Amplify current of a flickering candle LED

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ThomsCircuit said:
What is confusing me is that a POT is one resistor.
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A potentiometer is often manufactured as one resistor, but the wiper connects to some point along the resistor, effectively making it two resistances that are connected at the wiper. Some applications do not connect to one end, or connect one end to the wiper, so one resistance isn't used, but it is still there. Your application uses both ends.

Potentiometers do not have to be made as one resistors. Have a look at these:- https://uk.farnell.com/bourns/3683s-1-502l/potentiometer-digital-5k/dp/1200095

Those are potentiometers, so the total resistance is what it is specified as. Each digit works by having two resistors, and one resistor is increased while the other is decreased.

If you have a 1 kOhm, 3 digit potentiometer, and it is set to 2 6 9, then the first digit has a resistor of 200 Ohms on one part and a resistance of 700 Ohms on the other.

The second digit has a resistance of 60 Ohms on one part and 30 Ohms on the other part.

The third digit has a resistance of 9 ohms on one part and 1 Ohm on the other part

The first parts are all in series, so that adds up to 269 Ohms. The other parts are also all in series so that adds up to 731 Ohms. The total resistance is 1000 Ohms.

Physically that is 6 variable resistors, two can vary from 0 - 900 Ohms in steps of 100 Ohms, but they will always add up to 900 Ohms. Two can vary from 0 - 90 Ohms in steps of 10 Ohms, and will always add up to 90 Ohms. The last two vary from 0 - 9 and 1 - 10 Ohms, change in steps of 1 Ohms and always add up to 10 Ohms.

You do not need to know about the construction to use the pushbutton potentiometers, because the total resistance is always 1000 Ohms, and the wiper can be anywhere from 0 Ohms to 999 Ohms from one end, just like a rotary potentiometer. If you were to want to replace the potentiometer when it was set to 269, you just need one resistor of value 269 Ohms and one of value 731 Ohms, and the pair would behave exactly as the potentiometer but would not be adjustable.
 
Diver300 said:
To replace a potentiometer with fixed resistors, you need to replace both of the resistances with fixed resistors.
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ok so i add a 49K from C-B and a 4k from C-A

So am I correct in saying that R9 should be 50K and R3 should be 14K? or since The POT is in paralell with R9 do i subtract R9 from POT value C-B and make R9 48K?
 
ThomsCircuit said:
ok so i add a 49K from C-B and a 4k from C-A

So am I correct in saying that R9 should be 50K and R3 should be 14K? or since The POT is in paralell with R9 do i subtract R9 from POT value C-B and make R9 48K?
Click to expand...
You are over-thinking this. Just replace the potentiometer with two resistors. Do not try to combine values of the other resistors nearby.

Resistors in parallel do not add up like that, and anyhow you should ignore the other values.

In theory, you could replace R3, R9 and the two parts of the potentiometer with three resistors. However you would need three new resistors instead of keeping R3 and R9, the maths you need to work out the values is really complicated*, and it's absolutely not worth it unless you are making thousands of a design.

*https://en.wikipedia.org/wiki/Y-Δ_transform I don't understand that page. I could probably work it out if I had to, but it would be hard work.
 
To me, that original circuit is messed up.

For far less voltage sensitivity, the LED and transistor emitter should be connected to the same supply - both to positive or both to negative.

That way, the supply voltage is not affecting the relationship between the LED voltage and the transistor base feed voltage.

I've bought some flickering LEDs from ebay, so I'll do some testing on them when the arrive to see what the actual voltages are when they are running.
 
Diver300 said:
Not really. You would still need to adjust something to get the right effect and that might as well be a potentiometer.
Click to expand...
You have been more than helpful and I've experienced a great deal. Thank you. I'll be posting my attempt to place these new resistors in the schematic.
 
Here is my attempt to replace the POT with appropriate resistors. (the POTs value was 53K)
 
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That should work the same as the pot, in that particular build - no guarantees with different components.

The big problem is that the critical voltage for the transistor is between the +12V rail and its base (or point C), while the critical voltage from the LED is between ground and point A.

Any change in supply will change the relationship between the two (A and C), so may need different values.

I should hopefully be able to provide a more reliable circuit by the weekend.
 
Lightium said:
EZ-EDA is for designing schematics and PCB layouts. What you want is a simulator like this: LTspice
Click to expand...
UPDATE:
I believe the program was updating component models and not the actual program.

I did an install about an hour ago. after launching the program for the first time i was shown an update option dialog. Its not uncommon but after agreeing to the update it went on for quite a while. long enough to cause a concern. There was no progress bar or percentage indicating how long this may continue only a "current file" display that was moving slow enough that i could read each files name. After about 10 minutes i aborted the update. I am in no way complaining but the folder(s) it was analyzing had 15,000 files. I opened the program and was taken back by the 1999 style dialog box and menu bar. It reminded me of my programming days with Visual Basic.


Speaking of VB, it took me many years to perfect a set of screens and dialog boxes that allowed the user to operate the program in a fluid manner. Somehow by reading, sampling, and creating i was able to figure things out on my own. And i did this with books and samples on CDs in those books for there was no real internet. Nothing like today's internet.
I was under the impression that could learn and pickup circuitry in the same manner but It has been difficult to say the least. I am in need of a starting point. even though i understand components i cannot put a circuit together without help. I believe its current and voltage that puzzle me the most. for a while i thought that a resistor had just one function as it does for an LED but i can see now there is more to it.

Thank you all for the help. I will eventually get it and i ill build some pretty cool stuff too. Until then Ill experiment with this program, get the book that Lightum suggested and keep powering on.

T.B.
 
alec_t said:
Try this :
View attachment 142178
Click to expand...
hi Alec.
I wired this up and it works from 4-8.5V dc producing the desired effect. The effect is optimum at 8V. Above 8.5V and the 5 LEDs begin to flicker less and by 9v they are solid and bright but the effect is lost. I swapped the resistor at R2 for a 3.3k but the circuit remained unchanged.
Thank you for providing the circuit.
 
rjenkinsgb said:
To me, that original circuit is messed up.

I've bought some flickering LEDs from ebay, so I'll do some testing on them when the arrive to see what the actual voltages are when they are running.
Click to expand...
Hello, have you had an opportunity to improve the circuit?
I got the book "lightgum" suggested. Started reading it and noticed that the typeface and imagery looked familiar. Rummaged through my fathers magazine rack and found these from 1980 authored by the same person.
 
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