Talk:Relaxation oscillator

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Generic relaxation oscillators too[edit]

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)[reply]

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)[reply]

Diagram of classic relaxation oscillator[edit]

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)[reply]

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. 86.150.65.44 (talk) 19:07, 5 August 2012 (UTC)[reply]

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)[reply]

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)[reply]

Silly Choice[edit]

This article is made far less useful because all three resistors in the circuit are given identical values, R. Noodle snacks (talk) 11:35, 16 May 2009 (UTC)[reply]

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)[reply]

Does the op-amp oscillator fit the definition of a relaxation oscillator[edit]

The article states:

A relaxation oscillator is an oscillator in which a capacitor is charged gradually and then discharged rapidly.

and

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.

Either the op-amp oscillator is not a relaxation oscillator or the relaxation oscillator needs to be redefined. Rsduhamel (talk) 22:06, 29 December 2009 (UTC)[reply]

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)[reply]

Induction oscillator[edit]

I added the following short section just now (with illustration):

A blocking oscillator using the inductive properties of a pulse transformer to generate square waves by driving the transformer into saturation, which then cuts the transformer supply current until the transformer unloads and desaturates, which then triggers another pulse of supply current, generally using a single transistor as the switching element.

Note that I'm far from pedagogically sound on the theory here, so edits are encouraged. The text I wrote was intended to be (barely) enough to direct the reader to the better explanation at the target link. — MaxEnt 18:40, 31 May 2020 (UTC)[reply]