That's a bold statement ... Worlds Best. But it's even larger than that. Not just Worlds Best, but best for most all applications less than 30 Amps (limit of the tests). That means:
- duration ships that only pull 2 to 8 amps per rotor
- most all 6S and smaller ships (exception of nano-ships)
- any-size FPV racer
- any other ship in between
Why almost any size? Shouldn't a small FPV racer use a smaller and lighter ESC for response? Yes, if it does better on a net-lift response test. In other words, when you penalize the ESC for it's weight, is it still better and faster? What i continue to see is ESC manufacturers downsizing critical components of the ESC at a net loss. They weight savings is lost because of greater thrust loss and response. In other words, this heavier ESC will out accelerate, in the real world, a smaller and lighter ESC.
Why post this? To move technology forward, we need to report to industry what works and what doesn't. For some reason (i don't know why), this ESC works better than all others tested:
- for generating maximum thrust from the motor***
- for net-lift efficiency or the grams of weight it can lift (after it lifts the rotor) per watt
- for response (how fast it can generate targeted lift)
These tests were conducted on multiple days on multiple rotors of highly variant size, always being immediately compared back to another DYS 40A multicopter test to ensure that the baseline wasn't changing.
The ESC that dominated is a DYS 40A OPTO Multicopter using SimonK. The photo is included because there are two others that carry a similar or same name.
- Not the white cover DYS BLHeli 40A
- Not the one that is says "Programmable" versus "Multicopter" in the blue/purple band across the front
Have i tested all ESCs? No, but if you are convinced you know of one that would work better, let me know. I've tested most all of the following and one or more of their variants:
- DYS
- Multistar
- Turnigy
- T-Motor
- Afro
- Motortron
- Quattro
- 3DR
- Spider
- KDE
- ZLW
- Aris
- EMAX
- AutoQuad
- Exceed
- HobbyWing
- Lumenier
To do a test like this, a highly repeatable and finite test stand is needed. It took a while to develop one but what works is one that:
- measures (at a minimum) volts, amps, thrust, motor temp (shoots IR up the aft end of the motor)
- eliminates harmonics between the rotor and load sensor (this proved difficult but achievable)
- is calibrated and proves repeatable within 1.5%
- controlled by a system that can precisely repeat a rotor test (uses a Audurino Mega)
- directly feeds the data into Excel for analysis (uses DATAQ)
- uses a test script that produces repeatable results
- uses a test procedure that minimizes repeatability error (used average of multiple tests)
How much better is this ESC? On average:
- 4.4% higher net lift (after it lifts itself)
- 2.3% more net-lift efficient (usually the larger the better)
- from more than twice the response or the same response as other ESCs (usually the larger the better)
So how to make it better?
Step 1: Strip it naked. See photo below.
... remove the cover
... remove the heat plate (better to locate the ESC under prop wash to run cooler, see below)
Step 2: Right-Size the bullet connectors or wires (see above where heavy wires are replaced by 2mm bullets)
... remove the large bullet connectors or wires
... replace them with ones that are the most net-lift efficient (where heat loss = weight loss)
Step 3: Seal the ESC. Seal it with Electrical Sealant to protect from moisture and conductive dust
... tape or plug connectors and wires
... repeatedly spray each side from different angles
... a mistake i made was not sealing the bullet connectors and solder
- don't tape them off like i did
- insert a male connector into the end of bullets so sealant doesn't get inside them
Step 4: Locate ESCs under Prop Wash. See photos below. The turbulence generated by the prop does not adversely affect lift when the ESC is placed on edge to the prop wash.
... Use something non-conductive like hot glue to bond the ESCs to the motor mast or spar
... Face the FETS (the little square warehouses or Fire Emitting Transistors) to open air
... Protect the ESCs from below from ground contact (not needed here because of clearance)
back-side with hot glue
front-side with FETs completely exposed to open prop wash
Step 5: Tie up wiring. Use dental floss to secure wiring away from the prop.
***Note: The T-motor Air 40 in high-timing mode (an option) generated higher thrust, but at the sacrifice of efficiency and motor temp. Also, the T-Motor Air 40 was 2nd best and close in performance. If you are using an Air40, it probably isn't worth switching.
Replies
way too much fun ... what they need is a durable ship :-)
Yeah... well... a lot of us have settled on the ZMR250. It's cheap as beans, supports 6" props and 22xx motors stock, and is essentially disposable at ~$20 if we buy the China direct versions.
