Turnout Control

Alan,

I see you have that book too. Mines a bit older from the looks of yours. I don't remember a colored picture on the front. I've just about have all his cook books.

About your circuit to drive the Tortoise's. I tried that back around the late 70's early 80's. Can't remember what chip I used. I couldn't get it to work. A friend of mine whose hobby was electronics said I needed to de-bounce the switches. The contacts actually bounce several times before making solid contact. This causes the circuit to oscillate causing the motor to go back and forth before settling on a direction to go.

Here's a video on such a circuit.

BTW that fascia panel looks real professional. Good luck with the circuit.

Thanks for the link to the PCB house. That makes two for me. A friend of mine told me about this place. He had some turnout control boards made by them. http://www.expresspcb.com/

I'm going to check in on you every time I see a comment made on the thread.

Bernd

Bouncy

From the circuit description. Will find out for sure when breadboarded.

Seems like it should work...

If debouncing is a problem could you add a monostable flip flop to the trigger circuit to debounce the switch?

You gotta love the T-Flip Flop!

A nice turnout control scheme in the works, looking forward to seeing it come to life!

simpler circuit

Can't find simpler

You mean this one Prof Klyzlr?  http://home.cogeco.ca/~rpaisley4/CircuitIndex.html

Great site with tons of circuits. I had it bookmarked and looked through it to see if a solution was there. I could find nothing that will operate from a single MC push button.

drill down

Dear Alan,

Try drilling down, thru

http://home.cogeco.ca/~rpaisley4/CircuitIndex.html#Switch

thence to

http://home.cogeco.ca/~rpaisley4/556Stall08.html

and scroll down to

"Typical Switch Machine Driver Circuit"

(seperate physical Momentary Contact buttons for each route)

and

"Alternating Input Circuit"

(single Momentary Contact button, "toggles" the turnout between routes on each press)

Happy Modelling,
Aim to Improve,
Prof Klyzlr

PS don't let the pics and hints at "buy the parts here" put you off, all the details to DIY the circuit are there.

PPS compared to the circuit above, these techniques do not require additional transistor buffering stages or associated heatsinks, and thus should build into a much smaller package. I'd note that it's critical to include the 0.1uF filtering cap right up against the 556 chip's +ve and GND terminals to combat noise.

A thought

I'm wondering when you power up the circuits if some of the machines will change state or will they stay where they were set when power is turned off?

Bernd

Reset on Power-on = Yes

Dear Bernd,

The ones on Rob Paisley's site will reset, excepting those that are actually labelled "remembers last position"...

Happy Modelling,
Aim to Improve,
Prof Klyzlr

PS in my applications, this reset on power-up is not a problem. YMMV.

This one?

Referring to this one?

I saw it but could not determine if it would reset upon power up. A fellow on Railwire says it will reset just fine on power up. This certainly looks simpler to mass produce.

"Reset" in electronic terms...

Dear Alan,

If by "reset" you mean "move to a known predictable state",

Pin 9 = +ve

Pin 5 = GND
 

(IE will not actively recall and resume the last state it was left in,
as that state may not be the same as the predictable "reset" state),

then yes, I can confirm this circuit will "reset" on power-up...

Happy Modelling,
Aim to Improve,
Prof Klyzlr

no circuits

I thought the beauty of the tortoise was it is a stall motor and was always on so that all that needed to be done was changing the polarity and the points would change. On our club layout a lot of them are controlled with plain old toggle switches and they always stay in the position they were left in when powered up. The only time we use a circuit is in the yards and one of our members an electrical engineer by trade devised a diode control that is route selective.

Sorry if this is off the original subject, I just think simple is better in some regards. On my layout which is in the design stage I am planning on ground throws and mechanical linkages for those that are hard to reach.

Rob

Reset

Yep, that's what I mean by reset. Do the LEDs act like a diode across an inductive load? Is there concern about damaging the 556 by driving the Tortoise directly?

Why the circuit

Rob, I am seeking a solution that uses a momentary contact push button switch. I also want the turnouts to move to a default position when the railroad is powered up.

Dear Alan, The LEDs do

Dear Alan,

The LEDs do indeed act as diodes (only one of them conducts depending on polarity).
However, it is exactly this behaviour that allows them to act as direction indicators

and having a pair "back to back" means that there will always be a path to power the Tortoise...

