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Cirrus MicroJuoule Radio System Review
By Allan Wright
Sep 02, 2004, 11:00 AM
Introduction
I first heard about the Cirrus Micro Joule system last year a few weeks before the NEAT Fair on the RCGroups discussion forums. A Micro Joule set was graciously donated for the fund-raising raffle at the NEAT Fair indoor flying session, so I got a chance to take a good look at the system. I was very impressed with both the diminutive size of the components and the quality of the workmanship. After seeing the equipment, I put it on my list of things to buy for my next "serious" indoor project that was too large for magnetic actuators. As luck would have it, Global Hobby submitted the Micro Joule system for review. The E Zone editorial staff put up a posting for someone to do the review, but required the reviewer use the system in a twin-motor aircraft since the system came with two ESCs. I've always wanted to do an indoor twin, so I offered to review the equipment in a Modelairtech Innennachtjager (Indoor Night Fighter) that I had always wanted to build. While I waited for the equipment to arrive I cleared my workbench and pulled out the plans for the Innennachtjager.
The Micro Joule System
Upon receiving the Micro Joule system, I discovered that I'd have to wait to build the Innennachtjager. The system came with two Cirrus ESCs, but they were different! The S-5A1 is a 5-amp ESC with the BEC designed for a single LiPoly cell and the S-5A2 is for two LiPoly cells. Since the receiver and servos are both designed to work with the voltage provided by a single LiPoly cell, both ESC and BEC systems are designed to provide the proper single-cell voltage to the receiver and servos, while passing on the full voltage to the motor system. Both ESCs also have the proper low-voltage cutoff (LVC) settings to protect the LiPoly cell(s) from being drawn below minimum voltage. I now had a new challenge: build a testbed plane that could use both ESCs, one at a time, with an appropriate motor and battery for each ESC. Before deciding on a proper testbed, I collected some statistics on the equipment and also did some testing.
Since this equipment is designed for indoor and micro-sized planes, I decided the two most important properties were weight of the system and the size of the components. My scale only has 1 gram resolution, so I weighed all the components together. As you can see in the photos, the weight of the entire system for a single-cell plane with two servos is 10 grams. For a full-house two-cell plane with three servos the entire system weighs only 14 grams -- half an ounce! For those wishing to do some additional work, a few more grams could be trimmed by using lighter wires on the ESC and soldiering the motor system directly to the ESC, thus eliminating the connectors.
Both the servos and receiver use white micro-JST connectors instead of standard RC connectors. The micro-JST connectors are compatible with Falcon micro servos, and while the connectors are the same as the ones on WES-Technic servos, the wire order is slightly different. Those wanting to mix-and-match between these two companies need to swap the pins on the connectors. This is just like the old Airtronics/Futaba connectors that now are thankfully all standardized. I hope the manufacturers of micro components can come to a similar agreement in the future.
The Micro Joule receiver is clearly labeled on the connector block showing which wires carry which signals. The ESCs use red JST connectors -- popular for parkflyer and micro planes' battery and motor connections. The Micro Joule system I received is an improved, second-generation system. I decided to try to test each of the new improvements.
Range Check
The receiver comes with a full length, attached antenna made from lightweight wire. At first I wondered if this would be fragile, but the wire's coating is much harder than standard-sized receivers, adding to the strength of the antenna. In doing a standard collapsed-antenna range check at the RC field, I found that I got about 40 yards before losing signal. This is about 10 yards less than a regular full-sized receiver, but is good for a indoor/parkflyer receiver (about the same as the popular GWS R-4P single conversion receiver). In-flight I have had no trouble with signal reception, flying up to 500' away -- quite a distance on a very small model. Indoors I have had no trouble with signal bounce or interference from transmitters on adjacent channels.
Servo Arms
The older, first-generation Micro Joule servos provided no means to secure the control arms other than the press-on friction fit. The servos I received had very small screws to secure the arms. Initially, I couldn't find a screwdriver small enough to fit them so I had to use the sharp side of a #11 blade in the slot. Eventually, I found a tiny screwdriver in an eyeglasses repair kit that fit the screws perfectly. Another thing that I did was to place the screws on an upturned piece of tape when they were not in the servo, since if one was to drop onto the carpet it would be lost forever.
