1. Controlling Tortoise Machines with Momentary Contacts
and a Diode-Matrix By
Jerry Hoverson, MMR
15 November 2008

2. Controlling Tortoise Machines With Momentary Contacts
Why the Tortoise switch machine motor in the first place
Easy to install
Reliable
Rugged
Provides slow, quit movement of points
Provides constant pressure to hold points against stock rail
Provides 2 sets of contact points
Frog polarity control
Panel indicator lights
Switch indicator signals
Has become the hobby standard for remote control of turnouts
15 November 2008

3. Controlling Tortoise Machines With Momentary Contacts
The biggest disadvantage of the Tortoise switch machine motor is that it requires a constant, reversible 9-12 VDC power source.
15 November 2008

4. Controlling Tortoise Machines With Momentary Contacts
So what happens if you try to control that turnout from more then one control panel with that constant power source?
A SHORT!
15 November 2008

5. Controlling Tortoise Machines With Momentary Contacts
Enter the 556 circuit!
556
15 November 2008

6. Controlling Tortoise Machines With Momentary Contacts
Where you can control the Tortoise with MOMENTARY devices
Momentary
DT Center Off
Toggle Switch
Momentary
Pushbuttons - S 8 R 1 +
556
15 November 2008

7. Controlling Tortoise Machines With Momentary Contacts
Here’s the circuit diagram for those who just have to have one.
300 ohm R1
2.2K R2
10K R3
+ 12 VDC
- 12 VDC
IC1
LM556-B 6 2 1 7 5
LM556-A 14 8 13 9 12 C1
10uf + - D1 D2
Set
Reset
Tortoise
300 ohm
15 November 2008

8. Controlling Tortoise Machines With Momentary Contacts
OK, lets look at how we would install this
on a simple track arrangement.
Track A
Track B
Track C
Track D
MAINLINE
15 November 2008

9. Controlling Tortoise Machines With Momentary Contacts
One method is to mount the 556 circuits in one “master” panel and then connect additional “slave” panels to the master.
Slave Control Panel
Master Control Panel
556 - S 8 R 1 +
15 November 2008

10. Controlling Tortoise Machines With Momentary Contacts
What’s good and what’s bad about this method of installing?
PROS
556 Circuit is accessible inside the control panel not under the layout
Multiple circuits can be ganged together
Single board
Single power connection with Positive and Negative 12 VDC buses
Only 2 wires going from main panel to Tortoise
CONS
Takes up real estate inside the control panel
Depending on other items may be difficult to get to connectors
Large number of wires going between each panel
Hard to add another tortoise once complete
15 November 2008

11. Controlling Tortoise Machines With Momentary Contacts
Here’s a “ganged” set of 556 circuits in a control panel.
15 November 2008

12. Controlling Tortoise Machines With Momentary Contacts
Let’s look at a general setup using a “master” panel.
2-Wire from Master Panel
(1 & 8) for Tortoise movement
Tortoise
Tortoise
Tortoise
Tortoise
16-Wire from Slave to Master
(S & R) for control of each circuit
(1 & 8) for LED indicators for each circuit
Slave
Master
556
556
556
556
12 VDC
2-Wire (+ & -) 12 VDC
15 November 2008

13. Controlling Tortoise Machines With Momentary Contacts
Another method is to mount individual circuits near each Tortoise Machine
Control Panel B
Control Panel A
556 - S 8 R 1 +
15 November 2008

14. Controlling Tortoise Machines With Momentary Contacts
Why use this method of installation?
PROS
Frees up space inside the control panel
Multiple circuits can be ganged together if tortoises are close together (i.e. a yard ladder)
No massive bundle of wires between panels
Simple to add another circuit between panels
CONS
Takes 4 wires from each panel to the tortoise
Takes 2 wires to supply power to each circuit
Set up as a bus and daisy chained
15 November 2008

15. Controlling Tortoise Machines With Momentary Contacts
Here’s an individual circuit mounted near the Tortoise Machine
15 November 2008

