Radio Control: Electrics

Radio Control: Electrics

Bob Kopski 25 West End Dr. Lansdale, PA 19446

THIS MONTH'S TOPICS:

1. Electric Connection Service (five names)
2. Scheduled Electric meet—Michigan
3. Speed controls and BEC—review and new information
4. Some personal Electric trivia

WELCOME! The Electric Connection Service (ECS) is being well received. Here are current ECS contacts and reports from readers who want to connect with other Electric modelers.

Electric Connection Service (ECS)

Lloyd Schultz 270 Middlesex Ave., Metuchen, NJ 08840 Tel: 1-201-548-2343

• Lloyd is the sole electric flier in the Edison Recreational Model Airplane Club (ERMAC) and flies at Camp Kilmer in Edison, NJ. He flies a UHU and an Aerolectric, and has an interesting story about the latter.
• Club rules require a "check flight" for a beginning pilot to get the club "blue card" (the OK to fly unsupervised). The exam (in front of two club members) requires an ROG takeoff, climbout, 180° turn, low pass downwind over the runway, climb, loop, horizontal eight, and landing on the hard-surfaced runway. I fully support this kind of flight exam.
• Lloyd performed the check flight on his first try with the Aerolectric using the supplied motor on six cells. He’s anxious to share his Electric enthusiasm with others in the Edison area.

Jay Putt 123 Sheep Pasture Rd., Setauket, NY 11733 Tel: Home 1-516-689-6420 | Work 1-516-575-5813

• Jay has potential access to an electric-only flying site and needs others to form a group to secure use of a parcel of Suffolk County open-space land for environmentally safe (electric) model flying.
• He’s friends with Larry Sribnick (Mr. SR Batteries) and George Myers (MA’s "Radio Technique" columnist), which sounds promising for the effort.

Jon Auer 7012 Bareliff Dr., Charlotte, NC 28212 Tel: 1-704-563-1585

• A beginning flier interested in Electric RC and CL. He didn’t specify what he flies, so contact him to find out or invite him to the field.

Bob Afflerback 123 Harrington Circle, Willingboro, NJ 08046

• Bob is interested in quiet-powered flight; for example, he has a geared .40 in a Dirty Birdy. He wants to connect with other electric fliers in his area.

Larry Peters 248 E. Howard St., Clayton, NJ 08312 Tel: 1-609-881-1404

• Larry has access to a very large field plus an adequate school field and is eager to share these resources with other electric modelers.

• The ECS is turning into a Field Connection Service as well, which should make many people happy. New Jersey currently has a lot of contacts, but loners are everywhere—so please write in.

Scheduled Electric Meet — Michigan

• Event: Electric fun fly sponsored by the Livingston Co. RC Club of Howell, MI.
• Date: May 20, 1990 (fourth annual event)
• CD: Keith Clark, 2140 E. Highland Rd., Howell, MI 48843. Tel: 1-517-546-2462

• Last year’s meet drew 50 registrants (the largest in Michigan). Events planned include All Up/Last Down, Maxi-Flight, Most Loops, plus additional activities still in planning.
• The Livingston club’s events were also flown at the ’89 KRC Electric Fly; see results in the January 1990 issue of Model Aviation for planning reference.

Speed Controls and BEC — review and reader input

• If you missed my December 1989 column, it covered the differences between two categories of speed controls: "frame-rate" (low-rate) and "high-rate" designs, and showed how total power-system efficiency can be dramatically influenced by which type is used.
• Test results show high-rate technology is superior—by a large margin—in applications where the speed control is used continuously during flight (rather than as an on/off device). See December ’89, October ’89, and January ’90 columns for details.