The screws insure only that the servo arm cannot be removed; they do not assist in preventing the arm from pivoting on the shaft. This is still done by friction, which affords some nice benefits. Adjusting the arm position is as easy as twisting it into position, and in a crash, or with accidental surface deflection in transit or storage, the servo will be protected from damage. The only downside is that you need to be sure the arms are correctly positioned during ground checks. When flying, the arms withstood any flight loads, including those of my testbed plane which were quite demanding. Each servo comes with a spare arm which is nice if you have to cut one up to make a one-sided arm.
Improved Centering
I forgot to do this test on the bench, so I retrofitted my testing procedure to work while the servos were on the airframe. Lucky for me, my plane was not a cabin model! I created a template with one-degree measurements on it and affixed a piano wire pointer to one servo arm with double-sided tape.
The servos centered consistently every time, but in each direction centered one-half a degree from center for a total of one degree differential. This is quite comparable to other micro servos like the HS-55 and GWS Pico.
The Micro Joule Kolibri
With my bench testing done I started working on my testbed plane. My collection of indoor planes already includes a full-sized Kolibri and my living room Kolibri. Since the larger Kolibri uses standard parkflyer equipment and weighs 3.5 ounces, and the living room Kolibri uses a JMP combination receiver, magnetic actuators and a Falcon pager motor powerplant and weighs one ounce, I thought another Kolibri designed specifically for the Micro Joule equipment would be an excellent testbed. I could compare its performance to the other two planes and easily test both ESCs with different motor/gearbox combinations. I built my Micro Joule Kolibri without plans, using the T.L.A.R. method. I was asked by both Hobby People and the E Zone editorial staff to include detailed building information on my plane in case others would like to build one. Therefore I'll try to include all the information you'll need to build a copy of my plane. For those who haven't built a Kolibri before, my information will be only a supplement to the excellent building article on the E Zone. The three main changes to the original Kolibri were to lengthen the tail moment to reduce the strain on the servos, lighten the airframe throughout and create a motor mount that allowed for several different power plants appropriate to the Micro Joule ESCs to be mounted. Although I used both ESCs on this plane, I prefer the S5-A1 as my preferred setup, as the plane flies best with the lighter battery and power system.
Materials
Building Notes
1) Build main wing loop by overlapping the two .050" CF rods 1.5" at both joints. Attach 8.25" long .050" CF rod to make wing chord 8". Tie two outer loops of Kevlar thread to make entire wing chord 8". Thread posts at wing's tips are each approximately 11" from the wing's center. Vertical wing supports made from .070" CF rod are 4" long for front, 3.75" long for rear. The additional 1/8" of the wing's center rod will allow for easy mounting of the verticals with wraps of Kevlar thread and thin CA. Wing dihedral is achieved with 2 loops of Kevlar thread as shown in the original article. Secure center intersection with a drop of CA to prevent wing warping. If your threads are too long, shorten them by tyeing knots in them as seen in my version. 2) Fuselage CF tube is 22.5" long. Wing LE is at 4", TE at 12". The 1/16" balsa vertical platforms allow mounting the ESC right behind the motor, receiver right behind the forward wing post, and the servos at approximately 7" from the nose. After mounting all other equipment, locate battery mount to achieve a CG at 3" from the wing's LE. Wing is mounted by allowing the wing's two vertical posts to slide through holes in the fuselage tube. The posts are secured by wrapping with an elastic band allowing the wing to be removed for transport and for the incidence to be adjusted easily. 3) Landing gear is made from two hoops of .040" CF rod with nylon tubing protecting the areas that contact the ground. Each hoop is made from 13" long pieces of CF inserted into oblong holes in the underside of the fuselage tube at 1" and 7" from the nose. When they are positioned correctly, glue with thin CA, then reinforce with wraps of Kevlar thread and CA. Hoops will allow takeoff from smooth surfaces and landings on any surface. 4) Tailerons are made as the original only from 15" lengths of .040" CF rod. Each hoop is made using 13.5" of the rod with the remaining 1.5" protruding to act as a pivot. Tailerons are inserted into nylon tubing bearings glued into holes in the fuselage tube. Pushrod guides and taileron control horns are made from spare micro servo control horns. 5) Covering is colored Reynolds wrap applied with school glue stick shrunk minimally with a heat gun on the lowest setting. Be careful not to heat any of the CF rods directly as they will shatter. 6) As far as equipment installation, the CS-3 servos do not have mounting lugs, so mounting must be done by some other means. I used double-sided foam tape to attach the servos to the mounting plate on my airframe. I also used the same foam tape to mount the receiver and the ESC.
