# DCC Function Actuated Coupler Opening



## wvgca

I had seen these before, where a tiny electric motor was installed behind an HO scale coupler box, and used a spare function output to pull a Kadee or similar coupler apart, and uncouple a loco from a car, handy for doing switching anyplace..
So I thought that I would try to make my own version of this ..
The motor in the image is very small, 0.507 long by 0.138 at the widest point, so should fit quite nicely behind the coupler box ..

I had thought initially that a length of super fine chain would look ideal, but couldn't find any, so will probably try some good quality strong silk thread glued between the Kadee and around the small flywheel on the micro pager vibrator motor ..

Initially it will be fun to solder some wire wrap wire to the SMD pads on the motor, those are really tiny  and then try to determine what size of a current limiting resistor that will give the motor enough strength to uncouple, but not burn it out, it will be working in stall mode, and may not tolerate that for very long ..I got ten of these motors for $4.73 CDN, so I can afford to kill a few in testing ..

Most newer DCC decoders have spare function leads, and at 100ma rating they should be able to drive this motor quite readily .. and a function only decoder can be installed in rolling stock to get the same effect ..

So far this is just theory


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## jlc41

I am looking forward to see this develop. Sound like quit a challenge.


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## DonR

Don't most DCC controllers store a very
limited number of addresses? Wouldn't
that limit the number of cars you could
uncouple using this device? 

Don


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## Mark VerMurlen

jlc41 said:


> I am looking forward to see this develop. Sound like quit a challenge.


Me too.

Mark


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## wvgca

DonR said:


> Don't most DCC controllers store a very
> limited number of addresses? Wouldn't
> that limit the number of cars you could
> uncouple using this device?
> 
> Don


True, depending on the brand of controller ..
If installed on a loco [with a spare function output] no extra address would be required ...

If installed on rolling stock with a function only decoder, I "assume" that you could consist the two decoders and remap function buttons for the uncoupler ..back to one efffective address, but I have not done any consisting for years, 

I do assume that there would be only a few pieces of rolljng stock equipped by the average user, so filling a address roster "should'' not be a issue


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## wvgca

Here's the ebay link to these motors .. seller shows them as using 70ma / 1.5V, 90ma / 2V, so they will need to be cut back some on power for use in stall mode...

I also ordered another ten pack of single ended vibration motors, but those haven't shown up yet ..

http://www.ebay.ca/itm/391373300125?_trksid=p2057872.m2749.l2649&ssPageName=STRK:MEBIDX:IT


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## time warp

Could you energize them with a "flasher" function? Would cut the current draw sort of like PWM.


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## Bwells

Warren: wouldn't you need two function keys, one to open the knuckle, and one to reverse the polarity to close the knuckle? It would only be in stall mode for a short period of time then off. I see diodes!


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## redman88

Following as well. I am looking to install two on a pair of hustler that am going to rebuild.


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## Bwells

How about a servo instead of a motor?


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## redman88

Bwells said:


> How about a servo instead of a motor?




Size?


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## Bwells

Smallest one known to mankind with the shortest throw possible.

edit: http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=11735


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## redman88

Bwells said:


> Smallest one known to mankind with the shortest throw possible.
> 
> edit: http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=11735




Much bigger then the vibration motors


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## Bwells

10-4, bad idea.


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## Shdwdrgn

Hey, I have some of those same motors! The weights come off fairly easily, I just used some small needle-nose on each end to twist them off. I have a horse & buggy kit that I'm going to convert to a 1904 high-wheeler auto, and I want to use one of these motors to drive it.


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## wvgca

Bwells said:


> Warren: wouldn't you need two function keys, one to open the knuckle, and one to reverse the polarity to close the knuckle? It would only be in stall mode for a short period of time then off. I see diodes!


Actually just one function...my reference is HO scale and Kadee couplers which are spring loaded closed ..I have no experience with other scales, or experience with other coupler brands, well, except for horn/hook ...
the reason that I looked at small DC motors rather than servos is that no other circuitry / components are needed for DC, servos would need a control circuit of some kind that would have to be enabled by the function ground ..


