Decoder Tester.........

Sumner Jun 9, 2021 at 11:45 PM

  1. Sumner

    Sumner TrainBoard Member

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    Part 1:

    I had finished a number of decoder installs and hadn't had a bad decoder in any of them but decided to make a decoder tester so I could test or program a decoder before the install. That way I would know for sure it was working before going through the install. I'd seen some commercial decoder testers and some home brewed ones so decided at trying my hand at making one.

    I wanted to be able to test up to 7 functions, depending on how many the decoder actually had. I also wanted a speaker so I could test a sound decoder and wanted a motor on the tester so I could make sure the motor controls were working. I came up with a design with two strips of solder pads that I could connect a decoder to in a few minutes. One strip had 7 pads on it for the basic decoder with the traditional 7 leads (red-right track power, black-left track power, orange-one motor lead, gray-second motor lead, blue-common positive power, white-forward light, yellow-rear light). The second strip also has 7 solder pads (5 pads for up to 5 additional decoder functions and 2 pads for the two speaker wires if it is a sound decoder.

    The solder pads prove to be a quick way to connect the decoder to the tester and a quick way to disconnect it. I strip off about .1 of an inch from the end of each decoder wire. Tin them and then solder them to the appropriate pad on the tester. This only takes a couple minutes and un-soldering them takes even less time.

    I designed the parts for the tester with Fusion 360 and printed them with my Ender 3 Pro printer. The parts were pretty basic and easy to design and print. Only the sides of the tester and the top were long prints. I printed the smaller parts using the highest quality and the two larger parts using standard quality. On the remainder of this page I'll show the parts as designed before going on to assembling and using the tester on following pages.

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    The part above along with the next three are used to mount a motor to the top of the tester. I had a motor that came from a N scale Intermountain SD45T-2 that had a broken frame. The mount was designed around that motor which appears to be the same basic motor as in some of the other loco's I have but I never measured them. If you use a motor that doesn't fit I'll leave it up to you on how to mount it to the decoder. The parts don't use much printer filament and are quick to print so I'd suggest printing them and seeing if they work for a motor you have. If they don't look at modifying them or coming up with something different.

    The motor sits on the piece above.

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    The motor slides into the piece above and up against the bottom stop.


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    The motor slides past the piece above and into and against the previous bracket.

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    With the motor in the mount you slide this one against the bottom of the motor and it holds it in the mount using the screw hole.




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    Above is the case sides.


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    The top of the tester is shown above and is glued to the sides shown previously. The holes in the top are drilled out to accept two LED's. I put a while LED in the left one to represent the forward light on the loco and a yellow LED in the right one to represent the rear loco light if it has one. The motor mounts between the lights and will be show on a following page.

    The five holes on the vertical part of the top are for 5 LED's to be used with any additional functions the decoder might have. If you toggle one of those functions on or off one of the LED's should light.


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    The next two prints, one shown above are glued to the top of the case and next to corresponding solder pads and are for reference as to which decoder wires should be soldered to each solder pad. The ones above are for the traditional 7 colored wires coming off of the decoder, left to right (Red, Black, Orange, Gray, Blue, White and Yellow).


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    The letter board above is printed and glued next to the additional seven solder pads for the additional functions and the speaker wires if the decoder has them. From left to right ( F1, F2, F3, F4, F5 and speaker wires One and Two).


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    The print above is 1/2” in diameter and is glued to the inside of the tester case and you can screw another solder pad to it. You use that solder pad to solder all the common positive blue wires to. The blue wire from the blue solder pad which is the common positive from the decoder and then to the forward and rear LED's on their anode (+) side along with a blue wire to each of the five function LED's on their anode (+) side also. The rest of the wiring will be shown on a following page.


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    Last up are feet for the tester you can print if you so desire. I printed 4 of the ones shown above and will show how I used them on a following page also. You can glue them to the inside of the sides of the tester and use the screw holes if desired to mount the tester on a piece of lumber or whatever.

    The next page will go into putting the parts together.

    I'll eventually have these parts up on my thingiverse.com account ( HERE ) when I finish the build description.

    This is also documented on my site ( HERE ),

    Sumner

     
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  2. wvgca

    wvgca TrainBoard Member

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    nice .. more detail on the printing rather than having everything on a piece of gridded PCB, but easy to trad and -should- be less work to hookup ..
    the one i made from gridded PCB has only been used maybe two dozen times, but in the long run saves time.
     
  3. BigJake

    BigJake TrainBoard Member

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    Sumner,

    Good idea, but...

    Repeatedly soldering and de-soldering wires to & from PCB pads will lift the pads and destroy them.

