Locos running the wrong way around

[Gazah]

Morning!!!

anyone help me with how to change the default direction on locos, have 2 which go in reverse when set in RM to go forward

[Teedoubleudee]

Google "cv29 calculator"

[96RAF]

Select reverse loco direction in main setup screen.

[Chrissaf]

I'm fairly certain that if you "reverse loco direction in main setup screen" that this is a global RailMaster command so not only will you reverse the direction of the two affected locos you will also end up reversing the correctly operating locos as well. In order to reverse the direction of just individually selected locos you need to adjust the value of CV29 for each affected loco.

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The easiest way to do that is as follows (saves you Googling):

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Put your loco on the programming track connected to the e-link programming track output.

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In RailMaster (RM) click the "Set up locomotives" button. The icon with the little steam engine next to the cog at the top left hand side of the screen.

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In the pop up 'locomotives screen' click the locomotive settings ' i ' icon in the bottom left hand side, a 'Locomotive CV Settings' pop up will appear.

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In this window click the Green tick 'Get CVs' icon (bottom right hand side of screen).

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RM will now start reading all the CV's of the loco. This may take some time so be patient. If the reading process returns odd values such as a high number of 255 values or keeps giving 'error retrying messages' then cancel the reading task (using the pause ' II ' button) and disconnect the main track from the e-link then try again with ONLY the programming track connected to the e-link. In fact I would tend to do this first anyway just to be 'belt 'n' braces'.

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Once the read CV's process has completed successfully look in the list for the value of CV29. Take a mental note of whether this number is 'odd' or 'even'. If odd, then subtract 1 away from it (for example 1 becomes 0, 3 becomes 2, 7 becomes 6 etc). If the number is 'even' then add 1 to it (for example 0 becomes 1, 2 becomes 3, 6 becomes 7 etc).

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Now looking at the CV list. In the row associated with CV29 replace the old number with the new number arrived at in the step above.

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With the new number for CV29 entered in the value column, click the 'Write CV' button. It is the 'pencil' icon on the far left hand side of the bottom row.

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Once the write process is complete (should only take a few seconds, the decimal number you have entered should be re-read automatically by RM back into the CV list as a confirmation that the change of CV number has been accepted successfully) save and exit the pop up screens back the to the main RM screen.

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Replace your loco on the main track with the track re-connected, if disconnected earlier, and it should now run the opposite way from before.

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Explanation:

So what am I doing by either adding or subtracting the decimal number 1 from the CV29 value I here you ask. CV29 represents an eight bit binary word (Bit 7, Bit 6, Bit 5, Bit 4..........Bit 0). Each of the 8 bits controls a different decoder function. Bit 0 controls the default loco direction. Bit 0 in binary is decimal 1. Thus, if CV29 is an odd decimal number, then Bit 0 must be binary 1 and if CV29 is an even decimal number, then Bit 0 must be binary 0. Therefore by either adding decimal 1 or subtracting decimal 1 from the CV29 decimal number you are toggling the binary value of Bit 0 between binary 0 and binary 1 and changing the default loco direction configuration. For Hornby R8249 and R8215 decoders the default for CV29 Bit 0 is binary 0.

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Further reading for anybody who wants to know a bit more about Binary to Decimal conversion.

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Bit 7 represents decimal 128 (Bit 7 is the left most Bit in the Binary word)

Bit 6 represents decimal 64

Bit 5 represents decimal 32

Bit 4 represents decimal 16

Bit 3 represents decimal 8

Bit 2 represents decimal 4

Bit 1 represents decimal 2

Bit 0 represents decimal 1 (Bit 0 is the right most Bit in the Binary word)

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Thus:

binary word '00000000' is decimal 0

binary word '00000001' is decimal 1

binary word '00000010' is decimal 2

binary word '00000011' is decimal 3

binary word '00000100' is decimal 4

binary word '00000101' is decimal 5

and so on until

binary word '11111111' is decimal 255

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End of course test:

What is the decimal number represented by binary 01001100 - answers on a 'post card'.

[Chrissaf]

A terminology correction for my post above. I wrote "CV29 represents an eight bit binary word". This should read "CV29 represents an eight bit binary Byte". Wherever the text "word" appears in the post, this should be read as "Byte". It is multiple 'Bytes' that make a 'word'.

[Gazah]

A terminology correction for my post above. I wrote "CV29 represents an eight bit binary word". This should read "CV29 represents an eight bit binary Byte". Wherever the text "word" appears in the post, this should be read as "Byte". It is multiple 'Bytes' that make a 'word'.

Thanks for the clear simple instruction all working properly now.......... Gold star for teacher!!!!!!

[Chrissaf]

Glad it's sorted. Nice to occasionaly get a thankyou, not everybody does you know. Just to satisfy my curiosity were your CV29s odd or even before you changed them?. If they were even, that infers that the loco motors were wired 'back to front' at the factory.

 

Oh and just to note. If you don't want the replicated yellow box text to appear in your reply, don't click the BLUE reply button. Just put your reply text in the big white box at the bottom of the page and click the GREEN reply button.

[Chrissaf]

Oh and the answer to my end of course test, for anybody who has tried to answer it, is 76.

