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Paralleled dcc decoders?

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I would like to install tts sound in some old-ish Hornby ringfield locos.  However, I have found that these decoders either produce poor running, or, on occasion, get rather expensively destroyed.  I would like to use the sound decoder for sound and lights, and a separate one (such as Hornby Sapphire, which I have found works very well with these motors) to control the motor itself.  They would have the same address.  I do know that this approach does work.  However, as my post will reveal, my knowledge is lacking in this area, so I wonder if this is a clumsy way of arriving at a solution.  Incidentally, another approach could be to make a consistent, with the lead loco being the tts decoder (so that the functions would all be available from the lead loco).

 

Forum expertise welcomed!

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2 decoders should work on the same address. If you need to program them on a program track, you may find that only the Sapphire will respond, but any changes will be applied to both. This may not be a problem.

 

Regarding consisting, I can't remember basic consisting very well because I have not used it for years. I remember it has some limitations that made me prefer advances consisting. I think 'Lead loco' is an 'Advanced' feature. Sounds like horns etc only play from the lead loco & this is reversed with train direction.

I don't think TTS supports advanced consisting anyway.

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Forgive me but I don’t quite understand how consisting would get over the problem of poor motor control from the TTS or even if the proposal is for two decoders on one loco or one each in two. I think I must be mis-understanding something. 
 

But, concerning running a TTS ‘ piggybacked’ onto a loco with another doing the motor control then in my experience just giving them the same address is quite good enough. However, this only applies to diesels. I understand the TTS steam need motor control feedback to play properly. Perhaps someone with steam TTS will be able to say whether this is correct.

 

Izzy

 

 

ps. The lights would best be controlled by the non-TTS  as they don’t have a lot of power headroom for this aspect, which the Sapphire might (I have no experience/knowledge of them).

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42 minutes ago, Izzy said:

 

But, concerning running a TTS ‘ piggybacked’ onto a loco with another doing the motor control then in my experience just giving them the same address is quite good enough. However, this only applies to diesels. I understand the TTS steam need motor control feedback to play properly. Perhaps someone with steam TTS will be able to say whether this is correct.

 

 

By 'play properly' I assume you mean synchronise exhaust beat with wheel revolutions by using motor feedback? TTS doesn't do this at all, which is one of its limitations & causes many people to consider it unsuitable for steam locos in particular, so you won't use any functionality because it was never there in the first place.

 

I agree about using the same address. Consisting was mentioned by the OP, but this would be a lot of hassle to program the decoders separately without providing any benefit.

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I'm not commenting on whether two decoders is sensible or not, as I have nothing with ringfield motors.

 

Here's a way to deal with programming two decoders in a loco.  Arguably its a sort of "back door" consisting method:

 

Say the final loco address is 2456,  then 

Decoder 1 - program its short address to 51, and then its long address to 2456.  Record the value of CV29.

Decoder 2 - program its short address to 52, and then its long address to 2456.  Record the value of CV29.

Install both decoders into loco.

 

Now, for programming on-the-main, if needing to program only one of them:

Programming-on-the-main, call up 2456, and set CV29 to short address. 

Now call up either 51 or 52, as appropriate for programming, and make the changes needed.

Finally, call up 51, and set CV29 back to long address,  and then call up 52 and set CV29 back to long address.

 

The above doesn't help for programming track, there the only way is decoder locking, which requires (a) a decoder which supports it, and (b ) lots of reading of manuals to understand how decoder locking works for the specific decoders in question.

 

 

Nigel

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3 hours ago, Pete the Elaner said:

 

By 'play properly' I assume you mean synchronise exhaust beat with wheel revolutions by using motor feedback? TTS doesn't do this at all, which is one of its limitations & causes many people to consider it unsuitable for steam locos in particular, so you won't use any functionality because it was never there in the first place.

 

I agree about using the same address. Consisting was mentioned by the OP, but this would be a lot of hassle to program the decoders separately without providing any benefit.

 

I have no TTS steam decoders but have read several times that they won't work by just hooking them up to a DCC system without having a motor in-circuit. This you can do with the diesel ones I have and they will respond sound-wise to the throttle settings. I also understand the steam often don't match the wheel revolution, I guess this depends on the gearing ratio if it is different to that which the particular decoder was set-up to use.  This is where of course the better sound decoders such as Zimo score and why you pay the much higher price, the ability to tune to your exact preferences and that of the particular loco.

