Radio Control Aerobatics
Eric Henderson <[email protected]>
Ed Alt explains his Tech-Aero Designs FlexReg system
Innovative minds exist in all competitive categories of our hobby/sport. Finding out about new “stuff” is a particularly enjoyable aspect of being a columnist. Many times the innovations come from individuals who solve a problem. They do not stop there, however; they continue to develop their idea and turn it into a product.
Many of the products I use today to start my glow engines did not exist when I began flying RC in the early 1970s. Individuals developed products that are now the flight-box standard for most of us, such as battery-driven systems to electronically diagnose and light our glow plugs and cordless electric starter motors to turn over our balky engines and save our fingers in the process.
A great deal of new thinking is continually being applied to our onboard flight systems, not the least of which is regarding the on/off switch and the control of the batteries needed to keep our receivers and servos operating safely.
Ed Alt is a longtime RC pilot who has built and flown International Miniature Aerobatic Club (IMAC) and RC Aerobatics (Pattern) airplanes. He has competed in both categories on the national AMA level.
One area Ed has always felt could be improved is switch and battery management in the RC airplane. He wanted to make a reliable switch that, if it failed physically, would leave the receiver system turned on.
He also wanted a regulator system that would manage multiple and backup batteries. Ed recommends that regardless of the switching and regulator selected, we use the right batteries with the correct voltage and capacity ratings to deliver current under the loads created by multiple high-torque digital servos.
Ed also identified that you need to select a regulator system with a high-reliability design, preferably with a fail-safe switch. Then he saw the need to precisely program such niceties as low dropout ratings, fast response to load demands, and high current-delivery capabilities. He also wanted to prevent and provide protection against any reverse current flow between the different capacity levels of two batteries in the same system.
Ed met his own challenge by designing a programmable voltage regulator with a fail-safe switch system that has all the key features to meet the preceding requirements. Following, in Ed’s words, is a more comprehensive and technical description of how his product works.
"Tech-Aero Designs offers a precision fail-safe/backup switch that was designed with the RC Pattern and IMAC flier needs in mind. While preparing for the arrival of two new Prestige Pattern airplanes for the 2006 contest season, I had exhausted my search for an off-the-shelf regulator solution for a lightweight dual battery system.
"At a minimum I needed a simple, reliable system that would provide a balanced flow of current from each of two Li-Poly batteries simultaneously. None of the available fail-safe switch type of voltage regulators would allow me to select from a range of output voltages to fine-tune my setup in a way that would optimize servo speed and power and still have enough precision to let each of the two batteries draw down at similar rates during use while providing the safety backup in case one should ever fail.
"In checking around with some top fliers in the NSRCA (National Society of Radio Controlled Aerobatics) District 1 region, I found that I was not the only one with that need. The only solution was to build my own regulator system, thus the Tech-Aero Designs FlexReg was born.
"At first, there was no particular plan to go into business to sell these units. I built 30 to divvy up between myself and my local Pattern friends who expressed an interest. They're now competition tested and have fully lived up to the expectation that was set for their performance and reliability.
"The product offerings from Tech-Aero Designs include production versions of the original FlexReg, as well as a dual redundant regulator that combines everything into one lightweight and compact package that operates from a single switch.
"The FlexReg can also be used in a single battery, single regulator solution, since its 5 A peak current output has more than enough capability to handle any size Pattern airplane with ease.
"The main purpose of a fail-safe switch and dual redundant battery system is to protect against loss of control due to the failure of a battery or a switch harness. Mechanical switch contacts are much more prone to failure than electronic switches.
"The idea that is employed by the FlexReg, as well as some other regulators, is to use the switch to turn the regulator off when the switch contacts are closed (external switch in the on position turns off the battery power), thus eliminating the possibility of a failed contact causing a loss of power to your receiver, etc.
"No current flows through the external switch when the regulator is on and supplying power to the servos. In fact, the FlexReg will operate without any switch attached at all! This is preferred by some fliers with electric motor setups, since they are always reaching inside to plug in/charge batteries anyway.
