Ok, so I want to mess around with LEDs and Arduinos, but have been spending the past mnoths pulling my hair out of my head, looking for a resistor with random resistance. Not like a degree of error with resistance, I mean like peaks and troughs, either getting close to overvolting the LED, to almost underpowering it. And I am just stuck. Ive tried looking for flickering LEDs that are in a 28 segment display, and I can't find any. Its getting mentally tiring, and I havent found anything. Closest I have gotten are just websites talking about LED bulbs in houses flickering. This is one thing just weighing down my own mental health at this point, and my search is just being bone dry of any results. I don't know much about circuits and stuff, and I am thinking its gonna be at least the size of the center of an LED. I am just tired. Thanks if you can help. I have found entire ciruicts that do this, but I want it to be completely autonomous to an arduino. And I don't want to spend more nights trying to code something that will never work. All I have to use is TinkerCad, because I can't afford anything else. Thanks if you can help, sorry if I sound crazy, I sound crazy to me.

 

There's no such thing as a Random-Resistance-Resistor.

Start-out by explaining in detail what You expect as an end-result,
there's probably ~5 or ~6 ways it can be done,
1 or 2 of them "might" be simple.
.
.
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If you want a varying light output from an LED, then you can program the Arduino to output a changing duty-cycle PMW signal, which can drive the LED to generate a varying current proportional to the PWM duty-cycle in the LED with a fixed series resistor.

 

if you have Arduino, use it...
https://docs.arduino.cc/language-reference/en/functions/random-numbers/random/

 

What is not clear to me is if the TS is wanting to solve a problem of an LED that is flickering, or if the TS wants to produce such a display. I have suffered with48inch LED tubes flickering for weeks before failing completely. The TS is welcome to a few dozen for free. BUT wanting to produce that effect can be done with a shift register being loaded with A/D outputs when it is fed from a talk radio station broadcast.

 

Where did you ever get the idea that here was such a thing?

 

I HAVE seen poor connections produce that sort of effect.

 

What is not clear to me is if the TS is wanting to solve a problem of an LED that is flickering, or if the TS wants to produce such a display.

The latter:

looking for a resistor with random resistance. Not like a degree of error with resistance, I mean like peaks and troughs, either getting close to overvolting the LED, to almost underpowering it.

ak

 

Ok, so I want to mess around with LEDs and Arduinos, but have been spending the past mnoths pulling my hair out of my head, looking for a resistor with random resistance. Not like a degree of error with resistance, I mean like peaks and troughs, either getting close to overvolting the LED, to almost underpowering it. And I am just stuck. Ive tried looking for flickering LEDs that are in a 28 segment display, and I can't find any. Its getting mentally tiring, and I havent found anything. Closest I have gotten are just websites talking about LED bulbs in houses flickering. This is one thing just weighing down my own mental health at this point, and my search is just being bone dry of any results. I don't know much about circuits and stuff, and I am thinking its gonna be at least the size of the center of an LED. I am just tired. Thanks if you can help. I have found entire ciruicts that do this, but I want it to be completely autonomous to an arduino. And I don't want to spend more nights trying to code something that will never work. All I have to use is TinkerCad, because I can't afford anything else. Thanks if you can help, sorry if I sound crazy, I sound crazy to me.

It's very difficult to discern what you are trying to achieve. Why would anyone want the LEDs in a 28-segment display to flicker? Is that what you are trying to end up with? A flickering 28-segment display?

What do you mean by wanting it to be "completely autonomous to an arduino"? Do you mean that you want everything to be done by the Arduino? Or do you mean that you want it to completely separate and independent of the Arduino?

Please take a step back and explain the problem that you are trying to solve.

Imagine that you need to ask someone to build something for you and put it into a black box and give you the sealed box. You can only interact with what comes through the box, you can't look inside. You don't know if it's a circuit made of a resistor and capacitor, a mini-mainframe computer, or a leprechaun that has been captured and stuffed inside. You don't get to tell the builder anything about what goes into the box, you only get to describe how you want the things the come through the box to behave. Once you have done that, you will be in a position to inquire about what is in the box.

For instance: I would like to use an Arduino to create a flickering candle effect with an LED using as few additional components as possible (or practicable). I can power it with a USB cable. What might such a circuit look like and what would the code need to do?

Something like that can get a meaningful discussion started that can then meander into more detail, such as what kind of variability is needed to create a flickering candle illusion and how that might be accomplished in code.

 

"How to create the flickering light effect?" That title says it all.
The use of a shift register to provide a sort of long string of sort of random states is probably the simplest to simulate a flicker caused by a poor connection. Mixing half power and off states would make it more believable.

 

I would assume there is a random number generator function program for the Arduino which could generate the PWM duty-cycle and thus a varying (flickering) LED light.

 

One of the things I did when using a development board to learn about microcontrollers was to try to duplicate the behavior of a flickering LED.

I made an eight-bit RNG using the shift register and xor method and every 100ms updated the duty cycle of a PWM generator. To my surprise, it worked rather well, looking very much like the standard flickering LED.

 

THAT is the reason I suggested a shift register. It was not an original idea of mine, not at all.

 

One of the things I did when using a development board to learn about microcontrollers was to try to duplicate the behavior of a flickering LED.

I made an eight-bit RNG using the shift register and xor method and every 100ms updated the duty cycle of a PWM generator. To my surprise, it worked rather well, looking very much like the standard flickering LED.

Couldn't that all be done using software in the micro?

 

Another suggestion is to use an ADC input pin, digitize the picked up noise and use it as a seed for a shift-register-XOR function.

 

, of course!

Couldn't that all be done using software in the micro?

It was, of course!

 

Once i saw this, it always comes to my mind when there is mention of RNG

 

, of course!
It was, of course!

Well, with all the talk about using a shift-register, it wasn't clear.

 

If you rotate a potentiometer/trimmer to a random position.. that would be a (pseudo) random resistance resistor... kinda... ?!

 

RasPi or Arduino with RNG program >> stepper motor driver >> Potentiometer

ak