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## wvgca

just a small update, last night I tied some wire wrap wire to the SMD pads on the motor, and ran ir at 1.5V, draw was dead on 70ma, didn't matter either running or in stall mode, same draw, so that looks good ... didn't notice any heating, but hard to tell with such a small motor, held it in stall for 15 seconds and didn't_ feel_ warmer ..someplace I have one of those remote temperature reading thingy's, will try to find it and get a better idea of how much it warms up in stall mode


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## redman88

Quick question that I know I could look up myself but am going to ask anyway. 


Can a function be programmed to run for say 15 seconds then shut off and reset for the next function push?


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## wvgca

redman88 said:


> Quick question that I know I could look up myself but am going to ask anyway.
> 
> 
> Can a function be programmed to run for say 15 seconds then shut off and reset for the next function push?


As far as I am led to understand, no programmable timed function, on either decoder or controller ..
However I ''think'' some decoders an be set to either momentary or latched function outputs, [none that I have can], and apparently some digitrax and Lenz controllers can have function outputs also set momentary or latched as well, again I have neither nor any direct experience with either ..
My controller [MRC Prodigy} and decoder that I will use for test [NCE D13] do not support momentary as far as I know ..I will probably use output three, push on / push off


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## gregc

wvgca said:


> I had seen these before, where a tiny electric motor was installed behind an HO scale coupler box, and used a spare function output to pull a Kadee or similar coupler apart, and uncouple a loco from a car, handy for doing switching anyplace..



Not sure how you would mechanically use a motor to open a Kadee coupler.

wouldn't a solenoid, like an Atlas turnout switch machine, be more appropriate? Just needs short travel to open the coupler. Not sure about current draw and if a kadee spring is enough to reset the solenoid position.


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## redman88

There is one on the market. Can't find the link but did find a YouTube video


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## Shdwdrgn

@gregc: There was another recent thread discussing this exact thing. Basically you use a small thread, tied to the post that the Kadee spring attaches to. When you pull the thread towards the car, it compresses the spring, and the coupler opens. Using a small motor to wind up the thread should create this motion, then when power to the motor is cut, the Kadee spring unwinds the thread from the motor shaft.

You could get this same functionality from a very small solenoid, but there is a large difference in price. For example, I see a push-style solenoid on ebay the same size as the motors above, but they start at $2 each and they are only meant for short-time usage so 15 seconds could potentially burn them out.

Probably the 'best' item for this project is a miniature stepper motor with a screw shaft. I have some steppers that are even smaller than the motor above (approx. 3mm diameter and 5mm long, plus a usable shaft throw of 4mm) which cost $3.33 for ten pieces. This would give precise control over how much you pull on the release thread, it would provide some usable torque, and it would be a 'slow' action, much like you want to see on turnouts. The problem is that once again you need some control circuitry to 'step' the motor. One option here though is an ATtiny85... Because of the small size of the stepper, you may be able to drive it directly from the attiny's I/O ports. This leaves one more port free, which could be a signal wire from your DCC system... High means uncouple, low means return to the coupled state. These chips can run less than a buck each, but you still have to write the code and solder everything together. Not counting your own labor, this option is still less expensive than a solenoid though.


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## wvgca

gregc said:


> Not sure how you would mechanically use a motor to open a Kadee coupler.
> 
> wouldn't a solenoid, like an Atlas turnout switch machine, be more appropriate? Just needs short travel to open the coupler. Not sure about current draw and if a kadee spring is enough to reset the solenoid position.


I hadn't considered a solenoid before .. so just went on ebay looking for micro solenoids...found some around 11mm long, 5mm wide, size is okay, a bit pricey at around two bucks each, but it's not like a person would be buying fifty of these for a layout ..

but drawback is current draw, starting with 350ma, so would need extra driver circuit so as not to overload function sink current .. the extra part [one transistor], is not really a big deal though .but would need to find a ground tap [for sink] on most decoders, makes it a 'not so simple' version .

perhaps do-able, but for now I'm just going to see if the DC micro motor is viable


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## wvgca

redman88 said:


> There is one on the market. Can't find the link but did find a YouTube video


This is perhaps the one that I had seen before, if it is, the cost to try it with two motors and some thread , I think was around twenty dollars ..

