How to Make a Secured Parcel Pickup Box with Arduino -- Episode 575

I agree with al lthese points, the things that makes soldi state relays trippy is that they correctly switch on from a reset, but never deactivate, which makes debugging stupidly nervwrecking when you don't know whats going on.

I like the overall design. I could also see such a lockbox in a workshop to limit access to tools or materials.

It won't stop someone that REALLY wants to get in, but it also provides some basic access control with a potential for logging.

Other additions I would consider: NFC reader (especially for owner access), battery backup, and WiFi for remote access/logging.

Bummer about the solid state relay. I highly doubt you're the only one who didn't realize they require an AC waveform to work correctly. (They're basically just an SCR.) But, good job past-Clem for designing a mechanical relay footprint!

thanks DAB

Good build Clem.

thanks! mentioning the deciding factors of apart, in addition to a specific part is really valuable to understand the choice!

I don't know how big your solenoid is but a 1N5400 across the solenoid is probably fine - they can stand a surge current up to 200A.

I have different FETs for different applications, the FET you need should have a low on resistance so i x i x R < 0.3W where i is the current in your solenoid. The gate threshold voltage needs to be very low (about 1.5V) so the FET has low resistance when the gate has a digital high output. Something like IRF7809AVTRPBF should work.

I knew I could count on you for knowing the propper way to do this! I briefly thought about using a Mosfet, but kinda got distracted by the small relay listing...
specing the snubber diode is something I never did.
Do you have a go to NFET and Diode for such an application?

I would just use a big NFET on the low side of the solenoid with a snubber diode across the solenoid. Because a FET can be driven directly by a digital output.

You might need a way to open the door if the electronics fail. Maybe a normal key access.

Of course the box would need to be physically secured so they don't take the whole box.

If gets to the product stage, the internal stuff would be in an enclosed compartment.

Cool idea. There are some suppliers around here that could use it.

What are your ideas for making the Relay driving better, and did you spot some weaknesses on security? let me know down below.