16. Controlling Tortoise Machines With Momentary Contacts
Let’s look at a general setup using the individual 556 circuits mounted at the tortoises
4-Wire from Slave
(S & R) for control
(1 & 8) for LED indicators
4-Wire from Master
(S & R) for control
(1 & 8) for LED indicators
556
556
556
556
Slave
Master
12 VDC
2-Wire (+ & -) power bus
15 November 2008

17. Controlling Tortoise Machines With Momentary Contacts
Now let’s take this a step further and implement a Diode-Matrix to control several turnouts with a single button.
Otherwise known as “route control”.
Track A A
Track B B
Track C C
Track D D
MAINLINE E
15 November 2008

18. Controlling Tortoise Machines With Momentary Contacts
To implement a Diode-Matrix you simply wire each button to an input on the matrix and the outputs of the matrix to the “S” & “R” connections on each 556 circuit
We’ll start by
numbering each
turnout
If we push button “A” then 1=R, 2=S, 3=S, 4=S
The unmarked direction is then the “R” or Reset position A
Then we need to determine which direction is Set “S” or the default position S 4 B S 3 C S 2 D 1 S
Mainline E
If we push button “E” then 1=S & we don’t care about the others
15 November 2008

19. Controlling Tortoise Machines With Momentary Contacts
Let’s take a few minutes and set up our Diode-Matrix S R 4 A B C D E 3 2 1
if we push Button “D”
1 goes to “R”
2 goes to “R”
3 we don’t care
4 we don’t care
if we push Button “E”
1 goes to “S”
2 we don’t care
3 we don’t care
4 we don’t care
if we push Button “C”
1 goes to “R”
2 goes to “S”
3 goes to “R”
4 we don’t care
if we push Button “B”
1 goes to “R”
2 goes to “S”
3 goes to “S”
4 goes to “R”
Remember, if we push Button “A”
1 goes to “R”
2 goes to “S”
3 goes to “S”
4 goes to “S” A B C D E 1 2 3 4 S R
15 November 2008

20. Controlling Tortoise Machines With Momentary Contacts
So let’s wire up the Diode-Matrix with the 556 Circuits
Connect the buttons and the 556 circuits to ground
556 #1 - S 8 R 1 +
556 #2 - S 8 R 1 +
556 #3 - S 8 R 1 +
556 #4 - S 8 R 1 +
Connect the 556 circuits to + 12VDC
+ 12 VDC
Connect the buttons to the matrix inputs
Connect matrix outputs to the 556 circuits S R 4 A B C D E 3 2 1 A B C D E
And last connect the “1” & “8” outputs on the 556s to the tortoise machines
15 November 2008

21. Controlling Tortoise Machines With Momentary Contacts
OK, now that you’ve seen all the wonderful things a 556 circuit can do for you, what does it consist of and what does it cost?
Parts List
Part
Nominclature
Price
2 x circuit board $
14-pin solder IC socket $ C1
10uf Electrolitic Capacitor $ D1
"Set" Red LED $ D2
"Reset" Red LED
IC1
LM556 $ R1
2.2K Resistor $ R2
"Set" 10K Resistor R3
"Reset" 10K Resistor S1
3-Socket Connector "+", "1", "R" $ S2
3-Socket Connector "8", "S", "-" $
15 November 2008

22. Controlling Tortoise Machines With Momentary Contacts
Here is what individual 556 circuits for mounting near the Tortoises looks like
15 November 2008

23. Controlling Tortoise Machines With Momentary Contacts
The 556 circuit used in this presentation was developed by Rob Paisley
Rob has published a lot of model railroad circuits, for example:
Stall motor turnout controls like this one (several variations exist)
Automatic grade crossing controls
Traffic light control
Infrared detectors
Block occupancy detectors
His web site:
If you are interested in building this circuit and trying it out there are handouts available that include:
Electrical diagram
Parts list
Parts layout diagrams
Detailed step by step instructions on building the circuit
15 November 2008

24. Controlling Tortoise Machines With Momentary Contacts
Q & A
15 November 2008

25. Controlling Tortoise Machines With Momentary Contacts
- +
+ - + 1 R 8 S - 1 2 3 4 5 6 7 14 13 12 11 10 9 8
556
15 November 2008