They're made of 'glas with a CF skin and are actually quite a bit more durable than 100% 3K CF twill. I've flown mine into steel lightpoles and concrete at full throttle... 30-40 MPH... and it survived with a chunked corner or cracked top plate that's still serviceable. The weight penalty is 25-30 grams over 100% CF.
When we get good enough to need the lower weight and higher rigidity of 100% CF, we have a number of trustworthy vendors we can go to for a 100% 3K CF twill version at about $35-45 depending on options. Several of them have taken up the mantle of design improvement; We have inverted H and true X versions that are really popular with the Hyper FFF crowd.
Multirotormania.com is run by a friend of mine and he's a regular on the ZMR250 thread; one of the most popular on RCG. He developed the Zeus20A/FVT LittleBee 20A ESCs that are still one of the benchmark ESCs for racing, and right now I'm building a MRM250 V3... the third version they've released since we started way back almost 3 years ago.
We've got good gear for cheap; because you can't buy experience. ;)
We know that if you aren't crashing you aren't pushing your limits, and you need stick time to get good. You can't do that if you're replacing a $150 frame every time you break something.
Really... these little quads are more fun than DisneyWorld. And a lot more bang for the buck. :D
http://www.rcgroups.com/forums/showthread.php?t=2180331
Paul
@Paul
I'm going to go out on a limb and assume you...how do I say it...play a lot of video games? Just a hunch... :)
Hmm... I just "upgraded" to XBOX 360... so, no, not likely. :rolleyes:
I build and fly as a hobby. I'm retired from the life now. ;)
mnem
Dilbert can suck it; I got out with my sanity intact.
@Forrest, is it internal resistance of the transistors you are talking about?
great question Martin. if you solve that, you are on your way to building a great ESC.
My guess (i don't mfg ESCs) is that it's not the components (transistors, FETs, etc.), but the board. that is why fundamentals are so important with an ESC. And why if you don't have the fundamentals correct, then the rest is all hype.
All boards use etched traces to conduct the flow of electrons from one electrical component to another. Some traces only send communication signals that do not need a large trace because the amps are extremely low. But the main flow that goes through the FETs uses, in a FPV 250 racer, up to about 10 amps per ESC on a fairly sustained basis during a race (if the ship is properly designed).
An optimal wire size (one that you have to lift into the air) for a 10 amp flow is 23 AWG wire or a wire with a cross section of .26 mm sq (.0004" sq). That means that if the trace is 1.6 mil then the trace width would need to be .25" (6.3 mm) wide. So if you have an ESC with 3 rows of FETS, then that means the minimum width of the ESC is over 1" wide. So measure how wide the ESC is and ask, What???
The two best ESCs out there solve this issue in two different ways:
- DYS 40 Multicopter uses two different and separated layers of board. One can be light (thin copper) and the other heavy (thick copper). I'm not sure they do this, but they can. They claim they do it for EMF reasons. Their board uses 3 rows of FETs and is 1" wide.
- T-Motor Air 40 that uses a single board layer actually solders a 14ish AWG wire to the FET rail to achieve it's 40 Amp rating (they only need 17 AWG to be optimal).
I hope that answers your question. It was an extremely insightful question.
Hmm,
I'm thinking that the resistance of the traces shouldn't be the reason why an ESC is more or less responsive.
Resitance won't impede the flow of electrons, impedance does that. The voltage drop across the wires decreases the maximum power as some of the power goes into heating the wires. But the heating of the traces can't be substancial, otherwise the ESC would overheat very quickly.
I'm not an EE, but that's my understanding of the physics.
Martin - I can tell that you are a scientist, and a precise one, if not in trade, then in at least in hobby. With that in mind ...
With electric motors, Torque is Proportional to Amps. If you want higher response, you need higher torque. Thus anything that reduces Amps, reduces response. Of the things that reduce Amps, one, as you know, is resistance.
In comparing the ESCs, we aren't talking about a 30% difference in performance (well in most of the cases). So it doesn't take much heat to create the less than 5% difference seen across the top ESCs.
To get precise, Ohm's law I (amps) = V (volts) / R (resistance)
P.S. An ampere is defined as 6.241*1018 electrons, but who's counting :-)
FTW, using the Air40s... stoked... You had me on the edge of my seat til the end of the post when you didn't have the T-motor ESCs listed in your comparison chart... then boom.
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