sportflyer-RCU

My Feedback: (35)

Where can I buy toroids for EMI suppression? I cant seem to find them in stock in either Mousser of Digikey. What toroids frequencies should I need for this? Do I need to add one choke for each lead from the servo to the receiver? Are opto isolators more effective than toroidal chokes? Thanks

dirtybird

My Feedback: (5)

You can buy RFI chokes from Radio Shack. They don't have to be toroids. I have never found RFI chokes or opto isolators to be necessary.

PaulBK

ditto...a friend of mine likens them to holding live chickens over your airplane and chanting.

Volfy

My Feedback: (23)

Hmm... may be I ought to consult my local Voodoo practicianer next time I need a low pass filter.

sportflyer-RCU

My Feedback: (35)

I am having severe EMI from the engine and am at wits end what to do. I have been running the engine on a test bench with all the support equuipment next to the engne. Then I placed the Christen Eagle about 3ft away to check the range which came out to a horrible 30ft . it will be obviously much worse with the engine mounted in the plane.( I confirmed that before setting up the engine on a test bench to isolate the engine ignition system from the plane's receiver/servo system) . As a second check I placed another plane at about the same distance, the range check is just as bad. The receivers are Futaba , one sytem operates at 6V the other at 4.8V . Both are FM . I could switch to PCM or IPD receivers but wanted to reduce the EMI as much as possible before changing receivers. The servos in both planes are a mixture of Futaba and Hitec servos. The engine is new Fuji 64 EI . It seems like I have a lot of RF emanating from the engine unit itself. I even dispensed with the ignition sw and I am using a Resistor plug. ( tried 2 of them with no improvement) . This lead me to consider RF chokes . Maybe its the electronic ignition unit? Any suggestions?

mglavin

My Feedback: (31)

How is the ignition module grounded to the engine, thru the plug cable only?

There maybe other things present in your shop that are creating problems. Is there any metal to metal abrasion of the engine installation of the stand, throttle pushrod anything?

With today’s radio gear and proper installation practices problems are rare IMO. FM/PPM RX's should work fine without chokes.

sportflyer-RCU

My Feedback: (35)

The ignition module was grounded to engine via its own ground cable. Engine was radially mounted to a L shaped wood test bed . Throttle control was manual via a nyrod . The range checks were done both at the flying field and at home with the engine test bed clamped to wood benches.

Hurri

I have never bothered with chokes . I have used shielded cable for extensions , never a glitch ever . Can get the shielded cable in radio shack put it between the servo plug end & & receiver end . the shield is connected to the black wire ONLY on the receiver end & open on servo end . I wrote into RC Report a couple of issues ago , so it is in there .

Hurri

I have never bothered with chokes . I have used shielded cable for extensions , never a glitch ever . Can get the shielded cable in radio shack put it between the servo plug end & & receiver end . the shield is connected to the black wire ONLY on the receiver end & open on servo end . I wrote into RC Report a couple of issues ago , so it is in there .

mglavin

My Feedback: (31)

Can you describe the ground connection in more detail? There can be only one ground path between the module and the engine. Typically the plug cable provides the path from the engine to the module. Anything additional creates a resonant loop.

sportflyer-RCU

My Feedback: (35)

The plug wire is not grounded ie it is not a shielded plug wire. There is a separate ground wire coming from the ignition unit which is supposed to be connected to the engine directly. I sent the engine back to Hobbico for check up . They were able to duplicate my EMI problem and found that the ignition battery pack must not be placed near the ignition unit . ie keep both the receiver battery and ignition battery away from the ignition unit and from each other. Does this make sense?

rideon67

My Feedback: (1)

I'm chasing the same problem on the same plane. Your ignition sounds similar to mine -- separate black wire and unshielded plug wire. I've been told to keep the ignition battery away from the Rx. There's only so many places to put the thing in the fuselage -- by the ignition or by the Rx. Guess you could put it up in the top wing somewhere........

My range check is OK until the engine is running. Did I read yours is poor with or without the engine?

mglavin

My Feedback: (31)

Sorta kinda maybe... Ignition systems emanate EMI/RFI from the GND side of the supply (battery pack). The negative side of the pack acts as an antenna, as the primary side of the ignition circuitry is common. Add to this the proximity of the secondary windings to the primary, and the result can be a problem!

If I understand correctly a separate ground wire is provided by the ignition OEM and is coupled to the module and then you’re to fix it to the engine block. The best scenario is the shortest distance to GND, which would be the ground or braid attached to the metallic plug base or right nearby. A shorter length of braid is resonant at higher frequencies.

sportflyer-RCU

My Feedback: (35)

Rideon67 : I have the same problem as you have ie no range when engine is running.

mglavin: The ignition module is just behind the firewall and is about 10 inches from the receiver. The receiver battery is located way back just in front of the horiz stab. The plug wire has no braid over it . I tried to shield it by wrapping foil over it however the manufacturer advised against shielding plug wire and ignition unit. When I shielded both, the engine is difficult to start , probably changed the capacitance and affected the spark timing or something else.

Would shielding the ignition battery and grounding it to the same point as the ignition ground help?

dork_blaster

My Feedback: (14)

Wow, I commend them for actually going through the trouble to check it out!

