Providing decoder Stay Alive for better dirty track operation and dead frog points (turnouts).

 

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Seeing a demonstration of the Lenzs Uninterruptible Signal Processor (USP) that costs about A$70 that has to be connected to a Lenz Gold decoder (about A$70), I was very impressed with how good it works. This would be especially good for some of my steam locos and shunting diesels operating in a yard where there are two Peco Insulfrog Double Slip points that so many locos stop on.

 

Fitting a Lenz Gold and the USP would cost me $160, (and now I have one). I feel this is a little too expensive and this does not include sound decoders that I am aiming to fit into most of my locos. I started to look at a possibility of fitting a capacitor to NCE D13SR, Soundtraxx DSD-100LC, and a TCS T1 etc, that are the main decoders I use in my locos. This capacitor would provide some extra power when the loco experienced a dirty track or traversing Peco Insulfrog points or double slip points.

 

I needed to find a solution for my Soundtraxx DSD-100LC equipped locos, as any slight power interruption causes a really annoying sound reset of the loco, even though the loco does not hesitate.

 

Soundtraxx have recommended a stay alive capacitor installation on their DSX range of decoders. The 220 uF capacitor for this modification can be much smaller because the stay alive capacitor only has to supply power for the sound decoder and not for the motor and sound, as the DSD has to. The DSX have solder pads that are easily accessed to connect a capacitor to reduce these sound resets. The DSDs do not have this feature possibly because it would require this much larger capacitor that is difficult to locate and there are not the pads that modellers could attach a capacitor. Many other modellers have complained on the Yahoo Soundtraxx group about this annoying problem.

 

Some time ago (July 04), I had problems with Soundtraxx locos not allowing my EB3 DCC Electronic Circuit Breaker to reset. Discussion on the NCE-DCC Yahoo group suggested the problem was with the onboard capacitors causing too much inrush current and the booster thinking there still was a short. I used a 12Volt 21Watt lamp in parallel with the EB3. This allowed the EB3 to reset automatically. This was a work around solution. The final fix as suggested by Mark Gurries was to fit a diode and a resistor arrangement to charge the onboard capacitors to reduce this inrush problem. These could only be fitted to new decoders when manufactured but would not fix any decoders we have now on our layouts, now. I thought maybe if I fitted a capacitor to the decoder downstream from the decoders bridge rectifier, this could supply a little extra power for the motor and sound electronics, similar to what the USP does but without the control feature when there is some form of power interruption.

 

The Stay Alive capacitor is charged via the 100 ohm resistor to keep the inrush current low enough to prevent the booster from tripping and/or resetting. When there is a power interruption, the capacitor rapidly discharges via the diode. This diode enables a parallel path for the discharge current ONLY, so the current is not restricted by the 100 ohm resistor.

 

Using the largest electrolytic capacitor that could be fitted in a loco (or a combination of a few capacitors), this could possibly provide about a seconds worth of power. This would then allow the loco to get over the dirty track or dead frogs etc.

 

I have fitted a 4,700 microfarad 16 volt electrolytic capacitor to a NCE D13SR decoder by connecting the parallel resistor and diode to the blue function lead of the decoder and the other end of the parallel resistor and diode to the + of the capacitor. The of the capacitors is connected to the output of the bridge rectifier on the decoder. Available space in the loco will determine the capacitor value. Use two capacitors in parallel to increase the capacitance to increase the time.

 

Higher voltage capacitors will work but their larger physical size would make them even harder to fit. Remember Soundtraxx decoders including the DSD-100LC should only be operated on layouts that have 16 volts or less supplied to the rails, so 16 volt capacitors are very suitable.

 

Important: Knowing the layout voltage is very important for this modification due to the operating voltage of the capacitor is 16 volts. If the layout track voltage is higher than 16 volts, the 16 volt capacitor will be insufficient for this application. The track voltage can only be measured by using a DCC Pocket Tester, a RRampMeter or similar specialist DCC meters. You cannot use a digital multimeter selected on A.C. for this test. This is only an approximate reading. I have seen digital multimeters with A.C. Volts selected showing as low as 9.0 volts A.C. to as high as 22.0 volts A.C. with 13.8 volts DCC at the track. If not sure about the track voltage, another method of measuring the voltage that the capacitor will be operating at, is by measuring the decoders Function Output voltage. The decoders function voltage is really the operating voltage for the stay alive capacitor.

