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DCCConcepts High-power Stayalive


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Does anyone understand why these devices provide such a long run-time in the absence of the DCC track power?

 

I have opened one up and can see that the circuit is more complex than the "traditional" one I am familiar with - of Capacitor(s), diode and resistor.

 

It contains 6 off 0.47uF 2.7 volt capacitors in series. There also appears to be a resistor ladder, with each capacitor connected in parallel to one of these resistors - I take it that this is to ensure an equal/controlled voltage (and therefore charge) for each capacitor. There are also several other components which I cannot identify - nor is it clear as to how they are interconnected.

 

The most powerful devices I have made contain 3 off 0.47uF 5.5 volt capacitors in series. In principle, therefore, my device should provide twice the endurance of the DCC Concepts device. In fact, I get less than 1 second of running after the track power is lost, whereas the DCC device runs a loco for several seconds.

 

I would appreciate any insight anyone can add.

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19 minutes ago, ColinK said:

On the Lenz video, the loco changes direction, but how does it receive the DCC signal to do that if it is isolated from the track? 

 

The command to change direction received whilst on the live track. Deceleration and acceleration curves programmed into the chip.

Stay alive does its normal job in fooling chip into thinking it's still on live track.

Edited by Porcy Mane
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23 minutes ago, Porcy Mane said:

 

The command to change direction received whilst on the live track. ....

 

Can't be the case, because you can send commands whilst on the insulated section.

 

 

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46 minutes ago, ColinK said:

On the Lenz video, the loco changes direction, but how does it receive the DCC signal to do that if it is isolated from the track? 

 

Lenz, being Lenz, came up with something a bit different to most others.    Very very approximately like this: 

 

Its a capacitance trick.   With the rails being close by (piece of paper away, or bit of rail dirt), there is a little bit of the DCC signal available due to capacitance effects over the thin insulation layer.   So the decoder can sense the DCC signal, even though it cannot receive the DCC power.   

Consequently, the decoder can still receive decoder instructions and respond provided it has power from another source (the capacitor).   It also means the decoder can tell the loco is off the track, and stop (ie. the decoder won't run the loco over the scenery, unlike some other very simple high capacitance designs). 

 

The capacitor is also a low-voltage item, with a voltage multiplier to interface it to the DCC track voltages.  

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5 minutes ago, Nigelcliffe said:

......So the decoder can sense the DCC signal, even though it cannot receive the DCC power...........

 

Indeed.

Just to add to that...

DCC is a communication signal technology (a version of Bipolar DC encoding).

The motive power is effectively just a byproduct of the signal transmission mechanism.

So, as Nigel says, the signal is getting through the paper, but with a much reduced amplitude (effectively just RF), which is not enough (i.e. zero power) for a decoder to extract any motive power out of the signal.

 

.....sort of !

.

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1 hour ago, Ron Ron Ron said:

Can't be the case, because you can send commands whilst on the insulated section.

 

 

1 hour ago, Nigelcliffe said:

Lenz, being Lenz, came up with something a bit different to most others.    Very very approximately like this: 

 

And there you have it.

 

Thanks Nigel.

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1 hour ago, Zorcan said:

So . . . no one out there understands how the DCC Concepts device performs so much better than a "Conventional" capacitor/diode/resistor device?

 

Almost certainly they use supercaps which are 0.47F NOT 0.47uF. Six in series gives 0.078F or 78,000uF.

 

The resistors are, indeed, for charge balancing and also help discharge the caps when not in use.

 

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