Incorrectly installed loco decoder

[NormanQ4]

Will damage occur if an 8 pin loco decoder is inserted the wrong way around, or would the loco just fail to function?

Even using a magnifying glass to look at the socket and the blanking plug I am unable to determine which is pin1.

[The son of Triangman]

The orange wire on the decoder goes to pin 1. Pin 1 is usually marked on locos on the circuit board near the socket with a "1". The Blanking plug is marked with a "1[" symbol as pin one, the word DC will be at the top of the blanking plug with pin one on the blanking plug at the left handside. At the botom of the blanking plug will be the code "1606-X001 (E)".

The loco would fail to function, you could blow the decoder at worst case but this is unlikely.

[NormanQ4]

I should have mentioned I am using a Hattons NEM 652 and a Bachmann Fairburn loco.

The decoder only has one purple wire.

As I said before I am using a magnifying glass and now a headlight for extra brightness and can't see any of the markings that you refer to, either on the decoder,blanking plug or the loco.

[96RAF]

Look at the wiring from the loco to the 8 pin decoder socket to give you a clue. The wheels pickup track power and this is led to the decoder socket. Wires also lead from the socket to the motor. Normally these wires will be red and black or just black so tracing them is the only way to determine which is which.

Convention is for pin 1 (make this top LH corner) to be the motor positive (decoder orange wire) and the pin next to it on the socket short side (top RH corner) to be the right side wheel pickup (decoder red wire) at the other end of the socket (bottom LH corner) on the same side as pin 1 is the left wheel pickup (decoder black wire) and at the other corner (bottom RH) the motor negative (decoder grey wire). Placed on a DC track left wheels to left rail a loco would drive forward. 

As the track pickups and the motor connections are at opposing corners, you can visualise if you put the decoder in the wrong way round all you are doing is transposing the pickup direction (left to right) and the motor direction (pos to neg), so it will still work and should not damage the decoder. If it were a DC track then the loco would now drive backwards.

If there are lights fitted then it is a tad more complex but equally safe, except the lights won't work if the deocder is reverse plugged.

The lights (functions F0 whte and yellow wires and F1 green wire) connected to 3 of the inner 4 socket pins with function power (blue wire) connecting to the 4th inner pin. Connected correctly power leaves on the blue pin and is switched by either of the other 3 pins. Incorrectly connected power is put on the green pin which can only be switched by the blue pin but in reverse polarity for leds so nothing happens to the lights.

The purple wire is to switch an additional function in conjunction with the blue wire and is connected apart from the loco socket.

[Rog RJ]

No damage should occur.

 

The worst thing that normally happens if the chip is fitted the wrong way round is that any lights that atre fitted won't work but the motor will respond correctly. Turn the chip round so that it is fitted the right way round and everything should work as normal.

[NormanQ4]

Thanks to all for your responses.

Incidentally I don't have all these coloured wires, only red and black on the motor and purple on the decoder.

[96RAF]

Looking on Hattons website it appears you have a direct plug decoder, which only has a purple wire coming from it and no harness such as most 8 pin decoders have.

Hattons decoder picture here...

/media/tinymce_upload/Capture9.PNG

 

I would also make sure that the decoder insulation sleeve is not stopping it plugging in correctly.

To set up the lighting I quote from the manual that should have come with the decoder, if not you can download it from their site:

Using and setting up lighting:

The wires that control lighting are Blue – this is the common positive ground and should be connected to

ALL lights. White – this is the front headlight wire. Yellow – this is the rear light wire. Green – this is a spare

function, often used for drivers cab or a flickering firebox and Purple, which can be used for any other

function you choose.

By default, front white and rear yellow light wire are both turned on by function 0 or the “light” or “headlight”

function button. Green is usually turned on with function 1 and purple with function 2.

To change WHEN a light function is on (directional or constant)

CV49 controls the White wire (Headlight). Default is 0

Set it to 0 for only on forward, set it to 16 for only on reverse or 32 for always on.

CV50 controls the Yellow wire (Tail or reverse light). Default is 16

Set it to 0 for only on forward, set it to 16 for only on reverse or 32 for always on.

CV51 controls the Green wire (Aux1 or F3). Default is 32

Set it to 0 for only on forward, set it to 16 for only on reverse or 32 for always on.

CV52 controls the Purple wire (Aux2 or F4). Default is 32

Set it to 0 for only on forward, set it to 16 for only on reverse or 32 for always on.

[96RAF]

Norman - there is an answer coming, but its held for moderation as it has a picture of what I think is your direct plug decoder.

In the meantime this is shown on the decoder page:

Pin one is located by botton of the H on the decoder. There is also a number 1# at the bottom of the letter on the plastic sleeve.

[Flashbang]

Will damage occur if an 8 pin loco decoder is inserted the wrong way around, or would the loco just fail to function?

Even using a magnifying glass to look at the socket and the blanking plug I am unable to determine which is pin1.

Inserting an 8 pin plug 180 degrees out of normal will not cause any electrical harm at all to the decoder or the loco or the DCC system!!  

If you insert an 8 pin plug in the wrong way around (180 degrees out) the loco will still run, but may run in the opposite direction to that selected. On a loco with working lights the lighting will not work. These are always a good indication that the 8 pin plug has been fitted the wrong way around.

If your decoder has the 8 pins fitted onto the decoders circuit board then it's a direct fitting type which again doesn't matter if its plugged in the wrong way around.  The Purple lead (wire) is found on four function decoders and as the 8 pins are already used the fourth function lead (Purple) is always supplied as a free ended wire. If not required coil up and ensure its free end cant touch anything.