    I would suggest you install screw terminals/strips on the tester for the temporary connections to the decoder wires.
     
  4. Sumner

    Sumner TrainBoard Member

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    One has the option to use the solder pads or screw terminals. Hang in there that will be shown as I continue.

    I'll probably continue myself with the solder connections as the pads are large and you are on/off them so quickly I think they will last a good while. Also one could make new ones in 15 minutes or so if needed. I'll try and get more up tomorrow. Pictures, documentation and creating the web page all takes time ;),

    Sumner
     
  5. nscalestation

    nscalestation TrainBoard Supporter

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    When I built my new decoder tester about 10 years ago, I used push spring type binding posts for the decoder wires. I also added jacks next to each post in case I wanted to plug in something such as a test frame for board decoders. At that time I made a post on my DCC blog so you can see what this looks like.

    https://n-scale-dcc.blogspot.com/2011/02/building-decoder-tester.html
     
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  6. Sumner

    Sumner TrainBoard Member

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    Brad I'd seen your tester before and like it a lot. I forgot what you did to the flywheels on the motor. I need to do something similar. It was and still is your decoder installs that got me interested in buying less expensive older DC loco's and installing decoders in them. Thanks

    Sumner
     
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  7. Sumner

    Sumner TrainBoard Member

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    The first two pictures below show the top and the top glued to the base/sides.

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    The following pictures will show cutting, drilling and preparing the solder pads for the wiring and the resistors.

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    I labeled the holes above to show which are holes for the mounting screws, holes that a resistor lead along with a wire end will go in and holes that only get either a resistor lead or a wire end but not both.

    I drilled the pilot holes with a .037 bit but then ended up enlarging them to 1/16” (.0625”) with another drill and bit so you could just start with that size. I marked the holes where I wanted them along with where I wanted the isolation gaps in the PCB. I used a …
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    … center punch on the hole marks before drilling them.

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    I filed the insulation gaps in the bottom board but thought I cold do it faster with an abrasive cutoff wheel in a Dremel type tool I have so switched to it. I wouldn't of been able to make the isolation cuts that go across the pads where the resistors mount with the file so the cutoff wheel worked quickly in all the rest of the cuts and would use it from the beginning if I was to do this again.

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    Above one can see all the final isolation cuts in both solder strips. The strip on the bottom above will end up behind the top one on the top of the tester when it is done.

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    You need to also remove the copper on the other side of the board to avoid any shorting between any of the solder pads on the other side. There will be no soldering on this side but the resistor wires will protrude some along with possibly some of the wiring that is soldered to the opposite side.

    The next page will go into putting parts together and wiring.

    I'll eventually have the printable parts up on my thingiverse.com account ( HERE ) when I finish the build description.

    Link to this info on my site ( HERE ),

    Sumner
     
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  8. BigJake

    BigJake TrainBoard Member

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    I see now... those pads are huge, which helps them hang onto the substrate. Assuming the copper is not too thick... which it probably isn't if you can (de)solder with a quick touch of the iron. What weight is the copper plating?
     
  9. Sumner

    Sumner TrainBoard Member

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    Not for sure. Bought quite a bit of .031 PCB almost 2 years ago for making PCB ties for hand-laid turnouts I was making that was 1 oz.. Later I found some .031 that was advertised as 2 oz.. Haven't done a good job of keeping track of them so not sure but think it is the 1 oz. that I used.

    Yesterday I realized I also had some single sided .031 I had bought. If I need to replace the current ones at some point hopefully I'll remember I have it and use it.

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    Using it would save the time and worry about pads shorting together on the underside of the solder pads. I wouldn't have to clean the copper off near the wiring holes as shown above.

    As you mentioned having a 'blob' of solder on each pad results in just needing to barely touching it with a hot iron to attach or remove a decoder wire from the pad with the small size of the decoder wires.

    Sumner
     
  10. Sumner

    Sumner TrainBoard Member

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    Wanted to point out that although I'm using a 3D printed case one could make the case from other materials. Glue together styrene, use thin lumber, use a generic plastic project case. Also check out Brad's tester for additional ideas ( HERE ). Using the tester so far with just a couple decoders has convinced me that I should of made one sooner.

    I've found it especially helpful with the first sound decoder I've bought. The speaker in the case is probably a best case scenario for sound since it is larger and has a larger sound chamber than what I can probably get in a N scale loco.

    By hooking the decoder up and not using the speaker in the tester I was able to connect other size speakers with different size sound chambers that would fit the U28C to the decoder. That helped in picking the right speaker and sound chamber for the install. The one I was going to use didn't have enough volume. If I would have installed it I would of had to pull it out of the loco and then mill a larger opening for the speaker I did settle on. Using the tester I found out what to use. Hopefully it will work saving the time and frustration of pulling the loco back apart, un-wiring the decoder and milling the frame for the larger speaker.

