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Help with electrical connections

Old 01-06-2016, 09:01 AM
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lamarkeiko
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Default Help with electrical connections

I have read through the posts in gas engines for newbees, but I am not completely satisfied I have every connection correct. I would appreciate some experts looking at the components I've got for my VVRC 20 cc engine and comment on my connections. I do not not plan on installing the tack in the plane permanently. The dual switch would also have the second switch connected to the receiver battery, then out to batt in jack of receiver.
Thanks
Lamar
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Old 01-06-2016, 09:15 AM
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Done right, for now. I don't like NIMH's lsd withstanding.
Old 01-06-2016, 09:27 AM
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All Day Dan
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Those exposed solder joints look hazardous. Is that the way the switch comes from VVRC or is there a cover for them? Dan.
Old 01-06-2016, 09:34 AM
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All Day Dan
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As I understand it, you plan on using the same switch for the receiver and ignition battery. That can make your receiver very exposed to radio frequency interference and does not comply with the recommended setup by Futaba. Dan.

Guidelines for setting up gasoline engine models. All ignition equipment, including an electronic kill switch, must be mounted at least 12", and preferably 14", away from all radio equipment, including throttle servos, etc. Ignition kill switch should always be on opposite side of fuselage from radio kill switch. All pushrods going to anything related to the engine must be non-conductive (just nonmetal clevises is not sufficient).
Old 01-06-2016, 09:56 AM
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speedracerntrixie
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The setup looks fine except for the battery. I'm not a fan of NiMh either. That being said your ignition pack is on the overkill side. If I were setting up a 20cc airplane I would run a single 3000 mah LiFe battery. Your RCEXL opti switch can be modified to switch voltage via TX and I would also do that. Separation of components is pretty much a thing of the past but as always be sure to do a thorough range check.
Old 01-07-2016, 08:49 AM
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lamarkeiko
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Dan, this switch didn' t come from VVRC. It came from Skyward Hobbies. In my opinion, the solder joints on the back look safe. This switch unit is actually 2 separate switches. The receiver will be powered from a separate switch than the engine.
I may be understanding this wrong, but the Gas engines for Newbees was written 6 year ago, before the 2.4 FASST radio systems were the normal system used. I think then there was a lot of potential for interference to you receiver. Now, with the 2.4 FAAST, the radio interference is eliminated. Would appreciate some feedback on this.
Speedracer, you mentioned that you think that my setup may be overkill. I have read in several posts, suggesting using a manual switch, along with the optikill switch. It made sense to me to have both. The manual switch to easily kill the engine on the bench, and also preventing a trickle drain of the battery, which can also happen with only the optikill switch in the circuit.
Lamar
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Old 01-07-2016, 09:45 AM
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Truckracer
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Regarding the switch, the solder connections look OK but I see no means of mechanical support for the wires. Vibration can quickly work over the wires and cause fractures. Unless you are not showing something that would add that mechanical support, I would use a different type of switch.

Regarding the overall wiring layout, yes you can do it the way you have it laid out but it can be simplified. I prefer to use an IBEC (Ignition Battery Eliminator Circuit) that powers the ignition from the receiver battery. The device I prefer is supplied by Tech Aero .......

http://www.tech-aero.net/ultra-ibec

This device provides ignition isolation and filtering, over current shutdown, voltage regulation and engine cut off via one receiver channel. These have proven to be extremely reliable and their use greatly simplifies the wiring by completely eliminating the separate ignition battery and switch. The RCexl cut off device can also be modified to eliminate the extra battery and switch but it lacks the regulation, current control and isolation the Tech Aero offers. Both devices are in wide spread service.

I'll let others debate the separation of ignition / radio components in the aircraft but my experience has shown there are few if any problems if good installation practices are followed. This is one of those areas where we each do our own research and do what we think will be reliable in the long run.
Old 01-07-2016, 10:15 AM
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speedracerntrixie
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Couldn't have said it better Truck........
Old 01-07-2016, 01:53 PM
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lamarkeiko
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Thanks Truck & Speed for the replies back. Sense you think what I have now will work, I think I'll just stay with that for the time being. I'll work on insulating and supporting the rear switch wires better.

