Search results

Search Forums New Posts
  1. Shahriar

    What are the test condition for power Transistors?

    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...
  2. Shahriar

    Can Anybody explain How this Transmitter Works?

    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...
  3. Shahriar

    0-30 Vdc Stabilized Power Supply

    so SoooooooorrY I meant  "R16", Ityped it R17. ThanX Shahriar
  4. Shahriar

    0-30 Vdc Stabilized Power Supply

    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
  5. Shahriar

    What does 12V - 4.5Ah means?

    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
  6. Shahriar

    Can Anybody explain How this Transmitter Works?

    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)...
  7. Shahriar

    Light Computer

    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...
  8. Shahriar

    Can Anybody explain How this Transmitter Works?

    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-...
  9. Shahriar

    why output voltage of LM317 decreases?

    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...
  10. Shahriar

    why output voltage of LM317 decreases?

    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...
  11. Shahriar

    ??? Audio Expansion Circuit ???

    Dear Audioguru Can U give an explanation about what are Compandors and what do they do? I downloaded the NE570 Datasheet but couldn't guess what it does... ThanX in advance Shahriar
  12. Shahriar

    Time out circuit

    Dear coolcat14 There is a project in project section of this site named: "Courtesy Light " it is very similar to what U are looking for, but U should  make somechanges... HTH - Shahriar
  13. Shahriar

    NEC TV goes to stand-by when searching for channels!

    Dear vigosport I am still working on it and it is going to become an impossible for me to do it. ThanX In advance Shahriar
  14. Shahriar

    But can anybody tell me what is goin on in Silicon Chip website

    Thank U very much for all of your Replies.... But dear Kasamiko, about the thing that happens in My PC, I should say that:                                                 IT WORKSSSSSSSS!!!!!! truly, Shahriar
  15. Shahriar

    But can anybody tell me what is goin on in Silicon Chip website

    Dear Audioguru I found the DC-Converter as same as you said. but the funny thing is that when I try to see the link which I had seen before in MicroCHip product List, it do not show me the schematics. ThanX Shahriar
  16. Shahriar

    Help needed building a radio transmitter/receiver system

    Dear james120479 Use an Encoder IC In Transmitter and a its OWN decoder in receiver. for example PT2262 as Encoder and PT2272 as decoder. and if U are familiar with Microcontrollers U can send different codes and detect them in receiver by another Microcontroller. For Tx circuit, I should say...
  17. Shahriar

    But can anybody tell me what is goin on in Silicon Chip website

    Hi again Here is the PCB, You should open it with Photoshop Shahriar 30339_11106031-eps.zip
  18. Shahriar

    But can anybody tell me what is goin on in Silicon Chip website

    Hi Sorry I write this in this forum, But few days ago I found some good schematics in Silicon Chip website and saved them in my computer, but today when I tried to download some more schematics the website do not show the schematics any more, just showing the Commercial Specifics of the Kits...
  19. Shahriar

    How to sens a laser with No error?

    Hi I want to build a chornometer in an Outdoor place that when someone passes the start line the chornometer begines time measuring. the start Line width is variable between 5-10 meters. Someone told me to do the job with a laser. but the problem is the sensor for the laser. what is the best...
  20. Shahriar

    Sound Project

    Dear spleblem The best way is using UM66 IC. It is very small and funny with just Three Leads. it is very similar to an ordinary transistor that you may mistaken it with a transistor. It has three leads, two for Power and On for the Output. each IC has a unique code that represents the melody...
Top