Shahriar

Hi Sorry to say this in this forum; As I remember within these two years in electronic Lab, All people Teach good thing to each other; But this time I think Electronic Lab community is going to teach How to kill people; So I Do not welcome you PERSONALLY; Shahriar

Dear Ann I think there is no reply because nobody understand what you mean. What does "about d park aid.." mean? HTH - Shahriar

Dear smartsarath2003 A PC speaker is just a power amplifier. if you want to build a good one, look for a good Power Amplifier IC which you can find it in your area. there are two many kinds of these ICs. then download the datasheet and the rest is easy. your sound card acts as a good preamplifier so you do not need a preAmplifier. connect the volume to the Sound card and conect the output from the Volume to your power amplifier. there are some sort of these ICs which have Digital volume which are used in Televisions. If you buy one of them then you can increase or decrease the volume with two push buttons instead of a volume.... P.S. Just be carefull about shorting the sound card. because most of them do not have a short circuit protection. HTH - Shahriar

Hi Does anybody know how microwave ovens work? How do they get things so much hot during seconds? ThanX in advance Shahriar

Dear Ante, Than you for your link. I will check it. Dear Audiguru the theory you said looks a little bit strange and if telephone designers Have done such a thing then they have challange a big problem. Imagine that ten years have passed and the goverments have decided to increase or decrease the telephone bills. they they have to upgrade thousands telephone memory over a country. I beleive smart card telephones uses another theory. ThanX a million Shahriar

Yeah, It can be a possible. I will check it and tell you. Thank you very much Shahriar

ThanX all for your replies. Dear audioguru, I didn't say that long distance call sounds different. the pulses which I have heard about them is on both local call and long distance calls and you are not able to hear them. as I said I am not sure about this theory. I ask the question in another manner: Imagine you are asked to build a telephone with a smart card. the telephone should decrease the person credit which is stored in the smart card. this is different depending on the distance he/She has called. (Japan or India). How do you calculate the money which you are going to decrease from the person credit???? This is what have built and you see it every where over cities. ThanX Shahriar

Dear Alun The circuit is to creat a loud Beep. small buzzers can not creat such a loud sound. when I used a coupling capacitor between the output of opAmp and the transistor Base, the effect of my hand dissapeared, then I remembered that the PreAmplifier I had build, was a DC coupling PreAmplifier (it did,'t have any coupling capacitor). But the thing I didn't understand was the effect of my Hand!!!!!!!!! Anyway, I changed the circuit and build a sinewave oscillator with opamp and there is no Vizz with or without a coupling cap. ??? but the question still remains: What is the effect of Hand??? ThanX Shahriar

Hi I have build an square wave oscillator with LM324(which is a quad opAmp). I have connected the output to a TIP122(power Transistor) and drive a piezo to creat a beep sound. but the interesting problem: There is a VIZZ in the output sound. when I touch the Vcc or GND or some other points of the circuit, the vizz will dissapear. When i make the square wave with a NE555 there is no VIZZ and everything is OK. I don't think it is because of noise!!! I connected so many points with a Resistor or capacitor to ground or put some capacitors between Vcc and Ground but nothing special. I have used one of the opAmps from 4 opAmps of LM324, when I touch the floating inputs nothing happen but when I touch the floating outputs the vizz will dissapear.Few month ago the same thing happened when I built a preAmplifier with NE5532. there was a small Vizz in the Output which would dissapear when I touched the GND. P.S. I have used a speaker choke to drive te piezo. I hope you understood what i meant by a piezo. it is something like a coin and when connected to a oscillator it sounds like a buzzer. I do not know the exact english name!!! ThanX in advance Shahriar

Hi When I found a EEPROM IC which do not work in a TV, I write new data (which I have read before from a working TV with same model)and it always work fine! But in some TV, the memory is IC is 24Wxx instead of 24Cxx fasmily. the when I try to read from them I usally receive bulshit and when I try to write into them, always 00 is writen! Do anybody know the difference between them!!! ThanX in advance Shahriar

Tricky!!! ;)

Hi So I think I guessed true. during a long distance call, I will receive more pulses during a minute! (Am I right?) {Dear Audioguru, if this is right, then it is how I am going to calculate the money!!!) 2- Do anybody know anything about the amplitude of these pulses? ThanX in advance Shahriar P.S. I think you forgot to write the LINKS

