USB Solenoid lock controller for laptop charging cabinet

[dhicks]

Hello All,

We are going to put half a dozen laptops in our staffroom, in some kind of secure cabinet. I'm aiming for a cabinet with six individual slots, each with a power cable for charging the laptop and secured by a door locked with a computer-controlled lock. Staff will have to enter their username and password to open an individual door to get a laptop out. What's the bst way to do the computer-controlled lock part of things? Is there a simple USB-based interface available that I can control easily from a Python script or similar?

[glennda]

Hello All,

We are going to put half a dozen laptops in our staffroom, in some kind of secure cabinet. I'm aiming for a cabinet with six individual slots, each with a power cable for charging the laptop and secured by a door locked with a computer-controlled lock. Staff will have to enter their username and password to open an individual door to get a laptop out. What's the bst way to do the computer-controlled lock part of things? Is there a simple USB-based interface available that I can control easily from a Python script or similar?

Look at what I have used for the Network Kettle - you could use a Web relay (although around $130) which can control up to 4 doors and then just have a web form which once submitted is checked against AD or similar (ldap) which once authenticated you could then run the script to open a solenoid.

Or create something using the Arduino - HomePage Chips which can do the same thing

I have tested the first method not the 2nd (although will be soon!)

Edit - the http://www.arduino.cc/ chips can be usb/ethernet

[plexer]

You could look at the ilocker range from Salto but then all staff would need an rfid card or ibutton.

The locks themselves are approx £95 there would also be other costs and you would have to interogate them with the portable programming device once a week say for their audit logs.

Ben

[dhicks]

Or create something using the Arduino - HomePage Chips which can do the same thing

I'm just reading about the Ardunio again - I've been semi-tempted to buy one to tinker with for a while, and now I'm getting even closer to actually buying one... I've found some documentation that says communicating with the Ardunio via USB/serial is really easy - you just read and write data via an appropriate /dev/... Linux file object. However, what, exactly, you read and write confuses me - unless there's an Ardunio that comes pre-programmed with a handy API that I can simply send and receive data from input / output ports with, I assume I have to write my own code for the Ardunio, upload it to the Ardunio board and then communicate via USB/serial to get / set input / output values?

[Steve21]

I'm just reading about the Ardunio again - I've been semi-tempted to buy one to tinker with for a while, and now I'm getting even closer to actually buying one... I've found some documentation that says communicating with the Ardunio via USB/serial is really easy - you just read and write data via an appropriate /dev/... Linux file object. However, what, exactly, you read and write confuses me - unless there's an Ardunio that comes pre-programmed with a handy API that I can simply send and receive data from input / output ports with, I assume I have to write my own code for the Ardunio, upload it to the Ardunio board and then communicate via USB/serial to get / set input / output values?

Think it depends what you're trying to do. Think of it like a control panel for a projector.

It's sitting in the middle of the computer/projector. You're sending (in this case being a projector) an RS232 signal through the board to the projector.

Or another example, dial-up modem, it's pc-modem-pc. What you're sending is generally depending on what you want to control.

You'd be wanting (i'm assuming) some motor/servo that's connected to your board. And you're sending a serial (or what you choose) command to the board to give power to the servo etc etc.

If that made any sense, and helped at all

Steve

[glennda]

yeah they do what you program them to do - i'm going to be setting up an ethernet one to power on a solenoid for the Network Kettle we have!

[dhicks]

You'd be wanting (i'm assuming) some motor/servo that's connected to your board. And you're sending a serial (or what you choose) command to the board to give power to the servo etc etc.

Right: after speaking to the carpenter, we've had a slight change of plan. Individual auto-locking doors seem like rather a palavar to sort out, so we're now thinking have some sort of sensor, probably just a simple switch, under each laptop to sense when it is in / out of the charging trolly. Therefore, I'm now probably trying to get an Ardunio to tell me the status of a bunch of switches. I'll have, say, a Python script on a PC connected to an Ardunio board via USB. The Ardunio board will be connected to 6 switches, one in each of the charging compartments. The script can simply scan every second or so for switch status. It'll need to send some sort of command to the Ardunio via USB - "Scan switches!" or similar. How do I get the Ardunio board to understand the "Scan switches!" message? Is there a ready-programmed Ardunio available handily set up to deal with switches, or do I have to write my own Ardunio code that looks out for messages coming in via serial, reads them, and sets results accordingly?

[glennda]

TBH i would make the carpenter do what you want! not whats easier!

Something along the lines of one of these which is a swimming center locker and then rather then a key have a solenoid which releases a door

SSLfin1.jpg

[dhicks]

TBH i would make the carpenter do what you want! not whats easier!

No, he had a fair point, a simple sensor should be quite sufficient. I can easily make an alarm or something go off if someone tries to remove a laptop without first signing it out - this isn't intended to make the laptops hugely physically secure, it's just to get staff to remember to put them back on charge overnight. I can do the software bit, complete with AD integration and touchscreen interface, very easily, it's just getting something attached to the USB port and sending useful values back to my software that I've got to figure out!

[nicklec]

The arduino would do the sensors/missing logic for you(no need to script this externally) - you would need to poll the arduino for status updates to check against your bookings though.

[glennda]

You probably want something along the lines of

1 x Arduino USB (Uno) .omlout:.
1 x USB - Serial Cable (3.3v) .omlout:.
1 set of Pushbuttons (x5) from .omlout:. or maybe even Force Sensitive Resistor (Interlink 402) from .omlout:.

and a few bits to connect it up

[dhicks]

1 x Arduino USB (Uno) .omlout:.
1 x USB - Serial Cable (3.3v) .omlout:.
1 set of Pushbuttons (x5) from .omlout:.

Isn't the idea that I plug the Uno board straight in to a USB cable connected to a standard USB port on the PC? What does the USB to serial cable do? How do I connect up the push buttons - do I simply need to make two wired connections for each button back to a port somewhere on the Uno board? Would it be best to place each push button on a bit of breadboard and connect wires from that back to the Uno instead of trying to solder anything? Will the Uno board need powering seperatly, or will it be okay with the power provided via USB?

[glennda]

My understanding was that you needed the serial cable to setup the chip and program it to what you want it to do - but i've been looking at the ethernet version so the uno might be different.

I would setup each sensor on some wire on its own board embedded in the cuboard and then you would need to wire them back to the uno board.

[Steve21]

Isn't the idea that I plug the Uno board straight in to a USB cable connected to a standard USB port on the PC? What does the USB to serial cable do? How do I connect up the push buttons - do I simply need to make two wired connections for each button back to a port somewhere on the Uno board? Would it be best to place each push button on a bit of breadboard and connect wires from that back to the Uno instead of trying to solder anything? Will the Uno board need powering seperatly, or will it be okay with the power provided via USB?

You're right, It's controllable over USB (assuming you buy the USB one), "however" as with any style of controller boards (PIC programming etc) they need their own powersupply normally.

There is a module for arduino that provides a PoE module, but then obviously you'll be wanting ethernet connections, but if you do that might be able to remove USB totally? Not sure on that one.

You could put it via a breadboard if needed, but the issue you'll run into (imo) is trying to fit 16/32 w/e switches into one module. (With or without breadboard)

Steve

[dhicks]

My understanding was that you needed the serial cable to setup the chip and program it to what you want it to do

According to @nicklec's post above I don't need to program the Ardunio chip, I simply need to poll it. Also, that serial-to-USB cable seems to terminate in a 6-pin-wide female connector but I can't see any 6-pin-wide male connectors on the Uno board - would I need to buy an adaptor of some kind?