Constructing a diode matrix?

[kevinlms]

 

 

If you want to do away with having two half matrices and the split supply - just use AC instead at double voltage. Use fast diodes and it may be possible to use the DCC track supply in place of industrial frequency AC.

Except for the fact that DavidCBroad won't be using DCC in a hurry! Lots of excuses around here as to why he won't be.

[gordon s]

Thanks for your input guys, but can anyone provide an alternative to the circuit in post 22 that would be easy to build and easy to operate?

 

The requirements are:

 

A split 12v supply to run Tortoise motors.

 

The ability to select a route plus a manual override to select individual turnouts as required.

 

For instance a route is set into a terminus.  Train comes in.  Shunter removes coaches and loco then reverses out to the shed.  Access to the shed may be from a distant platform and may involve several crossovers and a couple of reversals to move across several lines, so has to be set up manually.

 

This was dead easy with solenoid motors as it used an AC supply and was just a pulse one way or the other.  If part of a route was set incorrectly, the action of setting the route would correct it, but with Tortoise motors the change is made by reversing the polarity of the DC voltage.

 

I'd be very grateful if anyone can come up with something.  The only stumbling block is that I'm not an electronics expert, but could solder up some basic components to a circuit diagram.  Much more than that and I'd probably be out of my depth......:-)

[Patriot87003]

+

This tread seems to have come to a stand still some time ago,

just when it was getting interesting.

 

In the "Shows You How Series", Peco issued a booklet 'Wiring

the layout - Part 2 for the more Advanced. Under Advanced Point

Switching the steps are given to translate routing using a Diode

Matrix to a piece of Veroboard using the "N" & "R" notation.

 

Veroboard Matrix.jpg

Each of the routes A-D fires 4 solenoids which takes a lot of current.

via a CDU. The tracks on the Veroboard are not heavy enough with

all the holes to take the current being supplied on the Bus for A-D.

The solution of course is to tie the tails of the Diodes on each track

and take them back to their respective terminals A-D. On the diagram

it would be best to invert them as D-A so they have a clear uninterupted

path to their terminals.

Peco have not re-printed the booklet for obvious reasons, but it still stands as a good

Thanks for this info! I have a diode matrix setup for a fiddle yard but at times one or two of the Peco solenoid point motors fail to throw, even with a hefty CDU included. I had always assumed that it was caused by a bit of voltage drop along the wire from the diode matrix to the point motor (approx 3 metres away), so had beefed-up the wire used to some success. I had never thought about the vero board being a weakness in the circuit .... And funny enough had designed my matrix using that leaflet that you included.

 

Good tip about the solution to this .... Many thanks!

[57xx]

0.1" Vero board is only good for about 0.5A. While the load is admittedly only momentary, I think this is a weakness in design.

 

There's an easy way to fix that; solder solid wire along the length of the tracks to form a thicker busbar. Even just tinning the tracks will help to a lesser degree.

[Suzie]

Thanks for your input guys, but can anyone provide an alternative to the circuit in post 22 that would be easy to build and easy to operate?

 

The requirements are:

 

A split 12v supply...

 

I'd be very grateful if anyone can come up with something.  The only stumbling block is that I'm not an electronics expert, but could solder up some basic components to a circuit diagram.  Much more than that and I'd probably be out of my depth......:-)

 

With these requirements you need the Post 22 solution if the motors will not stay put when power is released.

[meil]

You could of course use MERG's CBUS modules (CANACC5) to drive the point motors and then simply programme the route.

[martink]

Thanks for your input guys, but can anyone provide an alternative to the circuit in post 22 that would be easy to build and easy to operate?

The simplest answer was given in Suzie's post #23 - use a latching relay with each Tortoise, wired as if it were the traditional toggle switch (single or dual 12V supply, your choice).  Each latching relay is equivalent to a very low-power solenoid-type point motor, so can be operated from a diode matrix and/or individual buttons, driven off the same 12V supply.

