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Using Decoders as function-only decoders

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Using Decoders as function-only decoders
Posted by garya on Friday, May 22, 2020 7:43 PM

I have some older decoders that I have replaced or retired.  Usually something like a budget decoder that makes the motor buzz.  I am thinking of using them to control lighting in some passenger cars.  I also have a sound decoder that doesn't control the motor well; I want to convert it to sound only.

I figure I will need some sort of load between the orange and gray leads to spoof a motor.  Would a 100 ohm resistor do the trick? Or even a 47 Ohm?  I was thinking to set the motor outputs to zero, so it won't get warm.

For lighting, I figure I need to limit the current but I should be able to light some LEDs...

Gary

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Posted by wrench567 on Friday, May 22, 2020 10:01 PM

I've been away for about 7-8 years. If I'm correct you only need a motor is reading CVs. You can program without a motor. I programmed an old TCS T1 decoder in a tender without the locomotive. I just changed the address is all. It worked and was running it this morning.

   Pete

 

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Posted by tstage on Friday, May 22, 2020 10:32 PM

Gary,

I have a TCS FL4 decoder independently operating the rear taillights of an Aerotrain lounge car.  It's wired independently of the Loksound Select micro located up in the locomotive.  Both the Loksound and TCS decoders are programmed to the identical address so that I can operate them simultaneously but independently using button remapping.

So, all you need to do is connect your motor-only decoder to the motor and your function-only decoder(s) to track power.  You'll treat them like independent decoders but program them to the identical address.  You could program each decoder to a different address but then you have to remember two addresses rather than one.

I found Decoder Pro very helpful with this, as well as capturing all the proper CV settings.  In order to record and store the CVs for both decoders with identical addresses in Decoder Pro, I used a letter after the function-only decoder for the ID - e.g. "1001" (for Loksound) & "1001a" (for TCS FL4).  That way, if I should ever have to reset either decoder, I have the CVs recorded for each one.

Most likely you will need to do some remapping to make it all work properly together.  As mentioned, Decoder Pro was very helpful with this aspect.

Gary, here's a short video demoing both decoders wired up and functioning properly.  I darkened the room so that the LEDs and the lighting-effects would be more visible:

Tom

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Posted by garya on Friday, May 22, 2020 10:52 PM

Tom--

Impressive work.  I don't have function decoders, however.  I have old motor control decoders that I wish to use as function decoders.  Thta's what I'm getting at.

Gary

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Posted by ba&prr on Friday, May 22, 2020 11:18 PM

Yes they will work for lighting only. Read the manual for the decoders to see if a resister is needed for LEDs. I have several old Digitrax sound decoders I put in a 50' mechanical reefer. You can program them with out a motor or resister. You can't read back CVs with out a motor or resister across teh motor leads.   Joe

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Posted by tstage on Saturday, May 23, 2020 12:01 AM

garya

I don't have function decoders, however.  I have old motor control decoders that I wish to use as function decoders.  Thta's what I'm getting at.

Gary,

I understood that.  My point was that you could use a motor or a sound decoder as a funtion-only decoder.  Assuming you have enough functions to accomplish what you want, just leave off the motor connections and only have it connected to track power.  Then it functions exactly like a function-only decoder.

Tom

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Posted by garya on Saturday, May 23, 2020 2:22 AM

In the interest of science, I experimented with my decoders and LED light strips this evening.  I had some Lenz budget decoders, so I looked up the function output limit, which was 100mA.  I tried an LED strip at 12vdc, and they came in about 50mA, so no problem there.

I have JMRI with a home-built DCC++ system.  So hooking the decoder up with alligator clips, I tried turning the LEDs on with address 3.  Success!  I tried programming the decoder.  No dice--got "no response from decoder" errors from JMRI, and it didn't work on the new address, though it still worked on address 3.  I hooked a 100 ohm resistor across the motor leads and tried to reprogram.  I got the same "no response from decoder" errors, but when tested on the new address, it worked.

So it appears a resistor is needed to program these decoders.  I'll try some more decoders and sound decoders this weekend.

Gary

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Posted by wrench567 on Saturday, May 23, 2020 8:44 AM

  Gary.

  I didn't know there were any old Lens decoders around. They belong in the DCC museum of tried it and didn't work out so good. Once programmed they worked decently but tender to burn up motors. The heat from the motor on an Atlas RS3 actually melted the shell. Another issue was if you or someone else derailed and tripped the booster or CB the decoder forgot it was a decoder and needed to be reprogrammed.

  I used to do the club's decoder installations for many of the members. Lenz value line and first gen Digitrax I wouldn't touch.

   Pete.

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Posted by tstage on Saturday, May 23, 2020 9:46 AM

Good work, Gary.  Sometimes I've gotten that same error from Decoder Pro because the alligator clips weren't making good contact with the track.  I'll look forward to seeing what you find out.

