Mi Digital High Torque MG Servo 6.0kg / 0.11sec / 26g
The HK Mi Series servos represent the next break through in high precision servo technology. Using Magnetic Induction, rather than a potentiometer, for an unsurpassed level of accuracy and performance.
Hi HK. Noticed your Orange receivers work at over 9V, Can or will these and other HK servos work at the same (lipo 2s)? That is the new standard so we are hoping.
Can you check with manufactures about running HK servos higher than 6V?
Don't run these at over 280hz, the digital amplifier can handle the frequency (as per the specs on blue Arrow's website) but the servo's heat dissipation isn't enough to get rid of the excess heat and it will cook itself to death, especially if used on a gyro. Stay at 250hz and it's a good servo.
It's not an ordinary servo either. The HK Mi Series servos represent the next break through in high precision servo technology. Using Magnetic Induction, rather than a potentiometer, for an unsurpassed level of accuracy and performance.
Looks great to me but is this a magnetic encoder and if yes in how many steps resolution? A magnetic encoder if the best solid divice for positioning feed back. Is it a a/d conversion of a magnetic field? If so its not so great because then it could have influence from magnetic fields and RF noise! Or does it works like a mouse weel? In that case the servo has to search for a zero startpoint at startup and then count the movements.
Manufacturer specs found elsewhere on net are: > "zero dead zone" less than 0.001ms dead zone > "zero error" travel accuracy > "zero error" centering accuracy > all-digital circuit processing > 360 degree output gear (2BB Rotation 1BB) > Coreless motor > Copper/Titanium/Aluminum alloy gear tooth(most aluminum's have ti in them naturally) > O-type rubber ring, for shock, dust, and oil. > J-Plugs.
They are using a magnet on output shaft and sophisticated hall effect rotation sensor. You can see similar devices at austriamicrosystems with 12-bit resolution per turn. This kind product is way overdue, but I'm happy they finally made it.
4.8V and 6V represent voltage of a four and five cell receiver packs, all servos are rated for these voltages. It is also typical output range of a BEC which would be used in lieu of a receiver pack whether a separate component or built into the ESC for electric models. You can't run a receiver on 7.2V
Some servos are starting to come out rated for 7.2 volts and I'm not sure but I think some receivers too. It sure would be handy if everything new coming onto the market was. No more worrying if the bec can handle the job, reduced weight and one less thing to go wrong.
the 4 and 5 (old NiCD or Nimh) cell standard is from way back, representing 4,8 and 6 volts. Indeed most receivers and servo's are still max powered by these voltages. Pls. note that a fresh charged 4 cell NiCD or NiMH pack contains approx. 5 volts and a 5 cell pack approx. 7 volts. So when you switch your fresh charged 5 cell pack on, this means that your servo's and receiver can handle approx. 7 volts. This drops later on when power is consumed. When not used, the voltage and capacity from NiCD and NiMH cells tends to drop by itself. This could even be to approx. 30% afer a day.
Luckely servo's that are powered by 2S (7,4v) or 3S (11,8v) Lipo's or 3S LiFE (6,6v) are offered more and more. To my knowledge most $pektrum (DSM2) receivers can be powered by 2S lipo's at the moment. Needless to say that this makes life a lot easier and cheeper to use ie. a 2S lipo as Rx power pack. Lipo's are more than 30% lighter in weight. Pls. note that a fully charged 2S lipo contains 8,4 volts and a 3S lipo 12,6 volts. But the good thing is that Lipo's and LiFe's hold their voltage and capacity, so even after a year they would still be 8,4 or 12,6 volts.
LiFE's are a little heavier than Lipo's, but can be charged at very high rates, can be fully drained and charged at maybe 1000 times, and still be happy. Lipo's cannot be fully drained, you must keep approx 20% or they might get damaged.
Just my two cents.
Jepp I fully agree with JeffBr (was thinking this is a old story)
Thats the reason why Im asking...I use Life in all of my models this year with no issue (when little bit more weight doesnt hurt). You dont need any BEC or something else (ok some plugs *) ) between the receiver and the Life - Lipo.
