Controlling small AC switches with a DC circuit

[Riccarr]

Hello,

I'm working on an automation system for my hobby model train system, n-scale.

I have developed a Arduino based circuit that uses IR sensors and shift registers to detect train position and then uses an h-bridge circuit to send forward/reverse DC power to throw track switches (turnouts) to divert the train down one track or another based on the Arduino programming.

My issue that I want to solve involves some of the track switches which are actually AC based, 3 wire electric switches. I'm not sure how to integrate these into my DC based system.

I know you don't know anything of my system, but at its basics, I can control numerous sets (pairs) of DC +/- wires going to each of the DC switches/turnouts, and I can reverse the DC polarity on those pairs of wires so as to throw a switch in forward or reverse.

Now the AC switches are 3 wired. Here is a link to a installation instruction picture which will give a good understand of how they are wired; mine are just like this. The real information is the wiring diagram at the bottom.

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

The control switches are those buttons on the "switch control box", which are sliders, left/right and press to activate the power. So the slider buttons are control direction. You'll notice they are powered from the AC power pack via 2 wires.
This further confuses me because I thought AC was "alternating" current, so I didn't think a motor could be made to spin opposite direction by flipping the wires around, like a DC circuit would.

Nevertheless ... how might I deal with these 3-wire AC switches in my DC based system, which uses h-bridge design to reverse DC power?

Ideally I would like to just expand on my DC h-bridge controlled DC power and send that to the AC switches. Might this work if wired properly?

How would 2-wire DC be wired to those 3-wire AC switches?

Thanks for reading, and looking forward to any input or comments.

Cheers,
Eric

 

[throbscottle]

It looks as though your switch machines have 1 wire to push out, one wire to retract, and a common. They might work using DC, you'll just have to try it - just stick with the same wiring scheme - the voltage probably won't be the same as for AC though. Depends what they are using to drive the pushy-pulley bit. It would be better though to use relays or opto-isolators. It shouldn't be hard to arrange that the polarity of your controlling signal switches 1 relay/isolator or the other. In fact, with opto isolators, if the LED has a high enough reverse voltage, you won't need any extra components, just connect a pair with opposite polarity inputs to each pair of control wires.

Hope I've understood your question correctly and not just written a load of rubbish!

 

[alec_t]

The switch control box has an AC input, but may have DC outputs. Can you check with a multimeter?

 

[Riccarr]

hey guys ...

throbscottle ... though I'm not for sure clear on what your getting at, I believe I am already doing what your suggesting. I didn't give much details on my circuit so I broken down and finally completed by Fritz design of the circuit. Warning... its has mucho wires.

Alec ... I checked with multimeter, the power in/out of the switch controllers is AC.

Here's the Fritz design: https://fritzing.org/projects/train-track-and-turnout-control-system/

If you can take a look, I put on a little servo meant to represent the 3 wire AC motor. How the heck can I get one of those as part of the system. I tried running some straight DC power to the AC turnout motor and I didn't get any movement, though I wasn't completely sure which 2 of the 3 to give DC power to. I checked the AC power from my track power control module (that powers the AC switches) and it gives out 17 AC volts to those little switches; I was surprised so much and they don't fry.

If I have to add a separate AC power source into this design, how might it be possible to integrate that into the controlling approach of the opto couplers, one for each motor. Also, I am not designing this for a specific layout, this is meant to be customizeable, so what I rather not do is anchor specific opto to specific AC or DC motors. But in the end if I have not other option then I may have settle for a design to allocates a portion to AC and a portion to DC. Still the same questions ... how to add the AC into the system. Remember ... only one motor switch needs to be powered at a time.

Thanks for reading; I hope the design doesn't freak anyone out, its a bit hairy, I know.

Cheers!

 

[throbscottle]

This (attached) is what I was trying to say. The two "M" symbols in the turnout represent some kind of motor/servo assumed to be inside. You could probably modify your H bridge to to the job without the extra relays (which in theory could be opto isolators)

 

[alec_t]

Here's how you could do it with solid state components. Your H-bridge (or two output pins of the Arduino) would connect to In1 and In2. The opto-isolators prevent any switching spikes from getting back to the Arduino.
I have assumed that the AC switch machine is similar internally to the DZ-1000 and simplified it for simulation purposes.