I ran across this simple little decoder terrier and wondered if someone might be able to identify the two missing wire colors. From left to right the screw terminals appear to be painted gray, orange and yellow, white and blue, ? and ? and black and red. The first terminal block on the far left only has one the one gray terminal connected and applying power to it and the adjacent orange terminal make the motor run. I'll be very greatful if someonetsomeone can tellmtell mewme the ? colors should be and how to use this to test a decoder?
Judging by the LEDs and 820Ω resistors I'm guessing yellow, white, and the 2 unknown ones are for testing decoder functions (ie- headlights). Blue looks like the common. EDIT: Should add, to test you would connect one of those colours to +ve and the blue to -ve, then turn on the functions of the decoder one by one until the relevant LED lights up. Not all decoders will have 4 functions mind you.
Found this: RED WIRE – this is to pick up power from the track. Traditionally, this should be connected to the pickups that collect power from the RIGHT rail BLACK WIRE – this is also to pick up power from the track. Traditionally this should be connected to the pickups that collect power from the LEFT rail ORANGE WIRE – this is to connect the decoder to one of the motor brushes. There is no “normal” left or right for this one, as motors do not always face the same way in the chassis. Don’t worry – if the loco runs backwards, simply swap for the Gray wire OR use the instructions to change CV’s to make the loco run the other way (easy and works every time) GRAY WIRE – this is to pick up power from the other motor brush. IMPORTANT – Red and Black wires must NEVER share any form of direct electrical connection with the Orange or Gray wires. Nor should the Gray and Orange wires ever share a connection with the pickups in any way. Fail to check or ignore this and you will destroy your decoder immediately – The result of this contact, no matter how slight, is usually a puff of smoke and a black hole in one of the decoder IC’s. BLUE WIRE – This wire is the COMMON wire for all functions. It is used with other “accessory: or lighting wires. It is always POSITIVE, and is the common partner for every function. For example, front light = white + blue, rear light= yellow + blue. WHITE WIRE – “Front lights/functions”. To connect the headlights or “front” function, use the white NEGATIVE wire and the BLUE POSITIVE wire. How your decoder controls this wire will be clearly stated in the instructions, but it is usually via Function Zero on your controller (Often helpfully marked “lights”) YELLOW WIRE – “Rear Lights/functions”. To connect the rear lights or “Rear” function, use the Yellow NEGATIVE wire and the BLUE POSITIVE wire. How your decoder controls this wire will be clearly stated in the instructions. Please note as follows: o Rear light functions can often be used for things like firebox flicker on steam loco’s\ o If the function needs more than 100mA, you can parallel two functions to make a higher power function – i.e. Yellow+ white to one side of the smoke unit, blue to the other side. o Lighting can be configured to be manually or automatically reversed, plus MANY other options. GREEN WIRE – “any other function” including lights or accessory control. Use the Green NEGATIVE wire and the BLUE POSITIVE wire. How your decoder controls this wire will be clearly stated in the instructions. Usually 100mA Max. On non sound decoders, this will be set ex factory for operation by function 1 PURPLE WIRE – “any other function” including lights or accessory control. Use the Purple NEGATIVE wire and the BLUE POSITIVE wire. How your decoder controls this wire will be clearly stated in the instructions. Usually 100mA Max. On non sound decoders, this will be set ex factory for operation by function 2.
Thank you TrinityJay and especially rray for your ilkucidating explanation. This will serveIserve me welltwell and I think that I can try this thing out without fear of the dreaded blue cloud.
Ok, I am totally confused. I hooked up this unknown decoder as shown in the attached picture. (The black decoder wire that goes out of frame on the lower right side comes back into frame and connects to the black terminal on the tester. This is also the connection to the black wire from my Zephyr.) When I attempt to read back the decoder's address on my Zephyr in the direct mode by pressing PROGRAM, LOCO and toggle for Ad2 and presst CV-RD, the 2 LEDs on the left side representing yellow and white flash on briefly, I hear a faint buzzing sound from the tester motor, and the Zephyr responds with "d 255". If I attempt the same procedure for an Ad4 address, the Zephyr responds with "d nr" after about 15 seconds of motor biz and the same two LEDs being lit. After trying the above, if I switch the Zephyr from program track to RUN, the motor on the tester takes off at neck breaking speed. Anyone have any idea about what's happening?
