> Note:  Any "ring of three" (or any odd number) of CMOS inverters will
> self-oscillate.  One problem is that the more (active) gates there are in
> sequence the greater the power consumption will be.  A better bet might be
> to use a HCMOS Schmitt trigger package, such as a 74HC14 Hex Inverter or a
> 74HC132 Quad Schmitt triggered NAND.
>
>    Either of these can be configured as a self-starting astable using one
> resistor and one cap.  Unused inputs must be tied Hi or Lo to minimize 
> power
> consumption.  Because of the relatively proportional trip levels the
> frequency should be fairly stable over a range of voltages.

I will correct myself before anyone else does.  Looking at the specs for the 
HC parts I see that they don't have the supply voltage insensitivity that 
the CD4093 and CD40106 had which gave them their great stability. 
Unfortunately the 4000 series gates should have a minimum 3V supply.

Bruce 

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