BEC (Battery Eliminator Circuit) — reader comments and recommendation

• BEC products use the motor battery to provide operating voltage for the receiver/servo system. Aircraft versions are intended to automatically shut down the motor while there is still enough battery reserve to safely run the receiver.
• Reader reactions are mixed: several report satisfaction with their BECs, while others reported crashes after BEC-related failures. One reader cautioned against using some RC car controls in airplanes because they can become less reliable at low throttle margins.
• One successful BEC-equipped product noted by readers is the Futaba electric receiver, which also includes a built-in frame-rate speed control.
• My recommendation: If you don’t know for sure that a BEC product works well in an airplane, don’t use it. Personally, I’m staying with separate receiver batteries and speed controls for now.

Ferrite vs. Cobalt Magnets with Speed Controls

• Over the years there have been many references to adverse effects on ferrite magnets from frame-rate (low-rate) speed controls. Some folks believe low-rate controls can cause demagnetization of ferrite magnets in high-power applications because of the high-amplitude, repetitive current pulses present in the motor circuit with frame-rate controls.
• High-rate controls do not produce the same high-current pulses. It is also claimed that cobalt (e.g., samarium-cobalt) magnets are harder to demagnetize and tolerate high motor temperatures better than ferrite.
• In fairness, I’ve personally not experienced problems with ferrites and low-rate controls in my installations, but I have not run very high current levels in those cases.
• My current practice: I use high-rate controls and most of my motors have cobalt magnets—though not all.

Diodes and High-Rate Controls

• All speed controls have diodes connected across the motor to suppress high-voltage spikes of polarity opposite to that being applied. These diodes protect the speed control MOSFETs.
• In the past, diodes were often installed at the motor; now they are usually inside the speed control.
• Important point raised by reader Steve Hageman: in high-rate controls, the diodes must be rated for the same current as the motor at full load. With the high currents seen in many electric installations, these diodes should be low-forward-drop types (Schottky or similar) to minimize diode losses.
• This generally requires physically larger and more costly diodes. I suspect many high-rate controls on the market may not have proper diodes, which could explain some unexplained motor control failures: an ordinary diode overheats and fails, then the opened diode can no longer protect the MOSFETs, which then fail from motor voltage spikes.
• Industry input on this would be welcome; if I hear back from manufacturers, I’ll share responses in future columns. Many thanks to Steve Hageman for his detailed, professional input.

Motor Capacitors

• Motors commonly have one or more capacitors at the brush terminals to reduce interference. Typical small-value caps are ceramic, Mylar, or polystyrene, ranging from about 0.001 to 0.05 microfarads.
• Do not use large electrolytic capacitors of several microfarads when using high-rate controls. High-rate controls switch voltage on and off rapidly; large capacitors oppose this switching and create a contradiction that can worsen performance.
• Larger capacitors usually do little to reduce R/F interference, so more is not better. I use capacitors in the 0.001 to 0.01 microfarad range.

Mail, Manufacturer Response, and a Request

• Despite the large amount of mail I’ve received on the speed control issue, none has come from manufacturers so far. That was unexpected; several readers shared my surprise. Remember, my only purpose is to help all in matters Electric.
• Please include a self-addressed, stamped envelope (SASE) when requesting a reply. In 1989 I received over 371 letters (I failed to log a few), and answering them has required substantial postage—about $100 worth. SASEs help me respond in a timely fashion.

Personal Electric Trivia

• I began keeping a better mail log in January of last year; I received over 371 letters in 1989 and answered nearly every one (some did not want a reply).
• I also keep a flight log (discussed in detail in my August 1984 column). In 1989 I recorded 668 Electric flights spread over 10 planes. Two Sky-volts alone accumulated 319 flights. The real total is higher due to unrecorded flights and instructional flights I don’t log.
• Yes—I like to fly, and I really like to fly Electric.

I’ve got a new electric project underway at the building board and will share it in a future column.

Please forward any comment or question (the latter with SASE—pretty please with sugar on it!) to me at the address above. If you send letters to the Model Aviation office, it slows things down because they have to forward them to my home address.

Happy Electric Landings, everyone!

Transcribed from original scans by AI. Minor OCR errors may remain.