I don't mind spending time to try something, but I'm kinda frugal


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## Shdwdrgn

@wvgca: I think you just missed my post, sounds like you found exactly the same solenoids as I did. Note they are a 'push' style, not a pull.

I think I'm going to snag some of the attiny85 chips and play around with using them for the micro steppers I have. I found a programmer for the individual chips real cheap, just have to get some of the chips now. This setup could also be used to run a larger stepper for a turnout, I just have to throw something together and test it out.


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## wvgca

Shdwdrgn;1322425
I think I'm going to snag some of the attiny85 chips and play around with using them for the micro steppers I have..[/quote said:


> I took a really quick look at the attiny85, I like the size, just under an inch square .. cost seemed to start around $1.50 or so, but it should be able to drive a micro stepper directly??
> 
> It would make a nice [and very elegant] 'slow motion' uncoupler with a stepper, just need a pretty low power one, I think there may be a fine line between enough power to open, and too much where it actually cants the coupler off to the pulled side ..
> 
> Actual code shouldn't be too bad, depending on whether you use a 'normal' stepper or one with a worm drive reduction or with some type of end limits


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## redman88

One thing I noticed with the video I posted it does look like it pulls the whole coupler to the side not just open


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## Shdwdrgn

These micro steppers I have are extremely low power, so yeah the chip should be able to drive them. However for something beefier like a turnout, I think I'd need to add some transistors.

You can get the complete attiny85 boards with a USB port for around that size, but if you get a programmer then you can just use the bare chip for this setup -- and that is only an 8-pin DIP or SOP package, so quite a bit smaller. In those 8 pins, you have V+ and ground, plus at least 5 I/O pins. The 6th pin is normally a reset, but it too can be used as I/O. So in the case of a turnout, ideally you could use four pins for the stepper, and two pins as signals for which direction to position the turnout. This particular instance I would rather have a separate signal for each direction, rather than holding one pin high/low. It just seems it would be more reliable that way.

@redman88: I had thought about that too. I think I would run the thread through the coupler pocket, and route it around the opposite side of the center pivot pin. That should prevent the coupler from being pulled to the side, and should also minimize any changes in thread length as the car goes through curves. This is also why a stepper would be more ideal, because you could control exactly how far back the thread is pulled, preventing excessive unwanted motion.


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## redman88

I think that it would need to pull the whole coupler to the side since you are only moving one side. With the magnets it pulls the whole coupler to the side.


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## wvgca

Did some basic load testing with an IR non contact thermometer, cold was 69F, running for five minutes with no load 70F, stall mode two minutes 71F, so there should be no issues at all with possible overheating damaging the motor ..


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## redman88

wvgca said:


> Did some basic load testing with an IR non contact thermometer, cold was 69F, running for five minutes with no load 70F, stall mode two minutes 71F, so there should be no issues at all with possible overheating damaging the motor ..




Nice. I have been thinking it would be cool to 3D print a coupler box with a holder for these vibration motors.


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## wvgca

Got rained out today, so spent a little time on this project..

The eccentric weights are slightly larger than the main motor body, so needed a 0.020 bit of styrene spacer.. the Athearn switcher has some pretty tight clearances from trucks to the coupler box, on this one I couldn't mount the vibration motor behind the coupler box, it had to go underneath it ...

first test was a fail, not strong enough to open .. so pulled off the weight, and attached thread directly to shaft ..trying for more torque 

second test was a fail, moved by hand, but not under power, may have damaged motor or gotten CA in someplace

third test, replaced motor, still weak, only opens one out ten tries .changed limit resistor from180ohm to 150, opens about half of the time, but not usually all the way..

fourth test, changed resistor to 100ohm, opens eight out of ten tries, but maybe half of the time wide open ..

