Query on use of old Futaba 35Mhz equipment with modern electrics

[John Bisset]

This may well be a set of silly questions. However, I was taught a long time ago that the only really stupid question is the one you don’t ask. So, since I am still slowly grappling with modern electric systems, here goes.

I am debating converting a couple of old glow plug models to electric power. I’d quite like to use some of my old 35 MHz Futaba equipment – since I live in a fairly quiet area interference is not likely to be a problem and my up to date equipment is already in use in other models.

So my question is –can I safely control a modern electric motor using an old style Futaba 35Mhz receiver? Can it send a signal to an electronic speed controller – is its signalling compatible? It seems probable that it will be sending compatible signals, however in the modern systems I have the ESC also provides power to the receiver down the same wiring – the BEC set up. Will that correctly power my old Futaba 35Mhz set up or should I connect a 4.8v battery to the receiver as before. Alternately, can I use an ESC programming card with a 4-6volt output to power my receiver. I’d rather ask now than blow up some equipment out of stupidity!

All thoughts appreciated, any knowledge of snags will be helpful.

Thanks,

John B

[Cuban8]

Well John, electric models have been around for quite some years before 2.4 came along and although the old sets could give problems with glitching if your installation and wiring wasn't well planned, I'd be inclined to give it a go. Just think of all those old noisy brushed buggy motors sparking away near your RX! The BEC should be OK, but I did find it was better to use opto isolated types. Range test thoroughly under power, and if in doubt, stay on the deck.

 

Edited By Cuban8 on 03/05/2018 18:06:25

[Nigel R]

Will the RX drive an ESC? Yes, analogue servo drive signals are the same.

ESC with BEC to power the RX? yes - RX / servo power requirements are no different.

4.8V battery to power the RX? you can do, but make sure the ESC +ve wire is disconnected first.

The caveat, is, 35MHz is much more susceptible to noise vs 2.4GHz gear, and ESCs do an awful lot of power switching, at quite a rate. You might find, after doing the conversion, that the setup glitches.

 

 

 

Edited By Nigel R on 03/05/2018 18:08:17

[Paul Marsh]

The older brushed motors gave more interferance than modern brushless motors, although I remember some glitching on 35mhz, it was all from old brushed motors anyway..

[Mike Etheridge 1]

I flew my twelve year old brush motored Twionstar 2 today,and up to last year used Futaba 35 MHZ radio which worked OK for at least ten years before the odd glitch. I have flown at least 3 other brushed motor models with 35 MHZ radio without problems.

The Twinstar now has Futaba 2.4 GHZ radio installed.

[ken anderson.]

hello john another thumbs up for electric/35 MHz gear ..... I also flew my electric jobs using as you say "old Futaba 35mhz gear"..... no problems..... and i'm sure there are lots who still do....

ken Anderson...ne..1... 35 MHz dept

[Don Fry]

Keep the receiver at the back of the radio area. So it is away from the potential interference. And someone sells round doughnut shaped magnets. Might even be supplied with the speed controller. Make sure one is installed in the speed controller wires to the receiver, so the moter noise does not get to the receiver. Do a range check, motor on and off. But occasionally you get a 35 meg receiver that just is not happy. Mind my past problems were not Futaba units.

[Allan Bennett]

I did a lot of electric flying on 35MHz before 2.4GHz came along, and did suffer some glitching even with a reasonably modern brushless motor and ESC despite all the standard precautions such as receiver and servos as far away as possible from ESC and motor, and their connecting wires. I cured the problem completely by using an opto ESC (a genuine opto-isolated one by Jeti, not the no-BEC type that are often called 'opto' these days) and a 4-cell NiMh receiver pack. Thenceforth, until I changed to 2.4GHz, I used opto ESCs and NiMh receiver packs for all my models from the outset.

I also had a TwinStar with brushed motors on 35MHz without taking all those precautions (no space to move things around much), and had no problem.

[J D 8]

I still use 35 for several low use aircraft some electric and have not had any problems.

[PatMc]

I've flown over a dozen different electric models on 35meg and a few on 27 before I moved to 2.4GHz with a FrSky module. Never had a glitch with any including with models powered with brushed motors, ESC with built in BEC & using 27meg gear...

BTW the doughnt shaped item Don's refering to is a ferrite ring, not a magnet.

[Steve Hargreaves - Moderator]

It's almost impossible to say John...I've had some electric set ups on 35MHz that were fine & others that were unflyable due to constant glitching.....

