Tortoise remedy - an alternative

[chaz]

In MRJ issue 252 Brian Self detailed a modification to Tortoise point motors using a microswitch. The internal switches can be unreliable and the microswitch will certainly effect a cure.

 

On my Dock Green exhibition layout I have had problems with a brand-new batch of Tortoises which has caused the live crossings on some of the points to go dead for one or both routes. Brian's solution involves removing and dismantling the offending motor which I wasn't keen to do - one or two mine are in very confined spaces and would be a pig to refit. I wanted a solution that would not involve disturbing the Tortoise (let sleeping Tortoises lie?), so instead of a microswitch I use a relay.

 

I bought a batch of ten automotive 12V SPDT relays from Rapid Electronics - their order code 51-0665. If you buy ten the unit cost is £1.52 - bought singly they cost a bit more. They come with a tab which can be used to screw them to a baseboard member near the Tortoise. The wires that ran to the Tortoise switch can be rerouted to the relay. The relay has very chunky tags with holes in which wires can be soldered - just dwell with the iron until the solder flows nicely. Two wires from the relay coil can be piggy-backed onto the two wires that run to the Tortoise motor. In the diagram "T" is the Tortoise, guess what "R" stands for!

 

 

You need to include a diode as shown in the diagram (a 1N4001 is fine) in one of the wires from the relay coil so that the relay is off for one setting of the point switch and on for the other. It doesn't really matter which way round the diode faces - you just need to ensure that the combination of the diode direction and wires from the relay switch to your DC section wiring or DCC bus gives the correct polarity to match the point setting. You can work it out or you can do what I do - put some temporary connections in with croc' clip leads and then test that the polarity matches the route setting.

 

I do the connections on a tag strip rather than the switch or the Tortoise PCB tab - it's much easier to be neat.

 

The relay is more expensive than the microswitch (Rapid quote £1 for a suitable switch - but I guess if you are driving your points with Tortoises cost is not top of you priorities?) I don't claim that the relay is better then the microswitch - they will both do the job equally well - but if, like me, you don't want to disturb your Tortoises this will do nicely.

 

Chaz
 

[RFS]

Surprised you are having problems with the reliability of the switches on the Tortoise? I have had 70 of them on my layout for several years now and no problems at all.

[chaz]

Surprised you are having problems with the reliability of the switches on the Tortoise? I have had 70 of them on my layout for several years now and no problems at all.

 

I too bought a batch several years ago which have worked for a long time without problems, but a later batch bought for Dock Green have proved a lot less reliable. Brian Self's article In MRJ issue 252 shows that I'm not the only one to encounter the problem. I have heard it suggested that the QC might not be what it was.

 

Chaz