 

The usual story across a wide range of consumer goods, price versus features.

 

Izzy

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You can’t use a TTS and a non sound chip in parallel, I tried it and the TTS chip went up in smoke! I had a similar problem with the TTS cutting out so I disconnected the motor wires and to my surprise the sound still was still working so left it like that, then put a1.5amp chip to power the motor which worked OK but I forgot to insulate the TTS motor wires and putting the body back on they must have made contact with the PCB as the loco started running then the smell of chip frying but the loco kept running but NO sound. Took body off and the TTS chip was black.

So you can use them without a motor connected but not with a second chip in parallel, I was told it is because of back emf from the second chip.

 

regards mike 

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17 minutes ago, mikeg said:

You can’t use a TTS and a non sound chip in parallel, I tried it and the TTS chip went up in smoke! I had a similar problem with the TTS cutting out so I disconnected the motor wires and to my surprise the sound still was still working so left it like that, then put a1.5amp chip to power the motor which worked OK but I forgot to insulate the TTS motor wires and putting the body back on they must have made contact with the PCB as the loco started running then the smell of chip frying but the loco kept running but NO sound. Took body off and the TTS chip was black.

So you can use them without a motor connected but not with a second chip in parallel, I was told it is because of back emf from the second chip.

 

regards mike 

 

I don't understand how a 2nd chip in a loco is electrically any different from being in another loco/coach/DVT etc.

It sounds more like you simply shorted out the motor terminals.

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I must admit I would never have considered connecting the motor outputs of two decoders to the same motor, and I apologise if in any of my posts concerning using TTS  decoders just for sound with another controlling the motor I have given the impression that this is what should be done. 
 

Izzy

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Red and Black to the Track, Orange and Gray the other way...

 

Yes, you certainly can use 2 decoders, one sound, one non sound to run a loco.  

 

I would recommend putting a resistive load of 30-100 ohms on the decoder that does not have a motor connected to its orange & gray (motor) connections.  A light bulb works well.

 

You may not be able to program the decoder otherwise.  

 

I see the ^ upthread about how to program the decoders so you can use Programming on the Main for most reprogramming.  I would recommend installing some way of "quick disconnect" so that you can reprogram both decoders individually if really needed.

 

I have done so in at least one of my locos- the Lego F9's have a total of 5 decoders spread over the 3 units- 1 sound, 4 motor.

 

James

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I've been thinking about doing this on my Hornby Class 40 with TTS.  Disconnect the TTS from the motor, but leave other connections intact, and Install a Zimo for motor control. Using 2 separate addresses. In my case, under computer control.

 

This would enable me to simulate the behaviour of prototype class 37 and class 40 English Electric locomotives, where the motor revs up and down periodically, especially when moving away from rest. Also it would enable a more effective simulation of starting a heavy load, where the engine revs strongly for a while with, initially, no movement, and then, a very slow gradual increase in speed. Finally, it would give a more effective simulation of coasting. None of these behaviours are convincingly manifested with the TTS decoder as is.

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Hi,

 

No problem electrically if the paralleling the decoders means connecting the two wires from the loco pickups to the track connections on the two decoders and not connecting any of the other connections on the two decoders to each other.

 

As to using the same DCC address for both decoders it is a form of consisting - the most simple of the three types of consisting. TTS does not support the third type  - advanced consisting.

 

You might be able to save yourself some money by using Zimo budget decoders (currently £20 each in the UK) instead of the Sapphire. If you have a number of locos it might be worth buying one to experiment with (Zimo decoders have a lot of internal features so the manual can be a bit overwhelming - just skip the bits that you don't need to use).

 

Take care.

 

Nick

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TTS steam requires bemf to make the chuff work. It is bemf that drives the chuff/coast transition and tells when to pick up on the next chuff sound byte in sequence versus speed step selected.

TTS diesel doesn’t need bemf as it works on fixed sound notches. The change point can be adjusted by use of TTW settings.

Beware hanging a resistor on instead of a motor as when you apply throttle the resistor will heat up.

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12 minutes ago, RAF96 said:

TTS steam requires bemf to make the chuff work. It is bemf that drives the chuff/coast transition and tells when to pick up on the next chuff sound byte in sequence versus speed step selected.

