JJRC H28 - RTF Quadcopter with "some assembly required" ;-) ( work in progress ) - RC Groups
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Apr 02, 2016, 02:11 PM
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Mini-Review

JJRC H28 - RTF Quadcopter with "some assembly required" ;-) ( work in progress )


Though many new quadcopters and multirotors that are released, seem very similar, every now and then a model is released that has something really special. The H28 for instance, comes with a catch, instead of being a fully assembled quad, it can be broken down into pieces, for easy transportation. Banggood offered me to check this one out, and it seemed interesting enough to have a closer look at.



Disclaimer: I don't get paid, or in any other way make money with reviews like these. Product specifications and quality may vary at the manufacturer's discretion, and are beyond my influence. I cannot guarantuee you will get a product that performs exactly the same as seen and described in this review. There is always room for a general discussion on the reviewed item, but no affiliate links!



Warning! So far it's unclear if the release version of the H28 has failsafe. When considering buying this quadcopter, please check with your preferred seller if this has been added by now. This quad has good range, so a fly-away is not very likely, but if you want the added safety of fail safe cutting motor power when flying out of range, contact your seller.



For easy navigation, here's a list of contents:

1: Specifications (posting #1)
2: Unboxing (posting #1)
3: Transmitter (posting #1)
4: Flying Performance (posting #1)
5: Preliminary Verdict (posting #1)
6: Suitable for a Beginner? (posting #1)
7: Camera & FPV Performance (posting #2)
8: Hints, Tips & Modifications (posting #2)




1 - Specifications:


First, let's start with a link and a picture:

http://www.banggood.com/JJRC-H28W-Wi...p-1038371.html




Specifications according to the Banggood website:


Description:


Brand Name: JJRC
Item Name: JJRC H28W RC Quadcopter
Item NO.: H28W
Color: Black
Frequency: 2.4G
Channel: 4CH with 6 Axis Gyro
Camera Pixel: 2 million
FPV: WIFI
Battery for Controller: 4"AA" batteries( not included)
Battery for Quadcopter: 7.4V 1200mAh Li-poly
Charging Time: About 150 mins(USB charging)
Flying time: About 8~10 minutes
Controlling Distance: More than 200m
Product size: 47x47x19cm
Color box size: 40.8x15.6x23.6cm


Features:

Headless Mode allow to auto rolling 360,one key to rolling,more stability
With one key automatic return function(this function is not complete the same as "one key go home",the return position may not be very accurate.)
With HD Camera, 2 million pixels and One Axis Gimbal.
Modular design,can be easy to carry and change parts.
The 6-axis system allows the quad to be hand launched.
The quadcopter can fly both indoor and outdoor.Including 4CH digital proportional RC system.
Rechargeable high performance battery.
Function:up/down,left/right sideward fight,forward/backward,turn left/right,with gyro/flash lights,A 360-degree 3D and special functions(continuous rolling)
With rechargeable high performance battery,7.4V 1200mAh battery,Flight time will be more longer,about 8~10minutes.


Package Included:

1 x JJRC H28C Quadcopter
1 x Transmitter
1 x Protection Set
1 x Blade set
1 x Monitor mounting holder
1 x USB Charger
1 x Manual



2 - Unboxing:


The H28 comes in a relatively small box, one side showing the removable arms:




And the other side showing the WiFi version, completely assembled:




Inside we find a few stacked plastic inserts, the top one showing the parts of the quad itself:




Once the inserts are unstacked, the transmitter, prop guards and landing gear are unveiled:




And surprise, surprise... a JJRC sunglasses!


Nice gesture, but unless these can project the image of the camera, it's basically a gimmick. Much more important are the 4 arms, with motors and props already mounted:




Connection with the center part of the H28 works with Deans/T-plug:




Because there are only 2 contacts, the leds at the bottom of the arms will only light up when the motors receive power, and can't be switched off. The props and design of the motor pods looks a lot like the H26 series.

The center part, with no arms installed, looks like this:




At the bottom we find the access door to the battery bay, with a 2S 1200 mAh LiPo installed, the on/off switch, and 2 connectors, one for the camera, and one marked "gymbal".




3 - Transmitter:

The transmitter uses a well known shape, and has a display. It may look a bit cheap, but has a display, and the buttons are clearly marked.




It uses 4 AA batteries, and can also be run with Eneloop type NiMh cells.




4 - Flying Performance


After powering on the quad and transmitter, moving the throttle stick up and down, unlocks the throttle. Earlier I made a remark about the motor pods looking like the H26 series, well the gear noise is very similar too. You can almost close your eyes, and fly by ear, instead of line of sight.

Despite that, it hovers rock solid. Each of the 3 speed settings affects pitch angles, as well as yaw speed. Since it's a "big bird" and there was some breeze, I went straight for highest rate. It moves around nicely at that setting, though it's not as lively or as fast as the H26.

Leds are very good on this one, the front arms feature green leds, and the rear arms have red ones. On top of that, the front has 2 large brightly lit square eyes, with bluish leds, and the rear has a big round green led. Keeping track of orientation is easy. Maybe on a very bright day, the leds will not be that well visible, but the props come in white, making it easy to mark the front one with a bright color sharpie. Like neon yellow or neon orange.

