Simple Data Transmission Project

[Dave75002]

I am very new to HAM and have an idea but not sure if it's easily possible and wanted to get thoughts on what protocol, hardware and software may be best to use.. I am actually so new I am about to take my first exam and can’t even transmit yet on ham but will be able to soon. Already starting to think of a lot of projects but this is the first I want to try.

I am looking to first build a data logger with a Raspberry Pi/mini PC or something similar that line that can collect simple data from a couple different sources (USB or RS-232) and software that can turn it into very simple data.
1. Two channels of Temperature (indoor/outdoor)
2. Battery Voltage of the house batteries in the motorhome
3. Maybe a couple of simple open closed (on/off) sensors, like door or water or even smoke sensors.

For this first part of the project I realize I may be on the completely wrong forum and might need to look at a different sites for the programming/software information on building the data logger and connecting sensors.

The 2nd part of this project, that is within this world, is using a Ham radio to transmit, receive and read this data. What I am trying to do is have the transmitting equipment in our motorhome. We spend a lot of time at amusement parks or away from our rig but usually under 5 miles so I figure simplex 2 meter would work. We are in Texas and run the generator non-stop because our dogs stay in the motorhome while we are away when we can’t take them in somewhere. Due to how dangerous the heat could quickly kill them in Texas summers I want to build and carry simple receiving equipment in a backpack to occasionally check on these values. I want the data logger/mini computer in the motorhome to transmit all the channels data every couple minutes… or even only respond somehow if I can query it from the portable side in between for an instant response. It would only need to be very low data rates since each channel would literally only be giving a couple digits for the temp part or an on/off (0/1) signal for the simple (open/closed) sensors.

I know this is a ton of info to ask for and just didn’t know where to start or if it’s even possible. I know radio’s/TNC’s will be needed on both ends (thinking cheap Baofeng UV5r’s with good antennas or something) along with an alphanumeric display of sorts on the portable end to read the data, I just don’t know what else would be needed or how to do it. Even being pointed in the right direction of forums or websites for projects like this may help me figure it out.


Thanks for any help

 

[KB3KBR]

check out Byonics - an look at the Tiny Trak 4, it can do just about everything you've asked for, it can also be connected to a gps for location and a computer for maps and messaging. Also see APRS: Automatic Packet Reporting System.

 

[K7MEM]

I want the data logger/mini computer in the motor home to transmit all the channels data every couple minutes… or even only respond somehow if I can query it from the portable side in between for an instant response.

Two meters would probably work for that distance. But you would effectively be claiming that frequency as your own and using it at you own discretion, without any consideration for other hams who might want to use that frequency. A ham license doesn't entitle you to use of a frequency for your own purposes, at the exclusion of everyone else.

Plus, a transmission, with no expectation of a response, would constitute a one-way broadcast. Broadcasting is no allowed in the amateur bands. If someone was using that frequency at the time, it could be considered intentional interference.

You would be better off looking into the APRS system that KB3KBR referred to.

It would only need to be very low data rates since each channel would literally only be giving a couple digits for the temp part or an on/off (0/1) signal for the simple (open/closed) sensors.

The amount of data may be small, but everything you send needs to be formed in a packet, so that it knows where to go and what data it contains. Blurting out a 0 or 1 would be useless unless you know what it is for.

Wrapping a single 0/1 in a communication packet would be very inefficient. It is probably more efficient, at least for your on/off signals to clump them together in a byte. One byte of data could then give you the status of eight on/off sensors, in a single packet. Simple masking can then be used to determine the actual meaning of each bit.

Martin - K7MEM

 

[Dave75002]

Thank you both for your input. I didn't realize APRS could include other data besides location and maybe a simple message. It's also exactly why I am joining a club and getting my license. I am going to do a ton more research on APRS and it's packet ability along with that hardware mentioned. It sounds like its exactly what I am looking for and would never mean to monopolize a frequency or cause intentional interference. Knowing there is a frequency (APRS) that is allotted for this kind of transmission is exciting.

 

[AK9R]

Do a Google search for "APRS telemetry". You'll find some useful information.