Product for use with a diode matrix?

[nickelplate759]

Naïve question - does the physical size of the LED (not the plastic case, the gizmo inside) have any correlation to its robustness?

[peteski]

Naïve question - does the physical size of the LED (not the plastic case, the gizmo inside) have any correlation to its robustness?

The die (the light emitting semiconductor chip) size of most standard LEDs is roughly the same (and very small).  I would estimate it to around 0.010" - 0.015" square.

Only some of the high power white LEDs have larger dies, but that will not make them more robust as far as the reverse voltage is concerned (the most common cause for LED failures).  Some LEDs (usually blue or white, since they are most fragile) have internal protection diode wired in reverse parallel with the LED die.  That is for clamping the reverse voltage which could damage the LED.

[John]

John,
that schematic implies that the switch machines will only remain powered up for the duration of the throw (momentary push buttons).  Stall switch machines should remain powered up after the throw is complete (that's why they are called "stall switch machines).  Almost seems that this circuit is meant for the solenoid-type switch machines which throw one way or another depending on the polarity of the power fed into them. Like Kato Unitrak machines.

look at the link right below it .

http://www.circuitous.ca/StallMatrix.html

[Rasputen]

Interesting.  This is the first item I've heard of this problem. On my friend's layout we use standard green and yellow LEDs.  Their chemistry is similar to standard red LEDs.    By "standard" I mean the Gallium Arsenide material with Vf of 1.7 - 2.0V.  Same as has been used since LEDs were first invented.   If anything I would have expected the newer blue, true-green, or white (blue LED with yellow phosphor) LED getting damaged. Those are much more sensitive to voltage.   

Are your LEDs wired the same way as my friend's?  Are you using a 12VDC power?

Also, if the LED failure model is an open circuit then the Tortoise would be able to still throw in one direction (not that this  would be very useful).  On the other hand, if the defective LED was shorted internally, the switch machine would still function normally (but the other working LED would not light up).

Like I mentioned,  I'm not dismissing your claims of the problem, I'm just really surprised to hear about this problem, since if you do a Web search for Tortoise wiring diagrams, a majority show using LED indicators wired in series with the motor, and in the past I have never heard of the LEDs getting damaged (likely due to to the reasons I mentioned).  If this is as serious of a problem as you say, I suppose adding a 0.1uF (500V ?!) in parallel with the motor terminals might flatten out those voltage spikes.  Those caps are available dime a dozen, although 500V rated might be a bit harder to find. Maybe a 200V rated cap would suffice?

EDIT: This whole 300V thing just doesn't seem to add up to me.  Was a x1 or x10 scope probe was used?

Yes, mine are connected like your diagram.  On the S scale layout I referred to, I'm not sure how they are connected.  The scope measurement I took was about 1 1/2 years ago so I don't remember the details.  We were diagnosing noise issues with an Arduino, which is mounted close to the turnout controls on an HO layout.  Adding high voltage caps did eliminate this problem. 

[rodsup9000]

  When I started building my layout about 15 years ago, I was using Minitronics bipolar red/green LEDs. A few of the red side burnt out within a few weeks. They were wired as in Pete's diagram. When they go out, the tortoise wouldn't work in some cases. Then I switched to ones I got from "MPJA.com" and they seam to last, although I've had a few of them burn out too, but the tortoise will still work. I also lowered the voltage to somewhere around 9 volts and haven't had any go out in quite some time. The Tortoise's are a lot quieter and slower too.

[peteski]

look at the link right below it .

http://www.circuitous.ca/StallMatrix.html

Ok, this is a totally different circuit than the schematic you posted.  But this one is not set up for a diode matrix.

[John]

Ok, this is a totally different circuit than the schematic you posted.  But this one is not set up for a diode matrix.

Peter . did you look at the entire page, or are you just interested in nit-picking every time I try to answer a question    ?  There are other examples in there that might help the OP!!!

I'm done with this!!!

[peteski]

Peter . did you look at the entire page, or are you just interested in nit-picking every time I try to answer a question    ?  There are other examples in there that might help the OP!!!

I'm done with this!!!

No I didn't John.  Guilty as charged.  Sorry!

[John]

No I didn't John.  Guilty as charged.  Sorry!

I apologize as well - I'm having a bad day

[mmagliaro]

I never upvote or downvote ANYTHING.  But I upvoted those last two posts.  Two people being nice.
50 quatloos!

[MK]

No I didn't John.  Guilty as charged.  Sorry!

I apologize as well - I'm having a bad day

Damn, I'm going to have to find another forum.  TRW is getting too soft.   

[jbonkowski]

There haven't been any responses to my actual question about an off the shelf (OTS) product. I want to know what it will cost if I don't make my own from scratch.

The best thing I found, so far, is the NCE Button Board + Switch8-MK2. It has 8 pairs of normal (N) and reverse (R) inputs that will work with normally open (NO) pushbuttons, which means it will work with a diode matrix.

The downside is the price $30 + $70 = $100 to control 8 tortoises. This is actually a DCC solution, allowing throttle control of the turnouts as well, but that's not a requirement for us, or even something people will use.

So is there anything cheaper that does the job, besides building from scratch? It doesn't look like it, not anymore, anyway. Route control seems to be a DCC thing now, with the higher price tag that comes with it. [ Guests cannot view attachments ]

Jim

[mmagliaro]

I think you (and all the responses) answered your own question.  There isn't anything off-the-shelf that is inexpensive that you can drop in there in place of your Tractronics boards.

Is copying the tractronics board and then soldering them up yourself absolutely out of the question?
That does require some work, but once you do it, you are set for life.  You can make more any time you want, and you can replace bad ones yourself. 

[peteski]

Blank circuit boards and full kits for the Stall Motor drivers John pointed to earlier are available at http://www.circuitous.ca/556Stall08.html
Diodes are available from electronic supplier for dime a dozen.  A diode matrix (to control those stall motor drivers) can be wired ob a piece of blank perforated PB board (also readily available).  Yes, it will take some work to get it all assembled, but you will have a reliable solution.

And Max does have a good idea.  Maybe the Tractronics Switchlock circuit could be copied to make more of them.

[mmagliaro]

...

And Max does have a good idea.  Maybe the Tractronics Switchlock circuit could be copied to make more of them.

Thanks, Pete.  My thought is this.  As I understand the situation, the OP has an installed base of a bunch of those boards working well already, and was originally looking for something that performed an "equivalent function".  So if you *have* to make something, why not just make more of those?  I bet those boards are simple enough that all we need is a close-up photo of each side (or one in hand that actually works would be awesome) to draw up the PCB plan (I'm a big fan of kicad), and then have them made.  My experiences with Aisler is that for a small board like this, it should only cost about $4 each or less, and of course, if you go the route of a China maker, it will be literally less than dollar a board.

I will volunteer to draw up the PCB if somebody can get me a board or the photos.