Page 1 of 2
DCC chips and their pin configuration
Posted: Wed Feb 26, 2020 4:42 pm
by IanS
I'm struggling to understand the differences between the 6-pin, 8-pin, 21-pin, 18-pin and 22-pin chips.
I understand that some have more functions and some come with either a stay-alive capacitor or the wires to use a stay alive capacitor/unit. I also understand that sound requires extra wires to leave the PCB.
I'm not, at present, interested in the sound options as I intend to by DCC Sound fitted locos if possible. The main reason for buying chips (with and without harnesses) is to update DC older locos, including a fleet of Pocket Rockets that are not DCC ready that I seem to have collected over the years and a few co-co and bo-bo's as well as a few HST 43's and 91's.
I'd be grateful is someone can explain the differences in a practical way as obviously I can see some differences such as the size of the chips and the number of pins.
Can someone explain why I should by 21-pin rather than 8, or 6-pin decoders, or NEXT18 etc? What should be governing my choice (apart from price and amperage - which needs to be as high as I can find).
Re: DCC chips and their pin configuration
Posted: Wed Feb 26, 2020 5:51 pm
by Rog (RJ)
8 pin are the easiest to fit in many non DCC ready locos. You can, if you want to, fit an 8 pin socket first so that decoder replacement is easier if you should ever need to. Some loco don't have enough room to fit a socket though and direct wiring in would be used. 6 pin decoders can be similarly fitted but most of these don't have wires attached and you may need to solder wires direcly onto the decoder pins.
All other types of decoder fitments are really best used with a socket that has been fitted by the manufacturers onto a PCB (Printed Circuit Board).
There is also a 4 pin decoder that is used exclusively by Hornby in a few locos. These are just their standard R8249 decoders but fitted with a 4 pin plug and only 4 wires instead of the normal 9 wires that are used with the R8249.
Re: DCC chips and their pin configuration
Posted: Wed Feb 26, 2020 6:39 pm
by IanS
I've already fitted a few 8-pin sockets ready for 8-pin decoders. I was wondering if 6/4-pin would do the same job. I understand 21-pin ones have more functions such as internal and directional lights and cab lights as they have more 'wires'. None of the extras would be needed. Soldering onto pins won't be my route.
Re: DCC chips and their pin configuration
Posted: Wed Feb 26, 2020 10:53 pm
by Ron S
Re: DCC chips and their pin configuration
Posted: Thu Feb 27, 2020 9:45 am
by IanS
Thank you Ron S, but the document isn't really helpful as it is a technical one and which pins do what isn't the information I was after. (As an aside, the document looks like a poor translation into English with at least a few errors still in it.)
From the replies so far, I have gained that the number of pins on the decoder isn't significant to me if I wish to not use extra features like lights etc. The 21 pin one allows for sound, again not needed by me on my Pocket Rockets.
Re: DCC chips and their pin configuration
Posted: Thu Feb 27, 2020 12:45 pm
by teedoubleudee
IanS wrote: ↑Thu Feb 27, 2020 9:45 am
Thank you Ron S, but the document isn't really helpful as it is a technical one and which pins do what isn't the information I was after. (As an aside, the document looks like a poor translation into English with at least a few errors still in it.)
From the replies so far, I have gained that the number of pins on the decoder isn't significant to me if I wish to not use extra features like lights etc. The 21 pin one allows for sound, again not needed by me on my Pocket Rockets.
In theory a basic DCC control chip really only needs four pins. Two inputs from the wheel pick ups supply the power for the chip and motor speed request. And two connected to the motor to provide the required DC volts to drive it.
Re: DCC chips and their pin configuration
Posted: Thu Feb 27, 2020 1:21 pm
by yelrow
I really must get round to grasping the nettle, and removing a body or two from my locos to investigate possibilities. The only locos i have ever removed bodies from , regularly are 3 rail Dublo ones, to remagnetise , or fit new carbon brushes. I did look at a couple of DCC ready loco instructions, but once they mentionned, speedometer cables removal, i gave up.
Re: DCC chips and their pin configuration
Posted: Thu Feb 27, 2020 4:59 pm
by Brian
IanS wrote: ↑Wed Feb 26, 2020 4:42 pm
I'm struggling to understand the differences between the 6-pin, 8-pin, 21-pin, 18-pin and 22-pin chips.
I understand that some have more functions and some come with either a stay-alive capacitor or the wires to use a stay alive capacitor/unit. I also understand that sound requires extra wires to leave the PCB.
I'm not, at present, interested in the sound options as I intend to by DCC Sound fitted locos if possible. The main reason for buying chips (with and without harnesses) is to update DC older locos, including a fleet of Pocket Rockets that are not DCC ready that I seem to have collected over the years and a few co-co and bo-bo's as well as a few HST 43's and 91's.
I'd be grateful is someone can explain the differences in a practical way as obviously I can see some differences such as the size of the chips and the number of pins.
Can someone explain why I should by 21-pin rather than 8, or 6-pin decoders, or NEXT18 etc? What should be governing my choice (apart from price and amperage - which needs to be as high as I can find).
Hi
If you're updating a good running DC none DCC Ready loco (It doesn't have a DCC socket) then opt for a 8 pin decoder or one sold without any socket and just leads and hard wire the decoder in place. Some users fit an 8 pin socket of their own if there is room to allow later decoder changes to be made more easily.
If your you're going to fit a decoder to a DCC Ready loco then because it is DCC Ready it will have a DCC socket factory fitted. What type of socket will depend on the make and type of loco, so you then obtain a decoder that simply plugs into the socket proved 4, 6, 8, 21, Plux or Next etc.
Note: 6 pin, 21 pin, Next and PLUX decoders do not normally have any wires and are a direct push on fitting. 4 and 8 pin generally have wires. Some 8 pin are sold as push on direct fitting and these have no wires.
Re: DCC chips and their pin configuration
Posted: Thu Feb 27, 2020 5:11 pm
by IanS
Thank you for the replies. It seems the choice is made for me with DCC ready and for those that are not the choice is 8-pin with our without socket but with harness (or 4-pin).
Re: DCC chips and their pin configuration
Posted: Thu Feb 27, 2020 5:29 pm
by Brian
Just remember these main facts when purchasing a decoder...
A) Current to motor - ideally 1.0Amp or more.
B) Size of decoder - It has to fit the space available.
C) Number of Functions. Typically this will be 2, 3 or 4 with some decoders offering 6 or more functions, but these tend to be direct plug in type.
You can get a 21 pin to 8 pin convertor with leads, but again space taken up is the governing factor.