But not all Servos handle the more Voltage...
Thanks for the good up to date information JeffBr. I like the idea of just running the whole system straight off a 2s lipo but even better the 2s Life a123s. Much safer than the lipos and as you mentioned they can be charged very fast so you don't necesarily need a huge pack to last a whole days flying since it's practical to recharge between flights with them. I've recently made a flight pack with a balance charge cable out of 2 of the smaller cells sold here. I haven't used it yet but it worked out something like 30 grams lighter than my 5 cell Eneloop nimh pack, less amp hours of course but I only need enough for one flight at a time with a safety margin left over.
JeffBr made one small err: a 2s (not a 3s as JeffBr said) Life/A123 battery has a nominal voltage of 6.6v! I run my nitro 50 helicopter with a 2 cell a123 rx pack and love the simplicity of not using a regulator!
I've been running 2S lipo unregulated in almost all my stuff w/o any receiver or servo issues for about 3 years now. I wouldn't do it with Futaba servos, but my Hitec servos have held up just fine for quite a while. My receivers are XPS and Hitec. No issues. Lipos are much lighter than A123's as well.
Perfect size and really enough of power for a HK-500 or T-Rex 500.
If this servo is reliable, it's a revolution !
I've directly compared to a S9254 wich have many many problems with potentiometer and thinked: Waaa no problems with it !!! Damn good think, isn't it ?!?
Probably this servo will be comapable with Align DS510 or PowerHD3688HB (but with MG) and Savox 1250MG. Well, the metal gears are must have in every heli. For me even in F3A competition airframe. These could be good as the elevator servos each one in horizontal stabilizer halves. Wondering if tey have coreless motor or not. Please HK give us more info about this servo.
God! Have you ever seen hobby servo with gears made of titanium itself??? Mostly there are two steel gears and other gears are aluminium with titanium coating, making them lightweight and yet strong with low moment of inertia. This servo is smaller than standard size. So gear have smaller module, it means that they breakable in easier way. I would not use this size in plastic i 57-60" wingspan class 3D airframe cause about 10 years ago i broke gears in HS-225BB on ailerons during flight without any crash.
Yes, Birdy, exactly my point! HK should roll out 7.4V-compatible servos, then 7.4V-compatible recievers, and so on. If I had to pick between 3.7/4.8/6/7.4V, I'd choose 7.4V anytime**more power transferred with thinner wires.
The idea is a good one and with more units being made they will improve and eventually match the current market in stats vs cost. being a new tech though you would expect to pay more at the start.
Great little servos, we need some decent full size ones now for us F3C Heli nuts :)
How do you extent the degree of rotation? are they programmable? Where is the programmer? If I adjuste the endpoints on my radio the max I can get is about 90deg. These servos say they can rotate 360deg and thats what I want.
Not a new idea. F&M Electronics had a magnetic encoder about 40 years ago. Kraft had a servo that used a variable capacitor in place of the potentiometer. Both of these servos proved to be more trouble than the servo with the potentiometer.
* Richard==> brushless are also not a brand new technology but sold as if it was a brand new tech. since maybe 5 years ...
BTW* High Torque ?
4.20kg.cm (4.8v) - 5.0kg.cm (6v) this is absolutely not a hi torke with the actual things aviable on the market :=)
> Let me know when they release a 10 - 15kg version at a decent price...
...I doubt there will be such strong 26gram mini-sized servo anytime soon. They might release bigger 70gram version in this torq range, definitely NOT "mini" sized :)
This is actually a Blue Arrow DMS28013MG.