7) All balsa and nylon parts can be colored black with a permanent marker. This makes for a nice appearance. Three pushrod guides made from servo horns should be placed evenly between the tail and the servos. (If you have any questions about building your own Micro Joule Kolibri, feel free to drop me a personal message on The E Zone.)
Flying
I built the Micro Joule Kolibri with a longer tail moment than is usual to allow me to use shorter throws in the V-tail paddles. I did this to insure that the torque demands on the servos would be modest. The first test flights of the plane showed that it flew nice and slow, but because I set up the push rods on the inner hole on the servo arms and outer hole on the control horns I had poor resolution on the control surfaces and too much slop. This meant I was constantly over-controlling the plane and it seemed divergent in the air. The good news was the servos were much more powerful than I had originally estimated, therefore I reversed the pushrods, using the outer hole on the servo arms and the inner hole on the control horns. The result was the the plane flew much more predictably and was more stable. With a wing loading under 1.25 oz./ft2 the plane can slow to almost walking speed. As you can see from the video, flying in half of a basketball court is very easy; the servos provide plenty of torque and speed for crisp quick maneuvers. Indoors the landing skids allow for short takeoffs, touch-and-goes and nice landings. Outdoors, hand-launch is in order, unless you have a table or similar smooth, flat surface you can launch off of carrier style. Landings are fine on the skids outdoors on most surfaces including grass. One word of caution when flying outdoors - wing loadings this low require dead-calm conditions. The Micro Joule Kolibri will not handle any wind. Dawn or dusk patrols are best.
Video
Conclusion
The Cirrus Micro Joule system does a great job at filling the void between actuator-based control systems and standard micro/parkflyer equipment. The components perform their duties as well as their larger equivalents, but at a weight that will allow you to use them in much smaller aircraft, or to achieve very low wing loadings in slightly larger aircraft. The CS-3 servos are surprisingly powerful considering their small size and light weight, and the two ESCs designed specifically for one and two LiPoly cell operation make using these cells worry free. I would recommend the Cirrus Micro Joule equipment for anyone looking for a very lightweight system for micro planes weighing anywhere from 1.5 to 3 ounces. |
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Sep 03, 2004, 02:44 PM
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#2 |
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Registered User
Join Date: Oct 2000
Location: Garden Grove, CA, USA
Posts: 5,819
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I'm a fan of converting Guillows and Dumas or even peanut scale rubber FF planes to R/C. It looks as if this R/C gear plus one of the new Felagio IPS-replacement motor/GWS geardrive and two small Lipo cells will make such conversions much more flyable with less hard-landing damage.
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Sep 03, 2004, 02:46 PM
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#3 |
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Gambler-AG DLG Designer
Join Date: Jun 2001
Location: Lee, NH, USA
Posts: 4,665
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Guillows for sure, and the larger Dumas planes, but peanut scale might be better suited to acutators, JMP receiver and a single LiPo cell with a Falcon PU-04 pager motor/gearbox.
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Sep 05, 2004, 12:48 PM
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#4 |
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Pedestrian! Don't Shoot
Join Date: Sep 2002
Location: Lambertville, Michigan, United States
Posts: 4,968
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Nice review. Of course, only days after the Hobby People sale ended. The Flight pack prices don't look bad when compared with the cost of the indivdual components. A single ESC with adjustable cutoff voltage for one, two, or three cell operation would be a nice improvment.