Hi to everybody I plan to build a device that many of you may have thought about it before. (or may have heard about it ) The project is to be connected to telephone line. then when somebody hangs up the phone, he is not able to dial a number till he dial a specified number (i.e. 1111 for Person#1) then the device will allow him to dial his number. during his conversation the device calculates the money and saves it to Person#1 bill. every person have a password (i.e 2222 for Person#2). then at anytime the device can specify how much money should every person pay. Two important problems with the device are: 1- I want to connect the device to telephone line in parralel. the how I disable person in Number dialing before he Enter his password. If I want to connect the device in series then I have to place the device at the Home Telephone lines Entry which sometime is very difficault specially for Institutes and departments. 2- How should I calculate the bill during conversation? Do telephone center sends pulses on telephone line to calculate the bill? If yes, How to Detect those pulses? ThanX in advance Shahriar

Dear nylon Can you explain a little more. What is a Long distance meter????? Shahriar

Dear kosoniscs A diac Acts like a zener diode. in those usual dimmers, where a diac is places at the gate of triac, the diac breaks when the voltage acroos it, reaches somthing around 30V. the cap discharges. and the diac will turn off when the voltage across it becomes lower than 30 Volt. Diacs are in diffrent voltages, the usal ones are just like Diodes. A very usual dimmer is attached!!! HTH - Shahriar Dimmer_switch.zip

Dear jarmund the sound of a human (your circuit input) consists of too many harmonics and difeerent frequencies. Usaully, the input of frequency meters are PURE sin or Square Waves. U can take a look at your graphic equalizer to understand what I mean!!! If you want a circuit to determine the frequency of a pure wave, then it is just a simple frequency meter. Too many of them on the web. HTH - Shahriar

ThanX all for your replies Shahriar

Dear jarmund I do not have any plan for building such a high power project. But if you convince with a less power project, why don't you use a TV flyback transformer. it will gives you 25kV and nearly 100 watt (as audioguru said). and the schematics are available. but it really differs with what you are looking for. HTH - Shahriar

Dear 4-1000A Thank you very much for your replies. I took a book from my university. Its name is "Modern communication circuits". In one of its chapters all of the RF Power amplifiers is described. ThanX again Shahriar

Dear shri_sam What I got from your writing is: you plan to use a TV remote control IC and connect many keys to it. then connect the output of IC to you micro. I said: use the whole remote control as a keyboard just use a Infra-red Receiver to convert the codes sent by remote control. I hope I had not mis-understood. HTH - Shahriar

Dear zb10948 I also plan to do the same project and i am trying to build my own transceiver. 1- you'd better to use an AVR MCU for ADC conversion. because micro will give you more flexibity in your project. for example If several people are talking to each other, you can allow someone to hear you or not and many other abilities. 2- The most important thing with transivers is STABILITY. The easiest way for you is to buy a TLP434/RLP 434 (Transceiver, receiver). because they use SAW resonator and have nice stability. but the problem with them is low baude rate. typical baude rate for them is 4800bps.the max rate is 200,000bps. there are some othere modules with higher power and more data transfer baud rate. Look for them in your area. 3-for TLP434 the typical input is Vcc. I mean the data amplitude should be equal to the Vcc of transmitter. Because they are workong at 434MHZ the antena is very small. (approximately 18cm for TX) so you do not need any special amplifier just a transistor for switching if The Vcc of your ADC and your TLP differs HTH - Shahriar

Dear wimsloe Designing Switch mode power supplies are not very easy and need Calculations. Specialy the transformer. You should buy a book and read it completely. The topology, frequency and current limiration are some other important factors. there are many books. I am sure nobody can teach you SMPS designing on the web but others can help you to solve your problems. HTH - Shahriar

Dear shri_sam If you are doinfg it for fun, why don't you build a wireless calculator? Download the datasheet of your IC, then use an infra red receiver and connect it to your MCU, then you can do everything with your remote control. In this case you do not need any key. your keyboard is packed and very beautiful ;D HTH - Shahriar

Hi Does anybody have a tutorial for designing RF amplifiers? for example how to calculate L2 or L3 in "4 Watt FM Transmitter " in project section. or where th Base-Emitter voltage of T2 or T3 comes from to turn on the Transitor? ThanX in advance Shahriar

Hi It is said that a very simple calculation for antennas length, is 1/4 * wavelength. my question is: if we select a longer antenna, do we have lose output power? The anttena I mean is for transmitter. ThanX in advance Shahriar