The journey is complete! The last couple of weeks have been spent building up the "final" incarnation of the transmitter. I now have a (mostly) historically accurate, fully working Transroc.
From a technical perspective, here's where the time was spent.
First of course, was winding the coils. I know I had photos of completed coils in my last post, but as I was ordering boards for another project, I added some Transroc boards to my JLCPCB order. These latest boards are more historically accurate as they have the solder mask across the entire board (as opposed to just the copper in the previous post). Getting new boards also gave me the opportunity to streamline my build notes. While tapping the coil forms, I did learn one good lesson -- make sure the threads are all the way through the form, and DON'T force the slug through the form -- if the slug binds, run the tap through a few more times to clean up the threads. I learned this the hard way, and now have a cracked slug for the trash bin. :-(
With the coils wound, it was time to place the first component! The assembly order followed the original Transroc manual for the most part with a couple of exceptions. I built this as I built the breadboard version, and that means the Modulator was assembled and tested first. Once that section was verified, the RF Section was added and tested.
As the 15v "Eveready 504" batteries are over $10 USD a piece, all testing was done with my new
EEZ BB3 Bench Power Supply .
The Transroc can be built in several configurations:
Rocket Finder - Pulses the transmitter once every second or so.
Temperature - Uses a thermistor to modulate the transmitter at an audible frequency.
Spin Rate - Uses a photocell to modulate the transmitter at an audible frquencey.
Microphone Mode - Sends back audio of your rocket in flight.
This incarnation was build in Spin Rate mode. I felt Spin Rate would give the most useful data.
Here is a quick video of the Transroc in action.
Turn your volume down -- the tone is a bit nails-on-the-chalkboard! The audio is from a walkie talkie just out of view. You can hear the varying tone as the photocell sees more and less light. It was pretty cool to hear this for the first time!
The obvious final step is to actually fly this thing and analyze the data. It's definitely on the list, and I'm building out a custom rocket for the event. It should be fun!
So What's Next
Over the next couple of weeks I'll be getting all of the files and build notes up to GitHub. I'll post the link here once I get most of the files posted.
Can you build one? Absolutely! After dealing with modern circuit boards and 0406 SMD parts, this project is relatively tame. Most parts are commonly available either through standard channels or via eBay. The coil slugs are samples graciously sent by the manufacturer
Micrometals . I don't know what they cost in single quantities, but perhaps if there's enough interest, I could see if they'll be up to a small purchase. The boards are literally pennies to produce, and shipping ends up being more than the boards. I did order a bunch of extras, so PM me if you'd like one.
The Future
In my original post, I mentioned a possible future. Assuming this recreation went well, wouldn't it be neat to see how much telemetry we could get, using modern parts, packed into the same volume as the original Transroc. LiPo batteries are small and light, and there are tons of sensors out there that could be crammed into the ~2.75 in3 of available space. ...not sure when that project will start as I have a few other projects in mid-flight, but I have a feeling I won't be able to stay away from the modern challenge for long.
Thanks for all the kind words from folks on this forum who have followed me throughout this eight month journey!
Stay safe!
-Frank
