# What diode to use?



## wombat457 (Jul 15, 2015)

Hey Guys,

I have the following SPDT switches for operating my electrical switches:



The plan is to run wiring from the ACC terminals on the MRC Controller to a Power Terminal Board then to the Switches via the above Momentary Toggle Switches, like this:



I think that is right. 

Apparently I need to include Diodes some where in the wiring. I am assuming the diodes get connected to the "Power" side but am unsure where they would be located, and what size diode I am going to need.

Thanks in advance.


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## Jerry McColgan (Feb 8, 2008)

​I use pairs of mini SPST NO push button switches:










Once you have the 1st pair wired you can wire as many as you like in parallel (power is only used momentarily on one switch machine at a time).










I use the black buttons for normal switch position and red for when I am turning a loco into a siding.

Running my fingers across the black buttons assures me that everything is in the drive past position.

I used to buy the MINI SPST 1.5-AMP MOMENTARY PUSHBUTTON SWITCH (2-PACK) and project boxes etc. from Radio Shack.

http://comingsoon.radioshack.com/mini-spst-1-5-amp-momentary-pushbutton-switch-2-pack/2751556.html​
Jerry


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## wombat457 (Jul 15, 2015)

Jerry,

Wow, thank you BUT what in heck does it all mean ??????

Sorry, but looking at your great schematic is like looking at something written in Swedish to me


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## toddalin (Jan 4, 2008)

Wombat,

You run one leg of an A/C power supply (between 16 and 24 volts) directly to your turnouts. For consistency, this will be the common ground and use the side on the LGB turnouts with the black spot.

Take two 1-amp diodes (4001-4006 series ) and solder them "head to tail." Run the other leg of the a/c supply to the _solder joint between the two diodes_ (where the head meets the tail).

Wire the remaining head and tail of the diode pair to outter legs of your _momentary_ spdt switch. Wire the center leg of your momentary spdt to other connection on the turnout (red spot).

If you want to add the capacitors (recommended), use those mentioned above. After you have made your "diode/wire T", take your voltmeter and determine the anode (+) and cathode (-) by measuring between the outter legs (not both at once) of the two diodes (with the red + probe on the volt meter) and the other wire that you ran to the black spot on the turnouts with the black - probe. Take note of the voltage reading (should be about half the a/c coming in) and determine which side of the two diodes is giving + and which side is giving -.

Wire the + leg of one cap to the outter + leg on the two diodes that you determined with your meter. Wire that cap's - leg to the "black spot" wire. Wire the - leg of the other cap to the outter - leg on the two diodes. Wire that cap's + leg to the black spot wire. Now take note of the voltage and it should be ~1.3 times the input a/c but will bleed down to ~half the a/c if held under load (e.g., toggling a turnout that jams and you hold it for a few moments).

That's it.


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## Jerry McColgan (Feb 8, 2008)

wombat457 said:


> Jerry,
> 
> Wow, thank you BUT what in heck does it all mean ??????
> 
> Sorry, but looking at your great schematic is like looking at something written in Swedish to me


Hi Wombat,

Toddalin answered it pretty well. Its not my schematic but it is what I have used for years.

This might help you visualize it other than it is a single switch as used in the LGB switch box.

Use the diode & capacitor descriptions from the original schematic. 

As Toddling said "two 1-amp diodes (4001-4006 series)" - rated for 100 Volts or higher plus two 470 microfarad capacitors rated for 35 Volts.









The diodes simply tell the switch machine which way to turn and the capacitors add a bit of extra energy to push harder.

This diagram might make more sense for the type of switch you illustrated. Electrically it works the same as the 1st schematic - it just looks different and does not have the 12030 and 12070 DPDT switches (which you do not need).

If you have any further questions don't hesitate to ask.

Good luck,

Jerry


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## Jerry McColgan (Feb 8, 2008)

Note: you can ignore the reference to the 12030 and 12070 those are DPDT switches that mount on the end of and are activated by the LGB 12010 switch machine. The 12070 is a newer version of the 12030 with switches that require less pressure to activate.

That illustration is showing both how the 12010 switch machine is activated and also how it in turn activates the 12030 or 12070.

If this is still confusing you can send me an email with your phone number and I can call you and talk you through it or I can give you my phone number and you can call me.

Jerry


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## wombat457 (Jul 15, 2015)

Thanks guys and Jerry, I might just take you up on your offer of that phone call.


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## Jerry McColgan (Feb 8, 2008)

wombat457 said:


> Thanks guys and Jerry, I might just take you up on your offer of that phone call.


 Sometimes I don't explain things as clearly as I would like to and sometimes schematics can be confusing to me as well. It's been a very long time since I got and used my electrical and electronic training. As a salesman I generally told customers what the engineers told me.

I often think it is easier to understand DC voltage if you think of it as water. A diode is just a check valve that does nothing more than to allow electricity to flow through the wire in one direction and not in the other direction. 

Diodes turn AC (alternating current) into DC (direct current) but it is not always a smooth flowing direct current (especially if you only use two diodes).

DC is like the 12 volts DC of your car's battery. If you connect a 12 volt DC motor to it, the motor's shaft will rotate clockwise or counter-clockwise. If you reverse the clips to the + or - of your battery, the motor's shaft will rotate in the opposite direction. That is essentially what this circuit does - it chooses which way your turnout switch machine will flip the turnout (track switch) and when to do it.

DC loses voltage (pressure) more quickly if your wires are on the small side or the distance from the switch to switch machine is great. That is where you normally will need capacitors.

If you want to push a switch in one direction you want a diode to allow electricity to flow in that direction. If you want to push that switch in the other direction you have to either turn your diode around or use a different diode (electrically and physically) facing the opposite direction. The band on the diode tells you which direction it will allow the voltage to flow (I even forget which direction the marking means but you can simply Google it - or if your switch is flipping in the wrong direction, reverse your diodes). A capacitor is like putting a balloon in the circuit that smoothes out the flow of electricity and gives you a bit of extra pressure when you first energize the circuit.

If anyone has a better explanation, feel free to jump in. I am always happy to meet folks who are smarter and or more qualified in something or who can explain it better than me.

I am kind of swamped right now with other stuff but if nobody else can, I can send a photo, explain it to you over the phone and you will be amazed how simple this whole thing is. 

It's just a two wire circuit from your AC power supply through the diodes (turning the AC into DC power - with the switch or switches deciding the direction the electricity flows), across the capacitors (smoothing out the flow of the electricity), and then to your switch machines.

IPads don't have PC Paint or I would have drawn a diagram showing the layout of the diodes in my switch boxes.

Jerry


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