[Makerspace] Projects eShow and Tell?

Greg Hall greghall at brushbox.info
Sun Mar 17 23:17:59 AEDT 2019


Felix, et al.

The second antenna was a 'passive coupler', as most modern phones don't 
have an external ant connex. In areas of poor reception, it's done to 
produce a little 'warm' spot in the house where a phone will work. 
Typically the external antenna is a Yagi or dish, and the coax is fat, 
low loss stuff.

The idea is that the second antenna both receives the emissions from the 
phone and they are conducted up the wire to the external antenna, and 
vice versa. Doubtless lossy, and measurements will tell how much, but 
6dB can be the difference btw working and not.

-

Your Flyball project looks fun. I have a few mechanical 7-segment 
displays that might find a home in some tournament timing thing one day. 
They're in 2 digit modules, about 200mm high overall (digits ~150mm). I 
can send a photo if you can use them.

-

Are the Lithium batteries that bad? Surely a proper BMS and a thermal 
fuse in the battery pack would do it? (While harvesting 18650's, I 
learned the hard way to cut the thermal out instead of unsoldering it 
after a few came out open-circuit!)

Cheers

Greg Hall
0265504481
0428850144
-

On 17/3/19 12:34 pm, Felix Sheldon wrote:
> Thanks Greg,
>
> Good idea, yep!
>
> Could you explain why it's hooked up that way? Is it to bring the 
> signal from the first antenna in there for measurement?
>
> -------------------------------------------------------------------------------------------------------------
>
> The project I'm working on currently also needs radio, but only short 
> range, and so I think I will just use Wi-Fi.
>
> The project is a timing system for Flyball:
>
> https://en.wikipedia.org/wiki/Flyball
>
> I'm starting with the "start lights" which count down to the race 
> start with 5 LEDs - Red, Orange, Orange, Orange, Green.
>
> It should be possible to get those to work with an existing commercial 
> timing system which does not provide the start lights. That system 
> uses the 915 MHz band with little packet radio chips like this:
>
> https://core-electronics.com.au/sparkfun-rfm69-breakout-915mhz.html
>
> But the plan is to later do all the other parts as well, and use WiFi 
> instead.
>
> I'm going to build a series of prototypes to get the design to a point 
> where it's reliable, tested and fairly easy to make.
>
> The main parts are currently:
>
>  - The Onion Omega2, which is basically a WiFi router chip running OpenWRT
>
> https://onion.io/omega2/ - https://docs.onion.io/omega2-docs/omega2p.html
>
>  - Some 3W LEDs - should be visible in any conditions.
>
>  - MOSFETs to switch the LEDs.
>
>  - 4 x 18650 Li-ion batteries and some protection modules from Ebay.
>
> -  3D printed modules to mount all the other bits and allow them to 
> fit inside:
>
> -  A 65 mm acrylic tube for weatherproofing
>
> I'm not real sure though that I should have used lithium batteries, 
> due to the safety risk, but they are just so good!
>
> A couple things I'm considering to avoid mistreatment of the batteries 
> are:
>
>  - Put the batteries in a sealed 3D printed module and then make a 
> matching charger from an existing commercial one.
>  - Don't add an off switch so that the users are forced to remove the 
> batteries after use. Maybe beep annoyingly after inactivity.
>  - Take apart a commercial charger and build it into the project.
>
> But after sorting all that, and building the next components, I'm 
> pretty much left with a software project to do all the hard work.
>
> I'll just keep it simple and use TCP/IP for all the parts to talk to 
> each other, and write a cross platform control software that can run 
> on laptops or tablets.
>
> There's a great UI library for Python:
>
> https://kivy.org/#home
>
> And this project can synchronise clocks:
>
> https://chrony.tuxfamily.org/
>
>



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