Control System: PWM Pulse Width Control
Processor: Digital IC
Required Pulse: 3 to 5 V Peak to Peak Square Wave
Working frequence: 1520 μ*s /333 Hz
Rotation angle sensor: MAGNETIC INDUCTION
Rotation: Left Rotation: 46, Right Rotation: 46
Voltage: 4.5V to 6.0V
Temperature Range: -20℃* to 60℃*
Driver Type: MOSFET
Operating Angle: 45 Deg. one side pulse traveling 400μ*s
Direction: Clockwise/Pulse Traveling 900μ*s-2100μ*s
Pulse Width Scope: 900-2100μ*s
Neutral pulse: 1500μ*s
Resolation: Minimum resolution:0.088°*/0.9μ*s
Rotational speed of magnet: Maximum 600RPM (r / min)
Magnetic offset: ±*10mT
Magnetic input field amplitude: 45 to 75mT
Speed:(No-load ): 0.14sec/ 60°* * 4.8V
0.11sec/ 60°* * 6.0V
Torque:(Stall Full load): 4.50 kg . cm * 4.8V
5.00 kg . cm * 6.0V
Idle Current: <0.05 A/ 4.8V <0.05 A/ 6.0V
Running Current: <0.10 A/ 4.8V <0.20 A/ 6.0V
Stall Current: <0.10 A/ 4.8V 1.2 A/ 6.0V
Motor Type: Coreless Motor
Bearings: 3 Ball Bearing
Bearing Type: MR74 (4mmX7mmX2mm)
Gear Material: Titanium Gear
Servo case: （*Aluminum Radiator）*Metal Center
Plug: "J" type
Connector Wire Length: 260.00 mm
Connector Wire SPEC: OD1.2mm/30 x 0.08mm 3p x 260mm "J" type
Weight: 26.00 g
Dimensions (L x W x H): 35.50*15.00*30.00 mm
JR uses this technology (hall effect sensors) in their high end servos and charges a premium for it, which is bull because these hall effect sensor chips were developed to provide a lower cost alternative to high quality pots in consumer electronics not because they're more accurate.(they aren't, just better price vs performance and they last longer)
6 thumbs up!
In my experience these are rubbish servos. I have bought 5 of these and 3 have failed on a Turnigy ccpm servo consistency master tester and ripmax type tester running on no load for just over an hour on 6V NIMH pack. First one blue one of the chips on the servo amp board. The other 2 just stopped with no visible signs of damage on the boards. I suspect motors are at fault as if you move the arm it sometimes picks up and then stops again - and there are no pots in these servos. I have not stripped them down and investigated any further. I was going to put these in my HK/Trex500 hybrid Heli. I always do a reliability test on my servos before they ever go into my helis. These have shown a 60pcnt failure rate. I believe if I left the other 2 on test they would have gone the same way. As a result they will NOT be put into service in any of my models! P.s. I bought 3, one failed so bought another 2 to replace this plus a spare one - both of these failed - I thought the first one might have been a faulty chip and a bit of a fluke the rest speaks for its self or I am extremely unlucky!
3 comments. Reply..
5 thumbs up!
All 3 Servos have noticeable, or even big sloop in the gears, increased by the Ballbearing having a lot of sloop inside the case too. On one Servo I can easily move the shaft 0,5mm sidewards, the Ballbearing is moving inside the case. Problem is that the housing seems to be made with high tolerances.
The Hk MG930 Servos I have are BY FAR preciser and stronger !
Whats the Use of precission magnetic sensors if the Gear spoils the Result. 2 Stars as they are working, but not as expected.
1 comment. Reply..
5 thumbs up!
Bin von den Servos überhaupt nicht begeistert, da alle 4 Axiales Spiel haben und das nicht gerade wenig! Die Abtriebsachse kann ich bis zu 0,5mm bewegen. Bin sehr Enttäuscht von den Servos
No comments. Reply..
4 thumbs up!
Don't use this servo on the tail of a 500-sized helicopter, it does NOT have enough torque to move the tail pitch slider when the head is at full RPM. The HK28013DMG should be ok for cyclic, but it's not nearly strong enough to be used as a tail servo.
5 comments. Reply..
4 thumbs up!
Output shaft on both my servos has a lot of slop due to the bearing being loose in the housing. Pulled them apart and applied CA around the housing and now its fine. But looks like I'm not the only one with this problem, sort it out HK! Otherwise its a fast powerful servo, no other issues.