e-Link voltage problem

[AusMod]

Hi guys,

 

I have a problem with the voltage coming out of my e-Link.

 

When I use a multimeter to check the voltage at the track terminals of the e-Link,

I get a reading of 8 to 10 volts. Is this normal? I thought it should be 15 volts

or

 

close to it.

 

Thanks in advance for any advice.

[gilbo2]

My elite output on my multimeter meter reads 18 volts when no load. Meters are designed to read AC sine waves though, which DCC is not. Chances are therefore it could be just you meter reading low.

[gilbo2]

Another thought, are you measuring AC or DC, my post is regarding AC measurements.

[AusMod]

dgilbert2 said:

Another thought, are you measuring AC or DC, my post is regarding AC measurements.

[AusMod]

Thanks for the reply.

 

My multimeter is an "el cheapo" It doesn't specify a difference

between AC or DC. It just says "power"

 

Maybe I should invest in a better meter.

 

I measured voltage across the tracks and was seeing a reading

of

 

8 volts. My locos still run which surprised me.

[Gregd99]

If your meter says "power" then this is in watts rather than volts (P=VI)

 

This link provides some info on the dcc waveform applied to the track. http://www.dccwiki.com/DCC_Tutorial_%28Power%29

 

As you can see it doesn't look much line the

 

sine wave that your meter can probably measure. This means that measurements with the meter might not be very informative.

 

Do you have a problem with the trains operating on the layout or are you just puzzled by the meter reading?

[AusMod]

Gregd99 said:

Do you have a problem with the trains operating on the layout or are you just puzzled by the meter reading?

Thanks for your advice. My trains are running slowly, with a jerking movement every few seconds. I thought

this may be caused by low voltage, hence I measured the volts across the track and at the output of the e-Link. I've tried cleaning the tracks and the wheels on the locos. I'm thinking the multimeter may be giving a wrong reading.

[Fishmanoz]

AM, slow and jerky movement is symptomatic of a range of things, starting with dirty track. So I suggest you start by cleaning it, and your loco wheels and pickups, and see what you get then.

 

The actual voltage you read with your meter is going

 

to tell you more about your meter then the DCC voltage being produced. The best you can say given the waveform and frequency of a DCC signal is that your meter should always read the same but that is unlikely to be the "real" voltage. I could get more technical

 

on this but don't think it likely to help you get a better understanding.

[Gregd99]

"Slow" and "Jerky" get a fair bit of discussion....

 

Many locos will run around 200+ (scale) km/hr on DC when a more realistic speed might be 100km/hr. ie you can often run locos >2 "scale" speed. On top of that on a small layout - mine is 2.7 x

 

1.2 m I find that slowing down a bit more is realistic as things are so close together. if you google model rail scale speed you will find more info.

 

considering the comments above are you locos running slowly?

 

jerky can often be related to the

 

back emf setting in the loco decoder. often the decoder and the motor/mechanism can fight against each other leading to jerky running. try adjusting the back emf CV.

 

Please let us know if any of the above is helpful.

[AusMod]

Gregd99 said:

jerky can often be related to the back emf setting in the loco decoder. often the decoder and the motor/mechanism can fight against each other leading to jerky running. try adjusting the back emf CV.

Please let us know

if any of the above is helpful.

Thanks for your reply Greg.

I've cleaned the tracks and wheels numerous times, without any real improvement.

What I really have trouble understanding is why the volts measured at the output
of

the e-Link are so low. I've tried measuring with two different multimeters and
still the output is about 10 to 12 volts. My understanding is that it should be about
15 volts. Am I expecting too much?

Thank you to all who have replied.

[alan10]

AusMod said:

What I really have trouble understanding is why the volts measured at the output
of the e-Link are so low. I've tried measuring with two different multimeters and
still the output is about 10 to 12 volts. My understanding

is that it should be about
15 volts. Am I expecting too much?

Your meter is designed to display the value of a sine wave. The DCC waveform is not a sine wave so your meter isn't going to display a proper reading. If you have access

to an oscilloscope this will give you a better idea of what's going on.

