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#1 matto3868

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Posted 02 October 2018 - 19:46

Can anyone tell me which DC controller's use smoothed DC ?
I know the Morley ones do and I know that gaugemaster do not ( well the 4 I have don't anyway)



#2 Theakerr

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Posted 02 October 2018 - 20:16

 If it helps I seem to remember a U-Tube video where several smoothed and non smoothed were tested.



#3 matto3868

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Posted 02 October 2018 - 20:33

I have seen the one comparing Morley and gaugemaster,quite interesting.

#4 Bino

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Posted 11 October 2018 - 18:32

What is a smoothed DC controller?



#5 royaloak

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Posted 11 October 2018 - 18:41

What is a smoothed DC controller?

One with all the rough edges sanded down.

Or have I misunderstood the question?


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#6 John ks

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Posted 11 October 2018 - 23:56

The graphs show voltage over time

The black line is the 0V reference

With AC the voltage increases from zero to max & back to zero (positive polarity) & then to max & back to zero (negative polarity)

This is one cycle, in Oz, UK & other power grids this happens at 50 times a second or 50Hz (60Hz in US)

A single diode blocks every ½ cycle & you get ½ wave DC

 

A rectifier flips every ½ cycle & you get full wave DC

 

If you add a capacitor you get smoothed DC

 

If you need to reduce the ripple on smoothed DC you need a regulator

A good regulator will give DC that is ripple free like the DC you get from a battery

 

acdc.jpg

 

Hope this helps

John

 

PS the astute among you will notice that the AC wave is not a sinusoidal, but for the purposes of  explanation I think it is close enough.


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#7 Junctionmad

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Posted 13 October 2018 - 06:53

Just a small point , a regulator does not generally play any part in ripple control , the output capacitor is the primary determinant of ripple

Dave

#8 Crosland

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Posted 14 October 2018 - 08:59

Another small point, a regulator 

 

Just a small point , a regulator does not generally play any part in ripple control , the output capacitor is the primary determinant of ripple

Dave

 

The regulator is actually quite important.

 

The circuit should be designed in such way that the regulator output voltage is lower than the minimum of the "smoothed" voltage from the rectifier + reservoir caps, also allowing for the regulator "drop out" voltage. Otherwise the regulator is not actually regulating at all, and the output could still have considerable ripple.


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#9 Junctionmad

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Posted 14 October 2018 - 23:25

Another small point, a regulator 

 

 

The regulator is actually quite important.

 

The circuit should be designed in such way that the regulator output voltage is lower than the minimum of the "smoothed" voltage from the rectifier + reservoir caps, also allowing for the regulator "drop out" voltage. Otherwise the regulator is not actually regulating at all, and the output could still have considerable ripple.

 

indeed, 

 

however what I was trying to say is that the reservoir cap determines the ripple voltage , before the regulation stage and the regulator can ( if designed properly ) remove that , i.e. the regulator is not a determinant of the ripple voltage per se ( even if it removes it ) 



#10 AndyID

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Posted 15 October 2018 - 00:19

the regulator can ( if designed properly ) remove that

 

It's not much of a regulator if it doesn't :)



#11 Junctionmad

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Posted 16 October 2018 - 01:54

It's not much of a regulator if it doesn't :)

 

well the LM317 "only" reduces it by around 50 dB !! :onthequiet: 


Edited by Junctionmad, 16 October 2018 - 01:54 .


#12 AndyID

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Posted 16 October 2018 - 03:03

well the LM317 "only" reduces it by around 50 dB !! :onthequiet: 

 

dBV?



#13 Junctionmad

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Posted 17 October 2018 - 16:11

dBV?

 

no dBs , ie a ratio , works out round 700:1 reduction in 120 Hz ripple 



#14 matto3868

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Posted 17 October 2018 - 18:22

I am pretty certain the gaugemaster controller's output is 100hz.

#15 Junctionmad

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Posted 17 October 2018 - 22:00

no dBs , ie a ratio , works out round 700:1 reduction in 120 Hz ripple


I merely quote the lm317 data sheet

#16 AndyID

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Posted 18 October 2018 - 04:13

no dBs , ie a ratio , works out round 700:1 reduction in 120 Hz ripple 

 

The decibel (dB) is a measure of relative power. If the LM317 data-sheet writers are using it to describe relative voltage they should probably use dBV instead. Alternatively they could use "ripple attenuation factor" or something similar.



#17 Junctionmad

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Posted 18 October 2018 - 09:56

The decibel (dB) is a measure of relative power. If the LM317 data-sheet writers are using it to describe relative voltage they should probably use dBV instead. Alternatively they could use "ripple attenuation factor" or something similar.

 

while we are way of topic here , 

 

dB was originally defined in the context of power in telephony applications, but the modern SI definition of dB is a ratio of a "level"

 

dBV is a ratio from a level of 1 volt ( as dBm  is to 1 milliwatt) etc ,  Hence this would be an inappropriate suffix for the LM317 ripple rejection ratio 

 

dB is a simple ratio, when applied to power its 10 x Log 10 ( ratio ) whereas to Amplitude (as in this case ) , its 20 Log10 ( ratio) 

 

dB is therefore correct in this context , with a dB of 0 being 1:1 and 57 around 700:1 ( for amplitude ) 


Edited by Junctionmad, 18 October 2018 - 09:57 .

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#18 matto3868

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Posted 18 October 2018 - 15:25

So can anyone say what rating/type of capacitor would be best to smooth out DC from a gaugemaster controller. Would 1 or more in series or parallel be better? I am currently using a 3300 16volt bipolar one and it definitely smoothes out the feed to the track,the reason for this is my layout is both DC and DCC (not at same time obviously) most of my locos are DC but the ones that are chipped with DCC concepts decoders will not run at all on DC (yes DC is turned on in cv29) plus my club layouts are all DC only and I can't run my chipped stock on them so other than buying a Morley control I'd prefer to use a capacitor for now at least.