Shahriar

Dear Audiguru Would you please give an explantion that what are Pre-emphasis & de-emphasis? The DATA frequency coming out of PT2262 is about 7-10Khz and its Amplitude is too big(nearly 10V) so I decreased it with a 50K volume. 2-what is the diference between RFC and an ordinary Inductor? 3-Is that PCB Inductor (L4 in main circuit) so important to cause a fail in the project? ThanX - Shahriar

Here My schematic

Hi I want to build an FM Transmitter to control two Realys. the range of the transmitter should be about 700 meters. I selected 4 watt FM Tx from project section I used PT2262 encoder to creat DATA. and schematic is as below. but some questions:"If you do not see any thing wrong" 1- Can I Omit those Inductors(L1,L2,...) and replace them with those Inductors which are similar to Resistors, instead of building them myself? If yes/ how to calculate their values? 2- What does RFC exactly do? 3-Can we use IF as a RFC? 4- there is an Inductor in schematic which is created on PCB. I am building my own PCB. How to creat that? Just draw it as it is? Your help is appreciated in advance. Shahriar

Dear MP Is it also true with LPT1 port. I mean: Is "Parallel port" short circuit protected too? I do not dare to check it out. Shahriar

Remember Two things: 1- Always connect your PC serial port directly to a buffer IC (i.e. 74245) because PC serial port is not protected from short circuit. 2- the other thing that many people forget is that the address of PC ports are in HEX, for example 370H, many people mistake it with decimal and misspell the "H" or "0x" HTH - Shahriar

Dear audioguru The High voltage of the CRT is not dangerous for human. The only thing happen is that it gives you a little shock, because when the FyBack Transformer amplifies the Volltage, It reduces current (Power on both sides of a transformer are equal) The only dangrous section of a TV, is the power section before the Switching tranformer of power supply, and this part is marked with a WHITE line around it, the other parts of a TV do not hurt you because it is isolated with SMPS Transformer. The only thing sometimes happen is that some Parts shock you in such way that you learn never try to repaire your TV Unless you are a expert. Shahriar

Dear Kasamiko Here a circuit with calculator you mean. but It didn't catch my Attention. click on " Telephone call meter using calculator & COB " here is the link http://www.electronic-circuits-diagrams.com/telephones_circuits.shtml HTH, Shahriar

Hi I want to build a device for time measuring in a horse race. A sensor will detect when the horse pass the start point and another sensor detect when the horse pass the finish point. both these two sensor will send a wireless signal to the refrees and so on... The problem is the range of the transmitter. sometimes the range should be about 400 meters. I want to use PT2262 IC for the transmitter, but how can i increase the range of the transmitter. One of my friends build the transmitter in the PT2262 Datasheet but it didn't work more than 50 meters. Any Idea is appreciated in advance... Shahriar

Dear Ante Thank you vary much. :) They are a little bit different. I donloaded CMC 531X from this Link: http://fileshare.eshop.bg ThankX again Shahriar

Hi I Need DEAWOO Monitor -14" schematic. ITS Chasis name is CMC531X. There is a CD on Internet that includes this schematic but they said we can not send it to your country. :-[ Your Help is appreciated in advance Shahriar

Dear MP As I said, I know how to power off the power supply and I know how to use timers. THE PROBLEM IS THAT how I detect that there is no AUDIO or VIDEO signal at the Input. I have think about it and I want to use the following circuit. Although it is not the FINISHED circuit Please tell me the problems you see with the circuit ThanX in advance. Shahriar

Hi I have build two laboratory equipment for two English Language Institue. Few days ago, When I went to one of these laboratory, I noticed that the teacher has forgotten to turn the centeral SET off so The VCR connected to the set has reached to the end of the Film, so the TV had Turned off automatically. but my set has been working for 3 Days. So I decided to build an AutoPower off Power supply. I know how to turn off the power supply But my problem is how to detect that there is no Audio Or Video signal at the SCA inputs of the set. The Power supply is to be turned off by a Microcontroller. ThanX in advance. Shahriar

Hi I have two questions... 1- Does anybody know how Laptop power supplies Or Mobile Chargers work? I think they are very similar to each other. They are very small and light. They are very lighter than usual Switching power supplies... 2- There are usually a cylindrical part on the wires which connects the power supply to laptop or the wire which connects the Joypad to palystation. What is Inside that? ThanX in advance. Shahriar