Give it a try but test thoroughly would be my advise.....

Good luck...

[John Bisset]

Thank you gentlemen, Some very useful and reassuring advice and information from you all.

I shall do careful checks and test various receiver positions- had not thought about motor/ESC interference. I note that two of my modern systems provide ferrite rings on the receiver leads. I had been wondering about those.

John B

[Mike Etheridge 1]

The replacement brushed motors I put in my Twinstar 2 were provided with capacitors that you soldered across the positive and negative connections to the motors. Knowing that capacitors can fail I wondered whether their replacement after a few years could eliminate some of the glitching problems ?

[Simon Chaddock]

Although I fly mostly by myself I use 35 Meg (old Tx, modern(ish) Rxs) on quite a number of my current models with absolutely no problem using brushless motors.

When I do visit a club open day there are so few using 35 Meg I still have no problem!

Brushed motors are far more likely to give problems. Even with motor mounted capacitors the brushes still spark and sparks create electromagnetic radiation over a wide range of frequencies.

[Stuart Z]

Hi

I thought of trying the same but was cautious as the 35mg tx doesn’t have the same safety on the throttle control that you find on 2.4gh. Not a major issue, but need to watch the throttle setting when hooking up the battery.

S

[Trevor Crook]

You should be fine, John, provided you follow the installation guidelines mentioned above. My father in law still flies all his electric models with 25 year old Fleet radio on 35Mhz, and has no problems powering the radio from the esc regulator.

[Peter Miller]

I have used 35 Mhz radio on electric power for many years. Never had any problems. The last was my Kitehawk just last year.

Some mentioned ferrite rings to prevent glitching. I have found that you can buy split ones that click together over the leads.This saves having to remove plugs from leads to get the wire through the holes. I used those on my Easter Eagle Sr which has the servos over a meter from the Rx.

[brokenenglish]

Further to Peter's remark above, and with apologies for going a little OT, do you gentlemen think that a ferrite ring could be used around a spark ignition plug lead, to suppress ignition interference?

[Denis Watkins]

The ferrite ring suppresses the received interference

Where your HT lead is the transmitter

Do not coil or tightly fit the HT lead with anything until further advice

Suppression used to be .included in plug caps

Do some tests 1st, and you may find that you don't need so much suppression

[The Wright Stuff]

Posted by Stuart Z on 04/05/2018 07:31:37:

Hi

I thought of trying the same but was cautious as the 35mg tx doesn’t have the same safety on the throttle control that you find on 2.4gh. Not a major issue, but need to watch the throttle setting when hooking up the battery.

S

Hi Stuart, you are absolutely right to be cautious, but it might be possible to use the throttle trim lever to prevent the ESC from arming on start up. It would depend upon the Tx and the ESC, obviously. You would teach the ESC with the trim lever down very slightly from the top, then move it to the top for normal operation. This is similar to how an IC throttle is usually set up. Instead of momentarily moving the trim lever down to cut the engine, you would momentarily move it down to arm the ESC.

Not as good as a proper interlocked throttle disarm, but better than nothing.

Edited By The Wright Stuff on 04/05/2018 14:52:09

[Geoff S]

Posted by Stuart Z on 04/05/2018 07:31:37:

Hi

I thought of trying the same but was cautious as the 35mg tx doesn’t have the same safety on the throttle control that you find on 2.4gh. Not a major issue, but need to watch the throttle setting when hooking up the battery.

S

It depends on your transmitter. I used a throttle cut switch on my Multiplex 3030 for glow, etrol and electric models on both 35 MHz and on 2.4 GHz (via Frsky diy module) well before I acquired a dedicated 2.4 GHz transmitter.

As others have said, there's reason why you shouldn't use 35MHz on electric models but you do need to be a bit more careful with installation. I have had glitching on 35 MHz with a brushless small Axi motor with a Castle Creations esc. I returned the esc but it was only slightly better. However most of the glitching problems come with brushed motors and the inevitable though minor brush sparks.

Geoff

[PatMc]

I used a throttle cut on my MPX Cockpit SX 35 MHz version for electric models, like Geoff I had a FrSky module installed but it would have been exactly the same on 35 MHz. The cut was (is) operated by a slider.

Out of curiosity I tried to set up a cut switch on my 35MHz Futaba FF8 this afternoon. I used the "Gear" switch via one of the "free" mix functions - it worked without any problem.