Lais DCC 870021

[DK123GWR]

I want to upgrade some of my old Hornby 0-4-0s to DCC but I am aware that they may will cut out on insulfrog points at low speed (experience with Bo-Bos that haven't  had pickups fitted to all wheels informs this view). Therefore, I would like to try fitting a stay-alive to these locos. The decoder I am considering is the Lais DCC 870021, which comes with wires to fit a capacitor to (I don't trust myself to solder to the PCB of the decoder). Lais DCC make their own stay alive but I have a feeling that this is unnecessarily expensive and would like to try fitting a cheaper capacitor (i.e. not one sold as a 'stay alive') if possible. With this in mind, I have a few questions.

 

1) What capacitance will be sufficient to clear the insulfrog points consistently? I don't need something that runs for 2m without track power, I am just interested in making it across the points.

2) The descriptions for Lais DCC decoders often state that Railmaster + eLink are unable to read/write all of the CVs supported by the decoder. Will the basic CVs found on the Hornby R8249 (from memory these are 1,3,4,7,8,17,18,29) be useable? What other CVs should work?

3) Will I need a resistor to prevent a surge when charging? I don't know whether there is a resistor on the decoder itself or on the Lais DCC branded capacitor. If there is one attached to the capacitor then I will have to find a resistor from somewhere else to replace it.

4) What are my chances of fitting this into locos such as the GWR 101, Desmond, and Percy (from Thomas)? This depends on the size of the capacitor of course. I see no reason that it shouldn't fit, but it would be useful if anybody has tried something similar and can confirm that it does.

 

I think I have everything else sorted. I plan to use capacitors rated at 25V which should be more than enough for an eLink. The decoder seems to be rated for higher currents than and R8249 (1A continuous, 2A peak compared to 0.5A continuous 1A peak) so I am not worried about this.

Thanks in advance for any advice.

[Guest Half-full]

35 minutes ago, DK123GWR said:

I want to upgrade some of my old Hornby 0-4-0s to DCC but I am aware that they may will cut out on insulfrog points at low speed (experience with Bo-Bos that haven't  had pickups fitted to all wheels informs this view). Therefore, I would like to try fitting a stay-alive to these locos. The decoder I am considering is the Lais DCC 870021, which comes with wires to fit a capacitor to (I don't trust myself to solder to the PCB of the decoder). Lais DCC make their own stay alive but I have a feeling that this is unnecessarily expensive and would like to try fitting a cheaper capacitor (i.e. not one sold as a 'stay alive') if possible. With this in mind, I have a few questions.

 

1) What capacitance will be sufficient to clear the insulfrog points consistently? I don't need something that runs for 2m without track power, I am just interested in making it across the points.

2) The descriptions for Lais DCC decoders often state that Railmaster + eLink are unable to read/write all of the CVs supported by the decoder. Will the basic CVs found on the Hornby R8249 (from memory these are 1,3,4,7,8,17,18,29) be useable? What other CVs should work?

3) Will I need a resistor to prevent a surge when charging? I don't know whether there is a resistor on the decoder itself or on the Lais DCC branded capacitor. If there is one attached to the capacitor then I will have to find a resistor from somewhere else to replace it.

4) What are my chances of fitting this into locos such as the GWR 101, Desmond, and Percy (from Thomas)? This depends on the size of the capacitor of course. I see no reason that it shouldn't fit, but it would be useful if anybody has tried something similar and can confirm that it does.

 

I think I have everything else sorted. I plan to use capacitors rated at 25V which should be more than enough for an eLink. The decoder seems to be rated for higher currents than and R8249 (1A continuous, 2A peak compared to 0.5A continuous 1A peak) so I am not worried about this.

Thanks in advance for any advice.

If you are wanting value for money, dont buy Lais decoders, spend a little more and get another brand.  They are cheap for a reason, unfortunately.

[Matt C]

13 minutes ago, Half-full said:

If you are wanting value for money, dont buy Lais decoders, spend a little more and get another brand.  They are cheap for a reason, unfortunately.

 

 

Flip side, I have fitted 30 ish Lais decoders to Hornby/ Lima locos over the last 2 years and have had no failures. If they run well on DC they run equal or better with the Lais, Yes you get what you pay for but when your running old cheap locos why buy more expensive decoders ?

 

 Not done stay alives so can help you there but will watch with interest as I may try some later   

[DK123GWR]

26 minutes ago, Half-full said:

If you are wanting value for money, dont buy Lais decoders, spend a little more and get another brand.  They are cheap for a reason, unfortunately.

What is value for money will depend upon your requirements. As long as the decoder is capable of meeting my requirements on paper then it may be worth trying one and re-evaluating the value for money based upon my experiences. If it doesn't, then I will discount it as an option and look at another option. At this point, I am trying to work out whether it does meet my requirements (as set out above) and what capacitor is required, which will apply to any decoder.

 

I also have no doubt that somebody will be along shortly who will say that Lais decoders do the job they need to do.

 

EDIT: It seems that they already have.

Edited June 16, 2020 by DK123GWR

[DK123GWR]

3 minutes ago, Mattc6911 said:

 

 

Flip side, I have fitted 30 ish Lais decoders to Hornby/ Lima locos over the last 2 years and have had no failures. If they run well on DC they run equal or better with the Lais, Yes you get what you pay for but when your running old cheap locos why buy more expensive decoders ?

 

 Not done stay alives so can help you there but will watch with interest as I may try some later   

Do you have any experience with RM and what CVs do or don't work properly?