[Fishmanoz]

Further, the DCC spec tells us that the voltage must be between a max of +/- 22 volts and a min of +/- 7 volts of a pulse width modulated square wave at over 10kHz. On DC,your multimeter will see this as zero. On AC, what it will see and read is quite

 

problematic but it will certainly be less than the peak to peak value of the voltage generated. So if you are reading 12 volts, that is probably not too bad.

[Gregd99]

did you have a look at the link I posted earlier? http://www.dccwiki.com/DCC_Tutorial_%28Power%29

 

if the info above and at the link is a bit complicated then I think it might be best to accept that a normal multimeter won't give a helpful result

 

if you try and measure DCC. (apologies in advance if you are an electrical engineer)

 

What were you thoughts on my earlier suggestions regarding scale speed and emf CV?

[AusMod]

Thanks for the link, Greg, but I found it a bit beyond my level of understanding.

I'm far away from being an electrical engineer.

 

I'll have a try with the CVs and see if that sorts things out. I'm a little more confident

dealing with CVs as

 

opposed to using a multimeter etc.

[Gregd99]

if you are using an 8249 decoder the manual is @ https://www.hornby.com/filelibrary/download/?FileID=137 and the EMF CV is #10.

 

do have a look at "scale speed"when assessing if your locos are slow.

[satts67]

AusMod said:

Hi All,

Either I know nothing about electronics or there is some confusion here.

The output voltage of the elink has nothing to do with DCC. On the bottom of the elink it says the output voltage should be 15 AC.

That's what your meter should read whether it is an expensive Fluke or B&Q special makes no difference. It should still read 10V-15V if set to AC. Your elink output appears to be on the low side the same problem as mine. I have asked them to look into this

as I could not get my trains to work at all.

The Digital signal (DCC) will come from your laptop (or elite) and squirts packets of data or digital signals down the a/c rails to the decoder. Don't confuse the two.

A/C voltage and Digital are different.

One is for power the other is for data processing.
Hornby motors are not driven by digital signals. In the new digital world they are driven by A/C power which is converted to DC by the decoder. Remember though that the decoder needs to be told what to

do. This comes from the digital signals coming from your laptop superimposed onto 15V (or low 10V AC) on the track. (In a similar way that Ethernet over the mains works) Someone please correct me if I am talking rubbish.

Thanks and regards.








Thanks

for your reply Greg.

I've cleaned the tracks and wheels numerous times, without any real improvement.

What I really have trouble understanding is why the volts measured at the output
of the e-Link are so low. I've tried measuring with two

different multimeters and
still the output is about 10 to 12 volts. My understanding is that it should be about
15 volts. Am I expecting too much?

Thank you to all who have replied.

[Fishmanoz]

Unfortunately satts you are talking rubbish and I need to correct you. There is no conventional AC in a DCC signal. Power comes from a square wave at over 10kHz onto which the signal packets are pulse width modulated. Your Elite or eLink produces these

 

signals, not RM. look again at my post on page 2 at 9.05 on 4th August where I describe it generally, and then Greg's immediately below where he gives the link to DCCwiki which contains the detailed specification of the signal.

 

Then go to http://www.brian-lambert.co.uk/DCC.htm#Basic%20decoder%20connections

 

and scroll down a little until you find the schematic diagram of the 4 function decoder which shows you how this is first put through a bridge rectifier and separated into DC power and signal packets through the motor and signal processors.

[Fishmanoz]

But welcome to the forums and don't be put off by my correcting you. Keep asking questions as there are many knowledgeable people on here to help.

 

And yes, if you want to know the details of how DCC works, rather than just using it as most do,

 

it takes a little to get your head around, at least it did me as my electrical engineering is from some 45 years ago.

[satts67]

Post a new reply...

[satts67]

Ok I understand different wave forms etc. The elink specifically says 15 AC(sine wave symbol) on the back. Shame there isn't a specific symbol for PWM? If that's what its spitting out then multimeters are not much good. Doubt many people have access to

 

oscilloscopes. I need to brush up on my digital theory then it would seem :-( The whole digital thing is white mans magic anyway. Once again my train has died and refuses to budge even after rebooting the laptop and elink.

Bring back analogue at least that

 

was reliable.

[poliss]

You can always buy a RRampmeter to give you an accurate reading.