will give you more attenuation than the bandpass filter posted. The reason bandpass will not give you the results you want is that Q is inversely proportional to Bandwidth. As you increase the bandwidth of a bandpass filter (300 to 3K is a wide bandwidth), you lose the Q, which directly effects the amount of cut or boost in a filter. The Sams circuit posted above is a standard speech filter used in many applications. I have used the same schematic, only different resistor and capacitor values. To get an even better cut point, you can build high order low pass and high pass filters which are in the 3rd or 4th order and just connect them together like in the Sams design. As sarma has mentioned, once you get rid of the frequencies that do not hold voice, how will you determine what is voice content and what is something else in the 300 to 3K range? Just curious. MP

"Ground" and "Earth" are actually two different things, but can be at the same potential. In other words, the ground of your circuit does not have to be connected to earth ground, which is the potential of the return or ground of the mains in your service box on the house. This is always at Earth Ground because it is connected to a rod that is driven into the ground. There are many situations where your chassis ground or case ground on the instrument would not be at the same potential as earth. There are also instances where you want a different supply ground or circuit ground than the earth ground or the chassis ground. Thus terms such as chassis ground and common come into play. When these potentials are different, the schematic will use different symbols to denote zero volts, common, analog ground, digital ground, chassis ground, and earth ground. Using different symbols to sort these out keeps this from getting too confusing. MP

N4, if you have a good quality voltmeter, you can measure the voltage directly. Most will measure 1000 and some better quality will measure 2000 volts. Check the specs on the one you are using. You might be surprised to find you already have everything you need. MP

You need the same ground or you will have different voltage potentials for the two sections of the circuit. Check the voltage difference between the commons. There should be no voltage difference. It should be "Common" to both parts of your circuit. MP

sundar, You did not mention how much attenuation/rejection is needed. If you need to eliminate the frequencies above and below these set points, you will need a high order filter. Neither of these designs are high order. They will give you some attenuation, but not rejection. Will this work for you? You did not mention much about the purpose of the design. MP

xerex, The 4047 is only giving clock signals of 50 or 60 hz which are complimentary to each other. If you cannot find a 4047, the same could be achieved with a 555 and an inverter chip. MP

Yes. There are several ways to do this. Voltage control has to be built in as part of the circuit. It is rarely an add-on. In the most basic type of this design, you can use the bandpass section of a state variable filter and use a voltage variable resistance instead of a pot. Can you post the circuit that you are currently using? Voltage Controlled filters can be made in a very wide variety of types. The auto-wah is also known as an envelope filter. MP

I have never seen one of them. I don't mean to take this off-topic, but if you happen to still have one or more of these magazines, it would be amusing to see some of these joke articles. Of course, it should appear as a new topic. MP

sarma, Thanks for the elaboration, but I was actually making a joke based on the old electronics addage that all electronic components have smoke in them and if you let the smoke out, they will stop working... of course, we all know that this is not where the smoke comes from. MP

However......if the diode is in-circuit and powered up when you short it, you run the possibility of letting the smoke out.... ;D MP

You are really a paranoid person, talking about secret emails and replacing projects. The inverter project that I corrected was on this site long before you first appeared. It was still on this site when I fixed the lines which were drawn badly by the author. You should seek professional help instead of trying to instill unrest on this site because you have a beef with me. Here in this forum you are doing the same thing that causes me to delete your posts in the forums that I moderate. Your posts have nothing to do with Theory or anything else. Just bitterness, grumbling and insult. I didn't pull your precious audio amp inverter off the website. I don't even have access to that area of this site. But you already know that since you used to be a moderator here and lost it. Smoke and mirrors. Just trying to get people angry to help your cause. Why don't you go peddle this crap on Aaron's website where they will take it. MP

Mik3ca, First, you should understand that I did not design this inverter. I only corrected the mistakes in the schematic. There were lines that were crossed and connected, and decimal places wrong in values. They were simple fixes. The design is still the work of the original author. Secondly, note that you do not need the current limiting resistors in a switched application such as an inverter. Such resistors are needed for a linear amplification such as an audio power amp. Look at the many designs all over the web for a square wave inverter circuit and you will see they are all missing the resistors. Square wave inverters are all basically designed the same. There is nothing different about this circuit than the many all over the world presently in service. I have actually had emails telling me the one that audioguru helped design works much better if the power resistors are removed from the circuit. Note that audioguru admits that he has never built an inverter. This is why I moved this thread to the Theory section. BTW...it is my understanding that Rhonn's design is not deleted. It is just being moved to it's own page. Audioguru is making a big deal out of nothing. MP

Ante, There were some lines connected wrong or crossed and the decimal of the cap and resistor for the clock were off. Very minor fixes. I cleaned it up and uploaded it. As far as the "open forum" questions, no, Projects Q/A is not an open forum. It is reserved for questions and answers to get help with a specific project. In order to keep the threads usable, I try to be very strict to keep all other conversations and/or grumblings out of this forum. We have plenty of forums on this site. Theory can be discussed in the Theory forum, general discussion of electronics can be posted in the Chit Chat area. Anything that does not seem to have a forum can be posted in the General forum and feedback to the site can be posted in the feedback forum. I don't think I am asking much to have this area reserved for those who are building projects to get help with their work. I seem to get a lot of "don't build that...build this" posts when someone asks a question here. That is not what the "Projects Q/A" forum is about. When members contact me through PM and email to get the help that they can't because of audioguru's grumblings and multiple off subject posts in this forum, I decided it is time for me to put an end to it. MP

Theory discussion regarding inverters has been moved from this thread to the theory forum MP

I have used both Lexmark i3 and X1100 series. Just print on best quality black and the transparency looks good. I have actually retired the i3 to the workbench since this model runs the paper straight through without bending it. I hope to get some time to examine it and see if it is possible to convert it to accept pc boards instead of paper. I hope to be able to print directly to copper clad if I can find a suitable ink to fill the existing cartridges. Take a look at one of these. You will see what I mean. Take care! MP

idevices, That used to be the case. I did exactly the same many years ago. However, Inkjet technology has changed. You can use the darkest available setting on a high resolution inkjet and it is much darker than laser printer transparency. I think the problem is not the technology used, but is the printer used, in his case. MP

You should post your schematic and board layout if you have it. If you know the specs on the steppers, please also post that. All of this information is needed to properly answer the question that you are asking. MP