[Gazah]

Both locos were at 000 hope that answers your curiosity, the locos are both circa 1978 have just had the retro fitted 

[Teedoubleudee]

Both locos were at 000 hope that answers your curiosity, the locos are both circa 1978 have just had the retro fitted 

 

Changing it to 6 should improve speed control then (128 steps)

[Gazah]

Both locos were at 000 hope that answers your curiosity, the locos are both circa 1978 have just had the retro fitted 

 

Changing it to 6 should improve speed control then (128 steps)

Do you mean CV29? Would I then set accelerate/decelerate to zero?

[Chrissaf]

Ahh, that makes everything crystal clear........being brand new 'after market' fitted decoders, the CV29 value had not been set at all. Hence the zero value. The person doing the upgrade had a 50/50 chance of getting the motor wires the right way round. Obviously in your case, he got them the wrong way round compared to the accepted norm as zero is deemed as being an even number. Thus CV29 Bit 0 was binary 0, therefore the loco direction should have been correct.

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If your after market decoders came with any instructions, the instructions should advise what the function of the other seven Bits in CV29 are (not all of them are used). It may be that you might benefit from tweaking these values too.

[Teedoubleudee]

Here is the cv29 calculator I suggested you google in my first reply (sorry didn't have enough time to type Chris's reply ;-). It's quite informative and saves you understanding binary arithmatic.

Chris is right about the 50/50 chance of getting it the right way round so cv29 is very useful - I've installed 4 decoders so far and got half of them wrong!

[Chrissaf]

Gazah, please ignore TWD advice, he has not fully read your original post. If you change the CV29 value to 6 then you will revert your loco direction back to being reversed again.

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To explain.

CV29 value 6 is binary 00000110 (Bit 7.........to........Bit 0)

 

the CV29 Bit 0 controls loco direction (default is 0, but in your case it needs to be 1 to correct a motor wiring error)

 

the CV29 Bit 1 controls the speed steps for acceleration / deceleration (smoothness). CV29 Bit 1 Binary 0 = 14/27 steps and CV29 Bit 1 Binary 1 = 28/128 steps

 

the CV29 Bit 2 controls analogue support. CV29 Bit 2 Binary 0 = digital only and CV29 Bit 2 Binary 1 = digital and analogue control is on i.e you could control the DCC loco on a DC layout.

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Therefore CV29 value 6 would give:

Loco direction normal (but in your case, because of the miswired motor your loco direction would be reversed).

Acceleration steps would be 28/128

Analogue support would be on.

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If you did want 28/128 steps and the analogue option on, then your CV29 value would need to be 7 not 6 because you need to have your default loco direction reversed.

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If you compare this reply with the CV29 calculator link given in TWD reply, then everything should be as clear as crystal.

[walkingthedog]

All due respect to your amazing knowledge byte wise but is all that info required to change the direction of a loco. It's enough to make somebody thinking of going over to DCC run a mile. 

 

Very interesting though, it's bringing a lot of long forgotten things back to me. We had to learn the basics of the world of binary when they introduced secondary radar transponders to civil aircraft in the 70's. 

[HFM]

Does railmaster do cv29 calcs for you once you have read cvs you either right click with your mouse or double clic cv 29 and up pops a window then you just uncheck or check little boxes

[Chrissaf]

Yes WTD I agree it is a very long winded reply, but I believe in teaching from 'first principles'. If you understand the basic theory then it can be applied to multiple scenarios. I did have a stint (career wise) in a training capacity.

[Chrissaf]

Does railmaster do cv29 calcs for you once you have read cvs you either right click with your mouse or double clic cv 29 and up pops a window then you just uncheck or check little boxes

 

I don't recall seeing that feature in the basic RM. Might be in the pro version - I don't know. Anybody else know for sure?

[walkingthedog]

Yes WTD I agree it is a very long winded reply, but I believe in teaching from 'first principles'. If you understand the basic theory then it can be applied to multiple scenarios. I did have a stint (career wise) in a training capacity.

I can tell that.  Maybe we need a Technical DCC section for those who want to know more.  If I asked the question about changing the loco direction and saw all that I'd go out and buy a DC controller. 

[Teedoubleudee]

Sorry, my confusion, there is a similar thread running regarding CV29 and the default setting of 6. and I mixed the two up.

If your loco was running the wrong way with CV29 set to zero then setting it to 7 will give you the correct direction + 128 speed steps + ability to run loco on a DC layout.

[RDS]

.... It's enough to make somebody thinking of going over to DCC run a mile... 

I agree entirely wtd.  I mentioned a few days ago how complicated an answer to a simple question had become and I mentioned a few weeks ago on another thread that the answer made DCC seem complicated, when it isn't.

[HFM]

Page 71 in the manual explains all

[Teedoubleudee]

Does railmaster do cv29 calcs for you once you have read cvs you either right click with your mouse or double clic cv 29 and up pops a window then you just uncheck or check little boxes

 

Yes it does (pro version) Double Click in the value box and a pop up tells you what to do.

Didn't realise that, only upgraded very recently.

[Teedoubleudee]

Page 71 in the manual explains all

 

Who reads manuals??  <smiley face>

[HFM]

Me about 5 mins ago dont think it is just the pro version can remember using it a while back