Wanted to have a self powered telemetry pack in order to save up the battery of my tablet.
So I tried this:

Hooked up the 3DR radio to a 2S lipo via a ubec.
This pack is then to be fixed to the back of the tablet.

The battery leads are external for charging purposes.
The ubec is to be changed by one with a build in lipo alarm.

This is still a work in progress and requires some fine tuning :-)

Views: 1322

Comment by Hugues on May 9, 2013 at 1:28pm
Nice work. Did you then have to cut the 5v and gnd wires of the usb cable ? Would be great if you could show your detailed wiring diagram'
Comment by Jan on May 9, 2013 at 1:47pm

As requested...

Comment by Rob_Lefebvre on May 9, 2013 at 3:44pm

Nice idea.  But I'd suggest using NiMh batteries instead.  There's not need for the complexity of LiPo in this application.  Worrying about balancing, overcharging, overdischarging storage charges, etc. Since power density isn't a big deal in this application, simple NiMh makes more sense I think.

Just provide a jack for a trickle charger in the case.  Plug it in when you get home.  Unplug it when you head to the field.  Easy peasy.

Comment by Jasja Dekker on May 9, 2013 at 3:46pm

If you do, you'd need 4x 1.2V -> 4.8 volt, is that sufficient? - Thanks,

Comment by Jan on May 9, 2013 at 3:54pm

Thought on the NiMh but then the box becomes a little bigger as well.
I have to admit it is less complex as a lipo and better to integrate (use of a jack).

4.8V should be sufficient as the 3DR radio module itself is powered on 3.3V.
There is a voltage regulator on the circuit board that reduces the 5V from the USB to the required 3.3V.
I don't know precise what is the allowed voltage drop (probably 1.25V) so with 4.8V you are still in the clear.

Comment by Jasja Dekker on May 9, 2013 at 4:15pm

Thank you Jan!

Comment by Joshua Johnson on May 9, 2013 at 6:56pm

I've been looking into this for my Tablet because I run my rover off a Wifi Link and when my tablet gets low on batteries the telemetry link gets weaker and the video and photo quality goes down with the battery power.  Please keep us posted on this project of yours!  I'm sure many of us here can find great use for what you're working on!

Comment by Josh Potter on May 11, 2013 at 6:25am

How about a single cell lipo (no balancing) with a 5v booster?  Sparkfun even makes one with a built in charge (usb or another source) https://www.sparkfun.com/products/11231

Comment by Kabir on May 11, 2013 at 8:37am

I have a spare 350mah 2S lipo, how long do you thing it can run telemetry?

Comment by Muhammad Al-Rawi on May 11, 2013 at 3:31pm

If you don't need the high discharge rate and are worried about over charging/discharging, you could simply solder a couple cell phone batteries together. They've got their protection circuits neatly integrated. I use this method all the time.

If the 3DR radio's regulator is a low dropout regulator, you could theoretically just run them off one cell with no UBEC or step-up in between. Is that logic sound? Correct me if it isn't :) 

Personally, I'd rather have the radio run off the tablets, unless you know your radio battery is going to outlast your tablet's battery. I'd hate to have my radio die out on me without knowing it. I'd at least you'd know your complete system's battery status running off your tablet.


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