An early prototype that SeByDocKy tested, didn't have fail safe upon signal loss. This one is a later version, according to SeBy, but it still lacks failsafe. I do hope that mine is still an early sample, and not the final release version. A quad this big, without failsafe, is not acceptable. Good thing the radio has excellent range. Even with the quad on the ground, so worst possible signal, it still can be controlled at 65 metres. Maybe even more, but already amazing.

Missing a low battery condition is almost impossible, the front leds start to flash, and the rear led turns from solid green to flashing red. You would need to be flying with your eyes closed, to overlook that. The warning voltage is a little low for my liking, battery being at around 3.60 volts right after the flight, but the pilot is allowed enough time for a controlled landing. Flight times are at least 8 minutes till LVC flash, on one flight I even got 8 1/2 minutes.

Here's some footage of the first flight:

First test flight with the JJRC H28 quadcopter (1 min 42 sec)





5 - Preliminary Verdict:


The H28 was already special due to it's modular design. But good thing is, it doesn't end there. No matter how useful or not it may be to be able to break down the quad into smaller pieces ( and not doing this by crashing it ) it is also a stable flyer. Hovers fine, and making smooth landings is quite easy, due to the smooth throttle response. It doesn't feel as fast as the H26 for instance, even though it has acceptable yaw speed on highest rate.

An area where the H28 really shines, literally, is the led lighting. Bright leds under the arms, as well as big headlights and tail light, make it well visible during night and day. Had it been fitted with bright color front props, that would have helped on very bright days, but at least the props are white, so adding some color with a Sharpie is a good option. LVC is also hard to miss, with the big tail light starting to flash red as warning.

Add to this a very good radio range, and the H28 has a lot going for it. Still have to test the camera, so that might affect it's value for money rating. However, there is one thing that hopefully has been adresses by now, and will not be an issue on any sold units, the failsafe, which is lacking in the review samples that SeByDocKy and I have tested. Even though the good radio range makes it unlikely to have signal loss, there should be some backup safety system, cutting the motors, or setting these to some idle speed, to ensure a softer landing.



Pros:

- Easy to break up into smaller pieces for transport
- Very good range
- Uses WL Toys 2x2 protocol, so already Deviation compatible
- Clearly visible leds
- Very clear LVC warning
- Very stable
- Easy to fly, rates are well balanced
- Very good flight time


Cons:

- Noisy gears
- Could be more sporty for a 2S quad
- No failsafe on early samples, not sure if incorporated into final release version
- Props front and rear are the same color, doesn't help with keeping orientation (can be fixed with bright color Sharpie for instance)



6 - Suitable for a beginner?


The H28 is a stable and gentle flyer, so when looking at that, it should qualify. However, the size and power of a 2S setup may not be ideal for a first quadcopter. I would suggest something smaller, H29 size as max size, but based upon flying performance, the H28 is not hard to get the hang of flying it. The long flight time of 8+ minutes means that the new pilot can get lots of flying time on a battery.


(to be continued)
Last edited by SoloProFan; Apr 03, 2016 at 01:11 PM.
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Apr 02, 2016, 02:11 PM
Fan of just about anything RC
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7: Camera & FPV Performance


The H28W camera slides onto the battery cover. On ine the fit was pretty tight, but this might get easier after removing and mounting it a few times. The camera can tilt up and down, using the throttle trim. Just like the gears, the transmitter beep as you operate the trim buttons, is rather loud. A rotary knob would have been a better solution.

The camera does have a trick on it's sleeve, it's self leveling. When you move the quad, the servo-motor will try to keep it pointing at the angle that was set from the transmitter. At least until it reaches the mechanical limits of it's movement.

Still need to test image quality, waiting for a brighter day, to have decent light.



(reserved)
Last edited by SoloProFan; Apr 26, 2016 at 02:14 AM.
Apr 02, 2016, 02:46 PM
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SeByDocKy's Avatar
I see you version is different from my pre-release version (I didn't publish a test for it)
Can you check if the failsafe is fixed (with mine, motors never stopped) ?
Apr 02, 2016, 03:12 PM
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Quote:
Originally Posted by SeByDocKy
I see you version is different from my pre-release version (I didn't publish a test for it)
Can you check if the failsafe is fixed (with mine, motors never stopped) ?

As also mentioned in your "new product" topic, the failsafe is not working. Maybe that is why they included the sunglasses, so you can still try to look cool, when it flies away...

