The crossing gate is pretty straight forward and the process should work for most any crossing gate that has a 'T' like structure .  It's probably a good idea to play with the servo before attaching the connecting rod.

Basic instructions:

1. Hardware:

   • Bachman crossing gate [click here]

   • SG90 servo [click here]

   • PCA9685 servo driver [click here]

   • Push rods [click here]
     --Note:  I just used 22 awg solid copper wire, but you may want to use the push rods to ensure long term stability. 

2. PCA9685 datasheet: [click here]

   • When a LOW level is applied to OE pin, all the LED outputs are enabled and follow the output state defined in the LEDn_ON and LEDn_OFF registers with the polarity defined by INVRT bit (MODE2 register).

   • When a HIGH level is applied to OE pin, all the LED outputs are programmed to the value that is defined by OUTNE[1:0] in the MODE2 register. 

3. Drill a hole in the crossing gate, see 2nd image

4. Mount the crossing gate to the top of the board

5. Mount the servo directly beneath the crossing gate.  Options: 

   • 3d printable bracket [click here]

   • zip tie

   • glue

6. Run a push rod from the servo to the crossing gate.

7. Schematic:  [click here]  It may look better if you download the image to your computer, then open it with your favorite picture viewer. 

8. Software:  [click here]
   Install and use the utility program to test your servo's.  The utility program does not control the OE pin, so you'll need to set it low manually.