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Author Topic: Fitting 2 decoders  (Read 550 times)

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Offline Philip.

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Fitting 2 decoders
« on: May 01, 2018, 08:27:26 am »
I have a Farish 2 car class 108 that I want to fit decoders to, am I right in thinking that I fit one in the power car, program it, then remove it and fit it in the dummy car, then fit the second one in the power car and program that one and that then should be ready to go?

Cheers  :helpneededsign:
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Offline cjdodd

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Re: Fitting 2 decoders
« Reply #1 on: May 01, 2018, 08:37:06 am »
Yeap you got it.

The reason you need to do this is the DCC chip needs a motor load on it.

Offline rhysapthomas

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Re: Fitting 2 decoders
« Reply #2 on: May 01, 2018, 08:38:23 am »
Yes that is how i did my Class 108

Offline ntpntpntp

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Re: Fitting 2 decoders
« Reply #3 on: May 01, 2018, 08:47:17 am »
Yeap you got it.

The reason you need to do this is the DCC chip needs a motor load on it.

The load is required to create an acknowledgement pulse back to the programmer. You can program a decoder without a load but the programmer will show it as a fail and of course you cannot read CVs back to check. On balance it's easier to fit the decoder in the loco or a decoder tester to create a load.
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Offline Steven B

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Re: Fitting 2 decoders
« Reply #4 on: May 01, 2018, 08:59:09 am »
As ntpntpntp said, the motor is used as a load to create the acknowledgement. Decoders can be programmed without a motor attached (otherwise function only or accesspry decoders couldn't be programed).

It's also possible to program both decoders at the same time if your programming track is long enough to hold the whole DMU.

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Online njee20

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Re: Fitting 2 decoders
« Reply #5 on: May 01, 2018, 09:20:29 am »
Yes I was going to say what Steven said - if you can put both coaches on your programme track then you can do both together. Slightly easier.

Offline Philip.

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Re: Fitting 2 decoders
« Reply #6 on: May 01, 2018, 12:04:26 pm »
It will fit on the programming track no problem, doing both together is definitely preferable  ;)
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Online Lindi

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Re: Fitting 2 decoders
« Reply #7 on: May 02, 2018, 12:41:33 am »
Another way is to solder a 100 ohm resistor across Pin 1 & 2 of the dummy trailer. I have done this as I have a different DCC code for each end. This allows me to control the lights separately when I have two DMU's running together   

Offline Philip.

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Re: Fitting 2 decoders
« Reply #8 on: May 02, 2018, 07:59:39 am »
Decoders fitted (first time i've done it  :D) and all working like a dream. The only stressful part was removing the bodies, fiddly as heck  :o
still trying to get the body off my 350!!!
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Offline Nigel Cliffe

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Re: Fitting 2 decoders
« Reply #9 on: May 02, 2018, 08:47:55 am »
Another way is to solder a 100 ohm resistor across Pin 1 & 2 of the dummy trailer. I have done this as I have a different DCC code for each end. This allows me to control the lights separately when I have two DMU's running together

Sort-of OK in a maybe-ish sort of way.   

Yes, it allows programming. 
But, if you don't make further adjustments, its also a potential electric heater inside a small plastic model which isn't such a good idea.    With 15v DCC track voltage, and the throttle for that loco accidentally raised to "max", the resistor could be seeing 14v DC, and thus putting out ~2W of heat.  Now that's not massive, but it is still significant (there are 12W soldering irons around for model use). 

So, either do the resistor as a temporary measure, then remove it.  Or (slightly less safe, but still a big improvement), alter the speed curve on the decoder on the dummy unit so the max-speed is almost zero, and thus the heating will be a tiny amount.   Or fit a heat sink in the unit to spread out the heat generated. 


You can control the lights separately in each half of a two-car unit by function mapping changes (CV changes) to the decoders.  For example, set the trailer car to have the lights controlled by a different key, or even different keys for "front" and "tail" lights.   The exact changes possible vary on brand of decoder fitted, though the minimum function mapping in the most basic of decoders will allow something to be done. 



Offline daversmth

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Re: Fitting 2 decoders
« Reply #10 on: May 14, 2018, 07:31:11 pm »
Just to add,  because the trailer car decoder only controls the lights you can use a cheaper one than in the power car which controls the motor.

It is discused here
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Offline Bramshot

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Re: Fitting 2 decoders
« Reply #11 on: May 15, 2018, 10:05:30 am »
...and to add to daversmith’s comment, you might also be able to use one that has popped for motor drive, but still works lights, so don’t throw those away!

Offline Philip.

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Re: Fitting 2 decoders
« Reply #12 on: May 23, 2018, 11:14:03 am »
I need 3 x 6 pin decoders for my Class 350, are these OK https://www.aliexpress.com/store/product/DCC-LOCO-DECODER-WITH-6PIN-NEM651-FOR-MODEL-TRAIN-with-stay-alive-wires-LaisDcc-Brand/2977030_32816241710.html?spm=2114.12010608.0.0.a142498cHnl4R6 from LaisDCC and what are the blue and black wire for please, they're not on the Zimos  :)
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Offline Carmont

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Re: Fitting 2 decoders
« Reply #13 on: May 23, 2018, 11:24:48 am »
I think from reading customer reviews on the Lais chips, they are fine for secondary purposes, such as lights in the non-powered end of a DMU, but not so great for motor control.

At a guess, might the extra wires be for a stay-alive capacitor? Just a guess.

Online njee20

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Re: Fitting 2 decoders
« Reply #14 on: May 23, 2018, 11:39:22 am »
Yep, extra wires are for a capacitor.

I use them for function use, and find them spot on. I don't, personally, think they're all that good for motor use Zimos offer far better slow speed control, but I've not spent ages fiddling with the LaisDCC ones. I got a few new ones last week so I may try one again, there was an inference the latest firmware was better.

 

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