Good thing this quad has very good range, I did a short test on the ground, no landing gear, so quad sits very close to the ground, and still had full control, with the option to do a controlled take-off, at 65 metres.
Apr 02, 2016, 04:48 PM
Registered User
It's an interesting quad this one. But without a lower price tag, I don't see any major reasons (besides its break up ability) to buy it.
Apr 03, 2016, 12:55 AM
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Added some preliminary verdict comments, and a flying video
Apr 03, 2016, 02:59 AM
PALE OTAK KAU!!
KCreep's Avatar
Does the failsafe react differently if you fly it out of range vs turning off the transmitter. I'd like to see an out of range test by putting the quad on one hand with blades spinning and moving away from the transmitter to see if it shuts off after a certain distance.
Apr 03, 2016, 03:02 AM
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SeByDocKy's Avatar
The Radio protocol is still the "V2x2" ? (same than the tarantula )
Apr 03, 2016, 05:32 AM
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Quote:
Originally Posted by KCreep
Does the failsafe react differently if you fly it out of range vs turning off the transmitter. I'd like to see an out of range test by putting the quad on one hand with blades spinning and moving away from the transmitter to see if it shuts off after a certain distance.
Should not make a difference, out of range means no signal strong enough for the receiver to see any commands. But I could try, problem is that I need a big enough place to test. In the field the grass is often too high to leave the props turning, and the parking lot I come often is maybe 80 metres max.


Quote:
Originally Posted by SeByDocKy
The Radio protocol is still the "V2x2" ? (same than the tarantula )
I will test, should bind to JJ1000 TX as well then, right?
Apr 03, 2016, 05:39 AM
Registered User
SeByDocKy's Avatar
Quote:
Originally Posted by SoloProFan



I will test, should bind to JJ1000 TX as well then, right?

Yes
Apr 03, 2016, 05:42 AM
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SoloProFan's Avatar
Quote:
Originally Posted by SeByDocKy
Yes
Then I can test, I have a JJ1000.
Apr 03, 2016, 01:14 PM
Fan of just about anything RC
SoloProFan's Avatar
Tested flight duration, can stay up over 8 1/2 minutes on the stock battery.

And yes, it binds to the JJ1000 transmitter, no reverse channels, it can fly with it. Didn't test the rates though, because the JJ1000 TX battery was running low.

Did some more range testing, I can still turn off the leds at 100 metres with quad on the ground. If the battery had not been down to LVC at that point, I think it would have been possible to lift off at that distance too. Amazing range for sure, especially after we had so many "range impaired" quads lately.
Apr 04, 2016, 03:19 AM
Registered User
B.t.w., for natural stability (as opposed to giro-AS) the prop/rotors need to rather have negative coning angles ("anhedral").

You can work it out for yourself, but decades ago, in his office, world-famous helicopter pioneer Stan Hiller explained to be that since the airflow in a helicopter (any kind!) goes from top to bottom, while that of a fixed-wing aircraft goes from bottom to top (easiest to picture & understand with a kite), the effect of dihedral (positive coning angle, for helis) is also OPPOSITE.

I have worked extensively in factories in China and found more ignorant engineers there than not (am a degreed physicist + engineer, also with MBA in Prdn. Mgmt.). LOTS of "fights", with them finally thanking me -- months later -- for showing them the [correct] way. Proven with real-world tests, of course.

Positive coning angle is inherently UNSTABLE in this case. Gives the AS more unneeded work and wastes energy. Find better prop/rotors and install 'em ....

L
Apr 04, 2016, 03:31 AM
Fan of just about anything RC
SoloProFan's Avatar
Quote:
Originally Posted by xlcrlee
B.t.w., for natural stability (as opposed to giro-AS) the prop/rotors need to rather have negative coning angles ("anhedral").

You can work it out for yourself, but decades ago, in his office, world-famous helicopter pioneer Stan Hiller explained to be that since the airflow in a helicopter (any kind!) goes from top to bottom, while that of a fixed-wing aircraft goes from bottom to top (easiest to picture & understand with a kite), the effect of dihedral (positive coning angle, for helis) is also OPPOSITE.

I have worked extensively in factories in China and found more ignorant engineers there than not (am a degreed physicist + engineer, also with MBA in Prdn. Mgmt.). LOTS of "fights", with them finally thanking me -- months later -- for showing them the [correct] way. Proven with real-world tests, of course.

Positive coning angle is inherently UNSTABLE in this case. Gives the AS more unneeded work and wastes energy. Find better prop/rotors and install 'em ....

L

Interesting info. But with the 6 axis already giving this quad a very solid feel, I wonder if there is much to gain in stabillity. The thing this H28 would benefit most from, is more pitch. Maybe a different tx can help there, I am not sure if the 3rd rate setting is already 100% throws, or maybe just 60 or 80.
Apr 04, 2016, 05:18 AM
Registered User
Quote:
Originally Posted by SoloProFan
Interesting info. But with the 6 axis already giving this quad a very solid feel, I wonder if there is much to gain in stabillity. The thing this H28 would benefit most from, is more pitch. Maybe a different tx can help there, I am not sure if the 3rd rate setting is already 100% throws, or maybe just 60 or 80.
You are correct. Yes/but > from a physics/engineering point of view, "you get nothing for nothing"

[ 0 = 0 ]


In this case, since stability costs energy which must come from usable power, power available for high performance, maneuverability and endurance .... as well as product life .... the fact that the AS system must work the motors harder to overcome the natural instability of the up-turned "dihedralled" protors, simply eats the motors quicker and depletes the LIPO quicker too.

So different prop/rotor selection with diff. pitch should also have a slightly neg. coning angle. Even a seemingly flat prop/rotor will flex upwards under flight load (and moreso in maneuvering).


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