USB Power Buffer to stop ignition reboots

[crystalmark]

Hi all,

As part of my pre-start-up checks, I connect SkyDemon to PilotAware.  After starting the engine, Rosetta reboots and I have to sit around with the motor running until PilotAware is ready to connect.

Does anyone know a small battery/UPS/capacitor to keep the Rosetta alive for 5 seconds or so while the motor starts?

Thanks, Tim

[Admin]

Tim

What software version are you running ?
20190621 now reboots in less than a minute (about 40s I think)

PilotAware Team

[neilmurg]

I looked at this and didn't find a suitable UPS-Battery. My Anker batteries won't work that way, they're either supplying power or recharging. There is a DIY circuit description somewhere on the Internet to achieve this, but not for the correct power supply size.
[edit]To add: apparently having a 'USP' circuit for the battery will adversely affect battery life and capacity[/edit]
As a result I changed my startup procedure to boot PAw AFTER engine start (power supplied from aircraft power). This avoids PAw brownout problems and keeps the setup simple.
My alternative would be to power PAw by Anker for the whole flight from before Engine Start so that I can have SD record Engine On and Chocks running times as well as Flight time. It's not worth the hassle for me.
As Lee says PAw startup is now 35-40s and completed before I finish my checks / taxi / power checks, I can then select 'Go Flying' in SD

[Ian Melville]

For a different project, I was concerned about iffy electricity supply so fitted a capacitor across the DC in. Worked well for very minor interruptions but was a pain if you wanted to reset the Pi by disconnecting to reboot. I would have to leave it disconnected for several minutes until the charge was completely gone. It neither maintained the Pi running nor allowed a clean boot.

I thought there was a thread on this but searching does not reveal it. I have some emails somewhere if that is of interest?

[Paul_Sengupta]

You'd need to design your own case and have a Y lead for power, but I've had success using one of these:

https://www.ebay.co.uk/itm/UPS-HAT-Power-Source-Extension-Board-Battery-Raspberry-Pi-3-Model-B-2B-BSG/123247775068

I haven't fitted it in a case yet! 

[neilmurg]

@Paul_Sengupta Nice find, you must live on eBay/Alibaba!
: and you have to switch off the UPS as well as the power supply to turn off the PAw?

[crystalmark]

Thanks Chaps.

The Rosetta is only a couple of weeks old so I gather it's running 20190621 - I'll double check when next at the airfield - but after boot, it does take another minute or so to get enough GPS connections.  The microlight has quite a beefy LiPo battery mod so theirs plenty of juice to power the electronics before I start the engine.  Not essential but it would be nice to have Rosetta + SkyDemon happy and connected before engine start.

I'm going to try this USB UPS: https://www.amazon.co.uk/gp/product/B07BF4SR6S

but I must remember to unplug the Rosetta from the USB when putting the microlight away else the battery will spend most of it's life discharged.

It's rated for continuous 2A, not the required 2.1A for Rosetta so I'll do bench testing before relying on it in the air.

[exfirepro]

Hi Tim,

The spec quotes 2 amps at 12 volts. You would need to check what it provides on the 5 volt USB output.

Regards

Peter

[JCurtis]

I'd check that the 5v stays up during the power, it isn't clear if the USB is an output.  The test says...

Mini UPS can charge Router and light cat at the same time more than 5 hours of operation during power failure at a low price. Constant 12VDC output.

So it might need wiring into the 12v side before whatever you use to power the PAW.

Only one way to find out I guess...

[Paul_Sengupta]

@Paul_Sengupta Nice find, you must live on eBay/Alibaba!

One does one's best to keep the Chinese economy running.

: and you have to switch off the UPS as well as the power supply to turn off the PAw?

Yes, it's got a button on the UPS board to switch the unit on or off from the internal battery. Hence you'd probably need a custom case with an external button to push through for this.