Right now it's pretty much at the 100ma limit, don't want to go higher than that, tomorrow I will go to walmart and see if they have something like a one pound test braided fishing line .. 

failing that option, might have to wait and see if the other batch of ten motors will work better


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## gunrunnerjohn

How hard was it to pull the weights off the shaft? I have some of those motors, haven't gotten around to trying to pull them off yet.


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## wvgca

grj:
those little dents in the center of the small side of the weights are mechanical stakings .. a pair of needle nose pliers will get one weight off fairly easy, but don't have enough grab on the shaft itself to get the other side off, but my pliers are pretty old, and the teeth are dulled somewhat


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## Shdwdrgn

FWIW I used smooth-jaw needle nose on the bare shaft side to pull the second weight off of mine. Wiggle the weight slightly as you pull, the movement will help walk the weight off the shaft. I think once it started moving, it pulled right off.

@wvgca -- have you tried using regular cotton thread? That string in your photo looks massively oversized for the task. Also, after seeing your photos, I might suggest adding some kind of washer between the thread and the motor. Might help prevent getting any fibers pulled inside the motor body?

Oh one more thing... you had mentioned previously that these motors are 1.5v, but all of the listings I've seen for them specify 1.5 to 3v. Maybe try bumping the voltage to 3v and see if that gives them the extra kick they need?


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## Lemonhawk

Instead of using a string to the knuckle, what about attaching a wire to the dangling part that would act as a lever that back under the car you could move with a small cam attached to the motor or a small electro magnet. what do the old floppy drives used to actuate the heads, squeeze them not move them? When I lived on my small farm in IN it was always dry in the spring and wet in the fall .. at least it seemed that way!


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## wvgca

Shdwdrgn said:


> @wvgca -- have you tried using regular cotton thread? That string in your photo looks massively oversized for the task.
> 
> Maybe try bumping the voltage to 3v and see if that gives them the extra kick they need?


In the photos, that's just plain light thread, not heavy ..

with the 100 ohm resistor, voltage should have been around 3.3, and draw right at 100ma, about the max that a normal decoder can handle ..

I tried putting a final pass transistor in just now, and it works, through a 70 ohm, current draw about 150ma, but the motor gets warm quite soon, in maybe 20 to 30 seconds of on time, if it was accidentally left on, I think the motor would die fairly soon
..
the x'tor needs to be tied to ground, on this decoder it wasn't too hard to find, but won't be that easy on most decoders, unless they are setup for stay alive connections

hopefully the other motors show up soon, maybe they will work better??


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## Shdwdrgn

Floppy drives used stepper motors with screw shafts to drive the head back and forth. As I mentioned above, steppers would be ideal for this because of the fine control and additional torque, but they're more complicated to use.

I don't think using a lever on a motor shaft would work at all. That would greatly reduce the available torque, and he's already having trouble getting enough pull on the string.


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## wvgca

I looked at the web page, and installation manual for the versions sold on ebay, from Switzerland, and it seems his have the same limitations ... need 150ma to operate, greater than the recommended max function sink on most HO scale decoders, he also shows an add-on final pass transistor option, and the warning about heating in a very short time period .. while this may work on O scale DCC decoders, it's not a great idea for HO, extra parts needed, and short operating periods ...

sigh .. guess this one isn't a total fail, but may not be worth the time and effort needed ,,

one other possibility is for me to find a very low speed vibration motor [around 1000rpm], that will run at 100ma or less, as the lower speed may give more torque


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## Shdwdrgn

I have some attiny chips on order, and the I/O ports can handle up to 40mA each. I should be able to just connect power across one of the coils in these steppers and read how much current it draws. If this solution works out, it would operate from a 5v source, require the stepper to be mounted near the coupler, and an 8-pin chip (DIP or SOP) to be mounted elsewhere. A single 3.3v-5.0v digital signal will be enough to activate the uncoupling, and the loss of that signal will return the coupler to its normal state. And not including the price of the programmer, we're only looking at less than $2 in parts. Sounds promising, but it could be awhile before the chips arrive...