No, no fear or issues driving the Tortoise directly from the 556,
this is one of the reasons I was drawn to this family of circuits.
(IR no extra transistor buffer stages, large physical heatsinks, or other acoutrements required...)

For a large example, please check my "Brooklyn:3AM" layout on Carl Arendt's SML site. I'm using the "2 discrete button" version of the circuit to drive the Traverser, via a MicroMark Switchtender motor, and have tested it with multiple Tortoises under "heat of battle" show/exhibition conditions.

http://www.carendt.com/scrapbook/page87/

Happy Modelling,
Aim to Improve,
Prof Klyzlr

Thanks Prof

Nice cost reduction by removing relay. Have 556 datasheet. See that it can supply 200mA well beyond Tortoise need. Will breadboard and play with it. Thanks again.

circuit does not assure power up in a known state

The circuit you referenced in This one? is an symmetrical bistable circuit with out a known power on state. Use of this circuit will not assure that your switches will be in a "NORMAL" position at power on. The power on reset in the referenced series of circuits is provided by a 4.7 uF capacitor wired to pin 2 as in the example below.

The 4.7 uF capacitor was removed in the momentary pushbutton circuit because it would prohibit setting the circuit to the normal state, and add a time delay / instability to setting the circuit to the Reverse state. Additional components can be added to hold one of the reset pins (Pin 4 or 10) low during power on as shown in this circuit.

Simple R C delay circuits can be used, but can be unstable thus unreliable.

Wish I had greater understanding of electronics

Hmmmm.... breadboarding is definitely called for. Prof and a guy on Railwire say the circuit powers up in a defined state. Your explanation more parallels with another person on Railwire who says power up state will be determined by slight production variations of the components - repeatable because of construction but not predictable by design.

I do not want an additional reset circuit. Long ago on my slot car track I learned that long wire runs and ICs are a bad combination. Panels will be spread all around the railroad. Adding optoisolators or some other long distance compensation doesn't thrill me.

Thanks Ken for adding your voice to the discussion.

Actual deployment says....

Exactly

Right on Prof. That is exactly what is going to happen. All that is holding me up is a run to Radio Shack.

Dear Alan, Just remember to

TI Launchpad maybe?

Alan,

Perhaps a TI Launchpad (http://model-railroad-hobbyist.com/node/11299) to solve this problem and keep the component count to a minimum while ensuring a known state at power up? A single TI Launchpad setup could even be configured to drive 2 or maybe even 3 or more switch machines with push buttons.

Ofcourse now I can't find the blog post where someone was using a standard radio shack "double IC bread board" to lower the cost of a TI Launchpad setup to a bare minimum. Both the search here and google with 'MRH launchpad' is failing me for whatever reason in locating that article.

http://launchpad4mrr.blogspot.com.au/

Dear Yaron,

Could you be thinking of

http://launchpad4mrr.blogspot.com.au/

???

Happy Modelling,
Aim to Improve,
Prof Klyzlr

launchpad4mrr

Prof, nope, that's not the one. I thought that it might have been on there too, but it wasn't. The post was on MRH itself or one of the users posted here a link to their own blog with the article. But if that was the case, obviously no launchpad keyword in the referral post and thus goole nor the MRH search will find it

I'm pulling my hair out trying to remember! I might have to go over the last few pages worth of forum posts to find it. It was no more than 4-6 weeks ago *gasps*

UPDATE: I can stop pulling my hair out as I found the link to the site:

http://therustyspike.com/2013/05/04/howto-run-an-msp430g2553-in-a-standalone-environment/

LaunchPad

While the LaunchPad is way cool it is overkill for me. I have enough trouble getting the simple circuits to work let alone programming too. If I had visions of much greater digital control of the railroad then the LaunchPad would be the way to go.

Amazing isn't it, how inexpensive digital chips have become? $3.00 for a complete microprocessor!!! The 556 is only $0.52. And the 4013.... $0.30. Thirty cents!!!! You can't even buy a pack of chewing gum for thirty cents. Unbelievable.

Thanks for hunting down the LaunchPad web site.