part to use

Robert.IT

I would like to create a 4 digit security panel to unlock my car doors. What parts should i use from Parallax that will help me. Please I NEED HELP

Bean

Pretty much any of the SX parts would work for that purpose. I would use the SX28.
Bean.

Robert.IT

Thanks Bean. I also had another question. What LCD screen do you prefer to work with the SX28?

Bean

Well the serial displays are the easiest, but are more expensive.
If you are planning to use SX/B for programming the SX28 there is an LCD controller example program in the help file.

Bean.

Robert.IT

Hey Bean, Thank you very much for all your help. You might be hearing from me more seeing that this is my graduation project.

Bean

Glad to help. Keep in touch...

Do you have a programmer yet ?

If not I would recommend the SX-Tech kit ($99)·http://www.parallax.com/detail.asp?product_id=45180

If you can swing the extra $30 for two more books get http://www.parallax.com/detail.asp?product_id=45181

You'll need a computer with a serial port to use the programmer.

Bean.

Robert.IT

Hey there again,

Earlier you told me about there is an LCD controller example program in the help file.
Where might I go about finding this file? And Is it on the Parallax website or the free CD's that Parallx gives out?

Bean

At the top of this forum is a thread to download the SX/B help file (SXB.CHM). The example is in the help file.

Bean.

Jon Williams

As it turns out the SX/B help file may have all the "parts" you need as it shows how to connect to an LCD as well as scan a keyboard. You add the glue code and control output and you have a security panel!

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Jon Williams
Applications Engineer, Parallax
Dallas Office

Robert.IT

Hey does anyone know the link to download the SX/B help file.

thanks

Paul Baker

try:
http://www.parallax.com/sx/sxb_commands.asp
http://www.parallax.com/dl/docs/books/ExploringTheSx.pdf
http://www.parallax.com/dl/sw/sx/SX-KeyEditor3_0.exe
http://www.parallax.com/dl/sw/sx/SX-KeyEditor3_0sm.exe

The bottom two are the actual programs, but they contain help files within them, both are same but the second requires internet connection on the machine your installing.

Since SX/B is very new, there is not a dirth of information on it yet, you can try comparing the first link with the Basic stamps's available commands and use the help files for the basic stamp, also check out John Williams' article on SX/B at:

http://www.parallax.com/dl/docs/cols/nv/vol5/col/nv116.pdf

since he discusses some difference between the two.

Hope some of these help,
Paul

Robert.IT

Thanks guys these site will help me out a long way.

p.s. keep in touch

Robert.IT

Hey im going to change my project. Instead of using a car door. i am going to use a house door. do you think the SX Tech Tool Kit PLUS would work for this as well?

Bean

Sure, you just have to find an electronic house door lock.

Bean.

Paul Baker

Hey Robert,
·
I was going to mention this before, but the required security for an electric·car entry is not as critical as for a house entry since the total value of things left in a car is not as great (besides the value of the car itself) as items left in a house.·You want to make hacking into a house entry keypad as difficult as possible. So just providing a "confirm access" signal (say by the shifting the level of one of the output pins of the SX) is a rather insecure method, a potential thief only has to place a voltage (or sink the voltage) to gain access and circumvent your security system.
·
You can "toughen up" the security of the system by using a serial identification (SID) and decoder (accomplished by storing the code on two serial eproms and a serial comparator)·so that an entire string of bits is necessary to activate the solenoid. But even this has a weakness, a particularly knowledgeable thief can place a bug that taps the signal line and records the correct series of bits (entirely possible in today’s micro-miniaturization of electronics)·and replay the signal to activate the solenoid.
·
The most "bullet-proof" (while still being economically viable) solution today is what is called a rolling code generator, which produces a different SID for each and every confirmed access (the codes will repeat eventually but through standard use, years pass before the codes are reused). So a bug is useless, since replay of a previous access code will be rejected (This system is used within the ignition system of my Mini Cooper (and all BMW's) to make hot-wiring the car problematic enough that a thief will opt to steal someone else car instead, all·remote control car entry systems use them as well). There are chips commonly available that do this for you,·and the·codes have been analyzed by cryptographic experts to ensure that a future SID cannot be derived by past SIDs. One last comment is that most likely there will be a weak point between the rolling code decoder and the standard "off the shelf" solenoid since the solenoid·only needs an activate voltage, so place the rolling code decoder as near the solenoid as possible and encase the combination in a casing that is resistant to manual tampering as possible.
·
I know this is only a project, and you may find these to be "over the top", but these steps are necessary for a commercialized system, and besides it would likely impress the hell out of your professor that you went to such lengths to make a commercially viable system.
·
You may choose to not go with an off the shelf electronic house door lock (EHDL), since you may find it difficult to convince your professor that the system was completely derived by your own hands and not the prefabbed EHDL. The basis of a homebrew system is·a keypad, a controller, and a solenoid. You want a solenoid that is extended when not activated (otherwise a thief only has to turn off the power to your house to gain entry). One source of cheap solenoids (as well as other miscellaneous electronic parts) is http://www.allelectronics.com , I remember seeing a little while ago a solenoid for sale that was originally designed for the locking mechanism of a prison cell door, this would be a perfect fit for your application. Actually I just visited the site, and they no longer have that part, but this one looks like it would work as well: http://www.allelectronics.com/cgi-bin/category.cgi?category=575&item=SOL-58&type=store·and its only $1.50, with 3.7 lbs of pull force this solenoid will make a very impressive sound when activated, just make sure you drive it at 10% duty like they say, or you will end up with a dead solenoid in a heartbeat. It also·appears that some modification of the mounting assembly (that long bracket under the spring/bar assembly) may be required for your application, and you'd likely want to fuse a standard dead bolt post to the end to make it usable in a standard lock assembly. An additional advantage of the 10% duty solenoid is that if a thief does gain direct access to the solenoid, and he tries to activate it, unless he is smart enough to start at a very low duty activation signal and slowly work up to higher duties, he will fry the solenoid so quickly that the solenoid will fail before he has a chance to open the door, this means you can no longer open the door even with punching in the correct code, but at least your valubles are still safe.
·
Paul (needs to learn to post messages which aren't so lengthy )

Post Edited (Paul Baker) : 11/16/2004 5:28:41 PM GMT