Again LED dimming and fading on

Thread Starter

Chillum

Joined Nov 13, 2014
546
What about transistors? NPN and PNP... I assume you have no problem finding resistors and caps, and perhaps 555s, right?
15xNE555 (was before I discovered TLC555)
15xTLC555 (3 in breadboards)
15xNE556
15xTLC556
wide range of caps from 0.022uF upto 4700uF
wide range of resistors 68 values with stock ranging from 5 to 20 (1R to 1M1)
wide range of diodes SR360, 1N5817, 1n4148, BAT85, 1N4007, 1N5402,1N5822 3 to 20 of each
9.5V 0.4A tranformers x2
transistors:
2N3904, 2N3906 approx 15 of each
MJE3055, MJE2955 x4 each
BC327 x10
2N2222 x4 (I thought I had more of them!)
inductors
100uH 3A
150uH 4A
various POTS and 2 LDRs (10K I think)
 

ian field

Joined Oct 27, 2012
6,536
Chillum,
There are many, many ways of building a PWM circuit without resorting to a 555 chip. And as you have probably seen already, the 555 circuit cannot normally be used in the full range of 0 t 100% PWM.

.
The 555 can get *VERY* close to 0 - 100% - you just have to design the charge/discharge path correctly.

You simply have 2 separate paths for charge and discharge, that is; you have 2 resistors, each in series with a diode so one resistor only acts during charge and the other only acts during discharge.

As long as the 2 resistors have a common point, you can replace both with a pot and sweep the MS ratio.
 

cmartinez

Joined Jan 17, 2007
8,220
Thanks Ian... I've been searching everywhere for a sample of a 555 circuit that ramps up and holds a voltage... got any ideas?
 

#12

Joined Nov 30, 2010
18,224
Thanks Ian... I've been searching everywhere for a sample of a 555 circuit that ramps up and holds a voltage... got any ideas?
All you have to do is cause the feedback voltage to never achieve 2/3 Vcc at the upper voltage sensor. That will get you a ramp of almost 2/3 Vcc. A jfet will give you a ramp to Vc-2V and a bipolar constant current configuration will give you a ramp to about Vcc-2V.
 

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Thread Starter

Chillum

Joined Nov 13, 2014
546
excuse the fact that I'm still very noob, but what part of the circuit is that, and how does it work, I don't see the diodes working? does this circuit fade the diodes? how will base be controlled by the resistor and potentiometer? should this be obvious?
 

cmartinez

Joined Jan 17, 2007
8,220
excuse the fact that I'm still very noob, but what part of the circuit is that, and how does it work, I don't see the diodes working? does this circuit fade the diodes? how will base be controlled by the resistor and potentiometer? should this be obvious?
I'm under the impression that #12's circuit is a current-limiting device, which would later be used to charge a capacitor, thereby providing a voltage that increased with time... shaping the ramp that we need. Am I right @#12 ?
 

#12

Joined Nov 30, 2010
18,224
Oops. Forgot a resistor.
That's a constant current generator with rate adjustment. If you plug it in to a capacitor, the voltage on the cap will ramp very straight until it gets to about Vcc-2V.

What I'm doing here is throwing in sub-assemblies without taking responsibility for understanding and designing the whole thing.
 

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Thread Starter

Chillum

Joined Nov 13, 2014
546
Oops. Forgot a resistor.
That's a constant current generator with rate adjustment. If you plug it in to a capacitor, the voltage on the cap will ramp very straight until it gets to about Vcc-2V.

What I'm doing here is throwing in sub-assemblies without taking responsibility for understanding and designing the whole thing.
makes more sense now, absolutely, whatever you contribute, I'm infinitely gratefull for every piece of the puzzle, my old friend (this is not the first time he's taken control of one of my threads) cmartinez will help me ;-)
 

#12

Joined Nov 30, 2010
18,224
If you're looking all over the forum, you will see I have a sick Laptop computer to figure out today.
R!f@@ seems to know the diagnostic options.
 

cmartinez

Joined Jan 17, 2007
8,220
makes more sense now, absolutely, whatever you contribute, I'm infinitely gratefull for every piece of the puzzle, my old friend (this is not the first time he's taken control of one of my threads) cmartinez will help me ;-)
Yeah, I can take it from here.... I just hope @#12 doesn't spend all of the patience he had reserved for today in that stubborn lappy of his and saves an itsy bitsy tiny bit for us... ;)
 

cmartinez

Joined Jan 17, 2007
8,220
Chillum, let me model #12's circuit in LTspice and then I'll get back to you.

And by the way... your understanding of electronics would increase exponentially if you downloaded that software (it's free!)
Then I can send you the sim's files and show you how they work. It will be like having your own virtual oscilloscope.
Just google "download LTspice" and follow through.
 

#12

Joined Nov 30, 2010
18,224
The bipolar KI is much like the jfet KI except uses very cheap parts and is a bit more sensitive to temperature changes. Many ways to skin the cat.
 

Thread Starter

Chillum

Joined Nov 13, 2014
546
Chillum, let me model #12's circuit in LTspice and then I'll get back to you.

And by the way... your understanding of electronics would increase exponentially if you downloaded that software (it's free!)
Then I can send you the sim's files and show you how they work. It will be like having your own virtual oscilloscope.
Just google "download LTspice" and follow through.
I primarily use linux, have a windows virtual machine, but I'd like to keep it Linux (Gentoo)

package (free) options
* sci-electronics/gspiceui
Available versions: 0.9.99 ~0.9.99-r1 ~1.0.0 {examples schematics waveform}
Homepage: http://www.geda.seul.org/tools/gspiceui/
Description: GUI frontend for Ngspice and Gnucap

* sci-electronics/ngspice
Available versions: ~24 ~25 ~26 {X debug readline}
Homepage: http://ngspice.sourceforge.net
Description: The Next Generation Spice (Electronic Circuit Simulator)

* sci-electronics/spice
Available versions: 3.5.5-r1
Homepage: http://bwrc.eecs.berkeley.edu/Classes/IcBook/SPICE/
Description: general-purpose circuit simulation program


think I'll install all of them and if it's incompatible with you ltspice, I'll go to my virtual machine
 

Thread Starter

Chillum

Joined Nov 13, 2014
546
Chillum, let me model #12's circuit in LTspice and then I'll get back to you.

And by the way... your understanding of electronics would increase exponentially if you downloaded that software (it's free!)
Then I can send you the sim's files and show you how they work. It will be like having your own virtual oscilloscope.
Just google "download LTspice" and follow through.
I dunno what ltspice's gonna look like, but gSpiceUI looks scary ;-)

edit: downloading ltspice as we speak
 

Thread Starter

Chillum

Joined Nov 13, 2014
546
you can run LTspice through wine (recursive acronym: wine is not an emulator), and wine is not an emulator but rather a reimplementation of the win32 API in linux, so I can easily run it though my linux side of things, will try...
 

cmartinez

Joined Jan 17, 2007
8,220
you can run LTspice through wine (recursive acronym: wine is not an emulator), and wine is not an emulator but rather a reimplementation of the win32 API in linux, so I can easily run it though my linux side of things, will try...
I suggest you do... so we can speak in the same language... :)
 
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