I didn’t want to start mucking up the thread. I think the time is coming for Metal shop to get at least one RFID locker. We are getting a spool gun & want to lock it up. The spool gun will be a training required item. It’s not just a pick it up & use it type of thing.
The demand would certainly be there to create several RFID locker/cabinet for other committees as well.
I wouldn’t mind helping build some & think if we created a build day could make several of them.
So the 3D Fab RFID cabinet is very simple. Using off the shelf parts and the Seville Tall Storage Cabinet from Sam’s Club ($199). I hacked the metal rods that lock the cabinet with the key and attached them to the car door actuators screwed into the cabinet (you can’t loosen them from the outside). I used a pi face digital 2 on a raspberry pi 3 with wifi for the dual relays (it’s $50 but I would just use a relay board with the GPIO controlling it next time, I wanted it plug n play). The relays open and close the lock by pulsing the actuators for 0.5 seconds, the actuators stay open or closed by the friction of the mechanism. There’s a long level arm switch that I have bent and screwed in to detect if the door is open or closed so it should lock when closed. 12VDC and 5VDC power supplies for the pi and relay/motors. @benemorius wrote the code for it to work with the generic RFID reader. @styler93gsx helped me as well wire the cabinet.
Sorry I haven’t documented this all on the Wiki, I’m sure it’s not the best solution but it’s the solution I came up with off the shelf parts just to get it done, since DMS has been trying to come up with an RFID locker solution for years and nothing has come up yet, I wanted to be the first to actually make something that works.
I know of three ways to electronically lock a cabinet…
Bar / bolt. @themitch22 has a good example above. They work. They’re cheap. But, when they are “locked” the door cannot be closed.
Magnetic. The little cabinet for the MultiCam pendant is a good example. @themitch22 described some drawbacks here. One of the other drawbacks is how trivial they are to defeat if power is provided from an outlet (just unplug it). But, the door can be closed without having to rescan the RFID tag.
Slam latch would work. You’d just need a relay board (the pi has low source
current on outputs). For these stainless cabinets though it wouldn’t work
but for whatever purpose you have you could make it work.
They might. With a latch on the top and the bottom of the door. The door is formed sheet so the latches would probably have to be “raised” into the interior. The latch would contact the face of the cabinet then hook against the inside lip. In other words, roughly replacing the car power door locks may work. (But I am not suggestion we do that. As far as I’m concerned the 3D fabrication cabinet works well.)
I’m thinking a slam latch would likely be the better choice. Magnetic locks are great, I have 2 on a personal project. However they are large and have to be mounted just right. Additionally the magnetism may not be to good in the metal shop. You can add a battery backup, mine has the capability but I haven’t got to the recharging circuit. It would last 8 hours of being unplugged with 2 mags.
I was thinking of adding a 12V SLA battery parrallel to the power supply as a backup, but really if the power is off, you wouldn’t be doing much 3D printing, the mechanical failsafe works for me.