"With a dual battery system, each regulator's voltage output must be set and maintained very closely to the other. If one is set just a small fraction of a volt higher than the other, it will always be favored and thus supply the bulk of the battery current.
"The key feature that makes the FlexReg unique for redundant battery applications is its very precisely programmable voltage output. Each regulator can be set to one of 32 different output voltages in a range from 5.75 to 6.65 V, which lets you get them close enough to achieve the goal of a well-balanced shared load.
"In the event that something does fail, the other regulator and battery continue to supply the full load needed without the slightest interruption and at the same voltage level. This happens without any reverse flow into the failed battery since that path is completely blocked by the regulator circuitry.
"The FlexReg is ready to run out to most needs as supplied. For different voltages, etc., it can be easily reprogrammed. There is a programming port that connects to an optional programmer and digital voltmeter (the E-Z Set). The E-Z Set port is also very useful for preflight battery voltage checks via the battery/DSC port.
"The programming procedure is simple: just plug the regulator output to the E-Z Set and then plug the programming lead into the programming port. With the regulator switched on, you just 'tap' either the up or down programming button to make a change, which is immediately shown on the digital display. To save the new setting, you just turn the regulator off or disconnect it from the battery. It's that easy!
"The FlexReg is designed for a two-cell Li-Poly or Li-Ion battery pack application. It will work just as well in five- and six-cell Ni-Cd/NiMH battery applications.
"A Quick Start manual provides the key information to get going right away. For those with more of a curiosity in the details, a full manual is also downloadable at www.tech-aero.net.
"There is also a Tech-Tips section, which has a write-up to explain redundant battery techniques in detail, including how to easily reconfigure two regulators (or one dual regulator model) to employ a 'hot standby' battery backup, which purposely holds the spare battery in reserve to come on line instantaneously if the primary ever fails."
The Tech-Tip makes for persuasive reading for why we should all have a rock-solid redundant power-delivery system in our model aircraft. Even though you can successfully fly with just one battery and regulator, having a high-availability backup in case of battery failure is great insurance.
The NSRCA, which is the AMA Pattern SIG, recently had an unopposed election for the 2007–2008 national officers. For the next two years Derek Koopowitz of California will be the NSRCA president. He is a former NSRCA treasurer and is well versed in the NSRCA Pattern SIG business.
Ron Van Putte of Florida returns as the NSRCA vice president. He is a former NSRCA vice president with many valuable years of NSRCA and Nats experience. The two "rookies" are NSRCA Secretary Jim Quinn from upstate New York and new NSRCA Treasurer Ron Davies of California.
On the subject of Derek Koopowitz, I have the details of his exciting new Astral-XX. This version of the model debuted in 2005, and Tetsuo Onda of Japan flew it to a second-place finish at the 2005 F3A World Championships in France.
This model is the latest in a series of designs from Giichi Naruke that have been proven repeatedly in competition. The airplane's specifications are: fuselage length 1.97 meters; wingspan 1.99 meters; weight 4.7–4.9 kilograms.
Derek reports that there has been an additional upgrade to the XX, and it is now called the Astral-XX Plus. The differences are in the wing and the vertical fin/rudder. The wing is slightly smaller than the XX's and the fin shape is slightly different. In addition, the stabilizer is configured with some anhedral.
Derek received his Astral-XX in January 2005 and said that it is by far the best airplane he has ever flown. He got his model directly from XTreme Composites in Thailand, but they are now being imported into the U.S. by Bob Violet Models at www.bvmprops.com.
This aircraft is extensively prefabricated and molded in a lightweight vacuum sandwich composite and comes fully painted. The Astral-XX has a one-piece wing and comes with a complete set of fuselage and wing/stabilizer covers.
All Derek needs now is an Ed Alt Tech-Aero Designs FlexReg to keep his investments supplied with battery power.
MA
Transcribed from original scans by AI. Minor OCR errors may remain.