TTS diesel doesn’t need bemf as it works on fixed sound notches. The change point can be adjusted by use of TTW settings.

Beware hanging a resistor on instead of a motor as when you apply throttle the resistor will heat up.

Hi,

 

Providing the resistor is the right value to produce an ACK pulse for programming and is the right wattage there should be no problem. The correct current will have to be checked but I think its 60ma. So for OO the minimum voltage at the DCC decoder is 7 volts so the resistor should be less than or equal to 7/0.06 ohms (which is 120 ohms, so maybe use a 100 ohm resistor for an engineering margin). The maximum voltage for OO DCC is 27 volts so the wattage of the resistor can be equal to or greater than (27/100) squared = 0.0729 watts so a 0.125W (1/8th Watt) 100 ohm resistor will do.

 

Take care.

 

Nick

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Posted (edited)

 

On 29/04/2020 at 22:08, NIK said:

The maximum voltage for OO DCC is 27 volts so the wattage of the resistor can be equal to or greater than (27/100) squared = 0.0729 watts so a 0.125W (1/8th Watt) 100 ohm resistor will do.

 

Power is V^2/R (NOT (V/R)^2) so in your case (27*27)/100 or 7.29W!!!

 

First thing to do is set the max speed [edit: to zero] and/or the speed table [edit: to all zeros] so that you cannot accidentally heat up the resistor by sending throttle commands to the decoder.

 

The ACK pulse is only a few milliseconds and the resistor can actually be quite a low power rating, IFF you perform the above step. I would go for 1/2W.

 

Edited by Crosland
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I am fully aware that during programming the use of a resistor is warranted to produce an ACK for some decoders in a dummy car. What I was warning about was someone inadvertently leaving the resistor in place and using the dummy car decoder on the same address as a motored decoder, because when the one is throttled up, so is the other and that is where the danger lies.

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On 29/04/2020 at 18:10, Mike Buckner said:

I've been thinking about doing this on my Hornby Class 40 with TTS.  Disconnect the TTS from the motor, but leave other connections intact, and Install a Zimo for motor control. Using 2 separate addresses. In my case, under computer control.

 

This would enable me to simulate the behaviour of prototype class 37 and class 40 English Electric locomotives, where the motor revs up and down periodically, especially when moving away from rest. Also it would enable a more effective simulation of starting a heavy load, where the engine revs strongly for a while with, initially, no movement, and then, a very slow gradual increase in speed. Finally, it would give a more effective simulation of coasting. None of these behaviours are convincingly manifested with the TTS decoder as is.

 

I'm now pondering fitting lights.
One decoder has forward and backward lights fitted to the No. 1 end, and nothing to the No. 2 end.
The other decoder has forward and backward lights fitted to the No. 2 end, and nothing to the No. 1 end.
Both decoders agree as to which is the No. 1 end, and which the No. 2 end.
When running light engine, both decoders have lights on.
When hauling a train, one decoder has lights off.

 

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Sounds to me like two decoders one for speed and the other for sound has to be the way forward for diesels as sound and speed have next to no relationship to one another, Lots of noise at lots of revs on starting, and  just about ticking over while running light engine or slowing down.  

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I don't know if any sound decoders do this already, but for a while I've thought that there should be an option for the motor speed & sound production to be controlled by entirely separate commands.

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The TTS diesels have, like others, the ability to be notched up or down/thrashed/idle using the allocated F key as well as automatically doing so as the throttle level changes. Much of course depends on the particular sound project as to how they respond to the throttle settings. 
 

Izzy

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8 minutes ago, Mike Buckner said:

I don't know if any sound decoders do this already, but for a while I've thought that there should be an option for the motor speed & sound production to be controlled by entirely separate commands.

 

Yes, its present.   Either in the form of manual notching (been around for as long as I can remember), or newer features such as "drive lock" (different names used for similar behaviour) in the higher end decoder makers offerings (where speed is held, and the throttle knob/buttons now alter engine noise settings).  And other methods implemented in various maker's decoders.    Whether the writers of sound projects exploit those features is a big "depends".   

 

 

 

 

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Thank you both for pointing this out. Somehow I overlooked this. I shall have to get a control unit with more function buttons!

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You can fine tune the notching transition points on a TTS diesel by altering the associated TTW CVs per the blurb. A bit like ice, sport and normal mode on your posh car.

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