Thursday, October 4, 2012

Cell phones cause headaches

So the hardware part of this little gadget was completed yesterday as you saw. Had the code worked out for the unit but I could not get the GSM cellular device to connect to the ATT network.

To begin troubleshooting the issue I read article after article. Then I decided to look at a few images of devices that others had made. As you see in my images posted yesterday my unit is lacking something, an antenna. I felt a little silly.

I checked with electronics stores in the area. Can you believe that stores havn't sold cellular quad-band antennas since the 90's? Outrageous! Some of you probably never even knew cell was sort for cellular or that mobile phones had antennas once upon a time.

Ordered an antenna online. But, I am very impatient so as I sat and thought. I remembered a device that had a similar connection (SMA connector is actually what it is called). Wireless router antennas are about the same size, not sure if they are quad band but who cares. Had an extra wireless router in my office at work that I picked up from a thrift store for 25 cents. Took the antenna off, harvested a few extra components for a rainy day, kept the casing for a project box and tossed the rest of the unit. Money well spent I think.

Had to add a wire to the makeshift cell antenna (will add photo later). Connected it to the GSM/GPS tracking device, loaded up the script, hit run and........... NO CONNECTION!

After hours of research I loaded up a different script that allowed me to send commands to the device. Same result, thus, it wasn't my programming at fault. Found later that unit is set to work in a different country. I found the command that changed the frequency to the USA frequency. I attempted to send the command and nothing happened. Surprise surprise, It still didn't work. Added some code that supposedly did something for someone else, not really sure, but it didn't help me at all.

Finally, after hours of headache I saw an option at the bottom of the serial console (this is he screen that shows me what the device is trying to do). Chose this previously undiscovered option, re-sent the command to change it to the US frequency, checked for connection and WOOT! It worked. Loaded my script back on the device. Checked connection again and CONNECTED!

It is always good to have some success. It is nice to have something to show for the hours spent tinkering around with things you know little about. I feel pretty accomplished. Learned a lot and actually got the stupid thing to work.

A little worried now though. Through all the research, I am starting to worry that if the payload lands in a place that has no cellular reception we might never get it back. 

Steven believes hat we should look into the telemetry stuff that others are using. Lucky for him I agree. The main part to this came in today. It is the Radiometrix HX1 RF transmitter. Not sure what to do with this little guy yet but I'm sure we will figure it out.

That's all for now. I know this post is a little tedious to get through, but I thought the information was worth posting.

Hope you injoy the update. I will add something more interesting tomorrow!

2 comments:

  1. Dear Joey, how did it work for you with the Radiometrix? We were looking at a possible designed which included a radiometrix....but then we ran into your blog and we thought, GSM is even better than radio signals (specially 'cause they have limitations in length to send the signal)....I really really wonder how this went for you.

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    1. Roy,

      GSM works well only in areas with coverage, and the radiometrix works well when the payload is in flight, and only for constant data retrieval. I would not recommend going with the GSM solution at all, as it has not worked for us above 36,000 feet. Also, if your payload decides to find it's way into a GSM "dead zone" good luck with recovery. Your best option for recovering the payload is going to be the SPOT Tracker. It is worth every penny and does its job. Our current setup is list on the main page of the blog. I suggest reading the entire blog as it describes the problems and solutions we have come across in our launches. Thanks for commenting. Please don't hesitate to ask other questions. I will assist you the best I can. Also, Please make sure to send me a link to your project and link our page on your site.

      Thanks for reading,
      Joey

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