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Topic: Hobby train (n-scale) track switch controller system (Read 2 times) previous topic - next topic

holmes4

Micro servos are about 5 pounds (GBP) on ebay, cost for a micro motor and control card is about 20 pounds (GBP).

Mark

Henry_Best



http://www.nscalesupply.com/atl/ATL-65.html


That doesn't state what voltage the Powerpack is supplying. It's usually 12 -16V for turnout motors (00 gauge). As others have stated, the motors are almost certainly a couple of solenoids on a single armature. The solenoids will work off of AC or DC. If you're using DC and powering them from any electronic circuitry, watch the back EMF, as it can be several hundred volts!

Another thing to consider is that one coil may need the common connection to be -ve and the other coil may need it to be +ve. This wouldn't be a problem using AC. Also note the warning in the instructions about only having the power on for less than 1 second. Any more than that and you're likely to overheat the coils, melt the plastic casing or both.

AJB2K3

In the old days the simple way was to connect all the neutrals (negative) on the 4 wire solenoids (converting to 3 wire), Use swithches to set which side you want to switch the use a single momentary push button to discharge a capacitor discharge unit through the path.(ofter 16VDC)

And yes model railway motors (conventional not DCC) was controlled just but switching the direction that the dc current flowed through the motors coil.

A simple way of doing the change ove was using a DPDT switch.

A good old ref book is
http://www.amazon.co.uk/PSL-Book-Model-Railway-Wiring/dp/1852601736/ref=sr_1_42?ie=UTF8&qid=1361691905&sr=8-42

With the Arduino, there are hundreds of ways to do a single thing but the Arduino must allways be isolated from the circuit control side to protect against damage.
Sorry for the noobish post but my knowledge is 10 years out of date!

Riccarr

#8
Feb 26, 2013, 07:16 am Last Edit: Feb 26, 2013, 07:27 am by Riccarr Reason: 1
I took on of the track turnouts apart and it is indeed a pair of solenoids with a metallic shaft running through the center of the pair. By powering either one of the solenoids causes the magnet field to draw the shaft one way or the other. The shaft itself is connect to mechanism to throw the track frog (rail). Also, I do believe a DC current flowing in either direction will magnetize the solenoid.

I did put multimeter on the AC coming out of the powerpack and it is amazing 17 volts for these little solenoids. For those who had warnings, my circuit uses optocouplers to isolate my external DC power from the arduino circuit. See my fritz link in my previous post for circuit layout.

Here's the Fritz off my circuit; warnings it harry! Each of the pair of wires going to the motors would be an example of a pair that would need to go to the 3 wire solenoid pairs.
http://fritzing.org/projects/train-track-and-turnout-control-system/

Therefore I need to design my 2 wire DC (with forward or reverse current) into the 3 wires of of solenoid pair. I think I can put diodes on each of the 2 main wires to the solenoids, have one diode forward and the other diode in reverse. Then send one of my DC wires to the pair of diodes, and the other DC wire to the common. When the DC goes forward or reverse it should only go through one solenoid or the other. See my attached image as example.

I've yet been able to get the opportunity to wire this up and test it, but the online circuit simulator shows one bulb or the other to light when DC goes one direction or the other.

Henry_Best


Also, I do believe a DC current flowing in either direction will magnetize the solenoid.

The current direction determines which direction the solenoid pulls/pushes.

Quote


Therefore I need to design my 2 wire DC (with forward or reverse current) into the 3 wires of of solenoid pair. I think I can put diodes on each of the 2 main wires to the solenoids, have one diode forward and the other diode in reverse. Then send one of my DC wires to the pair of diodes, and the other DC wire to the common. When the DC goes forward or reverse it should only go through one solenoid or the other. See my attached image as example.

I've yet been able to get the opportunity to wire this up and test it, but the online circuit simulator shows one bulb or the other to light when DC goes one direction or the other.



You're still thinking AC!

Connect the common connection to ground and apply the +ve supply to each of the solenoids in turn. You should be able to get the switch (points in the UK) motor to pull both ways. If not, just reverse one of the solenoid connections so that the opposite end is connected to the common.

12volts will probably be enough to move the solenoids, especially if you connect a hefty capacitor (470uF or more) across the supply. You need to connect a reverse bias diode across each coil to kill the back EMF before it kills your circuit.

You also don't appear to know about 'common ground' wiring. Run a bare copper wire along the underside of your layout (I use a stripped piece of mains cable, 2.52mm cross sectional, I don't know what that is in AWG) and make ALL your ground connections (at both ends) to that. It saves up to 50% of your cabling and pins on multiway plug and socket pairs. You can also connect one side of an independent (not used to supply any other electronics) track supply to it after the DPDT reversing switch, the other side then becomes either +12v or -12v with respect to it, depending on direction of the switch.

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