[can a pwm create a radio wave?]

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! :)

[alarm circuit issue]

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.

[how does a PULSE code MODULATION WORKS?]

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

[my transistor gets hot, line follower/dark sensor]

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....

[i need a multichannel infrared control]

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

[i need help for pic programming...]

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?