Do the MJ ESCs still supply 3.5 v to the servos instead of the more common 5 volts? Do the servos still freak out and overshoot at 5v as was reported on the early productions sets? Last edited by tiberius; Sep 09, 2004 at 02:50 PM. |
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Sep 13, 2004, 12:44 PM
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#5 |
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Registered User
Join Date: Nov 2003
Location: Oregon
Posts: 28
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micro joule gears
I heard that the gears are delicate.....anyone have experience or are people just trying to treat like bigger servos?
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Sep 13, 2004, 01:53 PM
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#6 |
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Gambler-AG DLG Designer
Join Date: Jun 2001
Location: Lee, NH, USA
Posts: 4,665
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Well the servo arms will slip on the shaft well before any damage could be inflicted on the servo's gears in my oppinion.
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Sep 15, 2004, 11:41 PM
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#7 |
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Registered User
Join Date: Aug 2004
Location: Delaware
Posts: 68
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I have a question.
I was thinking about using the Micro Joule servos for alerons in a 28" plane. I was wondering if I can plug these servos into a FMA 5 channel reciever, and run them off of a 7.4 volt. Li-Po with a Jeti 8 amp advanced powering a Feigao brushless motor in an IPS drive. If I don't have the servo thrust for aelerons, would rudder be a good option? |
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Sep 20, 2004, 09:44 AM
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#8 |
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Gambler-AG DLG Designer
Join Date: Jun 2001
Location: Lee, NH, USA
Posts: 4,665
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No - the servos are not rated to work on standard receiver - you'll likely damage them with the extra voltage they will see.
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Sep 20, 2004, 02:30 PM
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#9 |
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Registered User
Join Date: Nov 2000
Location: Tucson, AZ, USA
Posts: 769
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My son's experience -
One servo works on any pins of the receiver. Second servo wouldn't work at all. The replacement wouldn't work either. One out of three servo being good is not a good bating average for these expensive servos. He is sending the defective servo back again. Next time it will be the whole system going back for a refund plus postage. 
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Sep 22, 2004, 02:02 AM
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#10 |
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Registered User
Join Date: Oct 2000
Location: Fountain Valley, CA USA
Posts: 416
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It is really unusual to have several servos in a row not work. Is it possible the rx is damaged? Maybe we're replacing the wrong part?
If you'd like, I'd be happy to test a new servo and rx and send them to you. Feel free to email me directly if you'd like Mike Greenshields Product Manager Global Hobby/Cirrus mikegreenshields@globalhobby.net |
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Sep 23, 2004, 04:54 PM
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#11 |
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Registered User
Join Date: Aug 2004
Location: Delaware
Posts: 68
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I was thinking about putting a cirrus system in one of the new Guillows Nieuport. A previous post suggested that a guy was going to go with a Feigao. Is there any way that the I can hook up a brushless motor to the Cirrus speed controller. Thanks for the help.
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Sep 24, 2004, 08:53 AM
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#12 |
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Gambler-AG DLG Designer
Join Date: Jun 2001
Location: Lee, NH, USA
Posts: 4,665
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I don't believe so, but why not use a GWS IPS system instead?
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Sep 26, 2004, 01:06 AM
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#13 |
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Registered User
Join Date: Aug 2004
Location: Delaware
Posts: 68
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I was thinking about an IPS unit, but I've heard that the motor doesn't provide the power, and that after awhile, the motor begins to lose its power. Would there be any way to use a different speed controller, in order to use a brushless motor? Thanks
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Sep 27, 2004, 09:01 AM
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#14 |
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Gambler-AG DLG Designer
Join Date: Jun 2001
Location: Lee, NH, USA
Posts: 4,665
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I don't think so, but PM Mike Greenshields (see above) to be sure.
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Oct 04, 2004, 09:06 PM
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#15 |
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Registered User
Join Date: Nov 2000
Location: Tucson, AZ, USA
Posts: 769
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I contacted Mike Greenshields in a PM. We corresponded a couple of times. Meanwhile, My son sent the servo back and received a replacement.
My son and I are happy to say that the new replacement servo works just great! Fact is, it is quieter than the first one which hardly makes a noise. We are very pleased with the service provided by Mr. Greenshields. Thank you, Bob reynolds |
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