I have ordered some BetaFPV BT2.0 connectors, they are about 1g lighter than XT30
Here you can find my old sub 250 arducopter (still flies well) with analog FPV and optical flow 2s 18650 20 minute flight time. If it helps the hakrc escs can be modified to work on 2s. But do cell phone batteries have a sufficient discharge current like 21700?
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Well, I thought they would but so far the phone batteries I have tested havenโt really been great. One was a cheap replacement for a Samsung and one was a genuine battery for some other brand. Both 5000mah cells got less than 4000mah when using 5A, so smaller cells running 3 or 4s might be better, but these donโt seem to have the output for 2s. im not sure if its just the quality of the cells im using or its what I would generally be looking at with mobile batteries but Iโm not spending more to test since the 21700 at 6000mah is looking much better.
my v2 build is currently adding up to around 205G with 6000mah 2s.
Someone else has informed me of that modification, Im going to try it on 3s to see how long it can fly for before I modify it, unfortunately itโs been raining since my last flight.
The problem is the weight of the 21700 with FPV, GPS, Compass, Optical Flow (a quad Arducopter without GPS Compass would make no sense in my opinion). But with a dedicated frame and other measures you could manage to make your quad fit around 110g (without battery).
at 3s no changes are needed (esc works well and discharges at 2.5V anyway). With modified esc I used 18650 at the limit of 2.5V li ion chemistry. The entire quad was flying on 5V power
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So far going with the listed weight of all the parts plus a few grams for 3d printed parts it should be around 65g without a battery, including a gps/compass and fpv.
frame 8g, motors + props 40g, GPS 2.6g, camera + VTX 2.8g, flight controller+esc+rx 3.6g, and a 6000 2s battery at 144g, battery connector 1g, motor bolts 1g,
its basically a 6 inch tiny woop with a giant battery.
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You could shorten the leads to the ESC and the battery lead itself to save a few more grams if needed? I canโt tell from the picture if the connectors are XT60 or XT30โฆif XT60, you could probably drop down to XT30 as well to save another gram.
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Its currently running XT30 connectors but I have ordered some BT2.0 connectors that are a little lighter. Im only going to be using about 8 amps at most so the BT2.0 should be enough.
I believe the f405 classic version of this will work with Ardupulot, itโs probably a better board for larger motors with its 12A escs. If it had an analogue OSD I would have got it.
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I built a prototype carbon frame using the โheavyโ 6mm tube and 0.5mm carbon i cut with some scissors (using a broken hand), Its not for flight, I just wanted to see if the araldite was going to stick and what it would weigh. Unfortunately, it must have got disturbed, so the carbon plates have moved.
This frame weighed 13.9g and was very rigid. I had to put a lot of force into it before I heard any noises from the carbon breaking.
Next version I will turn the centre around, I was trying to line the motor mounts up with the grid and got carried away and ended up with the centre in the same orientation.
The motors mounts are far narrower than I thought, so instead of the large square motor mounts its going to be a much smaller T shape piece of carbon.
The mavic mini 3 pro motors arrived and they are very light, only 7g without the propellers and around 8.9g with them.
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So I have made a version 2 frame using the light carbon tube, frame weight is under 10g, frame + motors and propellers is 44g I almost couldnโt attach the motors as they use m1.5 screws.
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I have done some optimisation to version 1, i printed a lighter thinner GPS and camera mount that took about 3 grams off, I have replaced the ESCs with a 2s 6a 4 in 1 esc that works down to 5.6v and moved the motor wires under the arms to give it a better aerodynamic cross-section.
I re-ran the indoor test and got 50 minutes, so those improvements have almost offset the weight of the GPS and mount.
the Eachine TX06 camera arrived is nowhere near 2.8g, possibly if you take off the wires and unsolder the antenna but out the box its over 4g, so I have an AKK 200mw camera +vtx thats only 4.7g so i might as well spend the extra 0.7g on the much more powerful vtx.
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I have been looking around for a HD video system for this, frsky make a nice HD zero monitor so that along with the hdzero tiny woop kit has been bookmarked for use after I get it running on analogue.
But I was thinking about what other cameras were available and i remembered that i seen this a long time ago, its basically Wifibroadcast digital fpv running on a ESP32cam module then using a pi to decode the video.
Up to 12Mbps video rate.
More than 90 FPS at 400x296 or lower with 20-50 ms latency.
34-44 FPS at 800x600 or 640x480 with 50-80 ms latency.
12 FPS at 1024x768 with >100 ms latency.
So my idea is if I can get that running on one of the tiny esp32cam modules then it would give me a 6g low latency digital FPV system, a whole gram lighter than any other digital system out there.
Interesting idea.
Not sure the 1g savings is worth the low fps and range compared to HDzero.
But if the price is right maybe worth a try vs the high cost of HDzero.
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This reminds me of the โWeight Weenieโ as applied to cyclists, of which I am one, going for every gram of weight reduction 
Not denigrating it by any stretch, I think itโs a worthy effort.
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Its not just the weight, Its only ยฃ12 for one of those little esp32cam modules + ยฃ30 for a pi and usb wifi adapter. Compared to the ยฃ90 for the hzero camera module and ยฃ200 receiver.
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@geofrancis,
this was a very interesting read and design.
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I agree the jump to a Digital FPV system is not just the weight but the cost is very high.
I wish someone would make an open source receiver that was low cost ( and multi protocol) but it seems the industry is not there yet.
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Itโs an interesting frame design, TBS are doing some lightweight sandwich frames using similar construction. whatโs really adding the weight onto his build is his FPV and electronics, the dji fpv system and flight controller he is using is around 40g compared to the 13g Iโm aiming for.
Since im going to be waiting a while for the parts tobuild V2 I am building another tube frame but this time to replace the aliexpress frame on the V1, its using some heavier woven carbon tube so the frame is going to end up around 15g, but thats still 20g less than the frame it currently has, so I think with just a new frame I should easily get an hour out of V1.
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openHD is pretty good, latency is under 100ms, itโs fast enough for anything flying with Ardupilot. you can get it set up for ยฃ80 for 2x pizero2 boards, camera and a pair of wifi adapters.
Thanks for that info. I will work on creating on of these systems. Unfortunately the high power Wifi adapters are quite high cost in Canada (~$200 for a pair) but I will look at the Taobao card and the low cost tp link options.
You donโt need a lot of power if you have a decent antenna, even the low power Rtl8812bu adapters will go a few km with a small patch antenna on the receiver.