cheap and easy pulsed dc?

[walsh350]

Hi, this is my first post     
Am hoping some one more knowledgeable than I can help.

Is there an easy and cheap way of achieving a pulsed dc power source?
I'd ideally like to have a separate control over the frequency of the pulses.
Don't want to spend to much on this and would prefer if the parts could be salvaged from some where.
Any suggestions greatly appreciated!

[FatBird]

Here are the cheapest ways that I know of:

1.  Just place a buzzer in series with a battery.  That will give you pulsed DC.
     A buzzer can also be a relay coil in series with its contacts, which causes it to buzz.

2.  The next cheapest is to use a 555 oscillator chip to drive a MOSFET.  The MOSFET will
     be in series with a battery.

Here are some sites that you can get some ideas from.

http://search.yahoo.com/search;_ylt=AhgJjVEM0WZad0A1qM3A.q6bvZx4?p=555+timer+driving+a+MOSFET&toggle=1&cop=mss&ei=UTF-8&fr=yfp-t-701

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