|WikiProject Electronics||(Rated Start-class)|
Generic relaxation oscillators too
I think this page is too specific. There are other types of relaxation oscillators---your heart and circadian rythm, for example. I think this page should be changed to focus on the concept of how an accumulating signal and thershold for release can be used to construct a relaxation oscillator. neffk (talk) 20:14, 4 September 2008 (UTC)
- Done. Linked to relaxation (physics) and tried to make lead as general as possible. It would be great for people to add in non-electronic examples. Diagrams of generic relaxation oscillators would be nice too. —TedPavlic (talk/contrib/@) 07:20, 30 December 2009 (UTC)
Diagram of classic relaxation oscillator
We need a diagram of the "classic" relaxation oscillator. Here is one in ASCII-Art, which may help. The symbols are poorly drawn, especially the neon bulb. Values are approximate; T ~ RC = 1 second (here) See also Pearson-Anson_effect.
|---------| Resistor, 100k | 200 V +|---------\/\/\/--------+-----------| | DC | | | | supply | capacitor + ------ ( o ) neon bulb | | 10uF ------ ( o ) | | | | | -|-----------------------+-----------| |---------|
- Okay. Added this fig and a link to Pearson–Anson effect. —TedPavlic (talk/contrib/@) 07:42, 30 December 2009 (UTC)
- If you want to be pedantic, the classical relaxation oscillator does not use a 'neon' bulb as the discharge element. It used a spark gap (and thus required a high voltage to drive it). The really really classical relaxation oscillator required a Wimshurst machine (or similar), a Leyden jar or two and a spark gap. The resistor was inherent in the Wimshurst machine. 22.214.171.124 (talk) 19:07, 5 August 2012 (UTC)
A simple relaxation oscillator may also be built from a 555 (wired as an inverting schmitt-trigger), and a single resistor/capacitor. Wiring is:
First, wire up an inverting schmitt-trigger from the 555. Pin 1 = Ground Pin 8 = Positive Pins 4,5,7 are left unconnected Pin 3 = Output. Pins 2,6 are connected together. Then, connect the RC between pin 3 and ground, with pins 2,6 connected to the junction: PIN3 ----\/\/\/----PIN2,6----||-----GND
- I will add this 555 example as an alternative to the comparator-based Schmitt trigger. —TedPavlic (talk/contrib/@) 07:46, 30 December 2009 (UTC)
Note: The "normal" 555 astable configuration (using pins 2,6,7, and having 2 resistors and a capacitor) is not a relaxation oscillator: it is more complex.
- Hm. I think you are incorrect. See the generic definition of a relaxation oscillator. As long as the storage element is "almost always" (using terms from measure theory) dissipating, we have a relaxation oscillator. The element is always trying to get back to its equilibrium... It just happens to be perturbed on a measure zero set. It is true that sometimes it is discharging at a different rate than others, but it is always trying to get back to its equilibrium, and it dissipates to do it. —TedPavlic (talk/contrib/@) 07:46, 30 December 2009 (UTC)
- Do you feel a different choice would communicate the concept of a relaxation oscillator better? It seems like a different choice would be better for, say, the Schmitt trigger page... not here. I think the point is communicated fine here. No? —TedPavlic (talk/contrib/@) 07:57, 30 December 2009 (UTC)
Does the op-amp oscillator fit the definition of a relaxation oscillator
The article states:
- A relaxation oscillator is an oscillator in which a capacitor is charged gradually and then discharged rapidly.
- The electrical output of a relaxation oscillator is always a sawtooth wave.
However, as long as VDD and VSS are symmetrical compared to ground, the op-amp oscillator's capacitor will charge and discharge at the same rate and the output will be a triangle wave.
- Wow. The introduction of this page had some major errors. A relaxation oscillator certainly need to involve sawtooth waves (additionally, the operational amplifier circuit on the page at present does not generate sawtooths nor triangle waves -- it generates exponentials and square waves). I think things are fixed now. Please review. —TedPavlic (talk/contrib/@) 07:58, 30 December 2009 (UTC)