[Flashbang]

In addition to the above... If the 8 pin decoder is a direct fitting type (8 pins on the decoders circuit board) or has an 8 pin plug on the leads and its has additionally 3 free ended wires, one Purple (which is as above and is function 4) plus normally a blue and brown wire, these latter two are used for connecting to a special Stay Alive capacitor unit that allows the loco to keep moving a little when wheel to rail power connection is lost momentary.

[poliss]

From Mr. DCC's University ref. NEM-652 (NMRA Medium) 8-pin socket.

"This connector is NOT POLARIZED. What that means is that you can plug it into the socket in either direction. The good news is that, except for the green pin discussed above, there will be no damage to either the decoder or the loco if you reverse it. If you plug it in backwards, the lights won't work and the loco will run backwards. Just rotate it a half-turn and plug it in. This "no damage" is not true if you plug it in offset."

http://www.mrdccu.com/curriculum/ready.htm

[The_Seagull]

evening all...........cant beleive that the majors allow this kind of confusion to continue....i am sure that most of us just want to be able to follow, clear, simple and concise instructions, that allow those of us with no interest in electronic wizardry to quickly fit a decoder, without harming either the chip or the loco.....

is it beyond the wit of these people to design a decoder, that, err....will ONLY fit one way round/up.....?

might make some of us a little more confident, opening em up...

thats my view anyway.........................

[96RAF]

evening all...........cant beleive that the majors allow this kind of confusion to continue....i am sure that most of us just want to be able to follow, clear, simple and concise instructions, that allow those of us with no interest in electronic wizardry to quickly fit a decoder, without harming either the chip or the loco.....

is it beyond the wit of these people to design a decoder, that, err....will ONLY fit one way round/up.....?

might make some of us a little more confident, opening em up...

thats my view anyway.........................

Although the 'spec' says the socket is not alignment critical (actual term - polarised) it would make very good sense to have a keyway or similar on the plug/socket arrangement to ensure a one way only fit. 

[poliss]

It's the NMRA that set the standards for how decoders fit.

[choralc]

Why can't they do what they do with camera cards (SD card is it)?

 

A little bit cut off the corner off the socket and the decoder or put a star, arrow head, dot or whatever - coloured orange or not in the corners.

 

Some manufacturers do, some don't or is there inconsistency within manufacturers products?

[Michael_A]

Sorry to say I do get frustrated with the rambling on this forum, which is actually why I don't bother much with it anymore. (And no wonder novices get confused)

 

The original post needed just one reply: "No, it wont harm the decoder, they are designed in such a way to prevent this happening. If plugged in the wrong way around then it will simply not function, so if this is the case, just remove the decoder and plug it in the other way around"

[Graskie]

There is a caveat to your suggested answer, though, Michael. You said, "If plugged in the wrong way around then it will simply not function." You should have said that all functions will still work apart from direction of travel and any lighting." This has already been stated by several other contributors. So even your suggested short and to-the-point approach to answering is not correct, certainly in this case. A lot of these issues need a bit of drawing out to get to the truth.

 

I'm afraid a lot of these things are perhaps not as simple to answer as you might wish, and adding any additional related information never does any harm, in my opinion. You only need to read what you want to. It would be a shame if you left the forums because answers are not as  concise and to-the-point as you would wish.

[poliss]

Can't do that choralc. It would mean old decoders wouldn't fit in new sockets. A pity the NMRA didn't think of that at the beginning.

As Graskie says Michael. If a decoder is plugged in the wrong way round it will still function. It's just that the lights won't work and it will run the opposite way than expected.

[choralc]

Poliss I was thinking of only the corner being cut and not a recess in the body so that even a current rectangular decoder could be fitted.

[96RAF]

Poliss I was thinking of only the corner being cut and not a recess in the body so that even a current rectangular decoder could be fitted.

 

You could easily DIY that corner cutting mod Ch (good simple idea by the way - the corner you cut off the plug you glue onto the socket), but it would be a case of stable door - bolted horse as to get to the correct configuration stage you have had to work it out already.

[choralc]

That's right enough but they could do all new decoders and sockets 'keyed'.

[96RAF]

That's right enough but they could do all new decoders and sockets 'keyed'.

 

Agreed and if the male key was on the socket with the female bit on the plug then they could make the switch and be backward compatible from the decoder side at least.

 

I'm thinking a plug with a notch or a corner missing would still fit an old socket whilst only fitting one way on a new socket.

[poliss]

You'd have to make the new decoders and sockets a bit bigger so that you could add an extra keyed bit.

The problem with that is that you want a decoder to be as small as possible.

It might have been better if the JST 9 pin socket had been adopted as the standard for UK decoders.

There would be no loose purple lead and are impossible to plug in backwards because they are keyed.

[mwchivers]

 hi all

Sorry if this has been covered before.

I am new to DCC and am looking to hard wire DCC chips into Thomas the Tank, and Percy for my sons track.  Im confident on doing this but i was wondering,

you have 2 wires on the decoder which go to the left and right side pickup within the Loco.  My question is, If the Loco was taken off the track and turned around to run in the other direction, would the Loco and the chip be ok and still operate, or would this cross the streams and desytroy both.

thanks

[Howbi]

Hi mwchivers and welcome to the Forum..........your locos and decoders will be absolutely fine whichever way round you place them on the track............the only thing to deal with is the contoller will show it going the other way but it is easy to get used to so have fun.... 😀....HB