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Timers -- notes for the less experienced (work in progress)
- Thread starter (*steve*)
- Start date
When dealing with timers, it is necessary to define the events desired.
An initial pulse that can go:
-Low
-High
Will start some timing
-At application of pulse
-At release of pulse
And the output state will
-Not change
-Will go high
-Will go low
When the time lapse ends, the output will
-Immediately go high,
-Immediately go low,
-Emit a pulse
During a set amount of time and then,
-Return to high state,
-Return to low state.
There is a large number of permutations of the above posibilities.
It is convenient that some flowchart or better wording than mine be made a standard to select the type of timer circuit desired.
Suggestions ?
An initial pulse that can go:
-Low
-High
Will start some timing
-At application of pulse
-At release of pulse
And the output state will
-Not change
-Will go high
-Will go low
When the time lapse ends, the output will
-Immediately go high,
-Immediately go low,
-Emit a pulse
During a set amount of time and then,
-Return to high state,
-Return to low state.
There is a large number of permutations of the above posibilities.
It is convenient that some flowchart or better wording than mine be made a standard to select the type of timer circuit desired.
Suggestions ?
Please feel free to suggest some text and I will incorporate it.
The original purpose of this was to discuss the problems with very low frequency oscillators and timers rather than the triggering aspects thereof.
I must get back to this with some circuit diagrams and graphs and stuff... Soon.
The original purpose of this was to discuss the problems with very low frequency oscillators and timers rather than the triggering aspects thereof.
I must get back to this with some circuit diagrams and graphs and stuff... Soon.
For either medium times or very long times up to weeks or months, there is nothing like a 32.768kHz crystal oscillator stuck to the side of a 4060 counter. Cascading counters is easy and they are cheap. A single 4000 series divide by n such as a 4059 can be used to make it time almost anything. Triggering is simply by the reset pin(s). No component tolerances to worry about and drift is very low. To make it even more accurate all you have to do is cook the cyrstal (electric temp oven using a thermistor).
Whilst the heating structure (and circuit) is referred to as an oven, I've not heard people refer to it as "cooking" -- cooking is almost universally an adjective used to describe bad things when used in conjunction with electronics.
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