Point control in fiddle yard with Arduino (or Pi?)

[F2Andy]

I am considering controlling points with an Arduino, using servos. This would be for a four or five track fiddle yard, with three or four sets of points at each end.

 

Each set of points at the left end will have a matching set of points at the right end operating in concert - can they both be connected to one output on the Arduino? I think they can be powered separately, so I guess if I do it that way, I could have several servos on one output, but can two be powered directly from the Arduino?

 

This would be for DC, so I would also want to switch power depending on how the points are set. What is the best way to do that? I.e., what hardware do I need?

 

Control would be by a set of four or five push buttons, one per track, which should be straightforward. I was also thinking of adding an OLED screen to show the currently selected track.

 

Is the Raspberry Pi with PWM a better alternative?

 

I have some programming experience, so the coding is not an issue, by the way.

[beast66606]

A downside with pairing points at each end of the fiddle yard road is you can't arrive in one road and depart another simultaneously

[Ian Morgan]

I would not advise driving two servos from one output. It would not be possible to set end points separately in the Arduino, so you would have to arrange this adjustability mechanically instead. Also, it is inadvisable to use long leads to servos as they will pick up electrical noise, particularly from analogue locomotives.

Frog switching can be done with a relay, controlled by an Arduino output, or by a micro-switch attached to the servo mount. Other methods include a small module created by a Merg member that is controlled by the signal to the servo, and detects the half way position and switches a relay automatically.

 

As an alternative to the Arduino, a single Merg CANMIO module could just about control your fiddle yard, as it can drive up to 8 servos and handle up to 8 push button switches. However, it is best not to have over-long leads to servos, so a better solution would use a CANMIO module at each end of the fiddle yard, close to the servos, and a CANPAN module in your control panel, all connected by just 4 wires (the CBus Layout Control Bus and 12V power supply). The CANPAN module allows up to 32 push button switches and 32 LEDs to be attached to it, so it could eventually control your whole layout using just the four wire bus. I have just completed installation of such a system to our 'Santa' layout that will be on the Peco stand at Warley this weekend. Come and have a look if you are visiting.

[KalKat]

.. @ Ian Morgan, that;s an interesting solution. I too am considering fiddle yard route setting and was thinking along similar lines to the OP.

 

I have had a look at CANMIO and CANPAN, I note that ;MIO is shown as a PCB so I assume you would have to acquire the relevant components. Is there any programming required to make this system work?

 

 

Apologies to F2 Andy for hijacking his thread.

 

 

Emma

[Ian Morgan]

CANMIO is available as a complete kit for operating servos now (cost £11 for Merg members). Different firmware can then be uploaded to the module to make it perform other functions (CANACC8, CANACE8C, CANCOND, etc).

 

The new Universal CANMIO firmware that will allow all 16 individual connections to be configured as either input, output, servo driver, RFID, etc. including signal bounce and other interesting functionality is still beta and under development.

 

Programming is not required, however, the modules need to be 'configured', telling the module how it should operate, such as setting servo end points, and speed. Then you need to 'teach' the modules which 'events' they should broadcast when something happens, and which 'events' they should listen for, and what actions they should take when an 'event' is received. Configuration and teaching is carried out using some free Windows software called FCU, and using a CANUSB module to connect the PC to the bus. Once the modules have been configured and taught, the PC is no longer required, unless the layout changes and new events are required.

[F2Andy]

I would not advise driving two servos from one output. It would not be possible to set end points separately in the Arduino, so you would have to arrange this adjustability mechanically instead. Also, it is inadvisable to use long leads to servos as they will pick up electrical noise, particularly from analogue locomotives.

 

Frog switching can be done with a relay, controlled by an Arduino output, or by a micro-switch attached to the servo mount. Other methods include a small module created by a Merg member that is controlled by the signal to the servo, and detects the half way position and switches a relay automatically.

 

As an alternative to the Arduino, a single Merg CANMIO module could just about control your fiddle yard, as it can drive up to 8 servos and handle up to 8 push button switches. However, it is best not to have over-long leads to servos, so a better solution would use a CANMIO module at each end of the fiddle yard, close to the servos, and a CANPAN module in your control panel, all connected by just 4 wires (the CBus Layout Control Bus and 12V power supply). The CANPAN module allows up to 32 push button switches and 32 LEDs to be attached to it, so it could eventually control your whole layout using just the four wire bus. I have just completed installation of such a system to our 'Santa' layout that will be on the Peco stand at Warley this weekend. Come and have a look if you are visiting.

 

I had not thought about adjusting the servos, and was not aware of the issue with long wires. Good points.

 

With regards to the relay, would something like this do?

https://cpc.farnell.com/coto-technology/9007-05-00/relay-reed-sip-spst-5vdc/dp/SW04891?st=relay

 

I will not be at Warley, unfortunately. I did talk to the MERG people at Wigan; that is a possibility.