[Makerspace] Projects eShow and Tell?
darkpaw at internode.on.net
Thu Mar 21 18:58:26 AEDT 2019
Aha, yep, that makes sense!
Yes, I might well be able to use 7-segment displays!
It turned out that 4.2 ish Volts was about right for the LEDs and the
computer with a 3.3V regulator.
But I want it to run all day, so I think that's going to take 4 18650s in
Do you think it would work to have 1 battery protection module and one
18650 charger module hooked up to each of them, then run 5V into the
charger modules for charging?
On Sun, 17 Mar 2019 at 23:17, Greg Hall <greghall at brushbox.info> wrote:
> 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!)
> Greg Hall
> 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
> > https://onion.io/omega2/ -
> > - 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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