 

FYI, the basic difficulty arises because Tortoise motors need a controller with a memory state (e.g. a simple toggle switch), while a diode matrix is inherently a stateless device.  Any workable solution requires adding some sort of memory to each point motor - switch, relay, flipflop, Arduino, etc.

[gordon s]

With these requirements you need the Post 22 solution if the motors will not stay put when power is released.

 

The simplest answer was given in Suzie's post #23 - use a latching relay with each Tortoise, wired as if it were the traditional toggle switch (single or dual 12V supply, your choice).  Each latching relay is equivalent to a very low-power solenoid-type point motor, so can be operated from a diode matrix and/or individual buttons, driven off the same 12V supply.

 

FYI, the basic difficulty arises because Tortoise motors need a controller with a memory state (e.g. a simple toggle switch), while a diode matrix is inherently a stateless device.  Any workable solution requires adding some sort of memory to each point motor - switch, relay, flipflop, Arduino, etc.

 

Suzie, I'm a little confused.  Were you referring to the circuit in my own post (22) or your comments in post (23)?

 

As I said earlier, my problem is my understanding of electronics is limited. I was in PCB and electro mech component sales for most of my working life, but that was from a mechanical perspective and not electrical, hence my blind spot. I can happily take a circuit diagram and build something to match, but cannot create the circuit in the first place.

 

If you are saying the circuit from Sue and Fred Horne will be fine, that's OK, but if anyone has a better solution using relays or solid state devices, then feel free to post a circuit diagram that I can work to.

 

Grateful as always for any suggestions you can offer.

[Suzie]

Suzie, I'm a little confused.  Were you referring to the circuit in my own post (22) or your comments in post (23)?

 

Yes, your post 22 solution.

 

If you have something that is a bit too complex for that it is well worth considering a computer based solution using JMRI or similar to make things simpler and cut out all the complex electronics and switching.

[DCB]

There is absolutely no reason why one point or one pair of points, or any other permutation cannot be built into a diode matrix system.  My system has a crossover at the door end of the Fiddle yard which is set across by either a local push button or an electric pencil ten feet apart and set straight either by a local push button or three studs on the outer circuit side of four studs on the inner loop, you just have to build in the functionality. 

 

However the other side of the coin is my Capacitor will throw three four or five big fat H amd M point motors,  Even with five it is s bit sluggish and with two it rips point blades out of the point tie bars .  I don't use a CDU only a big fat 32 volt Capacitor across a 12 volt 1 amp transformer tapping.

 

My solution is to use an old point motor as a dead load, the matrix feeds it current when ever only two points would otherwise throw, like my crossover, you could balance it exactly with three dead loads so five coils take current every time.  It has been working for 20 plus years.

 

I only use the matrix for hidden sidings, my mimic has a stud on the end of each siding so I just set the route each time, it does not matter which way anything is set I just reset it.

 

Using latching relays and Tortoise motors will get very expensive. compared to solenoid motors, I think my matix cost about £2 each at todays prices for a seven road siding fan, I have three matrixes all fed by the same electric pencil and studs on a mimic diagram.with common return from the motors.  Most routes need two or three studs to be prodded, 

 

As regards DCC I am quite happy with variable voltage train control and Relco.  Only a very few locos give problems, Bachmann 5MT and Hornby 42XX being the worst, and most locos double head with no problems. I can double head Bachmann Manor and Wrenn Castle or bank almost anything with a Triang Hall chassis under a Farish 61X Xtank body.  The same pairing on 16 volt variable resistors or PWM controls just don't work with one skidding violently while the other barely creeps along.  My current interest is in very cheap Radio control to give a limited number of speeds and forward /reverse. 

[Crosland]

I don't use a CDU only a big fat 32 volt Capacitor across a 12 volt 1 amp transformer tapping.

 

You have demonstrated a number of times that you have no empathy for the components you use

[raymw]

I've been sort of following this thread, not sure if folk are feeding the motor current through the diodes, or simply operating the equivalent of a low current relay, but either way it may be you need to be aware of the forward voltage drop of diodes, more or less half a volt.