Newbie - Maybe a stupid question

[david128]

Hi there - I'm new to all of this DCC stuff - so apologies if this is a stupid question

 

I've just received a sprogIIv3 and I'm trying to convert my first loco to DCC (Hornby class 56 R2477A)

 

I have wired a brand new Hornby R8249 decoder just to right & left rail, to see if I can talk to it from DecoderPro3, before I connect the motor

 

So, 

 

I can talk to the Sprog from DecoderPro3

 

I can see (with a meter) that I get about 11v AC on the rails when I switch power on from decoderPro

 

I have created a new loco - address 3

 

I've checked continuity to the decoder pins 4&8

 

But - DecoderPro fails to recognise any loco

 

I'm assuming the decoder should still communicate on DCC without the motor connected?

 

Any help welcome

 

 

[smokebox]

It might just work once the motor is connected. Many controllers and programmers (but not all, I think) will look for an "Ack"  (acknkowledgment) pulse being returned from the decoder before the programming/reading process starts and the vast majority of decoders won't return the Ack pulse if there is no motor connected.  An exception to this rule is "funtion only" decoders which have no motor connections.

[david128]

It might just work once the motor is connected. Many controllers and programmers (but not all, I think) will look for an "Ack"  (acknkowledgment) pulse being returned from the decoder before the programming/reading process starts and the vast majority of decoders won't return the Ack pulse if there is no motor connected.  An exception to this rule is "funtion only" decoders which have no motor connections.

 

Yep - I can see that DecoderPro is looking for an ack - so many thanks for that - I'll try connecting up the motor - job for tomorrow night now though

[Adrian Wintle]

The ack is generated by pulsing the motor (loading the bus), so without a motor attached there is no ack. Note that this doesn't mean that the decoder hasn't been programmed, just that the control station hasn't seen a response. Function-only decoders tend to not have an ack pulse - programming takes, but the control station never knows it.

 

Note that this changes if using Railcom, but that isn't the case in the OP's scenario.

 

Adrian

[david128]

ok - now wired the motor - guess what - it works    & it moves (off the end of the track I'm using for programming - guess I need to get some buffers)

 

Thanks for all the advice

 

Have another (possibly also stupid) question now

 

I'm trying to wire up the 'grain of wheat' bulbs (at least that's what I think they are) to the functions outputs

 

But the front bulb I wired didn't light up when set to forward or reverse - wired between 7 (blue) & 6 (white) 

 

So - I disconnected it & put a meter across 6 & 7 - expecting to see about 12v dc when in forward (but tried reverse also) - nothing

 

I also tried between 7 & 3 (function 3) - now according to JMRI thats mapped as function 1 - and I do see 12vdc on that when I enable function 1 from JMRI throttle

 

According to Decoderpro3 - function 1 (white) is F0/ forward & function 2 (yellow) is F0/reverse

 

So - I don't quite understand why white (& yellow) don't appear to work, when green (function 3) does

 

Should I expect function 1 (white) to be active (bulb on) if the direction is set to forward even if the motor is in idle?

[david128]

ok - it was a stupid question

 

You have to turn the lights on - Doh

 

I actually though F0 was used to set the direction - but it's apparently used with the direction

 

So - hopefully tonight will complete the wiring & put the body back on!

[david128]

All wired up now & body back on - still working!

 

Thanks for the advice