Attached to Program a&b. I have a dpdt switch that switches between program for programming and run for my test track. For testing the decoder tester, I have connected the cable from the center terminals of the dpdt switch directly to the tester where the test track would normally be connected.
The flashing light and quick motor buzz are perfectly normal for many brands of decoders on the CV read or write. The tester seems to be fine (I've seen these at shows, before, and they are extraordinarily simple) What is interesting is the response to the address read, it clearly isn't a valid 2 digit address. Try a writing CV8=8 for a decoder reset (couldn't hurt) Then, read CV7 and CV8 - that will give you the Mfg ID info
I wonder, if when trying to read back from the decoder, that there isn't enough physical load on the motor to draw enough current for a valid read? It might be worth holding a finger on the motor shaft while you try to do a read?
I have to do that on my n-scale programming track with one particular loco to get a good read of it's CVs. The loco is very small and the current it draws is normally so low, I have to hold a finger on it to create a bit more load. The controller's current sensing circuit can then better detect the pulsing data that the decoder creates when it sends the data back to the controller.
Thanks for your reply. I am still confused as to how pressing down on the loc. while the controller is in program mode from the test track output adds electrical load. I understand how adding a lighted passenger car to the test track would increase the load on the programming read or write path, but how does adding physical pressure to the wheel set, or in my case with a decoder tester motor, adding pressure to the motor shaft, increase the load. I'm asking this because I tried it with pressure on the decoder tester's motor shaft, and the results were the same. Thanks again, Don
Probably what is happening is that you have intermittent electrical contact. When a CV is written, a confirm pulse is sent to the motor, the wheels turn, and the loco moves a tiny bit. By holding the loco down to the rails, you are forcing the intermittent connection for writing the next CV to stay connected. Intermittent in that either grease, dirty wheels, dirty motor brushes, caked motor armatures, dirty wipers or other mechanical issue causing the intermittent connection when that motor pulse confirms that last CV written.
[this is my understanding] - The only way a DCC decoder (in a loco for example) can send data back to the controller is by pulsing the current it draws from the rails. The controller monitors these fluctuations in the current drawn. The simplest way the decoder can do that is to pulse the motor in the loco, which pulses the current drawn on the rails. If the motor is not sufficiently physically loaded, it will not draw enough current for the controller to detect the fluctuations. Restricting the rotation onf the motor makes it draw more current.
Thanks ray and Jimbo20, I didn't realize what was happening. This all makes sense now. The problem must be with the motor on the decoder tester. The tester is very old, hadn't been used in at least 10 years and was very reluctant to run at all when I first applied power. Once I did get it to run, I noticed that there was always the slightest hesitation before it took off at breakneck speed, (with the full 13.6 volts I'm reading when the switch is in run mode on the test track.) I'll try to get the armature and brushes cleaned up a bit more and report back Thanks again.
Nope, cleaning commutator to shiny did not fix it. If I try to read Ad2, I get a brief biz and LED flash and irratic numbernnumber results: usually 254 or 255,w but have seen 250, 238 and 124, allpall with no preceding zero. If I try the same with Ad4, I get "d nd". Would it be safe to try safe to try the above tests with the connection to the motor shorted?
Any suggestion on anything else to try? I have one of the simple basic 2-led gismos that came with some Digitrax decoders.
first, try hooking up a known good decoder to read that. Before thinking the tester is dead, make sure it isn't the mystery decoder
I would start by testing the decoder tester. 1 Loosen all the screws on the "decoder Tester" and disconnect all the wires from it. 2 Use a Meter and check to make sure the Red DCC in terminal (Black connector on the side) is connected to the red screw on the (blue connector at the bottom) Likewise The black screw on the black connector should be connected to the black screw on the Blue connector. 3 check the motor on the tester Use a regular DC train power pack and hook the track power terminals to the orange and Gray screws and slowly turn up the throttle. if the motor slowly comes to life and speeds up gradually matching your action on the throttle its probably OK if it suddenly comes on at high speed or dose not run at all, I would replace the motor. 4 Note:The two unknown screws should be Green and Purple, using a 9V battery i would connect the positive from the battery to the blue terminal and the negative to the White Screw and see if the LED directly in front of it lights up. Now one at a time move the negative wire to the Yellow, the Green and the Purple screws and each time the corresponding LED should Light. Now if everything checked out you know the Decoder Tester itself is not the problem. Next reconnect the DCC track wires and the decoder to the tester making sure each wire is making good contact with its screw terminal and try doing a Decoder Reset.