    I found there is quite a difference in volume and clarity between speaker manufactures, speaker size and sound chamber size. I was disappointed in the decoder with the stock speaker (which wouldn't fit in a N scale loco) and the first speaker I tried that I was going to install. Happy with the final selection which is close to what you'll hear from the one that is in the tester if you listen to the video below. I also bought an ESU Loksound 5 DCC Micro that I'm going to put in an U50 since they have a sound file for the twin diesel loco. I'm sure it is going to be better than the $40 XL but I can see still using the XL possibly at times. I'll know more once I get the U28C back together.

    Here is a video of using the tester with the $40 sound decoder connected to the speaker in the tester at the time....



    Sumner
     
    Last edited: Jun 11, 2021 at 5:21 PM
  11. Sumner

    Sumner TrainBoard Member

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    Rereading the previous page I feel some areas need to be addressed before going forward.

    I have my tester set up to where I can attach the decoder wires under screw head or by soldering them to the solder pads. You need to decide when making the solder pads if you want to only use the solder attach method or the screw head method or be able to use either.

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    Above I have a decoder attached to the tester by putting the decoder wires under the #4 self-taping screw heads and tightening the screws down. Next ...

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    … I have attached the same decoder by soldering the wires to the solder pads. This might seem slower but once you have 'blobs' of solder on the pads you can solder the wires to those 'blobs' very quickly with a hot iron, well under a minute. If you want both options I would move the screws more towards the center of the pads to have more room to solder wires if you take that course. The screws are not shown in the picture above. I normally have them in even if soldering the wires to the pads. I do unscrew them a couple turns so they aren't tight against the pad as they would suck the heat out of the pad when you are soldering to them. That would lengthen the amount of time you would need to have the iron on the pad and the wire you are soldering to it.

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    Above I have a XL sound decoder attached to the tester by soldering the decoder wires. I don't have it connected to the solder pads for the internal speaker since I wanted to hear the speaker that came with the decoder. Next I connected it to the track and ran the decoder as address 3 with a JMRI throttle.

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    Next I cut the speaker off and wired the same decoder's speaker output to the internal speaker so I could compare the sound and the internal speaker is of a size that I could use in the loco the decoder was being used with so a good comparison.

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    You will need to drill pilot holes in the solder pad strips like above. You will need to put in the 'green', 'red' and 'blue' holes for sure. If you don't want the screw terminal option don't drill the holes that are circled with the black circles. If you do want that option then drill all the holes circled with the black circles. I would move them a little higher (as shown in the picture) to give you more room to also solder on 'blobs' of solder for connecting the decoder with the solder method when you want to use that method.

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    Once you have the holes drilled if you are using double sided printed circuit board like I was you need to go to the back side and remove some of the copper around each hole. If using the screw terminal method drill those holes out now to the correct size as shown for the #4 screws and remove copper around those also. You don't need to remove copper around the end two mounting holes that are shown.

    The reason the copper needs to be removed as some of the stripped end of the wires to be used along with the resistor leads and the terminal screws might come into contact with the copper on this side of the board. If that happens then different pads could be shorted to each other. Not good.

    I didn't take this into consideration on the first go around and the terminal screw threads were touching the copper on this side and I had shorts between pads when I connected to the track. I was lucky and the DCC command station picked up on the short and cut power to the track before the decoder was fried. When you are finished use an ohm meter and test between all the pads to make sure you don't have short between the pads (with the terminal screws in place if you are using them). You will see a reading between the 'orange' and 'gray' motor pads if you have a motor connected as you will be reading the resistance of the motor winding's. It will not be zero though which is what you would read if there was a short (actually maybe not zero but a number under '1' on the meter.

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    Above is a picture of what the bottom of one of the pad strips looks like with some of the wires soldered to the other side (top side). Once the resistors are on it is going to be harder to look at the bottom. You should not solder anything to this side of the strip.

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    Picture above shows the tester in use and …...

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    .... connected to the track which is connected to an Arduino DCC++ EX command station. The command station is connected to a Raspberry Pi running Steve Todd's free downloadable image card that boots up JMRI automatically as shown above. I'm connected to the decoder with one of JMRI's throttle on address 3. I'm able to test all the functions of the decoder with the function keys and could also connect using JMRI's Decoder Pro and reprogram the engine number and any of the functions on the computer.

    You can setup a DCC++ EX command station with your computer or a dedicated train room Raspberry Pi computer for under $100 ( HERE ).

