ABC Braking problem

[Lester1707817999]

I am having difficulty in getting ABC braking to work I have tried every combination of cv27 along with cv125 126 and 127.

Braking works on all my locsound 4 & 5 decoders and also on the only sapphire decoder.

I have tried resetting the decoder and different profiles nothing seem to work. Could it be a faulty decoder or is the decoder is not compatible with the prodigy advanced sq

Lester

[Fishmanoz]

Lester, I’m assuming it’s an HM7000 decoder? Which one in what?

I’ll let those with better knowledge answer ABC problem but HM7000 decoders are compatible with NMRA compliant controllers and that will include your Prodigy.

[96RAF]

Although ADCC/ABC is a Lenz invention, not all ABC modules are the same and not all decoders work the ADCC ‘system’ the same.

To start with the module when placed in a cut rail makes the other rail more positive, and the instructions and settings for some decoders are vague about which rail is being monitored, with Lenz ruling the monitor rail should be the right rail in direction of travel (drivers view), hence the module is placed in the left rail.

ABC has been fiddled with during testing so make sure you are using the latest sound profile, by way of overloading the new one onto the existing profile. No need to remove the old one.

A simple way to check if you have your rail selection wrong is to select both rails. The decoder will look at both.

CV27 sets the mode - stop on brake or distance - with or without shuttle. Choice of four.

Once set, then go to CV125 which sets the detected rail.

CV126 sets the stop time and CV127 sets the stop distance.

Distance has to be assessed by test as each loco is different, so a hard cm/inch dimension cannot be set, simply an equivalence number for that logo. It is suggested a test table is drawn up for all your ABC locos for reference.

Stopping can only be either on brake or on distance.

It has been noted that the HM7K decoders are very sensitive to track voltage change due to grubby rails, etc and when set for ABC can react outwith the designated section.

Please report back if the two rail method works and also what ABC module you are using.

[Lester1707817999]

Thanks for replying I have tried everything you suggested Two or three times I have been using ABC since introduced with the ESU loksoud 4 decoder, and never had a problem with them, even the Hornby Sapphire works well. I can read and write the CVs I tried this via Bluetooth from the Prodigy on the programming track and on the main, is has if the decoder does not recognise the change although the CV has changed when read back.This is why I think I.either have a faulty decoder or there is some type of incompatibility with the Gaugemaster prodigy.

I have always used 5 diodes in series and 1 reversed across the 5.

[96RAF]

The 5 diodes in series forms a circle and you tap off either side of any one. No diode is reversed.

Extract from the HM7K decoder manual…

[96RAF]

Tell me exactly what is not happening and what you have set up to happen.

[Lester1707817999]

hi

nothing is happening I have tried every combination of cv 27 125 126 and 127 the decoder does not respond to any combination. It is certainly a looks like a faulty decoder as I have discovered some other CVs not related to abc are not functioning. I will email Gaugemaster to see if they have tried hm7000 chip on the Prodigy. I was hoping someone else on this forum had used the Prodigy with ABC on the hm7000 chip as said before I have used reliable ABC braking for many years on ESU decoders and the sapphire

Thanks for the help but your last post says no diode is reversed biased but the single diode has to be

Lester

[LTSR_NSE]

Toma(y)to, Toma®to - if you solder the 5 diodes in a ring then none are reversed, as RAF says. Equally if you solder 4 in a line & one over the top (as stylised image shows) - then top one appears reversed, (it’s actually upside down!) since you are confusing parallel appearance with series circuitry.

Provided the actual result is a series circuit ring with all diodes in the same polarity bias (or a stylised/PCB version of one with its ‘different’ appearance) it will work electronically!

[96RAF]

If you reverse one diode you block the voltage dropping action by one diode value. Likely your 1/4 arrangement isn’t dropping voltage enough to trigger the HM7K decoder.

My track voltages using an RRMS meter are 15.3 on the main and 13.4 in the ABC section using a diy 5 diode module.

If you look at the waveform diagram in the famous manual you will see the 4 diodes drop one side of the waveform and the single diode drops the other side, giving that overall less voltage offset to positive.

There is at least one person on here using a P2 with HM7K decoders but likely not playing with ABC.

[Lester1707817999]

Hi may be I am not explaining my self I have been involved in electronics more years than I care to remember when valves were used as diodes and rectifiers were selenium. my set up is as in the Hornby manual which is standard 5 diodes in series and 1 reversed connected in parallel across the 5 I have used used this combination since ABC became available on the loksound 4 series of decoders. I have put my scope on the track before and after the block and all is perfect each diode is dropping the voltage between 0.62 and 0.7 which is 3.9 volts well in spec

I only brought the hm7000 decoder because it had a shuttle feature and to see what it was capable of

If my time had a value I would have been able to buy many Loksoud 5 decoders at only twice the price and now they better value as some uk sound files are free on their web site and not rocket science to yuk your own sound files.( You need the programmer to do this.) I can see the slight advantage of being able to download hm sound files but after fitting the decoder how often why would you want to change the sound file for a different loco.the plus side is being able to use Bluetooth or dcc

Again thank you for your help again

[LTSR_NSE]

@lester - I only did electronics to the age of 14 (so am perfectly willing to be corrected) however I find your usage of parallel confusing. In this ABC/ADCC scenario the parallel circuits are the diode pack & the track (since the track is connected across one of the diodes) - however all 5 of the diodes are connected end to end (in a ring) therefore in series (with each other.)

Unless I am making a fundamental error?

[Brew Man]

I think the confusion comes from viewing the circuit as a DC scenario. View it in an AC or biPolar scenario and it is easier to see it as a ring.

[96RAF]

This is the BM1 module which shows the pcb tracks and it is fairly clear the diodes are in a ring going the same way and the pick off to the terminals is across one diode (top left).

I bow to your years of professional experience but what is right is right in my eyes.

My vero-board version, which works...

[Britannia Builder]

I've used the TXS ABC braking successfully with Railmaster/eLink. I used 4 diodes in one direction and one in the other, as in the schematic earlier in this thread. I set it to detect on both rails and stop in a constant distance with autoreverse and all works well - the constant braking distance is fixed under V2.

It seems to me very unlikely that your DCC controller would make a difference, since the ABC is activated just by the diodes and the decoder, and doesn't require any command from the controller. I suppose there could be some difference in the waveform or the absolute voltages, but that seems unlikely.

So I would agree that your decoder does seem to be faulty and worth returning to Hornby for checking.

Regards, John