Tom

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Posted by rrinker on Saturday, May 23, 2020 10:03 AM

 It would probably work if you programmed CV17,18, and 29 manually to set the address, even without the resistor. Depending on the decoder, it may also work in Ops Mode. If it's currently on the default of 3, in Ops Mode with address 3 selected, program CV17,18 and 29 with the calculated values for the desired long address.

 Be sure to configure a speed table or otherwise set things to keep the motor voltage low - with a 100 ohm resistor in place of the motor, at full speed it would need to dissipate close to 2 watts. If it's not rated that high, the resistor will melt. If it IS rated that high, contact with the shell will cause the shell to melt. Or remove the resistor after programming.

 One calculator is here: http://www.2mm.org.uk/articles/cv29%20calculator.htm

                                --Randy

 


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Posted by garya on Saturday, May 23, 2020 10:55 AM

wrench567

  Gary.

  I didn't know there were any old Lens decoders around. They belong in the DCC museum of tried it and didn't work out so good. Once programmed they worked decently but tender to burn up motors. The heat from the motor on an Atlas RS3 actually melted the shell. Another issue was if you or someone else derailed and tripped the booster or CB the decoder forgot it was a decoder and needed to be reprogrammed.

  I used to do the club's decoder installations for many of the members. Lenz value line and first gen Digitrax I wouldn't touch.

   Pete.

 

I have some Lenz LE1000a, a couple of Bachmann DCC decoders (probably made by Lenz), a couple of Digitrax DH121s, and a MRC motor decoder.  All make that horrible motor noise and don't work particularly well.  They're getting turned into function-only decoders, though the DH121s don't want to get programmed for some reason.  I also have a DH123 with bad motor output, but I'm not sure if I can reprogram it or not without a load.

I have a couple of old Soundtraxx decoders and an MRC sound Decoder that I will try to use as Sound-only decoders.

It was late last night and I couldn't find a 47 ohm resistor, so I think I used a 100 ohm resistor to spoof the motor.  That may be why I got some JMRI errors.  I suppose I could try with a spare motor and see if it works better, and keep looking for a more appropriate resistor.

Gary

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Posted by garya on Saturday, May 23, 2020 11:16 AM

I can try ops mode and see if it works.  That would be better for the sound decoders, so I could tweak them if needed.

The plan was to set motor output at zero, so the resistor shouldn't get warm.  But I suppose I could build a decoder tester, as in http://cs.trains.com/mrr/f/744/t/282536.aspx, and once programmed, install without a resistor.  I just want lights to come on and off in most cases.

I haven't installed one in a passenger car yet, but thinking ahead, I may get flickering problems, so that's another issue.

Gary

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Posted by garya on Saturday, May 23, 2020 2:21 PM

garya
It was late last night and I couldn't find a 47 ohm resistor, so I think I used a 100 ohm resistor to spoof the motor.  That may be why I got some JMRI errors.  I suppose I could try with a spare motor and see if it works better, and keep looking for a more appropriate resistor.

UPDATE: I tried it with 10 ohm and 47 ohm resistors and it works fine.  JMRI can program and read the decoder with the resistor.

The LEDs are really bright, so I used a 470 ohm resistor to tone them down some.  Maybe a separate topic, but I wonder if I can put a capacitor across the LED terminals to keep them from flickering if the passenger car hits dirty track or goes over a turnout frog...

Gary

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Posted by tstage on Saturday, May 23, 2020 2:45 PM

Gary,

I'm sure Randy will chime in but it will probably require a substantial (super) cap to keep the lights from flickering.  IIRC, you will also need a rectifier to accomplish that.

Tom

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Posted by rrinker on Saturday, May 23, 2020 7:03 PM

 Ypu can;t just put the cap on the LEDs, you need it on the decoder. Since you aren;t driving a motor and the motor settings are all low, there's not a lot of current drawn, so a reasonablly sized, say 470uF 16 (or better, 25)V capacitor connected as a keep alive would probbaly work fine. Since none of those decoders have provided points to attach a keep alive, you will have to figure it out by examination. The + side is easy, it's the blue wire. The - side is harder, you have to find the main rectifier on the decoder.

There are several examples here:

http://www.members.optusnet.com.au/mainnorth/alive.htm

To keep a motor runnign and the loco moving, you need the supercapacitors. But to just keep some lights on when using the decoder for lighting only, ordinary capacitors should be fine. They won;t stay on for minutes or hours when you kill the track power, but they should get over dirty track just fine.

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Posted by richg1998 on Sunday, May 24, 2020 12:26 PM

I used a 100 ohm resistor with a Tsunami Micro for sound only some years ago and adjusted a couple CV's I think to keep from over heating the resistor. Forget which CV's though. Maybe someone here will remember which ones.