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    Above or ( HERE ) you can see the decoder tester in use.

    The next page will continue with putting parts together and wiring.

    I'll eventually have the printable parts up on my thingiverse.com account ( HERE ) when I finish the build description.

    Link to the build on my site ( HERE ).

    Sumner
     
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  12. wvgca

    wvgca TrainBoard Member

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    links to the video of the decoder in action are not valid ... videos show set to private
     
  13. Sumner

    Sumner TrainBoard Member

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    Thanks, looks like I didn't finish the 'publish' button. It should be fixed now. Let me know if it isn't,

    Sumner
     
  14. Sumner

    Sumner TrainBoard Member

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    Time to finish the decoder tester.

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    As shown above glue the bottom wiring guide strip to the top.

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    Next temporarily mount the bottom solder pad strip in place above the guide strip. Then glue the second wiring guide strip in place and mount the second solder pad strip in place also.

    With the soldering strips in place drill pilot holes where the wires and resistor leads will be. This it the time to also drill the pilot holes in the case for the #4 Screws if you are going to use them for terminal screws. If you aren't sure I'd still drill them now in the case top and also in the printed circuit board if you haven't done so. Again make sure you remove any copper from the other side of the board near any of the holes to avoid any shorts that could take place on that side.

    If you used single sided PCB you don't need to worry about the other side and then you could also drill holes for the terminal screws later. I use a 3/32” bit (.094”) for the screw holes. If for some reason you ever stripped the threads out in the case you could glue on some of the feet found ( HERE ) for the screws to thread into.

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    Pull the solder pad strips off and enlarge the pilot holes some. This will make it easier to insert the wiring from the bottom side in the next steps.

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    Above is the wiring diagram. I'll take it for granted that it is obvious that the decoder wires are soldered to the bottom of the solder pads or placed under terminal screws there.

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    Above is the wiring for the basic 7 decoder wires that you will find on almost any decoder along with wires to the speaker that is glued to the top of a speaker enclosure/baffle. I've gotten some of my speakers and enclosure baffles from Streamlined Backshop and have also been 3D printing some custom height enclosures also.

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    Next make up LED's with wires to use for the 5 functions and the forward and reverse LED's. I used red for the functions and white for forward and yellow for reverse. You can use what you want.

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    Time to finish the wiring. I inserted the wires for the 5 functions and the forward and reverse lights from the bottom after tinning them and bent them over so they would stay in place. Then inserted the 1K resistors from the top and soldered the resistors and wires from below to the solder pads. There should be an isolation cut under the resistors. You want the wires to the LED's above the cut and soldered to the pad and resistor lead there. Next you can cut the excess resistor leads off inside the case.

    The 1K resistors should be fine for red, white and yellow LED's up to 15 or 16 volts.

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    Finish up the wiring to the top solder pad strip functions and speaker pads. I glued a 1/2” diameter post that you can print to the inside of the case and attached a simple PCB solder pad to it with a #4 screw. This made it easy to solder all the common positive blue wires to that go to all the LED's and the blue wire from the pad the decoder attaches to.

    NOTE: Most of the wires above are the correct color but I didn't have a gray one long enough to go from the solder pad to the motor so used a blue one for part of that distance. That is why you see a blue wire in the hole marked 'B' and 'G' above. The same with an orange wire for the hole marked 'O'. I had to use a length of yellow wire until I got near the motor.


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    I put a 2 pole solder pad on the back for the wires that go to the track. You can find the solder pad ( HERE ). Of course the wires that clip on to either the program track of the main can clip on in any order since it is DCC.

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    The tester is finished and I'm really glad that I made it. It has already come in handy, especially with the sound decoder I bought. I was able to test it with the speaker that came with it, Then connected to the speaker in the tester and finally I was able to pick a speaker and enclosure/baffle that I liked and that will fit in the GE U28C that the decoder is going in. If I would of started by installing in the U28C I probably would have had to cut the speaker out a couple times before finding the one I wanted. The speaker type and brand and the enclosure/baffle can make a big difference in the final sound. Above or ( HERE ) you can see the decoder tester in use.

    Again I'd like to encourage one to make a tester. Wish I would of sooner. Also it doesn't need to be a 3D printed case or be setup exactly like I've done. Lots of options for the case and how you set it up. Take a look a Brad's ( HERE ) and make it your own.

    If you have a printer and want to print the parts that I've used you can find them on my thingiverse.com account ( HERE ).

    A link to the whole build starts ( HERE ).

    Sumner
     
    Last edited: Jun 13, 2021 at 11:42 PM
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