Saturday, November 29, 2008

Eagle Tree Systems eLogger V3 Review

The eLogger V3 from Eagle Tree Systems is an in-flight data logger which continuously records volts, amps, watts, and milliamp-hours to enable pilots to analyze the performance of their electric power systems. In addition, it supports a wide variety of optional sensors to record altitude, airspeed, component temperatures, RPM, and more.


2.25%26quot; x 1%26quot; x 0.5%26quot;

0.7 ounces (20 grams)

5 to 70V

Up to 100 amps

0 to 424F

100 to 50,000

Street Price
$70 for the eLogger, $40 for the PowerPanel, $15 for the brushless RPM sensor, $10 each for either temperature sensor, $30 for the altimeter

The eLogger is a small device which continuously records these values to its internal memory. Once back on the ground, these log files can be downloaded to a computer for graphing and analysis. The device can also be used to display live values for all of its sensors, which means it doubles as a wattmeter on the bench.

Eagle Tree Systems provided me with the eLogger, a PowerPanel LCD display, two different temperature sensors, and an RPM sensor for brushless motors. All of these can be connected simultaneously, and still have room for a third temperature sensor and either a second RPM sensor or a throttle sensor. In addition, there is an altimeter, an airspeed sensor, a servo current meter, and a GPS module available. The variety of sensors and the ability to use so many of them at the same time is one of the major strengths of this product. The eLogger competes with the Oracle Data Recorder from Medusa Research and the eFlightWatt Data Logger from Mile High Wings .

To start with, I decided to test the eLogger as a wattmeter, by connecting the PowerPanel LCD and hooking it up between the ESC and battery in my Kadet EP-42. The logger I requested has integrated Dean's Ultra connectors, but another version is available with leads if you prefer a different connector. I found that installing the eLogger first made it difficult to connect the battery - I'm used to the ESC wire's flexibility helping to align the Dean's connectors. An easy solution is to put Velcro on the back of the logger, keep it unattached until the battery is connected, and then secure it in the fuselage.

The factory settings showed volts, amps, milliamp hours, and temperature on the LCD, which was good enough for a bench test. Everything worked fine for a few minutes, but then I noticed the PowerPanel display was corrupted. I reset the power and got a message to configure the LCD. It turns out that I had hit a bug in the software which had already been fixed. A newer version of the firmware was sitting on the CD-ROM that came with the logger, but of course I had skipped it (and the manual) in my excitement to try it out.

A short firmware update later I was back in business. Eagle Tree tell me that all new eLoggers going out the door already have the fix. Bugs are a fact of life, and I'm happy to see that they are responsive to fixing problems, and that the logger can be updated at home with the included USB cable. My advice is to hook a new eLogger up to a PC first thing in order to configure it and check for the latest software.

Besides acting as a simple wattmeter, all of the attached sensors can display their live values on the PowerPanel, which is very configurable. From the PC software, you can choose which parameters are displayed and where, give them customized three letter names, and set up multiple pages of information. For example, eight parameters can be spread over two pages, which alternate every two seconds.

Even better, there's an option to show the maximum values attained since power on when the current is zero. This is useful both on the bench to check peak amps, as well as at the field after a flight. The latter is particularly useful if you want to try out different props but not bring a laptop out to your flying site. On larger models the LCD could be mounted in the fuselage or under the canopy to make it visible. For smaller planes or helis, the PowerPanel is best kept on the ground, and connected when needed.

The desktop software can be used in live mode, where all parameters are displayed in real time on large readouts, and optionally recorded. There's even a live mode for the graphing feature, which is extremely cool (although perhaps less useful than the gauges and digital displays).

Next I moved on to recording in-flight data. The Data Recorder application is used to configure the logger's behavior, which is retained in the absence of power. You have a choice of which parameters to record, and how often to log them (from 1 to 10 samples per second). These choices affect the total logging time available, as does the data compression used internally. Eagle Tree state a minimum of 45 minutes of recording time. I set up the logger to record volts, amps, RPM, and one temperature value, sampling 4 times per second. In this configuration I'd estimate 2.5 hours of data can be stored.

There are three different RPM sensors available for this system. The first is a magnetic unit which requires the installation of a sensor and one or two magnets on a spinning surface. The second is an optical sensor which reads alternating light and dark areas on the back of the spinner or other moving part. Both of these are somewhat permanent setups, and are better suited to larger planes.

The third RPM option, and the unit I requested, is an electrical sensor designed specifically for brushless motors. It has the easiest installation procedure of the three, which consists of stripping a quarter inch of wire and attaching it to any of the three wires between the motor and ESC. I found it was easy to stick the sensor wire into the female 3.5mm bullet connector on the ESC, then reconnect the male side. Back on the PC, a configuration screen asks for the number of poles in the motor and the gearbox ratio, if one is used. The second setting is also used to indicate the ratio of the main gear to the pinion in a helicopter. One nice feature is the ability to see motor speed and prop/head speed at the same time.