Lamar
Old 01-07-2016, 04:54 PM
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All Day Dan
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"Now, with the 2.4 FAAST, the radio interference is eliminated." Sorry, but you are absolutely wrong. Ask any electrical engineer, especially one who specializes in radio frequency interference. All these guys are flying with pure luck and it runs out every now and then. I'm in a club with 400+ members and "then" does happen. I hate to be my usual PIA but you asked. Dan
Old 01-07-2016, 07:32 PM
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speedracerntrixie
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While I agree that interference is not eliminated, our CDI units do not emit anything even close to 2.4 ghz. The rx will remain solid in all circumstances. That being said, a loose or damaged plug cap/wire can emit enough noise to get picked up by long servo leads, regulators ect. This would happen regardless of equipment placement. My current gasser runs a Tech Aero IBEC and my dual rx battery packs aer two inches from the ignition. Going into my third season with that setup, approx 300 flights.
Old 01-08-2016, 09:05 AM
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dirtybird
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Originally Posted by All Day Dan
"Now, with the 2.4 FAAST, the radio interference is eliminated." Sorry, but you are absolutely wrong. Ask any electrical engineer, especially one who specializes in radio frequency interference. All these guys are flying with pure luck and it runs out every now and then. I'm in a club with 400+ members and "then" does happen. I hate to be my usual PIA but you asked. Dan
Well Dan I happen to be a retired Electrical Engineer.
That Futaba advise was written for the days we used a single frequency 72mhz. It remains in their site because there are still (choke) people that use 72 and it will do no harm to our 2.4 multi frequency systems.
Pay attention to spedracers post
Old 01-08-2016, 05:46 PM
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All Day Dan
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Lamar, you better get in touch with Futaba and have them take a look at your set up. You have no idea what the qualifications are of any of the posters on RCU. The problem is not the ignition module, it’s the spark. Any arc can contain frequency components from DC to light and 2.4 gigahertz falls right in that range. It can be radiated or conducted right along or in the wires from the spark plug back to the module, switch, battery pack, kill switch and anything else in the fuselage. The best defense is to keep the ignition system separated from the receiver system. Dan(former RF engineer who does not know when Futaba posted that advise on their website but it’s good advise no matter how you look at it.)
Old 01-08-2016, 06:35 PM
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Yes and that spark is grounded. Dan, Ever wonder why we don't hear ignition noise in our car radio anymore? Maybe things change. Qualifications, that's funny.
Old 01-09-2016, 08:05 AM
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dirtybird
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One of the problems with our current systems is that ground is dependent on the shield connection to the engine. If it is not secure there will be a spark external of the engine. Normally everything is contained in a steel pocket. But an external spark is unshielded.
Our old magneto engines had nothing but a resistor plug and an unshielded insulated wire. The magneto was internally grounded in the engine.Unfortunately there is no resistor plug for our little engines so the resistor is included in the cap.
One way to forestall problems is solder a wire to the shield and ground it to the engine. That way a loose cap is not a serious problem
Old 01-09-2016, 08:24 AM
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Truckracer
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Or you can use a small hose clamp around the base of the cap for additional security. This is kinda like wearing suspenders and a belt though as most caps are very tight as is and have to be pried off the plug. About the only time they fall off or come loose is when they are not fully seated on the plug in the first place.
Old 01-09-2016, 09:23 AM
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speedracerntrixie
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Correct Truck, I have been using these 10mm plug caps since 1997 and have never had an issue. Then again I am really careful when installing and removing them. I do like the idea of running a separate ground wire though. About 15 years ago I got my hands on a D&B 5.1 twin. Awesome engine except that it used no plug caps at all, just a small clip. My setup at the time was dual Hitec supreme 8 receivers. As you would guess, no joy in the range test. This had all separate components with the ignition battery and switch just behind the cowl, the receivers and batteries were located behind the wing TE. That was about 20" separation. A call to DA got me a couple of used plug wires and caps off an old 3W ignition. Threw those on the D&B ignition and grounded the plug shielding to the engine case as the ignition was mounted to the engine backplate. Worked like a charm and I got many glitch free flights with FM of all things.
Old 01-10-2016, 05:57 AM
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ahicks
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Lamar, so you know, All Day Dan has been hollering "the sky is falling" using outdated material to back his thoughts for quite a while now. His refusal to acknowledge the millions of trouble free flights by thousands and thousands of pilots while using newer technology is nothing short of remarkable. Not saying all of his thoughts/comments are wrong, just looking at the likelihood/potential for them to actually occur, and balancing that against the potential for other failures that rarely occur. If we were flying a manned spaceship, I might be more concerned. Thinking most sport pilots don't need to be at that level. Your call....

