sprogII flashing but no volts

[Jbees]

I'm new to DCC and have for the first time connected up a new SprogII to a test track and to my lap top running the latest DecoderPro. I have installed a new Lais 860021 in an old loco.

Both Sprog lights are on steady when powered up.

Putting the loco on the track changed nothing.

Pressing the identify tab in DecoderPro input page set Sprog flashing but no volts measured on the track or at the Sprog output.

The DCC Address field was populated with a 3 at an early stage before I checked for volts. Does that indicate the decoder was working at that point?

I have checked the decoder wiring against the Lais manual several times and it seems OK.

Can anyone suggest what is causing this? Is this a Sprog or decoder fault or something else?

Edited November 16, 2022 by Jbees
redundant word

[Nigelcliffe]

Sounds normal to me.  There are no volts on output except during very short bursts of data for reading a value (and I mean short: tiny fraction of a second).  

 

"Identify" attempts to match what it finds on the track with locos in your roster.  A new decoder is going to have address 3, so will match the first roster entry with address 3.   
"+ New Loco" will take you into the process which reads the decoder maker information to try to match it against correct decoder.     Try that, it should show attempt to read CV8, then CV7, and at least get somewhere towards suggesting a suitable decoder file.  

 

If your loco makes small noises, or small movements (can be very small, depends on loco and decoder), as data is read, then it is working correctly.    

 

 

[Crosland]

As Nigel says, it's a safety feature that power is on only when actually reading or writing CVs.

 

You can manually turn the track on using the power control in JMRI. This is useful if you want to use a throttle to test the loco after programming, e.g., test sounds or function mapping. If you have a long enough programming track, or a rolling road, you can run the loco up and down.

 

Andrew 

sprog-dcc.co.uk

[Izzy]

When you use the programing track to identify a loco I do find that sometimes it takes longer than you would expect. I also find I often need to press and hold a loco down on it to get a good enough connection for a 'read'. Because of the brief low power involved the wheels/track etc need to be really clean. Even then this helps.

 

When a loco is being read there should be a status in the bottom of the screen. Saying what is going on, reading cv so and so. This will be in red. Only when this has been successful will the dialog box highlight the list of decoders to choose from. You will need to pick one, click on it, for another dialog to open with a choice of how to program said decoder. I always choose 'comprehensive'.

 

To read a value is simple - 'read sheet' etc. To change value enter it in relevant box - it will change colour - and 'write' to sheet. Don't forget to save to roster to save the details.

 

Hope this helps,

 

Bob

 

 

Edited November 16, 2022 by Izzy

[Jbees]

Thanks Nigel and Andrew. Encouraged by your replies, I persevered and added some weight to the stripped down chassis plus a dose of switch cleaner to track, wheels and wheel contacts and bingo the loco grunted when I attempted write a minor change to the decoder. No more "no loco found on track" messages.

Does this problem mean that the package data is sent at a voltage much lower than the 14.5V supplied?

[Nigelcliffe]

No, it means the wheels or track were dirty :-) 

 

(If you dig around, you'll see the stupidly small and light locos that Izzy (above) and I build.  I've used a Sprog for 15+ years and its fine for sensing very small currents.   ).

 

 

 

[Crosland]

19 hours ago, Jbees said:

Does this problem mean that the package data is sent at a voltage much lower than the 14.5V supplied?

No, it uses the full DCC track voltage (a little lower than whatever power supply you use with the SPROG).

[Harlequin]

How are you measuring the voltage on your test track, @Jbees?

 

[Jbees]

Sorry for slow reply Nigel, I've been away from the fun stuff. I use a digital multimeter set to 20vdc to measure what i hope to be 12v. Battery is a bit flat though so I'll try again later when I've found a replacement.  John

[jamesed]

36 minutes ago, Jbees said:

Sorry for slow reply Nigel, I've been away from the fun stuff. I use a digital multimeter set to 20vdc to measure what i hope to be 12v. Battery is a bit flat though so I'll try again later when I've found a replacement.  John

If you are using a dc voltage setting on your meter then that's why you are reading zero volts.  DCC is not dc. You need to set your multimeter to read AC voltage.  The reading you get won't be accurate because dcc isn't a true ac signal.  In one polarity you'll get a higher reading than the actual output and the other way around it will be lower. The actual voltage will be somewhere between the two. 

[Harlequin]

Furthermore cheap DMMs can't handle the frequency of the DCC signal.

It's all explained here:

https://dccwiki.com/Digital_Multimeter

 

Edited November 21, 2022 by Harlequin

[Crosland]

58 minutes ago, jamesed said:

If you are using a dc voltage setting on your meter then that's why you are reading zero volts.  DCC is not dc. You need to set your multimeter to read AC voltage. 

It really depends on the meter. Some on DC will give an average. See https://www.digitrax.com/tsd/KB909/track-voltage-measurement-on-dcc-layouts-with-dire/ for a way to get a reasonable measurement using a DC meter.

 

58 minutes ago, jamesed said:

 

The reading you get won't be accurate because dcc isn't a true ac signal.  In one polarity you'll get a higher reading than the actual output and the other way around it will be lower.

There's no reason why that should be the case unless you have selected address 0 for an unchipped loco. Otherwise the DCC waveform is symmetrical and will measure the same either way round.

 

DCC is true AC, by the way, it's just not a 50Hz sine wave like the mains.