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## Lemonhawk

While the track movement on the floppy is a stepper, isn't there another actuator that handles head contact? Been some time since I looked at one. Wonder if Kadee is thinking about this?


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## gunrunnerjohn

If you could find a really tiny gear motor, that would do the trick. Here's about the size you need.

http://www.ebay.com/itm/Mini-3V-6V-...493272?hash=item2cb05db918:g:TwUAAOSwubRXGiQl


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## wvgca

thanks for the link to that seller, slowly wading through his offerings .. 
also looking at real small servos with the possible idea of removing the control wire and running them straight dc taking advantage of their gear reduction


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## gunrunnerjohn

After the discussion on torque, I figured maybe a gear motor would be the final solution. I'm using a model airplane servo in a project, and I bought a few sizes for the parts box in anticipation of my upcoming sound/motion board, it's going to control servos as well as sounds and light.


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## Bwells

What about hooking the thread to the end of the trip pin? That maybe easier to open that way as long as the knuckle spring could close on it's own. Try HobbyKing for a servo, They have a USA west warehouse that I think is located in Washington but the China place has a much larger selection.


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## wvgca

I took a quick look at what they call 'sub micro servo' on ebay, but size range is around one inch square by 1/4" thick, too big for HO but probably good for O scale ..
The other vibration motors [single weight] came in just today, so hopefully I can find time to try them soon


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## wvgca

made some progress tonight, the thread I had first used was 0.0035 , and I found some better thread at Walmart that was 0.0015 in diameter ...
by using the smaller thread and going from a slip knot to a regular knot made a difference .
Consistent operation before was at 150ma, but after 2.5V at 110ma was very reliable, even down to 2.2V at 100ma was reasonable, but seemed 'slower' ..?
Stall hold temperature at 110ma only went up two degrees in one minute ...

I did a quick check on the second batch of motors [single weight], and so far they seem like they will work better ..run current at 2.2V was only 40ma, and stall was 70ma ... might have a chance to try the second batch this week, hopefully


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## gunrunnerjohn

The single weight ones look more robust.


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## wvgca

at this point, the double end motors are usable by removing the weight, don't require an extra transistor, and should be capable of being driven by pretty much any standard HO scale decoder by using a 100ohm inline resistor .. the only small issue for anyone deciding to try this themselves would be the finickity soldering on the motor SMD pads ..and the motor that I had thought was damaged, was simply the thread being tight against the motor .. no motors were killed during this experiment  ...


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## gunrunnerjohn

The pads are small on those motors, that's for sure.


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## Shdwdrgn

I usually make new tips for my iron out of some 1/8" brass rod I have, as I have it on hand. I can go for quite awhile on a tip doing general soldering, but now I'm getting into this really fine stuff and had to make a new tip a couple weeks ago. The computer chip I'm working with has 2mm spacing between pads, and a new chip is coming out with 0.05" spacing. Pretty soon I'll have to break out the magnifier and get a smaller iron to be able to work on these parts. I haven't even tried to solder leads to one of these pager motors yet, and the flat ribbon coming from the stepper motors looks even worse. Ugh.


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## gunrunnerjohn

I use the Hakko needletip for finer work, but I limit myself to the .95mm spacing on the leads, no more .65mm or .5mm parts, too fine for these old eyes.


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## wvgca

Spent a little bit of time on this project tonight .. with success!

The first double weight motors were 0.13x0.17x0.51 long ... the second batch were single weight, and were 0.19x0.19x0.43 long .. on closer inspection, the square black surround is an easily removable plastic housing, inside the motor is a cylinder with a diameter of 0.19 .. very comparable to the first ones ..

As it was round I used gap filler CA to attach it, after using a dremel to slightly reduce the size of the weight, but that may have not been needed ...

With a 150ohm resistor current draw was at 70ma, and actuation was firm and crisp enough to make a small click when the coupler moved to the limit ..

In the video this should be able to be heard ..


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## redman88

With the new round motor how well does it handle stall? Does it get excessively hot?


