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can you give more details about your circuit and the frequency it operated at?

The article section of this site has some good article for your reference: http://www.electronics-lab.com/articles/index.html also, you can find more info from http://www.usb.org/developers/docs/ with lots of useful information

Just a reminder, the hot melt glue cannot withstand massive sunshine ....... it will easily fall apart after sometime.

for fast checking....... just build that transistor circuit on the breadboard....... apply 12V to the the collector side while 5V on the base and see if the LED can lit or not.......

I think you can make use of the LM555 pin 4 reset pin to reset the ICs while they are powered up. Just simple RC can do.

ok, I will open my monitor and take some photo..... before I throw it away.......... even it is still working......... :-X

haha...... ;D I have opened my poor monitor some months ago... since it got some strange color....... oh....... it is some loose connection between the PCB sockets and the cathode ray tube pins ........ I found that PCB, with high frequency components are all covered with a metal bracket........ so ........ if it is not a shielding then.... I will got a big buzz at my desktop amp......... :P

A nice story.,..... it is practical but need big coils for induce enough power to drive home appliances........

As Ante said, nowadays monitors are properly shielded. It is hard to beleive the "buzz" is from the monitor. May be the jack of the speaker has been oxidized , try to clean it up.

What I mean is both Ceramic capacitor and Electrolytic capacitors are worked together as a DC smoothing. You are right audioguru, 0.1uF Ceramic capacitors are as a low pass filter to shunt high frequency to ground while electrolyic capacitors are more like to handle the charge and discharge time of the DC voltages during the rippling.

I think is zener cannot handle the sudden goes up voltage and may fired the zener diode. I prefer to use opto-coupler as it totally isolated the high voltage part from your microprocessor.

Those capacitors are used for smoothing the DC voltage from ripple. If the loading current is high, the ripple of the 78XX regulator will be higher.

It is the matter of the "ON Load" and "OFF Load" voltage. They are normal.

I built a single transistor AM transmitter which worked from 300MHz to 600MHz (adjust the capacitor across the L) which is used for digital data transmission. I am so lazy that I use the L in the LC tank to act like the antenna and make it as a track loop on the PCB. Actually, I have no choice as I have to use simplest components in that part of the circuit. (I can use saw resonator as RF oscillator but the required transmit frequency does not have a standard one) The frequency drifted is approx. 5 to 10MHz and I have to use a wide band receiver to cover the drifted frequency.

The LC oscillation transmitter will not be stable as it will easily affected when your hand approach it. (frequency drifted) And also, what will be the modulation is? AM? FM?

I think a 486DX-66 with a lot of RAM can serve well as a web, ftp, mail and other servers if it is using Linux. :P Be honest, still, no Linux platform is as user-freindly as Microsoft does..... that is why I still using MS and pay some bucks to Bill Gates. Anyway.... back to the original topics......... Have anyone tried to use the free simulator of Linear Technology??

Please give more details like: AM? FM? Transmit data? Audio? What is the data rate?

Saw filter also applied widely in wireless products, it is nice with quite low attenuation. I also hear that a crystal can act like a filter..... I haven't tried myself.... any idea?

try to build an array of IR receivers to check the IR strength from the beacon.

2.4GHz antenna..... not easy to build especially if used in transmitter. The feedback loss will drive you crazy...... if the impedance is not matched......

More to play with ISD IC, you can set the address pin and record say for example, 2 messages with 5seconds time; and also can play them back also. I have done this in a keychain recorder which serve very well. 8) Later I will give out a schematic how to do it and also some pictures of my designed product. (next week I will post..... got a lot to work on with my examiniation......... )

can I use astable transistors oscillator to give signal to the clock input to 74HC4017?

I face this waiting also......

use ISD voice recorder IC. http://www.winbond-usa.com/products/isd_products/chipcorder/datasheets/1100/ISD1100.pdf

Thanks audioguru. That refreshes my old time memeory.... ;D One more question: if I got a sigal, say 1KHz, 2Vp-p with DC offset at 2Vdc; how can I use an opamp to adjust the DC offset to 1Vdc?