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Old 09-10-2017, 09:27 PM   #11
AviatorAtHeart
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Quote:
Originally Posted by Steve M View Post
I am no electronics expert (and I have many who will testify to that), but if the circuit is cheap to build, why build a number of them with different settings so that when they are used together you get what appears to be a random effect.
I recall that Maplins (expensive) used to do a project kit that used a potentiometer (already mentioned I think) to vary the times so a gaggle of similar kits could be set up to produce the effect.
Be cheaper to use a decade counter and some diodes like 1n914 or similar.....
EDIT!
(At least I think it will be!)
Double edit!
Neither am I an expert, hence all the silly questions regarding my layout wiring!
It's just a fun sideline hobby for me.......
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Old 09-10-2017, 09:49 PM   #12
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Using the 555 circuit and wanting to create something that looks like random timing , connect a light sensing resistor ,
like http://www.ebay.co.uk/itm/200-x-Lich...8AAOSww3tY4yrq
to the timing circuitry ( in series with the variable resistor or across it - depends on the value.) and hopefully the ambient lighting will change slightly giving a random timing.
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Old 09-10-2017, 10:04 PM   #13
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Same circuit with capacitance change.
https://flic.kr/p/Zdmngq
Original circuit with capacitor change. Effect on timing section.
From 10uF to 220uF (first part of video)
Then 4.7uf (second part of video)
This represents 22times increase and approx. half of the original value.
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Old 09-10-2017, 10:08 PM   #14
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Quote:
Originally Posted by scratchbuilt View Post
Using the 555 circuit and wanting to create something that looks like random timing , connect a light sensing resistor ,
like http://www.ebay.co.uk/itm/200-x-Lich...8AAOSww3tY4yrq
to the timing circuitry ( in series with the variable resistor or across it - depends on the value.) and hopefully the ambient lighting will change slightly giving a random timing.
Yes spot on. I think or was thinking of using these to hold or reset the decade counter (the second one)
So one chip works as normal with ldr or photo transistors to switch/hold the timing phase.

Trouble is, we are straying from simple....still fairly easy if you've fiddled about with the chips. I am not a clever bloke but I managed some pretty cool things with 555 (&556) chips, have experimented a lot with a decade counter and a few others, there must be a great way to solve this!

(It really fires my imagination!)
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Old 09-10-2017, 10:27 PM   #15
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@scratchbuilt.

Interesting result......
I hooked up an ldr in parallel with the 47k.
This was aimed at one LED which was shielded from the other LED (as it would be in a building)

The capacitor needed changing (I did that for speed of experiment, a resistor or the pot would've worked just as well)
The led with the ldr close to it turns off faster than that of the original spec.

Pretty cool!

Edit
Still not random.....
More like offset phasing....
Maybe useful for something?

I should add the cap needed a significant change back to 220uF!
Also normal ambient light changes (me moving about at a distance)
Produced no noticeable effect.......
Here's the link
https://flic.kr/p/YguQ3H
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Old 10-10-2017, 12:16 AM   #16
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The only real way to achieve total randomness is using a microprocessor and a randomise command. Use one with plenty of outputs that can be independently switched. If you dont want to play with mpus how about a motor driven cam wheel with microswitches. It will repeat over a period of time so not exactly random but use a gearbox to slow down the wheel to less than one rpm should give a decent effect. Or staying with the motor (or servo) how about a driven potentiometer in the 555 timer circuit? There are lots of options really depending on how much you are prepared to do.

Or you could ask to borrow the Enigma coding machine from the science museum.
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Old 10-10-2017, 12:25 AM   #17
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Yeah go with the enigma! (There's also one at raf hendon)
Gotta be the 5 wheel model though!
None of this mk1 3 wheel stuff.......
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Old 10-10-2017, 01:39 AM   #18
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As Terry said a microprocessor is most likely to give you a near random result. Picaxe which I am most familiar with does have a pseudo random command in that it will nearly always start with the same value but as it progresses the output becomes more random. Programming is not my strength but the structure of the program would use a random number generator to select which output/s would go high with a second random number generator to determine the delay thus how long the outputs remained high. Terry fancy a challenge?

For true randomness you need to have some unpredictability. For instance simple electronic dice circuits use 555 timers as a clock for a 4017B decade counter. If the clock is fast enough it is impossible to tell which number is displayed. The unpredictability is introduced in the timing of pressing a button to stop the sequence and display a number.

An alternative is to generate a complex pattern, the more complex the more random it appears. I have not tried this circuit but maybe using two 555 timers in astable mode with off set timings feed the outputs to an AND gate. The AND gate would only produce an output when the two inputs coincided. It would produce a pattern but may be complex enough to appear random.

555 timers I believe can produce delays up to 20mins in monostable mode( I have not looked at a data sheet in along while so maybe wrong). Setting the reset pin randomly would thus produce different length delays.

Richard
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Old 10-10-2017, 10:01 AM   #19
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Hi Richard,
I like the AND gate theory! I have a couple quad Nand ic knocking about
Coupled with a pair (Or would it be 4off?) of 556 ic.
Pair timers per gate.....4 gates....4x556 timers......
That's unknown territory but I like the idea, and I like mucking about with these things.

What's the chip......a hex Schmitt trigger, that would give you 6 ordered outputs (uses less components than the 555, just one resistor and one electrolytic per channel.......
Paired with the and gate idea.....

I think I have the basis of a plan, hopefully later I can get onto the breadboard, I certainly have the components to hand.

I think the electronic dice is an ordered pattern, just blindingly quick.
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Old 10-10-2017, 11:27 AM   #20
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Quote:
Originally Posted by AviatorAtHeart View Post
Hi Richard,
I like the AND gate theory! I have a couple quad Nand ic knocking about
Coupled with a pair (Or would it be 4off?) of 556 ic.
Pair timers per gate.....4 gates....4x556 timers......
That's unknown territory but I like the idea, and I like mucking about with these things.

What's the chip......a hex Schmitt trigger, that would give you 6 ordered outputs (uses less components than the 555, just one resistor and one electrolytic per channel.......
Paired with the and gate idea.....

I think I have the basis of a plan, hopefully later I can get onto the breadboard, I certainly have the components to hand.

I think the electronic dice is an ordered pattern, just blindingly quick.
Go for it AAH

I would be interested in the results. Unfortunately it's in the garden for me today moving things round in preparation for the building works for my mancave.

Richard
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