TECH HELP- DCC, DCS DIFFERENCES

I've been looking at adding DCC to my command control options and I'm far from an expert. Some key differences I've found so far are:

• DCS superimposes a digital signal onto the AC or DC track voltage.
• DCC changes the input voltage (AC or DC) to square-wave of varying amplitudes and frequency to compose the digital commands.
• DCS is proprietary -- MTH is the patent holder and the only source for the product and support.
• DCC is public domain. Equipment, decoders, sound decoders, polarity switchers, and other items are available from different vendors. Note, though, that the command base equipment (Booster/remote/transformer) from manufacturer "A" may not work with the command base equipment from manufacturer "B."
• DCS is offered in conversion kits for O scale/O Gauge and large scale. It is factory supplied in MTH H.O, O Gauge, and #1 Gauge (1/32) locomotives.
• DCC decoders are available for N, H.O./S, O/G. I had heard that there was one for Z, but I haven't verified it.
• DCS is polarity-sensitve -- i.e., can only read the signal through the "hot" rail with Proto-2 locomotives. This requires the use of "old school" polarity switching of rails for reverse loops using relays. Proto-3 locomotives can pick up the DCS signal from either side, plus they can operate under DCC.
• DCC picks up from either rail. This allows the use of "smart" polarity switching hardware in 2-rail operation.

So far, DCS is less expensive to implement than DCC for larger scales.

Interestingly enough, there are some DCC configuration recommendations that also seem to improve DCS:

• Only one feed per block.
• Don't make block size too long.
• Signal feedback is an issue. Use of "snubbers" (See Susan Deats Engineering Filters) at the ends of the blocks to filter out feedback.

Hope this helps.

Thanks Matt for your response, I already use DCS with my 2 rail set up and am very happy with it, DCS does have some draw backs however.I have a few non MTH locos and so the challenge is how to power them. The layout  covers 60 feet in length and walking back and forth when theres trouble is annoying, DCS is great with remote control no tethers to worry about,but running in standard control mode in DC (with a bridge rectifier on the output of the TIU) doesn't allow me to change the locos direction from the remote, i have to walk and flick a switch to change polarity, it also starts at 5volts. The DCS commander doesn't have remote control so that doesn't help either. I wish MTH would fix this for DC users. Iv'e also thought of incorporating DCC, but a remote set up is three times the cost of a DCS unit, and still doesn't allow control of my non digitally controlled locos.

SO! Im considering radio control (Aristo Craft) this gives me remote control in standard mode and the option of equipping individual locos with receivers and co-current operation with DCS locos, something DCC wont allow. So my question,I was wondering if the DCS signal would interfere with the radio receiver witch needs filtered DC.

If MTH would come up with something to plug into the back of my TIU that allowed me DC control,or a remote for there Commander much of the problem would be solved.

Stephen from Down Under       (cTr...Choose the Right)

Perhaps I'm missing the boat on what you're saying, but isn't the standard 'solution' to place a generic e-unit between the TIU variable output (AC) and the track?  Obviously not the normal application of installing it IN the engine, but it interprets the AC power interruptions and reverses the DC polarity to the motor (to the track in this instance).  One or more pairs of back-to-back diodes after the E-unit can lower the minimum output if your DC engines operate down to a few volts.

Or if you are up for some DIY wiring, I figure the polarity-reversal on power-interruption function of an E-unit can be implemented for under $10 US with a DPDT relay and a few components.  Again, diodes can lower the voltage applied to the track.

I think it was mentioned at York in October that they are working on a new TIU that will address this problem. As of now you can only put AC throught the variable channels and be able to reverse the polarity.

If you look for the minutes from the York DCS users group from October it should be in there. Plus I think it's suppose to come out this year. I will look and see if I can find it.

If you look up 12th York DCS User Group Meeting sumary, it does mention something about it. I do know that you will be able to controll polarity with especially with 2rail.

Ralph

Hi Stephan,

There is a new TIU under development that will directly control DC voltage without the need for a rectifier.  However, that is a ways off from delivery.

In the mean time I think there's a better solution for your situation if your conventional DC engines draw less than 5 amps.  Take the output from a variable channel and connect one wire directly to your track wiring.  Take the other lead and route it to an "IN" terminal on accessory port on an AIU.  Connect minimum 5 amp rectifier diodes in opposite polarity to the "1" and "2" terminals on the same accessory port.  Tie the output of the two diodes together and connect it to your track wiring.  This configuration would solve a couple of your problems.  First, it will give you remote control of DC polarity.  Program the accessory port into your remote and you will be able to change DC polarity by selecting "ON" and "OFF" with the DCS remote softkeys.  Second, because you are only using half of the AC sine wave it will drop the starting voltage in half.  However, it will also halve your maximum voltage.  If you are using a 22 volt power supply (that's the assumed voltage on the TIU variable channels) you'll have a maximum of 11 volts.  That might be OK with most traditional O-scale DC engines.  If not, your third option is to keep the bridge rectifier on the TIU variable output and decrease the input voltage into the TIU.  The voltage display on the DCS remote doesn't really represent voltage out put.  Rather, it represents a fractional proportion of the input voltage.  The variable channels range from 0-22 "volts."  If the display reads "11 volts" that really means it's putting out half the input voltage.  It only reads accurately if the input is 22 volts.

Hope that helps.

Dave

Dave..... Thanks yet another great idea !!

Stephen from Down Under     (cTr...Choose the Right)

Stephen, as I understand the Aristocraft TE system, you can run it simultaneously on the same track as DCS locos.I know Ben at the NJ Hirailers installed it in a number of locos and has not found any problems at all as far as I'm aware. I'm going to install some when they release the new receiver for O gauge.

As for DCC, I have been experimenting with it in my DC Darstaed locos and it works well. I've been using cheap Bachmann decoders (about $25 each) to control speed, direction and lights. They have a small DCC controller for about $75. It's hardwired. Their remote system is not very expensive though.

Dave , Iv'e heard you mention Aristo Craft Revaluation in another post,Its good to have verification that someone has already done this. I was wondering why your waiting for the O scale board, G seems to have very similar needs to O scale. I was hopping it would be slightly cheaper than the G board, but how long will it take for them to produce it, I see Train World lists the HO version. 

As for DCC its interesting that the Bachmann board handles the current draw.

Stephen from Down Under     (cTr...Choose the Right)

The 5-volt start-up can be fixed using "dropping" bridge rectifiers, where you tie the "+" and "-" leads together and hook the remaining leads in series with your source. This creates a 2.4-2.8 volt drop per bridge. I've used this technique to slow down O-27 locomotives that ran too fast at low voltage.

The Aristo system mentioned above represents a good option as it operates the locomotive independent of the track voltage. The only issue is interior space in the locomotive.

I received a new pair of Dash-8 with Protosound 3.0 and I can say the polarity issue is no longer an issue.  The loco automatically senses which rail has the signal, no more flipping switches.

That's good to hear that it works in practice. I have a couple of scale-wheeled Proto-3 engines coming.