Rich

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Posted by garya on Monday, May 25, 2020 1:02 PM

rrinker

 Ypu can;t just put the cap on the LEDs, you need it on the decoder. Since you aren;t driving a motor and the motor settings are all low, there's not a lot of current drawn, so a reasonablly sized, say 470uF 16 (or better, 25)V capacitor connected as a keep alive would probbaly work fine. Since none of those decoders have provided points to attach a keep alive, you will have to figure it out by examination. The + side is easy, it's the blue wire. The - side is harder, you have to find the main rectifier on the decoder.

There are several examples here:

http://www.members.optusnet.com.au/mainnorth/alive.htm

To keep a motor runnign and the loco moving, you need the supercapacitors. But to just keep some lights on when using the decoder for lighting only, ordinary capacitors should be fine. They won;t stay on for minutes or hours when you kill the track power, but they should get over dirty track just fine.

                                --Randy

 

 

Thanks for the info.  I looked at the examples in the link provided, and these cheapy Lenz decoders are similar in layout to the NCE D14SR.  I found the - side and soldered a purple wire to that side (I have lots of leftover purple and green decoder wire). 

When powered, I get voltage between the blue wire and the purple lead all the time.  I tried a 470 uF 25V cap betwen the leads, but the lights did flicker when I jostled the power leads.  I can try a single LED rather than the LED strip and see if it works.  I also have some spare caps in other sizes, so I will try them and report back.

Gary

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Posted by garya on Tuesday, May 26, 2020 1:51 AM

garya
can try a single LED rather than the LED strip and see if it works.  I also have some spare caps in other sizes, so I will try them and report back.

I tried it with my LED strip, and 470 uF, 680 uF, and 2200 uF caps.  Only the 2200 uF kept the LEDs on, and even then it was a noticeable dimming.

I had two single LEDs with 1K ohm resistors, and I repeated the test.  With one LED, the 470 uF dimmed, the 680 uF was slightly better, but the 2200 uF worked fine--no noticeable flicker.  With the two LEDs in parallel, the 470 uF dropped off quickly, as did the 680 uF.  Again the 2200 uF worked ok, just not as well as with a single LED.

So it should work for, say, caboose lighting or marker lights or a red tail light in a passenger car, but if I want flicker-free LED strips I'll need a more powerful capacitor or better pickup from the track.

Gary

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Posted by rrinker on Tuesday, May 26, 2020 7:43 AM

 Or bigger resistors on the LEDs - the strips tend to run the LEDs on the ragged edge to provide the brightest light, which is probably too bright for inside a car. For individual LEDs - even more than 1K, a lot more in some cases - 2mA to the LED is probably plenty for a nice glow. This is also one place where series LEDs will benefit over parallel - 3 LEDs with resistors for 2mA in parallel is a total 6mA current load. 3 LEDs in series with a resistor for 2mA is 2mA. The strips in their groups of 3 are in series, but typically resistors for maximum current at 12V, which is why they kill the capacitor so fast.

 Also, did you do this with the motor load resistor still connected or not? Because with it connected you've giving away a bunch of current there as well.

 Any interruption you make by moving things arounbd by hand is going to be longer than what actually happens when a wheel rolls over a speck of dirt on the track. And when adding block detection resistors to cars, I found it helps a LOT to polish the wheel treads. Just the tread - the part that is shiny on a running railcar anyway. My Dremel accosry kit has a brass brush, like a wire brush but soft brass instead of steal, that worked well to polish the wheel tread - and with polished treads on a short section of track hooked to my meter, an individual car detected perfectly. Without polishing, but otherwise clean wheels, I had to roll the car around and detection was somewhat intermittant. A whole train wouldn't be a problem, but so many were not detecting one at a time that I was wondering if I was getting the resistors installed properly - it was all the wheels, in 100 axles I think I ended up with 2 that were failures, the rest just needed cleaner wheel treads.

                                          --Randy

 


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Posted by Mark R. on Tuesday, May 26, 2020 3:41 PM

Did you install the resistor / diode with your capacitor ? Recommended if using capacitance higher than 1000mfd. ....

http://web.archive.org/web/20120729061658/http:/www.members.optusnet.com.au/mainnorth/alive.htm

Mark.

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Posted by garya on Tuesday, May 26, 2020 3:55 PM

Mark R.

Did you install the resistor / diode with your capacitor ? Recommended if using capacitance higher than 1000mfd. ....

http://web.archive.org/web/20120729061658/http:/www.members.optusnet.com.au/mainnorth/alive.htm

Mark.

 

No, because that wasn't indicated on the verison of the link referenced above.  No harm. 

I can experiment with caps, resistors and LED strips and LEDs in series and find what works best with these decoders, and/or I can just do what I have been doing; resistors, diode, and a capacitor with my light strips.

Gary

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