I tried two temperature sensors as well. One is a loop, which was easy to slip around a LiPo pack, but I found that it did not cinch tight enough, so I added a piece of tape. The other sensor is designed to be taped down, and can be used interchangeably. Both are appropriate for measuring the temperature of inrunner motors, ESCs, and batteries. I couldn't think of a good solution for an outrunner motor though, since the spinning can is bound to be hotter than the non-rotating base.

Before flying with the eLogger, I wanted to compare the static amp draw of my Reactor with two different props. I ran full throttle with the stock 10x4.5SF, then changed over to an 11x4.7SF and ran the motor again. I downloaded the log files to my laptop, which showed two sessions. Each time the power is connected to the logger a new session is created, which is convenient. As seen here, you can examine these sessions individually or see them all at once. Using the default graph, I was able to verify that the current increased from 17.5A to 19.2A - just under the 20A sustained the RimFire motor is rated for. This gave me the confidence to use the bigger prop.

With the logger wrapped in foam at the rear of the compartment, I slid my battery forward a bit more than usual to get the center of gravity right. I flew a variety of maneuvers and didn't notice any effect on performance from the extra weight. Between the bench test and the flight, I had about 16 minutes of data in memory which was reported as 10% capacity used. It took about 5 seconds to download over USB, and saved to disk as a 448K file. This FDR file format is just a big text file, which means it can be examined or modified with any text editor. Most users will never do this, but it's nice to know the data is not locked away in a proprietary format.

The graphing feature is really the heart of the Data Recorder app, and it revealed a couple things about the flight right away. The first is that the larger prop only peaked at 16.75 amps in the air, and seemed to average around 10A. The average reported in the legend takes into account the idle time before and after the flight, so it's a little low. But second is the temperature curve of the LiPo pack. Not only did it climb steadily in the air, it continued to get hotter for another minute back on the ground. This confirmed my suspicion that I needed a larger air intake in the cowl for cooling.

Back on the bench I used a Dremel tool to open up the hole in the fiberglass cowl. On my next flight the weather was about 10 degrees warmer, but the difference in the curve was significant. Not only did the peak battery temperature drop from 66 to 58 degrees, the increased ventilation let the battery stabilize and even cool a bit as I drew fewer amps around the six minute mark. I would not have known about this problem or have been sure of the solution without the eLogger.

Since the logger itself has no buttons or controls, the PC application is used both for setup and flight analysis. The main screen can be configured to show whatever parameters you like, and many like RPM can be shown as both a gauge and a digital readout. These configurations can be saved for different models. One thing I found confusing was that these models do not also save and restore the configuration of the logger itself, for example which parameters to record in the air, or how many poles the brushless motor has. It would be nice to save the complete configuration of the eLogger in these model profiles, and have the LCD briefly display the name of the model it is programmed for on power on.

If the default graph options are not to your liking, there is an incredibly powerful settings window which allows you to change almost every aspect, from colors to line thickness to axis labels. I really appreciated that one axis can be made logarithmic, which is useful for showing large values like watts and RPM at the same time. Although the controls aren't obvious, the graph can also be zoomed in and panned around with the mouse. Because you can spend a lot of time configuring a graph to look just right, I'd like a way to save all of these settings as a preset. That would be useful to jump between one graph of just amps and temperature, and another of all settings simultaneously.

Later in my testing I tried the altimeter sensor. This has an unusual calibration routine, which consists of putting it in the fridge for five minutes, then connecting a battery as it comes up to room temperature. The altimeter connects to the LCD port on the logger, but allows the PowerPanel to be daisy chained, so both add-ons can be used simultaneously. The airspeed and servo current sensors (not tested) can also be chained together in this fashion, which is a great feature.

I installed the altimeter along with both temperature sensors in a Great Planes Spectra two meter electric glider. By disconnecting the bullet connectors between the brushed motor and the ESC, it was easy to slip the loop sensor around the motor can. I used scotch tape to attach the other temperature sensor to the battery, and tucked the altimeter into a small free compartment. It was a tight fit to get the canopy back on, but it worked. I might have had more room by placing the eLogger in the battery compartment, but would not have been able to reach the motor. Eagle Tree seem to have thought of this, and offer an inexpensive 12 inch extension cable for the temperature and RPM sensors.

After the flight, I downloaded the log to find a few surprises. First, that 600-size brushed motor hit 40 amps when I tested it at full throttle on the ground. Note to self: throw that piece of junk out and go brushless. The second was a reported maximum altitude of almost 3100 feet! Looking at the graph this was obviously a bad data spike. I tried to use the Set Minimum and Maximum Parameter Values command to eliminate this spike, but it had no effect on the graph. It appears this feature only affects the logger as it is recording.

