More detail would be helpful - Propeller or Basic Stamp? Is the Schmitt trigger outboard or are you thinking of some internal hysteresis scheme?
Alternatively are you thinking of driving the Schmitt trigger IC with an RC circuit? Or a crystal?
Calculation of RC timing is pretty straightforward, but there is the question of how much power you need to drive the IC. Voltage changes the calculations. Are you using 3.3 volts or 5 volts?
The answer to your question can be found in the data sheet for each of those devices and will change depending on the technology used ... i.e "HC" or "HCT". Not to mention the frequency will also change with input voltage. Schmitt trigger oscillators also make very good VCO's.
pusink,
Try the link I posted above again. page #17
Still though, even with your attached image. The frequency will be different from one technology to the next, depending on which NAND gate you use. The Schmitt trigger threshold is set usually depending on some proportion of the input voltage, so as that changes, so does the frequency.
Notice how with the image that you included they also include VDD in the frequency equation?... in particular, this probably only applies to one technology, but from looking at it I don't see which one it is.
The diagram for the CD4093 has everything you need. But you need to have the Control connected to Vdd to turn on the oscillator.
It is up to you to do the math. Some math is always required to play with electronics.
R is in Ohms and C is in Farads. So you might use 1,000,000 ohms x .0000001 farads to begin to work with the formula. It also appears to require 'natural logs', so use the science calculator on your computer.
If you want to vary from 1hz to 200hz, you will need a variable resistor to adjust the frequency.
The voltages of the Schmitt trigger Vt- and Vt+ are on the first page of the PDF
pusink
Posts: 68
Comments
Alternatively are you thinking of driving the Schmitt trigger IC with an RC circuit? Or a crystal?
Calculation of RC timing is pretty straightforward, but there is the question of how much power you need to drive the IC. Voltage changes the calculations. Are you using 3.3 volts or 5 volts?
The answer to your question can be found in the data sheet for each of those devices and will change depending on the technology used ... i.e "HC" or "HCT". Not to mention the frequency will also change with input voltage. Schmitt trigger oscillators also make very good VCO's.
Reference:
http://www.nxp.com/documents/data_sheet/74HC_HCT14.pdf
i'm try to open your link, but page not found.
tq.
Try the link I posted above again. page #17
Still though, even with your attached image. The frequency will be different from one technology to the next, depending on which NAND gate you use. The Schmitt trigger threshold is set usually depending on some proportion of the input voltage, so as that changes, so does the frequency.
Notice how with the image that you included they also include VDD in the frequency equation?... in particular, this probably only applies to one technology, but from looking at it I don't see which one it is.
It is up to you to do the math. Some math is always required to play with electronics.
R is in Ohms and C is in Farads. So you might use 1,000,000 ohms x .0000001 farads to begin to work with the formula. It also appears to require 'natural logs', so use the science calculator on your computer.
If you want to vary from 1hz to 200hz, you will need a variable resistor to adjust the frequency.
The voltages of the Schmitt trigger Vt- and Vt+ are on the first page of the PDF