I'm trying to figure out a way to generate a messy pulse sequence. By messy I mean:
1.) average frequency of ~0.5Hz (adjustable from maybe 0.2 to 10Hz)
2.) duty cycle roughly 50%, but with polarity alternating, so +5, off, -5, off and so on
3.) frequency changing by ~2x in a "random" manner. A very non-random sequence is fine, as long as the pulse width varies roughly 2X around the mean, in the range of 0.25 to 1 Hz when set to 0.5Hz mean
I'm most stuck on getting item 3. I think a 555 timer, or any square wave generator, followed by a 4017 counter would give me the first two criteria nicely. The wave generator sets the frequency. Using the counter outputs for "0" and "1" gives me the reversing polarity.
Could I use the control pins of the timer to adjust the frequency as I've described, maybe by feeding in a slow triangle wave to change the voltage at pins 5 or 6? Maybe some other VCO arrangement would be better? I have a nice 1 MHz oscillator can I could use, but that doesn't seem the best way to go. Changing the frequency sounds easier than changing the divide-down factor, since I don't want to use a microprocessor.
The load is small, up to 1mA max into ~5K ohms. Power supply isn't set yet, but it will be AAs, one or two, possibly boosted to 3 or 6v with a big cap to smooth out the boosted voltage. Battery life is an issue but the load is tiny, so the main drain will probably be an LED power indicator.
Ideas?
1.) average frequency of ~0.5Hz (adjustable from maybe 0.2 to 10Hz)
2.) duty cycle roughly 50%, but with polarity alternating, so +5, off, -5, off and so on
3.) frequency changing by ~2x in a "random" manner. A very non-random sequence is fine, as long as the pulse width varies roughly 2X around the mean, in the range of 0.25 to 1 Hz when set to 0.5Hz mean
I'm most stuck on getting item 3. I think a 555 timer, or any square wave generator, followed by a 4017 counter would give me the first two criteria nicely. The wave generator sets the frequency. Using the counter outputs for "0" and "1" gives me the reversing polarity.
Could I use the control pins of the timer to adjust the frequency as I've described, maybe by feeding in a slow triangle wave to change the voltage at pins 5 or 6? Maybe some other VCO arrangement would be better? I have a nice 1 MHz oscillator can I could use, but that doesn't seem the best way to go. Changing the frequency sounds easier than changing the divide-down factor, since I don't want to use a microprocessor.
The load is small, up to 1mA max into ~5K ohms. Power supply isn't set yet, but it will be AAs, one or two, possibly boosted to 3 or 6v with a big cap to smooth out the boosted voltage. Battery life is an issue but the load is tiny, so the main drain will probably be an LED power indicator.
Ideas?