RX battery yes, keep it away from the ignition unit, but keeping the ignition battery AWAY from the ignition unit? Now THAT doen't make sense to me. Unshielded spark plug cable? That is probably you're biggest EMI/RFI emitter there (unless the ign unit isn't shielded) - that's how Marconi got his start by the way. A short, thick ground from the ign unit to the motor in this case is VERY good idea or swapping the spark plug cable for a shielded one like most of the higher performance motors use (DA, BME, 3W and ZDZ all use shielded spark plug cables). It's a wonder how all the old Zenoah/US Engine/Fuji motors with unshielded cables and magnetos worked with RC planes - I'm sure there's a million horror stories out there.

On the voodoo front...

Chokes are good for conducted noise, and if you use the wrong type (non-toroidal) and/or put one in the wrong place chokes can actually make things worse. Incorporating shielding, capacitive filtering, and a good ground (which is almost impossible in our RC setups) is a good way to reduce RFI problems in a receiver. So if you can't filter and shield the RX/servos, etc. then one viable option is to use shielded spark plug cables, resistor plugs and properly designed (low RFI) ign units - or go back to glow engines, ugh.

I actually have one setup where a choked servo extension helped, most of the time all I have to do is use twisted servo extensions or move things around. I conjectured that the servo electronics (for the throttle, mounted in the motor box) was picking up the RFI and was being conducted through the servo extension.

I have to go and double check all the transceivers I designed with chokes in them now, or get some chickens for my voodoo practitioner... my project manager is'nt going to like this (he's allergic to chickens).

Good luck! Let us know how things work out.

DB

sportflyer-RCU

My Feedback: (35)

Unfortunately my gasser is a Fuji 64EI . If I can't fix it I might have to go with another gasser or 2 stroke. I am not sure whether the ignition unit is shielded because its fully potted .

I am a bit frustrated because I have not been able to fix this problem for weeks. BTW when using RF beads , DO I place one bead in each servo lead ie 3 beads per servo set?

Hurri

I can't believe you guys with this choke biz . I have been flying gassers for 15 years never a single glitch . As i said early on in this site , I use shielded cable on the longer extensions if out to ailerons /flaps or way down the length of the fuse; Try it !!!!

sportflyer-RCU

My Feedback: (35)

Do I shield all 3 wires ? ie use 3 conductor plus shield cable and ground the shield to the _ve at the receiver end? Do I just shield the extension cable or I have to shield the whole cable right up to the servo .

It would be nice if I can find cable braided wire then I dont have to do much soldering

TKs

AirmanBob

My Feedback: (14)

I had much the same problems with my gasser. I have a Dynaflite Super Decathlon
powered by a US 41.
I ended up twisting ALL servo leads in the plane including the aileron wires. I shielded
the ignition switch and also the spark plug wire. I moved all batteries aft as far as I
could. I put FMA opto isolators on all servo leads. I use a nyrod throttle cable and have
the throttle servo moved way back also. I ran the reciever antenna outside and along
the bottom of the aircraft.
It flys great now...no more clitching and the US41 performs perfect. Starts on the
third flip and has power to spare.
Bottom line: twist and shield. And by the way, the opto isolators seperate the reciever
battery supply from the servo supply. I like that feature because I can use a big heavy
duty battery for the servos and a regular pack for the reciever.
Worked for me.....good luck and don't give up, it can be done
Bob

dork_blaster

My Feedback: (14)

Potted? Unless it's potted inside a metal can, it's probably not shielded.

I went back and more thoroughly read through the previous posts, and you might be SOL based on:

RC plane 3ft away completely isolated from the motor and you still get interference with two different airplanes.

Before you try chokes or beads, have you tried twisting ALL your servo leads and extensions? By the way, the beads would go on at least the signal and power leads. I don't think beading all three would hurt though (or do much good based on what I've read).

If that doesn't work, punt and get a mo betta motor. You've spent "weeks" on this when you could've been flying for gosh sakes! Or, maybe there's a way to retrofit a better ign unit to your Fuji?

DB

sportflyer-RCU

My Feedback: (35)

I have already twisted all the leads to the rear 3 servos and the throttle servo . I am only range checking with these servos in place. The wing servos are not even connected. I could have been flying iF I had used a glo engine (((

Hurri

Hi sportflyer , I saw the article written in RCM in around 1990 by Jim Oddino . You can either make up a length of shielded cable with a plug on each end like an extension cord or I cut the servo wire in middle & join the cable inbetween , cheaper & if its staying in the plane for a while better& leave it in . Ok I get the cable in Radio shack , it has 4 inner wires , so do away with one . The red pos; wire is connected at both ends as normal as is the signal wire . The neg;black wire is normal connect; at the servo end BUT at the receiver end it is soldered to the shielded cable stranded wire with the black wire ends . I fly a lot of WW1 with 6 long pull -pull 60lb test plastic covered fish wire & honestly never had a glitch , I have the antenna inside the fuse in a plastic tube on the bottom of the fuselage , as when looking up most planes fly more upright than not .

sportflyer-RCU

My Feedback: (35)

I will try the shielded cable next . I have re routed the antenna outside the fuselage to no avail. The Fuji engine/ignition unit must be one heck of a EMI generator (

chuck l

My Feedback: (17)

How many twists do you put in servo wires, ie twists per inch?

sportflyer-RCU

My Feedback: (35)

I didnt count . How many are you recommending? I twisted the servo leads with the servos in place. Looks like to do a good job I need to take remove the servo and really twist the leads with a drill.