RADIO CONTROL ELECTRICS
Bob Kopski, 25 West End Dr., Lansdale PA 19446
THIS COLUMN includes a meet announcement, the Electric Connection Service, more reader input on the SSC, some generalized thoughts on speed-control adjustment and use, and reader questions about BEC.
Meet announcement
Irvin Cooper (5380 Otter Lake Rd., White Bear Lake MN 55110) wrote to tell me of MARCEE 2000: The 4th Great Minnesota/Midwest Area Electric Fly in the St. Paul/Minneapolis area. The meet will be held on June 23–25 at the 3M R/C Flyers' field in Cottage Grove MN. You can get details from Irvin at (651) 429-0192, E-mail [email protected], or from the MARCEE Web site at www.isd.net/mnmpc535.
Irvin tells me that you can expect to fly with E-modelers from all over the country, and some foreign visitors. Sounds like a great time!
Electric Connection Service (ECS)
Al Jablonsky (5142 La Plata Dr., New Port Richey FL 34655) is relatively new to electric and is interested in meeting others of the electric persuasion in his area. This is the Electric Connection Service in action! Other E-modelers near Al, please get in touch with him.
For anyone else—anywhere—who is looking for others to fly E-power, just write me and ask to be listed in this column’s ECS. It’s free, and I’m told it’s effective too!
Sport Speed Control (SSC) — reader feedback and troubleshooting
Readers continue to report success and happiness with the Sport Speed Control (MA, 9/99 & 10/99), and some troubles as well.
One reader built two SSCs at the same time. Checkout of the Signal Boards produced mixed results: some things worked right away, some were close, and some were dead wrong. Both boards acted the same.
After several communications, it turned out that two uniform problems were masking each other.
- The first and dominant problem was a simple wiring error: a missed board hole with a transistor lead. The builder was sure he had done everything right, but on rechecking he found the miswire and fixed it. Then “almost everything almost worked.”
- The second problem was a parts substitution. He used an early bipolar 555 timer IC instead of the contemporary CMOS version specified. The early and the new 555s are not exactly alike and the substitution caused incorrect behavior. Note that replacing this IC is not the easiest physical task because other components cross over the IC.
To quote the SSC article: “Parts substitutions and value changes are discouraged, and in any case are your responsibility—OK?” Stick to the parts list and the published Assembly Sequence; then, if something doesn’t work, assume you have either a miswire or a bad part—in that order. I stand firmly behind the SSC design and will do everything I can to help you be successful with yours.
Another reader highlighted a misprint: in Assembly Step 13, page 78 of 9/99 MA, the writing "R61" is in error and should read "R63." Apparently most readers ignored the misprint because it makes no sense in context and could not be physically accomplished if all preceding steps were followed exactly.
Another reader reported happy surprise with the temperature stability of the SSC adjustments. He flew through a hot summer and a cold Northeast winter without having to readjust the SSC. Circuit temperature stability is something I take for granted from my military electronics background, but some ESCs on the market do not behave as stably.
One reader had difficulty with heat-shrink wrap that was too wide and opaque. The result was a poor mechanical package and the opacity hid the LED. Order the correct width (see the Parts List) and specify "transparent" color. New Creations R/C (Box 496, Willis TX 77378; Tel.: [409] 856‑4630) carries heat-shrink. I prefer "clear," but colored transparent (translucent) is much better than opaque.
The same reader noted that he can use the whole throttle stick on his transmitter with the SSC. Most ESCs function from full off to full on over a limited portion of stick travel, making the throttle feel touchy. With the SSC you can adjust so that full off is with the stick fully down and full on is with the stick fully up. The SSC’s nonlinear transfer function makes stick position and power level relationship much more meaningful (almost one-to-one).
Several readers have asked if I will make SSCs for them or manufacture them. Sorry, I can’t do that. If some readers wish to make SSCs for others, they are free to do so.
Speed-control setup and usage suggestions
Some readers have trouble establishing a sensible setup for their speed controls—no matter the ESC. Here is how I set up all of my airplanes, except where a simple full on/full off action is appropriate (sailplanes and some Old-Timer models).
- I use throttle full time—meaning over the full throttle range as needed for the flight task. I treat throttle as another flight control.
- I adjust the ESC so motor idle is about 1/2 trim and full on is roughly one click below full stick throw.
- Full down trim is motor off.
- Pull-down throttle stick brings the motor to idle (good for approaches), and any stick movement brings up power.
“Half trim” is my security blanket. Although this setup is easy with the SSC, many commercial speed controls don’t offer the same range of tune-up options. In those cases try to set up the half-trim behavior and then adapt the trim and stick behavior to your liking.
For sailplanes, some Old-Timers, and marginally powered models, a simpler “push the stick for full on” setup is often more appropriate.
Battery Eliminator Circuits (BEC)
Unending queries about BECs account for a considerable percentage of incoming mail. Many ESCs include a BEC function (as does the SSC) and with these you can power the radio and servos without a separate radio battery. This is lighter and quickly becomes addictive: no more charging the onboard radio pack! Almost all of my airplanes use BECs.
Here are some thoughts and guidelines:
- Every ESC with BEC will have limitations listed: maximum BEC current, number of servos, and possibly the number and kind of cells allowed. These considerations are driven by ESC power dissipation (heat). Honor the manufacturer’s guidelines.
- Recommended reading for those interested in RC electronics: A to Z Radio Control Electronic Journal by George Steiner.
- Fusing:
- When using BEC, put the fuse in the ESC-to-motor lead (either one) — not in the battery lead.
- If you are not using BEC, put the fuse in the battery lead.
- Using BEC in airplanes that may reasonably be expected to thermal (fly long with motor off): my rule of thumb is simple—don’t. Many factors affect available radio power/flight time after motor cutoff. Unless you have carefully characterized your specific power system on the bench, use a radio pack for thermaling machines and fly with confidence.
Resources and further reading
Check out www.ezonenmag.com. This monthly E-flight newsletter offers plenty of information. In particular, look in the site archives for articles by Bernard Cawley on speed controls; several issues delve more deeply into the subjects summarized here.
As with many aspects of life, there is often more than one good way to do something. Differing published opinions are not necessarily wrong—they're just different. If you find conflicting advice, query the authors involved to find what choices may be best for you.
So concludes one more column. This should appear at just about my favorite time of year: the threshold of a new flying season!
Please don't forget to include a SASE with any correspondence for which you'd like a reply. MA
Transcribed from original scans by AI. Minor OCR errors may remain.
