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  1. Shahriar

    transreceiver

    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...
  2. Shahriar

    high voltage switching power supply

    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...
  3. Shahriar

    calculator to TV remote conversion

    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...
  4. Shahriar

    Any document for RF amplifier designing!!!

    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
  5. Shahriar

    Do we lose power, If we select a longer Antenna?

    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
  6. Shahriar

    Infrared Activated Switch

    About your side Question Audioguru Gave enough explanation. What do you need that 50Hz  voltage for? Yours, Shahriar
  7. Shahriar

    Infrared Activated Switch

    Dear hamoodyjamal I didn't say that this schematic is exactly what You are looking for, I sent this schematic which is designed for a RF Application but the Amplifier and LM567 section is what You are looking for, Just Connect the input to Your IR Receiver and when the expected frequency...
  8. Shahriar

    MP IS EVERYWHERE

    Another Nice Guy who is always arguing with MP is Audioguru. If U saw these two in a discussion then try to read all replies!!! :)
  9. Shahriar

    How To Find Similar transistors!!!

    Hi I spend most of my time repairing TVs. Sometimes I need a trasistor but I can not find it. so I have to buy similar trasistors. My related Books are very old and small so do not have many of transitors. and the new ones are very Expensive. How can I find similar trasistors in Internet...
  10. Shahriar

    bout telephone

    Dear Ann Few days ago there was a topic in this forum with This Topic "Voice activated switch", (If I remember it correctly). You can find it and see what solution was given. For the thing you need is a sound recognition Module, or USE a PC and related ActiveXs, or maybe using XP sound...
  11. Shahriar

    Infrared Activated Switch

    Dear hamoodyjamal It is Possible to Use LM567 and 555 together and it will work. I attached the schematic you need. (See Page 5) But I beleive using Encoder and Decoder ICs is better. It is posible that You could't Find PT2262 in your area but I am sure there is At leats one of These ICs in...
  12. Shahriar

    Automated waste segregator

    Dear  J_a_k_e_007 The best way is Microsoft Access. I have wrote many accounting programs with VB and created the DATABASES with MS Access. It is as easy as drinking a glass of water. HTH - Shahriar
  13. Shahriar

    Infrared Activated Switch

    Dear hamoodyjamal The easiest way and chipest way for what you want to do is Using IC PT2262 as transmitter(Encoder) and PT2272 as receiver(Decoder). The PT2262 creat a special 11bit Pulse dedicated On how the Input pins are connected to GND or VCC. U can send the Pulse with a infrared ...
  14. Shahriar

    555 Timer problem

    Dear Birdie At first disconnect the 555 circuit from your digital circuit, (maybe there is a Short circuit in your digital section). Then connect the pin 3 of 555 to a usual LED through a 220 ohm resisor. The LED Shpuld blink. Just Use a normal LED. There are some LEDs that the current they...
  15. Shahriar

    How to calculate the crystal Value in Oscillators?

    Sorry, I forgot to attach the PDF.. Building Crystals for High frequencies is difficult and Expensive. For example if You want  to build a 150Mhz Oscillator, you will never find such Crystal, you should use a 30MHz Crystal and design a 5th Overtone Oscillator. Everything is explained in...
  16. Shahriar

    How to calculate the crystal Value in Oscillators?

    Dear prateeksikka Thank you very much for your answer but I found a Application note which contains answers. (I attached it) The reason is: "The practical frequency range for Fundamental mode AT-cut crystals is 600 kHz to 30 MHz. Crystals for fundamental frequencies higher than 30 to 40 MHz...
  17. Shahriar

    How to calculate the crystal Value in Oscillators?

    Hi In many crystal Tx oscillators, I always see that if the oscillator frequency is for example 98Mhz, the crystal value is sth around 12MHz.(a little bit more or less). I have heard sth. like second or third harmonic but do not know anything exact. My questions are: 1- how to calculate the...
  18. Shahriar

    voice activated door locking system

    Dear shri_sam So do not keep us in dark and send us what you have found. In case, that your findings is not secret ;D ThanX Shahriar
  19. Shahriar

    voice activated door locking system

    Dear shri_sam It is Impossible To do the project with a microcontroller if you are not a A Professional Programmer. Also you need some information about DSP. Any way. I have seen the same project that one of my friends did. he used An ActiveX in Visual Basic which would take some word from...
  20. Shahriar

    Cellular Phone Repeater for home use

    Hi As Alun Said, There is no op-Amp in such high frequencies. The FT for 741 is 100Khz and if you are lucky maybe you can find an op-amp which can work at 1.5Mhz. neither CFAs an WTAs can work at these frequecies. this is why you never see an opamp in Transimtters. anyway I am also looking for...
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