Simple oscillator circuit needed

I trying to modify a motion detactor (Pir) to run off battery power.
Every thing on the senscor seems to be running at 5 volts, except one conection that is looking for a pulse. ( I assume that this is for light timming.)
When the pin is left "floating" ( pullup resistor removed ) the senscor works as long as I use my body as the input. ( touching open pin )
What I need is a Simple way to inject an aprox. 40 - 70 Hz singnal to this pin. ( "Saw tooth" should be ok)
Anyone know of a way with a transistor are two?

The Simplest way would be to use a 555.

I seen that Reply comming. I was hopeing to save a few ma of battery power and not use a 555

Anyone know to get a LED flasher ( LM3909 ) to run at 60 HZ

How about a cmos version of the 555, as far as I know it draws very little current.