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connecting GPS and GSM

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I am doing a project and wanted to get some help in it...

Suppose i want to track the speed of a car(digital speedometer or somehting of that sort) and the car has been given a speed limit...the car has been attached with a mobile module or mobile phone and i want to activate the phone to send me sms when the speed goes above the speed limit and later stop when the speed decreases to the required speed.

so this is the basic idea ..track the speed of car using digital speedometer and if speed is above specific speed activate GSM to send location of the GPS receiver in the car which is also attached....

pls let me know how to d it..iam not a master in electronics..just know the basics and got this idea in mind..would appreciate if you can help me in this regard as soon as possible ...

as far i know we need a digital speedometer...i microcontroller to activate the system..a GPS receiver to keep track of the location and a GSM to send sms but dont know how to make it work..so if you could help me in this matter

so pls let me know these ...

hoping for a reply



I have a multi-tech GSM modem (called GSM Socket Modem), with service through T-Mobile. With just a plain voice account you can dial out from the modem and establish a connection directly to your home PC. However, you can NOT dial from your home PC to the modem unless you add CSD to the account (this is contrary to what over a dozen, no exaggeration, T-mobile tech support people told me).

Once you get the CSD number added to the account, you'll be able to call the modem but you'll have to use the CSD phone number associated with the modem. Getting that CSD number from T-Mobile is an adventure in itself. Took me two days and nearly 4 hours of talking to people that consistantly told me, "you don't need that number" and that could not comprehend that there are cellular devices that are NOT phones. I don't know how many times I was asked, "what kind of phone are you using with your modem?" When I told them that I didn't have a phone.

I'm babbling. Sorry.

The modem I have is an embedded product, and uses 5v signaling so it can be directly connected to a 5v CMOS microcontroller with a 115200 baud UART. It uses simple ASCII data strings and is compatible with a standard Hayes modem.

Garmin makes a GPS, I believe its now LVS-35 or something similar. If you go that route, make sure to get a CMOS logic level compatible one (CMOS and +/- 8V RS232 are both available). Mine wasn't, I had to use a MAX232 to work it with my microcontroller. Wasted board space.... You can get approximate speed from the GPS device. Use your microcontroller to get the data from the GPS, check the velocity field, if its too fast then wake up the modem and connect to your computer. You can also send the Lat/Long data as well at this time.

For SMS, I think its pretty simple, but I honestly don't know what is required. I do know that the modem is capable of SMS though, its one of the first things in the manual.
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