Dear vvv I think, at first you should decide what PCB software you want to use... I started with protel DXP, and i learned it from the books accompanied with the software. There are also some books about protel. Eagle is another good software for PCB design, But i don't know whether it has books with it or not... HTH, Shahriar

Hi If you are looking for a high quality and professional FM Transmitter you you can visit this site, In this site there are some schematics and PCB and lay out and Fabrication manual that are related to some Transmitter kit from different companies that normally you can not visit schematic before you pay, for example there is shematic of FM Trasmitter with LCD, or Some nice PLL FM Transmitters. http://www.geocities.com/Area51/Nebula/3736/ HTH, Shahriar

Hi I Want to build a device which can turn on a 100watt lamp gradually and then turn it off gradually and do this ever and ever. I emphasis that i DO NOT WANT To turn on or off the lamp suddenly, But I want to turn it on and off GRADUALLY. Any help is appreciated in advance. Shahriar

Hi As you may notice in shielded stereo cables, one of the inner conductor is thicker than the other one, for example one of them has 10 copper conductors and the other one has just 3, Is it really differ how we use them? ThanX Shahriar

Hi has anybody think about a device which can write something on TV. For example, imagin in an election you want to show the number of votes for each condidate on a large TV so that every body can see it in a large hall. for example we send the video signal through the RCA Jack or connect it to somewhere in TV chasis. Any help is appreciated in advance...

you can download the crack for eagle, here which i have used, but i recommand you to use Protel DXP 2002 or 2004, although many people use Eagle Crack.zip

*** Thank you very much for your always complete replies ***

Hi here the answer of your questions... 1- Sorry, TL072 is correct, I misspell it. 2- Yes, in the Original circuit i replace NE5532 with TL072, I have not build this second circuit i just post it to see maybe The 1Mohm(R4) resistor do the same as the 1Mohm I put in the original circuit. 3- In the Original circuit, I replaced Rx with 1M resistor. (one pin between Cx an 10k Resistor and the other pin to the SGND) 4- In the original circuit, the Output voltage of 'U1A' changes a little, I wrote this to tell you that the OpAmp does NOT saturate with or without Rx (1Mohm), in fact Rx(1M) resistor does not play any roll in DC Voltage of output. 5- This is the main question!!! This is why i call it Mysterious Resistor. dear audioguru, can you explain some more about the Reference voltage in the second circuit i posted, why output will go anywhere without it? Shahriar

Dear Audioguru & MP dear MP, There are so many guys in this forum with lots of information that want to share with others like you, Audioguru, Hotwaterwizard, ... and i really appreciate all of your correct or wrong comments... I replaced NE5532 with TL074 and because they are pin compatible & i had used IC socket it was a piece of cake... But what happened? Circuit did NOT work without 1Mohm Resistor, I checked the DC voltage of Output: Vout=6.04v without 1M res, Vout=6.32v With 1M res As expected... I found a schematic (that is attached), if you take a look you see R4=1Mohm, The author has said this: "Resistor R4 provides a ground reference for the pre-amp" not anymore comment, I sent an email to him and waiting for reply.

Here is the Original PDF that i substitute TLC72274 with NE5532 and i didn't understan the resistor R24(20K) Texas_Mic_Mixer.pdf

Hi I have made a preAmp From a datasheet from Texas Instrument that the PDF is Attached, But i Think somthing is missing because when my hand touched the Capacitor (Cx) accidently then i found that i have to Solder a big value resistor between the output of the Capacitor and SGND (Rx), but there is a little bit Hiss, at first why it is needed? If I don't put the Res The circuit will be mute unless i shout in Mic...secondly I have done many tests and a resistor less than 820K will mute the Circiut as it was at first how can i calculate the Best value for Cx and Rx to have the less Hiss, the Mid voltage in schematic is 6V to to bias the AC signal to the center of the operating voltage range to prevent positive or negative clipping of the audio signals. your help is appreciated in advance...

Dear Uman Software are usually expanded in one branch, I don't think you could find a software to be good at all of them, For PCB I recommand Protel DXP 2002 or 2004, It is very good in simulation too, but for simulation i have heard about 'Circiut Simulator' But not worked with it yet... By the way, Forget Protel 99SE