Low-cost and Waterproof MiniSG

[Lucas B]

Here's my attempt at making a low-cost (under $200 CAD), miniature Sensorgnome. And it also happens to be 100% waterproof.

The essential components remain the same, I just swap out a couple connectors for waterproof ones, and I stuff everything into a Pelican 1050 Micro Case.

Optional accessories include: battery pack ($50-$150) and travel solar panel ($60-$250). Note that the battery pack needs to have 'charge through' technology to allow for simultaneous charging and discharging (hence the Zendure products).

See schematics, parts list, and images attached.

I plan on making better instructions for building this device in the future. For now, let me know if you have any ideas for improving this design.

[Bryant Dossman]

Nice work Lucas! 

Basically looks similar to the ones I tested out this season. I used cable glands instead of interface specific connections so that I could keep the SDR outside of the housing to dissipate heat. I also used heatsink but no primary enclosure to improve heat dissipation. I ran into issues with humidity building up so I used some desiccant packs. I used silicone tape to waterproof the SDR and had no issues with water seeping though to the SDR or into the main housing. 

Costs were comparable at about $190 including the antenna but I skipped some of your features that gave it a more professional appearance. I'll post my materials list later today. 

I'm currently working on some power supply alternatives to these expensive battery packs. 

https://voltaicsystems.com/solar-chargers/ is another option with always on features and charge through. 

I've found that the setup I was running, with an active tag nearby 24/7 consumed on average a little more than 0.75 amp/hr so a 27 (8 3AH batteries) AH battery safely ran for a day and a half. 

[Thomas Rasmussen]

Hi. 

Just wondering have you tested this system for noise levels? 

I'd have quite a few concerns with how this is setup.. How are you attaching the switch? Those cables to the switch are not shielded and would be broadcasting loads of noise from the PI into the air and going back into your antenna.. 

Also, those GPS antennas are really bad and when you attach it you would have massive noise being broadcast.. even just the uFL connector would broadcast a lot of noise. I find I never really need the GPS antenna, just have your GPS hat facing upwards and it will get a connection even in a metal box. 

The pigtail coax cable you have looks like it is poorly shielded and probably would pick up noise being so close to other components.. 

Have you tested that power supply for noise? I have not yet found a powerbank style power supply that has acceptable system noise.. and I have tested dozens, albeit not that one.. 

Also, if you are using USB cables, you should use ones with ferrites, it can also help a little with noise.. 

Also, if you can avoid putting in the USB extension cables on that is better, some also are bad for noise but saying that a well shielded one is fine.. 

All these things add up to a massive difference in performance.. 

See (very roughly annotated) screen-grabs in link, taken on tests using radio-tracking.eu software.. and also a pic of the system that I use currently which is down to below -70dB noise floor! This can obviously be put in a smaller box but I like to have lots of room. I can post parts list if anyone is interested.

Hope this helps, let me know if any questions..

https://drive.google.com/open?id=1upq1mxUNTu0etrTMWaODghJaNds0G8N4

Regards,

Thomas

[René Janssen]

Hi Thomas,

Noise is a big problem indeed! GPS head helps indeed, but not everywhere... we needed to put a gps antenna 2 meters up to get good reception (tested two antennas), and than it was OK. 

Tha Anker 26.000 is quit noiseless; others has plenty noise indeed!

René

Op wo 2 okt. 2019 om 06:09 schreef Thomas Rasmussen <thomas.sk...@gmail.com>:

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[Lucas B]

Hi All,

Thank you for the additional input - it's great to hear others have been working on a similar design.

I haven't been able properly test the setup for noise, but sounds like Thomas has a good method that I should try - I just need to get my hands on a NooElec SDR first.

The pushbutton is attached via JST connectors, soldered directly to the GPS Hat as per John's instructions. I can put a ferrite bead around the cable to see if it makes a difference.

The power supply I use is fairly high-end so I suspect (hope!) it won't get much interference from that. Regardless, I have lots of ferrite beads lying around so I might as well add some to my cables and see how the noise levels change.

I have used this setup for manual tracking this summer and had a fair bit of success. I used it on Sable Island, NS with an omni antenna near a Parks Canada repeater that was tuned to ~167 MHz and still had many detections that weren't picked up by other local receivers. See detections here: https://motus.org/data/receiverDeploymentDetections?id=5125

Cheers,

Lucas

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