Solenoid Circuit

If you'd like to breadboard the circuit before soldering it together permanently, follow this fritzing diagram. (Note the picture below shows the Metro, the Grand Central wiring is identical)

If you'd like to jump into soldering, scroll down to see the steps.

Gather what you'll need

The N-channel Power MOSFET

Because solenoids draw a lot of current at once, each will be connected to a MOSFET transistor. From left to right, the legs of this MOSFET are Gate (G), Drain (D), and Source (S).

Cut and strip 8 red and 8 black each about 1 inch in length

Cut eight pairs of blue wires of varying lengths. These will be used to connect each solenoid unit to its digital pin on the board.

Eight pairs of short male-to-male jumper wires will be used to create robust connections to each individual solenoid. 

Set aside eight N-channel power MOSFET transistors and eight 1N4001 diodes

The N channel MOSFETs will handle switching power on and off to the solenoids. These FETs can switch an impressive 60A and 30V and are in TO-220 packages so they fit nicely into the proto-board. 

The classic 1N4001 power blocking diode will be used here for kickback protection for our solenoids.

Soldering the Circuit

Solder each of the 8 MOSFETs in place.

You will notice that 8 MOSFETs overrun the laterally connected pins on the proto board. This is ok, we will create our own connections where needed later.

Solder in the 1N4001 diodes. 

Be careful of orientation!

Clip off the excess leads, but be careful not to clip the leads further down! You will need these to make connections later.

Solder in the red wires connecting the power line to the circuit. 

Once again, clip off leads where necessary, leaving extra where the pads aren't already connected.

Time for the ground connections!

Use these wires to connect the ground line to the Source (S) leg of each MOSFET.

Using the blue wires, connect Gate (G) leg of the MOSFET to pins 2 through 9 on the Grand Central. 

Use the wire strippers to size your wires to the lengths you need.

Now, importantly, we must connect the ground line of this circuit to Grand Central's ground. Don't forget this step!

Solder the jumper wires in place, connecting one wire to each end of the 1N4001 diodes.

As before, trim excess where necessary.

Now it's time to fold over the extra length of wire we've left sticking through the bottom and make the missing connections where the pads aren't already connected.

The Plug

 

Connect a red and black wire to the female DC terminal block adapter.

Solder these wires to the ground and power lines on the proto board (labeled "G" and "+").

Connect JST Extension Cables

These male-male jumper wires make reliable connections between the proto board and JST cables, as well as making your bundle of wires easy to organize.

Add Headers

Finally, solder headers onto your proto-shield to connect it to the Grand Central.

Insert the headers into your board (you don't need to add the long 2x20 header for this project).

 

Place your assembled proto-shield on top of the headers.

 

Solder in place!

Time to move on to the next step!

This guide was first published on Feb 18, 2019. It was last updated on Feb 18, 2019.
This page (Solenoid Circuit) was last updated on Aug 14, 2020.