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  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

    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
  3. 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-...
  4. 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...
  5. 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...
  6. 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...
  7. Shahriar

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

    Hi I Have a NEC 21" TV (model= MH5) and it goes to Stand-By after 10-12 minutes working in normal condition with perfect Image and it goes to stand-by very quickly in Auto-Searching mode but It doesn't go to Stand-by when the antenna is disconnected. I thought maybe sth. gets hot so I made...
  8. Shahriar

    Need Ic which can Enable Its outputs One by One!

    Hi I need an IC (i.e. 74XXX Series) with 8 or more outputs. The outputs will be enabled on by on after each other when I trigger the Clock pulse Input. the important note is that the outputs should stay enabled until I reset the IC. ThanX in advance Shahriar
  9. Shahriar

    How to build a Hardware Lock?

    Hi I want to build a Parallel Hardware lock which can connects between Printer and PC Port. I would appreciate it if I could use a serial EEPROM to Store some data. Any schematic or Idea is appreciated in advance. ThanX - Shahriar
  10. Shahriar

    Long Range Remote Control (The problem of many People)

    Hi I Need a Long range remote control about 600 or 700 meters. No range Limit is in my area.I have some modules For those garage doors remotes. but their range is not enough, I made a try to make it by using that 4Watt FM Transmitter in project section but the frequency Of the ocillators...
  11. Shahriar

    If you are looking for good PLL FM Tx, Look at this Link

    Here is a PLL FM transmitter. I have not build it yet but I feel it will works nice. http://www.pira.cz/eng/index.htm Click on "FM transmitter 3 W" If it was in Cz Language, go to http://www.pira.cz/ and click English HTH - Shahriar
  12. Shahriar

    Have anybody Build that "4 Watt FM Transmitter " In projects section

    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...
  13. Shahriar

    Increase range of RF Remote control!

    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...
  14. Shahriar

    Monitor, DAEWOO 14", CMC 531X Chasis

    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
  15. Shahriar

    Auto PowerOFF Power Supply!

    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...
  16. Shahriar

    How does Laptop PS work?

    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...
  17. Shahriar

    If you are looking for good FM Tx, Look at this Link

    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...
  18. Shahriar

    Turn the lamp On & Off gradually...

    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
  19. Shahriar

    The thickness of inner conductors differs?

    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
  20. Shahriar

    Show something on TV?

    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...
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