1 hour ago, DK123GWR said:

 

2) The descriptions for Lais DCC decoders often state that Railmaster + eLink are unable to read/write all of the CVs supported by the decoder. Will the basic CVs found on the Hornby R8249 (from memory these are 1,3,4,7,8,17,18,29) be useable? What other CVs should work?

 

 

[Guest Half-full]

6 minutes ago, DK123GWR said:

What is value for money will depend upon your requirements. As long as the decoder is capable of meeting my requirements on paper then it may be worth trying one and re-evaluating the value for money based upon my experiences. If it doesn't, then I will discount it as an option and look at another option. At this point, I am trying to work out whether it does meet my requirements (as set out above) and what capacitor is required, which will apply to any decoder.

 

I also have no doubt that somebody will be along shortly who will say that they do the job they need to do.

I've only tried 2 Lais decoders, one hard wired, and one 21 pin, I found the hardwired one would exhibit erratic behavior such as surging/shuddering and kept losing its address.  The 21-pin lost its address a few times.

 

I decided to standardise on Zimo, for ease of supply and solid reliability.  I not the sort of person to mess about with settings, I just want to install them and let them do what they need to!  I dont use stay alive's though as my points are electrofrog.

Edited June 16, 2020 by Half-full

[Matt C]

Sorry never used Railmaster so cant help there 

[Matt C]

12 minutes ago, Half-full said:

I've only tried 2 Lais decoders, one hard wired, and one 21 pin, I found the hardwired one would exhibit erratic behavior such as surging/shuddering and kept losing its address.  The 21-pin lost its address a few times.

 

I decided to standardise on Zimo, for ease of supply and solid reliability.  I not the sort of person to mess about with settings, I just want to install them and let them do what they need to!  I dont use stay alive's though as my points are electrofrog.

 

 

Sorry don't want to hijack the thread but, I had a couple that were erratic/jerky where I had to turn off back emf which cured the problem , and on all of them I removed any tv capacitors/ suppressers  which can also cause jerky running. I use a Black Z21 system and in two years have not had a decoder fail or lose its settings/ address . (Drops head in hands waiting for everything to go bobblies up ) 

[Harlequin]

I agree with Half-full. There are numerous threads on here about Lais decoders proving to be unreliable or failing.

 

Zimo non-sound decoders are around £20 and won't let you down.

 

[friscopete]

1 hour ago, Half-full said:

If you are wanting value for money, dont buy Lais decoders, spend a little more and get another brand.  They are cheap for a reason, unfortunately.

My dozen or so always work well . Had a Zimo that died though, luck of the draw

[Sir TophamHatt]

There are slightly more expensive Lais decoders that come with a more powerful Stay Alive (like this one). The tiny ones you get (even with Zimo) are usually 470uF. These last less than half a second - pointless.

 

I'd recommend one that will last a good few seconds at least. Someone said I was silly to say that as they didn't want a loco out of control for 20 seconds. I said the loco would likely be back in communication with the command station after a few seconds - the 10 or 20 second stay alive is a "just in case" basis. Your locos won't go crashing anywhere.

 

I'd also suggest if you want to try them out, buy them. Yes, cheap but if it's going to teach you and help you see what's best what's not to like? 

 

I made my own stay alives that last 20 seconds. I can upload the drawings if you wish but it's more complicated than what you may think.

 

From what I understand (completely not from an electrical background here):

 

The capacitor voltage needs to be higher than the track voltage (or something like this). Unfortunately, the more power you add to the stay alive, the less volts it has. To be honest, I'm not entirely sure what I'm talking about. I just know that the capacitors I have must be added together properly or they simply won't work / may blow. I can't add any less than 6.

 

You need a resistor yes - this stops a rush of current, which may identify to the command station as a short. You also need a diode. This will force the incoming power to go through the resistor.

 

I have the kit to build about 4 or 5 more huge capacity stay alives but don't know if I'll buy the stock that can hold them.

 

Here's a video of the one I fitted:

 

Edited June 20, 2020 by Sir TophamHatt

[DK123GWR]

36 minutes ago, Sir TophamHatt said:

There are slightly more expensive Lais decoders that come with a more powerful Stay Alive (like this one) .

 

I'd recommend one that will last a good few seconds rather than half a millisecond.

 

I'd also suggest if you want to try them out, buy them. Yes, cheap but if it's going to teach you, best to lose a cheap decoder than a more expensive one.

 

I made my own stay alives that last 20 seconds. I can upload the drawings if you wish but it's more complicated than what you may think.

 

From what I understand (completely not from an electrical background here):

 

The capacitor voltage needs to be higher than the track voltage (or something like this). Unfortunately, the more power you add to the stay alive, the less volts it has. To be honest, I'm not entirely sure what I'm talking about. I just know that the capacitors I have must be added together properly or they simply won't work / may blow. I can't add any less than 6.

 

You need a resistor yes - this stops a rush of current, which may identify to the command station as a short. You also need a diode. This will force the incoming power to go through the resistor.

 

I understand what is required for stay alives in a general sense, but I was asking if anybody knew whether there was a resistor built into the circuit board (so that I wouldn't need to add another one) as well as questions about compatability with RM and capacitance. In theory I could buy a multimeter, measure the resistance of the loco, find out what votalge is required to keep the decoder alive, then substitute into V=V0e^(-t/RC) and rearange for C but:

a) I hoped that somebody would already know what capacitance was required for a few seconds of discharging

b) What works on paper never seems to work in practice (especially when I'm doing the practical parts)

 

I will also add that you are correct about the need to make sure that capacitors are rated for a higher voltage than the track supply. If they aren't, this may happen:

 

Edited June 20, 2020 by DK123GWR
Edited to shorten quote