Love the concept and style of the "super" switches as well, but not crazy about the design/long term durability prospects of the type switch it uses. It uses something similar to a set of points to make contact, vs. the much better plan of contacts formed by a sliding type switch. If you were using both sides of that switch to supply power to the receiver, you would have some redundancy, and the concern for the type switch would be reduced big time. Those wires easily supported by a simple plastic tie wrap placed an inch or so away from the solder joints. That bundle of wires then much stronger and better able to support themselves like that.

Last, wondering if you saw the pictures at the bottom of the Rcexl switch directions? They show how you can get the power for that switch and the ign. module using the same lead that plugs into the receiver (called a BEC at that point). It amounts to just 2 small solder joints on the board. If you can solder, not difficult at all - and the trouble to do that easily justified. At that point there is no further need for a separate switch or battery to power the ign. module (this would free up one side of the super switch to provide the redundancy I was writing about above, letting you use both switches to power the receiver). As far as the design/functionality of the mod. keep in mind that this module is made by the same company that makes most of the ign. modules in use today. Safe bet they know what they're talking about...

Note that the Rcexl switch case halves are not glued together. The only thing holding them together is the label, which can be easily sliced on one side with a # 11 and repaired with tape when you are done.

Last edited by ahicks; 01-10-2016 at 06:04 AM.
Old 01-10-2016, 10:15 AM
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Good call on the mechanical switches that use the small chrome toggles. I use to rant about them and how unreliable they could be but it mostly fell on deaf ears. So, I mostly stay silent about them these days. Vibration can easily cause the point contacts to make / break which can cause all sorts of problems with the radio. If that problem doesn't get you, the wires breaking and falling off will. Many of these switch types have since fixed their wiring problems with shrink sleeve and mechanical supports for the wires but the unreliable switches themselves remain. I don't know of any switches of that type that use knife contacts, they're all point contacts that rely on spring pressure for contact integrity.
Old 01-10-2016, 10:46 AM
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lamarkeiko
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ahicks Thanks for your input. I agree with you in supporting the wires on the rear of the dual switch with tie wraps. The solder joints look good, and with all wires bundled together, I don't see vibration causing problems.

As far as the dual switch and mention of super switch and redundancy of power to the receiver. These are 2 separate switch circuits. One circuit has a 4.8 vdc 2300 MA NiMH
battery powering my ignition with the Opto kill switch in series with the circuit. A lead from the Opto kill switch will go to channel 5 on the receiver so I can kill the engine with the transmitter. The second switch has a 6 vdc 2300 MA NiMH in series with output to channel 7 of my receiver, supplying receiver and servo power.

As far as using NiMH batteries, there were several comments on not recommending rhe use of them that I would like further explanation on why. My Hite servo instructions actually says better to use high capacity NiMH instead of NiCd battery.

Lamar
Old 01-10-2016, 01:35 PM
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ahicks
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Lamar, I was promoting the concept of doing a factory endorsed mod to your Rcexl optical ign. switch. The mod involves the installation of a battery eliminator circuit (BEC), and it's done simply with 2 small solder joints (as shown in the directions) as mentioned earlier. Not sure if you aren't following, or aren't interested.