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## wvgca

the second style [round] motor develops more torque at less current ... temperature rise was 3 degrees in a full steady 60 second application, five degrees in a full five minute application ..

here's the ebay link to these motors, $3.29 for ten with free shipping
http://www.ebay.ca/itm/162013701301...49&var=460983979869&ssPageName=STRK:MEBIDX:IT


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## gunrunnerjohn

Looks good, now you just need to equip all your rolling stock!


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## Shdwdrgn

I'm rather surprised it got enough torque while winding the thread around the weight. That's pretty impressive for such a tiny motor.

I'm not good with discrete components, but could you include a small timer circuit that would automatically cut power after a number of seconds?


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## wvgca

Shdwdrgn said:


> I'm not good with discrete components, but could you include a small timer circuit that would automatically cut power after a number of seconds?


Probably not at this time .. don't get me wrong, it should be able to be done, but it would require access to the ground on the decoder board, easy if it's a newer board with keep alive connections already fitted .. not so easy to find [and solder a ground wire] to older decoders .. 

the intent was to find a motor that was strong enough to move the coupler just by using a spare function lead on decoders that have those, an additional timer circuit would limit 'easy' installs to a much smaller percentage of decoders out there..

just out of curiosity, why would you prefer a timed release rather than just pressing a function button again?


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## Shdwdrgn

It figures... yesterday I got in the last part I ordered -- the surface-mount attiny85 chips. I still have to wait for the programmer and the adapter before I can do anything with this chip. Ah well.

The size is nice though -- about the same width as an HO coupler pocket, and half the length, should be easy to tuck into a tight space. Eventually I'll get something worked up...

@wvgca, if you were responding to me, I didn't mean a timed 'release'... What I was aiming for was to cut power to the little motor after a number of seconds so you didn't forget about it and start running the logo around the track with the coupler motor still activated. It's nice that you *can* run it for several minutes without a heating issue, but I would think that would be hard on the motor in the long run. If you, for example, didn't allow it to stay in the uncoupled state for more than a minute, wouldn't that help prolong the life of the motor?


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## redman88

Any further testing done?


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## wvgca

redman88 said:


> Any further testing done?



nope, second style of motor works fine ..
project is complete enough for me ...

any reason why you ask??


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## redman88

Just wondering if you had tried it with a decoder or just with an external power supply. Got a five pack of the motors on the way and a single one already in. Just need to get a spare decoder with enough functions.


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## wvgca

in the video, it's running off a decoder .. and works well...if it matters, I ran it "on" for thirty minutes continuous with no issues 
the red thread that worked well for me was from walmart, brand was Gutermann


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## time warp

All you need now is the stamp of approval from your "ghost engineer", then you'll be golden! :laugh:


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## redman88

Thanks keep forgetting to watch the video. Don't like watching videos when not on wifi. Eats to much data.


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## Shdwdrgn

I got in the ATtiny chips yesterday, so I have all the hardware on hand now to try my method... Only problem is I've been working out in the yard getting ready for Winter and I've been dead-tired by the time I go sit at the computer in the evenings. I'll get to it eventually!


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## wvgca

winter's coming, got two inches again a couple of days ago here ...


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## Shdwdrgn

wvgca said:


> winter's coming, got two inches again a couple of days ago here ...


*Snow???* Already? Sheesh. We had one night where we barely got a frost, then the temps shot back up again. I've been taking my time setting up the greenhouse around the garden because there's no danger of another freeze any time soon. I was actually thinking about trying to start some radishes under the greenhouse this weekend.


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## wvgca

that was second batch of snow, about four inches a week ago, plus a lot of rain ...still got 183 acres of canola out in the field, need maybe five days of warmth and wind to get started combining it ...it's my payday that comes once a year...


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## Lemonhawk

Hope you get some dry sunny weather soon. Its not fun to watch the weather close in on your harvest. I was just in Tucson, Az where the weather was great, even had a thunder storm last Saturday with a rainbow! Not too much farming going on other than large plots of Pecan trees that must require a lot of irrigation.


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