So, how to fix this spike? As I mentioned earlier, the FDR log files are just plain text, so I made a copy and found the bad data by hand. Just changing these 1.5 seconds of data resulted in a much better graph, and correctly showed the max altitude as 240 feet. The climbs are interesting to watch: the amps (in purple) come up first, followed by the altitude (in turquoise), then gradually the battery temperature (in brown) and the motor temperature (in yellow). One thing this graph shows is that the motor heats faster than the battery, but also cools quicker as it has better cooling.

Later I browsed the Eagle Tree site and found a list of all changes to the software , something I strongly encourage companies to provide. And wouldn't you know it, a newer version was already out with a fix for altitude spikes. The new software also improves the appearance of the graphs with a white background and logo. The eLogger software is being improved constantly, which is a tribute to Eagle Tree. They also host a forum and respond to questions on RCGroups , which is a great way to provide support and share answers with many people simultaneously.

Can you fly electric without a logger? Sure - and you can practice biology without a microscope, but you won't really know what's going on. As a sport flyer I have found the eLogger very helpful for setting up new models and making changes to existing ones. It's particularly effective at detecting excessive current and cooling problems. This is a very well thought out, expandable logger which doubles as a wattmeter, and is very reasonably priced. Highly recommended.

To learn more about the eLogger, visit the product page on the Eagle Tree Systems website .

Friday, November 28, 2008

How to go really fast Interview with Tony Lovering

Forget about squeezing a little more power from your engine, filing the ports or any of that nonsense. There have been some quite extreme RC machines before now and none more so than Tony Loverings 3 engine monster.

He managed to squeeze 3 engines onto an 1/8th scale on-road Kyosho Evolva (I think 2 chassis and a hacksaw were involved) and flew from the UK to last year to compete in the world fastest RC competition at the California Speedway in Fontana on the 28th of July. He picked up the trophy for the fastest nitro RC car with a speed of 88 MPH, but has since gone as fast as 103 MPH in speed trials in the UK.

Zero RC: How did you get into speed trials?

Tony Lovering: I got into the worlds fastest RC car after watching a film called The Worlds fastest Indian. Its about a guy called Burt Munro from New Zealand, who built a motorbike and took it to the Speed Week held every year at Bonneville Salt Flats in the USA. He manages 206 mph. After watching the film I thought I would build an RC car to beat the land speed record. I found out later there was an event in the USA for the fastest RC car so after building the car I went to the event at the California Speedway in Fontana near Los Angeles. I managed 88 mph and that was a record for a car powered by an IC (internal combustion) engine.
ZeroRC: What are the plans for this year?
Tony Lovering: The car I used last year is a 3 engines stretched 1/8th RC car but it had a vital flaw. It got stuck in 1st gear. This year I will be building a new car with special engines and a special gearbox called a Constant Variable Transmission. Its being built in Canada by CVTech-RD. Hopefully we will try to beat 150 mph this year.
The world record for any car is held by Nic Case with 134.4 mph with his electric car. There are classes for standard kit cars and if anybody is thinking of having a go then Tony suggests you enter the kit class. Its apparently very simple to get a kit car and convert it to go fast.
This years world championships are to be held on September 20th-21st 2008.

More pictures from last years event
Tony on BBC TV
Tony's destructive 88MPH run on youtube
Tony's personal blog
Pictures used with kind permission from Tony Lovering.

Monday, October 27, 2008

Radio Controlled X-Wing from Star Wars

Last week, Daniel posted some info about a custom built, 21 foot long radio controlled X-Wing built by the Tripoli San Diego rocket club.

Just last week they took the X-Wing for its first (and last) flight in Plaster City, CA. Jeff Hoy posted a link in the comments to this YouTube video of the flight with a short interview with Andy Woerner about how the X-Wing was put together, and what he expected was going to happen.

Have you seen any other out of the ordinary, ambitious radio controlled vehicles? Post a comment and let us know, or better yet, contact us to become a writer and get paid to do it.

Sunday, October 26, 2008

How To Build A Servo LED Driver

One way to get into night flying is to fill a plane with LEDs. You can do that by connecting them directly to the motor battery, or to a dedicated second pack, but neither approach gives you any control. Here's how to reuse an old servo to drive your LEDs, with either on/off or variable brightness from the transmitter.

1. Start with a standard size servo, perhaps one with stripped gears or a dead motor. Smaller servos will work, but won't be able to drive as many LEDs as they're designed for less current.

2. Remove the servo horn, and then remove the main screws which hold the case together. On some servos you may need to cut a factory sticker which is holding everything together.

3. Remove the top case and the gears. You might be able to put the finished LED driver back in the servo case, but to save weight I tossed it.

4. Remove the amplifier board from the servo case. I needed to apply pressure on the motor and the potentiometer from above as shown here.