The mod would mean you don't need a separate ignition battery (NiMh or other), or a switch to turn it on/off? The ignition would then get it's power from the receiver battery.

After the mod, you would no longer need one of that pair of switches to turn the ign. on and off. That would free it up to give you an alternate power source in case of trouble with the first.

NiMh has developed/is developing a bad reputation among those placing high demands on their batteries. Not saying they're junk, saying if you're buying a battery, there's a newer generation battery available based on newer battery technology. Most guys find the more they know about them, the better they like them. Some insist, as your directions state, that as bad as the NiMh are, they're still better than Nicad, though I'm not sure I would agree with that..... -Al
Old 01-11-2016, 08:07 AM
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lamarkeiko
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Al, I did read about the mod on the optical kill switch after you mentioned it in your post. At the stage I'm at with the parts that I have already purchased for the plane and engine I am building now, I don't see a benifit. If I understand correctly, the mod would allow me to only need one manual switch and one battery. Wouldn't I then need a larger capacity battery if it is then supplying two circuits?

If you think my setup for now won't work, please let me know.

I have one last question. I thought that I read in Gas Engines for Newbees, that the ignition battery couldn't exceed 4.8 volts unless you had a voltage regulator. My Rexel ignition unit shows a voltage range of 4.8/ 8.4 DC volts. Does that mean the newer units have changed? My new engine came with the Rexel ignition, but no manual

Lamar
Old 01-11-2016, 10:20 AM
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ahicks
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With a 2200-2500mah Life on board, there's enough power available where you can darn near arc weld, so the addition of the ignition power to what's already going on not that big a deal at all (negligible).

When speaking NiMH, you need to be much more careful. Depending on what type and size servos you are using (std. analog vs. high powered digital) and the number of them you are using, you could already be borderline overloaded - prior to adding the load of the ignition.

With a module rated for 8.4v in hand, you can forget about the 4.8v suggestions regarding the older/original modules we had not too long ago. This fact should also help illustrate the fact that the equipment we are using is constantly evolving for the better (for the most part). This requires one to pay attention to when the information he is reading was actually written - in order to prevent getting bad/misleading advice.......
Old 01-11-2016, 10:55 AM
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I agree with everything that Al has said. Running a small gasser on NiMh with analog servos shouldn't be a problem with current delivery. With larger airplane with much higher current requirements NiMh would be a poor choice.

There are are many ways to electrically set up our airplanes. Most work just fine, some are better at optimizing reliability and others are good for optimizing performance. My personal preference on battery chemistry is LiFe for an unregulated setup and Lipo for a setup with a regulator. The reason for that is I want consistant voltage going to the servos. This makes a setup that responds the same from the first flight of the day and the fifth. When I get to a certain size airplane I go to a regulated system to get away from mechanical switches and be able to use big batteries. My 40% Extra runs dual 5 amp Lipo batteries. There are new smart switches available now that do not require regulators but as stated, the regulation is more to keep a constant voltage going to the servos. An unregulated system gets LiFe batteries due to their flat discharge rate so from first flight to fifth there may be a half volt drop at the most before I top off the battery.

As my personal opinion, for your setup I would run dual 1500 mah LiFe 6.6V batteries into your switch with both outputs going into the RX. I would then be mod the opto switch and run ignition voltage through the RX so you can cut the ignition from the TX. I have found that by not using the throttle servo to shut the engine down the servos last much longer. In the event of a servo or linkage failure you have the ability to shut the engine down and land, some clubs/events require an ignition kill via TX as well.
Old 01-11-2016, 06:38 PM
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lamarkeiko
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Thanks AL & Speed for the replies back. I am in fact running 4 digital servos for my flight controls, and an anolog servo for throttle. To be exact, I have 3 ea Futaba 3152's, 1 Hitec HS 5645mg and a Futaba s3004. I was planning to power them and my receiver with the 6 volt 2300ma NiMH battery. Am I in danger with that setup?

Lamar

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