Link broken

[Hooch76]

You mention "Dual-relay module" in the "Bill of Materials" list, but the link (http://www.robotshop.com/en/2-channel-5v-relay-module.html) is broken. I am a complete electronics noob so I have no idea what is needed ;-) Thanks.

[rumlak]

This is the one I purchased from amazon. Works great.

2 pcs 5V 2 Channel DC 5V Relay Module with Optocoupler High/Low Level Trigger Expansion Board for Arduino https://www.amazon.com/dp/B079FGPC9Y/ref=cm_sw_r_cp_api_i_n1CsCbDP3Z2TB

[bjrolfe]

For most garage door openers a simple transistor acting as a switch is sufficient since we're only switching a logic level circuit and not a huge load (which would require a relay). I tested my door opener by activating the switch with my multimeter in current mode and it only drew 30mA so a relay (10A) is overkill.

I used a 2N3904 I had kicking around (good up to 200mA at 40V). You can get 100 of them for a buck on eBay.