 

To connect the stay alive capacitor you have to make a negative connection to the decoder. See below notes. I have fitted the same connection to both an NCE D13SR and a Soundtraxx DSD-100LC decoders. This will require a fine soldering iron and a steady hand. Any modification will void any manufacturers warranty, so be very careful with soldering.

 

The results I have achieved have not been as good as the Lenz USP but at the price (about A$2.50) and the fact that I can add it to my existing decoders, this is very attractive. This mod go part of the way to solve the problem that steam locos and short wheel based diesels have going over some points (turnouts).

 

Now the hardest part of the project is to get as much capacitance into the loco/tender. Capacitors are getting smaller, thats in our favour. Using electrolytic capacitors for power supplies are the only suitable ones and these are polarity conscious.

 

I will try this modification on TCS decoders that I have.

 

I have tried three 47,000 uF 5.5 volt super capacitors in series to get 16.5 working volts but this provides one third of the capacitance, i.e. 18,000 uF, but they DONT work. It must have too much internal resistance to supply 200 mAs of current. Super capacitors are for backup power supplies for keeping alive memory data that does not require lots of current. Thats my theory.

 

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The latest Stay Alive for the Soundtraxx Tsunami.

 

NOTE: Since I did this Stay Alive conversion, I have spoken to Soundtraxx and they confirmed that the 220uF capacitor that comes connected to the decoder IS a Stay Alive capacitor. Previously they told me that the external capacitor was not required for DCC operation and was only for DC. It was this information that led me to adding the Stay Alive as described below. Increasing the value of this capacitor will increase the Inrush current. For large values (above approx 1,000 uF) a resistor and diode arrangement should be added as shown below to reduce the Inrush Current.

 

Note: The Tsunami Micro comes with a 220 uF capacitor but is NOT connected to the decoder. For users that want a Stay Alive, connect the included 220 uF to the BLUE and YELLOW/GREEN wires.

 

 

 

 

 

 

 

 

 

 

 

 

I have a Peco Insulfrog point (turnout) on my layout that has really bad vertical alignment to a sagging joint in two connecting baseboards. My 4-6-0 Austrains 36 that has a tender BUT no extra pickups, gives the electrical equivalent of a 0-6-0 loco, does not hesitate and better still, the sound never misses a beat (no resets) with about 30 traverses of the section of track. Disconnect the blue wire no Stay Alive and straight away there are resets.

 

Sure extra pickups on the tender and re-alignment of the points, will correct this problem that the Stay Alive hides.

 

This poor track alignment and the fact that it is a Insulfrog point, demonstrates that my Tsunami Stay Alive works.

 

Note: With the Stay Alive, you cannot read ANY CV values, even with an NCE Power Cab. Disconnect the blue wire to read CV values.

 

With some spare room in your loco/tender, you can add the 16 volt capacitor, the larger value, the better.

 

 

NCE D13SR decoder.

 

 

 

 

 

 

 

 

TCS T1 decoder.

 

 

 

 

 

 

 

 

Soundtraxx DSD-100LC sound decoder.

 

 

 

 

 

 

 

 

 

 

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The black Stay Alive 4,700 uF capacitor in my 36 tender

 

 

 

 

 

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I have been asked to if I could find the connections for other Soundtraxx decoders. I took some photos of these decoders at my local DCC dealer. I have worked out the connections but I have not tried these decoders. I recommend you find the connections as shown then measure the DC voltage at these points. If there is 12 to 14 volts DC then this should be ok. I will post results of other modellers installations of the Stay Alive in these decoders when they tell me how they work. I have fitted a Stay Alive in a Proto 2000 GP9. See the photos below.

 

An alternative to fitting the 4,700 uF capacitor.

 

I have also fitted Stay Alive capacitors to a DSD-100LC decoder that I only use for sound in an Atlas RSD 4/5 with a Kato mechanism that I use as a 40 class diesel and to a DSD-LL110LC decoder that is used for sound only, in a Proto 2000 GP9. The motor and lights are controlled from the second decoder, a TCS T1 decoder. The Stay Alive capacitor is only 330 uF as it only supplies sound (not for motor). This is so easy to fit due to the much smaller size.

 

Finding room for the 4,700 uF capacitor might be harder than fitting a second motor decoder. This could be an option but it will depend on how much effort you want to go to make your loco run better. This will also improve the motor control and will eliminate and motor buzz or hum if present that is present in some locos with these noisy Soundtraxx decoders. Just another option.

 

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Below are the photos I have taken of some of the other Soundtraxx decoders.

 

 

 

 

 

 

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