5. Once the components are free, it's not a bad idea to plug them into a receiver and make sure the motor spins. You could also try an LED across the motor terminals.

6. Desolder the motor from the circuit board. It may be attached directly or by wires. If there are wires and they're long enough to be useful, just snip them at the motor and skip step 8.

7. Cut off the potentiometer, making sure to note the resistance. This pot is labeled 5K ohms.

8. If necessary, solder red and black wires to the motor terminals. These will be connected to the LEDs.

9. Make a W shape from two resistors as shown. I chose a 2.2K and a 4.7K resistor to simulate the pot being set to one side. If you use unequal resistors, try them both ways with an LED attached to see which gives the right polarity matching the red and black leads.

10. Solder the resistors onto the three posts from the pot. The twisted middle wire must go to the center post.

And there you go! Shown here is a 3S LiPo pack connected to a 25 amp brushless ESC, plugged into channel three as normal. The LED driver is connected to channel 6, which corresponds to the flaps knob on my Futaba 7C . Because the resistors are unequal, I had to reverse the channel and then set up the end points by trial and error. The result is the LEDs are completely off when the knob is fully counter-clockwise, and they come up to full brightness as the knob reaches 12 o'clock.

Alternatively, you could use two equal resistors, each about half the resistance of the original pot. In that case, the LEDs would be off at 12 o'clock, and could be setup to hit full brightness at the fully clockwise position. Either way, use a voltmeter to determine how many volts the circuit is putting out, and then calculate the resistors for your LEDs accordingly.

To finish up, I'd recommend covering the LED driver in shrink wrap for protection. I'd also install a micro Dean's connector or similar to the LED leads for ease of installation. Finally, remember that this driver is powered by the receiver, so you may want to use a separate BEC which can handle the current. The built-in BEC found in many ESCs cannot handle more than four servos when stepping down from 11 volts.

Thursday, September 25, 2008

E-flite Blade Micro-CX Coaxial Helicopter Announced

E-flite has announced the Blade Micro-CX helicopter, an indoor coaxial model with a main rotor diameter of only 7.5 inches. The MCX features two coreless motors which are powered by a single cell, 110 mAh LiPo battery. It operates using Spektrum's 2.4 GHz spread spectrum technology, and will be available ready-to-fly with a transmitter for $129 , or in a bind-and-fly configuration, with everything except the transmitter for $99 . Both versions offer proportional, four channel control and should be capable of all the same maneuvers as the larger Blade CX2. Horizon Hobby's web site indicates late September availability for both.

Our take: Indoor coaxial helicopters are a lot of fun and dramatically easier to fly than conventional tail rotor models. When we r eviewed the E-sky Lama V4 , a Blade CX2 competitor, we found it could easily be flown in a basement or large family room. With its smaller size, the MCX may open up even more places to fly.

Based on its size, expect this model to be indoor-only, as even the 12 inch diameter coaxials can't stand up to a breeze. Kudos to E-flite for making the new heli compatible with all of the Spektrum transmitters, the CX2 unit, as well as the E-flite transmitter bundled with their recent Vapor model . No word yet on how tough these little helis will be. In all likelihood, some spare sets of blades and possibly extra landing gear will be all you need. At one ounce (28 grams) ready to fly, it'll be hard to damage itself too badly. No doubt the MCX will be appearing under a lot of Christmas trees this year.

Wednesday, September 24, 2008

Attending A Radio Control Show

If you've never been to a radio control show, you're missing out. There are a number of annual shows like the NEAT Fair in New York and SEFF in Georgia which have an enormous variety of models, vendors, and activities, and give any AMA-registered pilot the opportunity to fly too. You can buy DVDs of last year's NEAT FAir or SEFF 2008 from SKS Video Productions to get a taste of what it's like to go. There are also conventions to attend like the WRAM Show , which is all about shopping instead of flying.

In July Zero RC will be attending the SCCMAS Airshow in Santa Clara, California. If you live in the area, come check it out!

Tuesday, September 23, 2008

Two New Electric ARFs

Fliton has announced an elegant looking 50" wingspan electric pattern plane called the Element 30 F3A . Like most acrobatic electrics it's designed for brushless power and LiPo batteries, and retails for $179 USD. From the manufacturer's site:

An airfoiled rudder and elevators also provide excellent wind resistence, while presenting the aircraft like its bigger predecessors. The Element also features a fully built-up hatch (not plastic) for more structural integrity. Our thorough testing has lead us to believe, beyond a doubt, that this is the best parkflyer pattern ship available in today's market. Another interesting plane is the Airfoilz Extra 260 Hybrid , a 40" foam model with a street price of $59. It's somewhat unusual in that the structure is made of balsa and plywood with a foam skin. This compact 3D plane has huge control surfaces for maneuverability and looks like fun for advanced pilots.