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  1. hi! correct me if am wrong... if i have a circuit: a DC power supply 5v, to turn ON a simple led and a switch, when i press the switch it will turn the led ON and it will create a radio wave...? soo... simply turning a device on and off many times will produce radio waves?! if i make an astable multivibrator, doest it create radio waves?! please help! :)
  2. hello!!! i made a alarm circuit with a fototransistor and ir led , when the door opens it turns ON and a siren HIGH sound activates and the only way to turn it off is manually…. anyway it works great! but when the power supply ( a 3.5 v battery ) is On for about 7 hours, it automatically turns the alarm ON! and that’s bad. my theory is that when time goes it spends current, so the 3.5 v battery doesn’t have the same amount of current like 7 h before, so the “sensor” is like more or less sensitive and triggers the alarm…. how can I solve that problem? do I have to use some sort of HIGH PASS filter? please help.
  3. how does a PULSE code MODULATION WORKS? When I press a button in my IR transmitter it will send binary codes example. 1 1 1 0 with a 38 KHZ carrier. The IR receiver device will detect the 38 KHZ ( with the filtered code, 1 1 1 0) and will let it pass. BUT… how does the device know where to put the 1 1 1 0 code? does it have some sort of low pass filter or something ? http://www.tpub.com/neets/book12/0217.GIF
  4. hi! i have almost made a line following car (toy) but i have 1 problem.... my transistor gets hot after a while... am using about 7 volts power supply, i have 2 transistor as a darlingon " bc337 transistors "( when i put the light off the dc motor run very fast like i want ) but when i touch the transistor 2, is hot! ) then i changed the transistor 2 to a 2N2219 ( it was working okei, but also hot, and i think its broke, cuz it doesnt work anymore ) then i used a BD243 transistor, its still alive, but it gets hot 2, i use resistors, so i dont know what to do....
  5. hi i need a multichannel infrared control, about 4-5 channels, transmitter and emisor I have 2 ic 555 chips and 1 t74ls00 chip. thanks
  6. hi! i dont have a serial port neither a printer port in my desktop, ( i want to program my pic16f84 ) i dont want to buy a pickit stuff. so what if i buy a "pci serial port" will my diy programmer work?
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