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Everything posted by Shahriar

  1. About your side Question Audioguru Gave enough explanation. What do you need that 50Hz voltage for? Yours, Shahriar
  2. 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 Appeared at the input the LED turns ON. I do not Know what that reset button does, But I don't think it is very important. I attached the LM567 Datasheet, You can find a very nice App in Page 5. Also See that AC test circuit on page 6. HTH - Shahriar LM567.pdf
  3. 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!!! :)
  4. 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. {{{the word "similar" is not correct, I have forgotten the real expression}}} ThanX - Shahriar
  5. 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 recognition ;D HTH - Shahriar
  6. 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 your area. Ask a professional seller for such an Encoder/Decoder ICs and tell him what they are and what you are looking for. maybe he could help you but If You couldn't find any IC, then Use LM567 and 555. Some of these Encoder/Decoder ICs are: HT12E / HT12D SC5262 You can find more by a search in http://www.datasheetarchive.com HTH - Shahriar circuit17.pdf
  7. 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
  8. 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 module. IF PT2272 gives the correct Pulse it enables one of It outputs otherwise, disable the Output pin. These ICs are designed for these purposes. There are many similar ICs call Encoder/Decoder. They are even multichannels and you can enable 2 or 4 relays. the Schematic is in the DATASHEET. Try them. HTH - Shahriar
  9. 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 need is around 30mA, So the 555 can not drive them. 555 Can sink current around 15mA. values of R1, R2 and C1 determine the Freqency and Duty cycle of your output pulse. HTH - Shahriar
  10. 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 PDF... ThanX Shahriar 00826a.pdf
  11. 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 are very thin and therefore fragile. Crystals are used at higher frequencies by operation at odd harmonics (overtones) of the fundamental frequency. Ninth overtone crystals are used up to about 200 MHz, the practical upper limit of crystal oscillators" {Copied from this PDF} ThanX again Shahriar
  12. 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 crystal value... 2- when the oscillator has a common-base Amplifier the crystal is placed in base(or Gate if mosfet). WHY? ThanX in advance Shahriar
  13. 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
  14. 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 the user and when ou repeat that word in PC microphone it would show that word to U. but it had some Error too. then you can open the door via parrallel port or serial port. You can find so many such free ActiveXs in internet. I Also beleive that it would be easier to use VB, Delphie or VC to do your project instead of C++. HTH - Shahriar
  15. 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 a transistor working at 1900Mhz,If you find it, please tell me the Part number and where can I buy two or three of them. And at last, can You tell me that how you understood that your phone is working at 850Mhz? Is it written on the back of it? ThanX in advance Shahriar
  16. Hi If you take a look at a TIP122 datasheet (which is a power transistor) it is written 8A - 65Watt. As I remeber the power of a transistor is defined as so: P = VCE . Ic. it means I can draw more than 3A when the voltage of the collector is 10V and the emitter voltage is around 3.5V. But when I just draw 1A from TIP122, it gets so much hot (Although it has heatsink) that I didn't dare to leave it more and the voltage of Emitter increases 0.01V every two seconds. I guess this is because the CE resistance Decreases as the temperature Increases. the same thing happens for 2N3055. In datasheet, it has written 15A, 105Watt. It means we can draw nearly 10A in 30V Stabilized power supply in project section when the collector is 32V and the output is 22V. My Question is In what test conditions the manufacturer has written these bullshits??? ThanX in advance Shahriar
  17. Dear Alun Here two schematics for Receiver. Figure 1 is from PT2272 datasheet. whivh is a decoder. Th second schematic is from a kit in my area that is goos for students. both are very similar to each other. in figure two the input section is a common-base amplifier instead of that dual gate Mosfet. but so many things are strange to me. 1- what is the value of The inductor i marked it. (there is no explantion in datasheet) 2- as you guest the first opamp is a amplifier (because of the feedback) and the second is a comaprator to convert analogue signal to pulses. the strage thing is why both inputs are connected to each other. 3- I guess the demodulator is AM dedicated to your explanations. Do you agree? ThanX in advance Shahriar
  18. so SoooooooorrY I meant "R16", Ityped it R17. ThanX Shahriar
  19. Hi everybody. I have made This project nearly a years ago. and it is working everyday. but today I saw sth which is strange to me. WHAT is the roll of "R17" ? (UP-Right, emitter Of 2N2219) Is it there for more stability. I have seen same resistors in ICs Spec too. ThanX in advance Shahriar
  20. Hi I have a Rechargable battery. Something is written on it. "12V - 4.5Ah". What does Hour ("h")means here. Does it mean it can gives 4.5A at 12V for an hour? ThanX in advance Shahriar
  21. Dea Alun As you know each transmitter have two important parts. Oscillator and modulator which mix the RF wave with your Data (data can be Pulse or sound wave or etc.) In most circuit the oscillator section, also plays the modulator roll too. (Like 4watt FM transmitter in the Project section). The PT2262 do not play the roll of a Modulator. It just creat a 11 bit pulse and gives it to the transmitter. now how this Tx modulate the 11bit Pulse. does it act like a FM Tx? When you buy a Tx module, for example TLP434, It has a maximum baud rate. What this Baude rate depends on? ThanX in advance Shahriar
  22. Dear steve1sws If if guess right the circuit is Sth. like a Light Dancer. if You meant 330mA for each bulb you can omit those triacs and R15 upto R21 and LD1 upto LD7 and connect the bulbs directly between 12V and Collector of your transistors...If you want to use LEDs instead of Bulbs, you should add some resistor beween the LEDs and Transistor Collectors. For example 560Ohm for Normal LEDs... HTH - Shahriar
  23. Hi This schematic is related to PT2262 IC DATSHEET which is an encoder used in transmitters. I have seen this schematic used in many RF APPs. As You see it is operating in UHF Band. Few Questions: 1- What's the Modulation Of the transmitter?Why? 2- How to calculate The operating frequency? 3- How to build the inductor which I have signed in the schematic? 4- What's the maximum data rate in this circuit and similar circuits depends on? ThanX in advance Shahriar
  24. Thank you very much for all of your replies. As audioguru said i mark r1 by mistake. the surge resistor is r1 on the left side. when this happened tomy circuit, at first I short circuited the R1 and noticed that the voltage raised to the correct voltage (5.1V). I didn't get suspecious to the coil because I was sure that there is no coil in the world with so much resistance. So what I did? I raised up input voltage from 8V to 10V, and what happened!!! The voltage raised to the right volatge (5.1V) although the surge resistor were in the circuit.... ;D This is related to the LM317 spec. if you take a look at it you will understand. the zener diode (6V at the bottom of the circuit) does not break correctly!!!!! ThanX a million Shahriar
  25. Hi I have made a power supply, the schematic is below. as you can see, i have put a surge resistor (R1 = 3.3ohm, 2watt). as You know this resistor controls the current at circuit start up. because all the caps act like short circuit at circuit start up, it protects diode bridge from high current. but he problem with my circuit is that, the output votlage decreases when connected to load. you may say because the current passing R1, increases the voltage of "C" point and causes voltage decreases in "A" point. but my theory is, the output voltage of LM317 proportion to its ground is always constant, so if the voltage of "C" point increases beacuse of load current, so LM317 should increase its output to keep the voltage constant, BUT WHY THIS WOULD NEVER HAPPEN. I hope u understand what I meant. here another short circuit protected application from LM317 Datasheet. so output voltage in this application should decrease like my circuit. ThanX in advance Shahriar
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