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Author Topic: A Lightweight, Cheap RC System for RC Assist Free Flight (Single Channel)?  (Read 900 times)
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Squirrelnet
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« on: March 16, 2021, 06:37:18 AM »

I wondered if there is any specialist knowledge out there about getting together a system I can use in Free Flight models as a simple guidance device to avoid fly aways, particularly in our new world under Article 16

 I'm looking for a system than will be useable on medium sized I/C powered FF models of around 36" but will work with smaller models too. Ideally it should work with a single cell LiPo and give decent enough range for flying outside

I have already been using single channel RX Assist in vintage free flight models using a 2.4 GHz Multiplex Cockpit TX and the RX5 Light RX but although without it's case it's only around 5g the RX needs 4.8v + to drive it, so you end up with a big battery to carry around in the model. I'm looking to convert Free Flight scale models and want to keep any weight gain to a minimum. The Multiplex RX's are expensive too at £40+ each

My first thought was to find a suitable receiver and work back from that and as nothing but Multiplex works with Multiplex it will mean finding a suitable TX to go with it.


A look at the Micron RC site shows a Lemon DSM2/DSMX receiver at under 5g that will run on a single Lipo for about £10. I could couple that with a 2.2g servo £4.80 and 100Mah single cell Lipo £3.95. Under £20 a model is very attractive

Tx would need to be DSMX and an OrangeRX TX6i for about £70 seems to fit the bill

There's a lot of much cheaper TX's on HK but they don't seem to work with the smaller RXs or am I missing something ? some seem to only work with supplied RX even though they all state they AFHDS

Another alternative could be the FrSky Micro 4 Channel Rx , slightly more expensive at £16 but a WT8 Tx is only £30. There does seem to be some question over the range of the small FrSky Rxs from the description on the micron site, are they mainly for indoor use?

The Orange/Lemon system sounds the best so far, to me but before I commit I thought it worth asking what others are using for small free flight type Rc guidance systems


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billdennis747
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« Reply #1 on: March 16, 2021, 06:50:47 AM »

I'll follow this with interest Chris. Whenever I've been tempted, it's the battery weight that puts me off.
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RalphS
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« Reply #2 on: March 16, 2021, 06:52:05 AM »

I use a Lemon Rx with small servo and a 1S 200mAh lipo coupled to Spektrum Dx6i Tx in my Foam Provost.  It also powers a brushless motor and 2 other servos.  I don't have a range problem.  You should be able to get a good used 6i for about £50.  It runs off 4AA batteries that last ages.  

Ralph    
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Robmoff
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« Reply #3 on: March 16, 2021, 07:14:53 AM »

If you are going down the DSMX or DSM2 route I have a few of the 'game' transmitters that came with RTF UMX planes. Four channels, no whistles or bells at all.  You can have  one of those for nowt, and upgrade if/when you have done experimenting.
Rob
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Yak 52
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« Reply #4 on: March 16, 2021, 07:20:21 AM »

Chris, I use Multiplex for serious gliders and also Spektrum with Lemon/Orange/Redcon knock off receivers for park flying and smaller stuff.

If battery weight is your main issue - what about running a small 2S battery with a 5V volt regulator? I make some inline regulators than weigh around half a gram (I'll send you one if you'd like to try) A 2S 180mah weighs around 14g.

Otherwise, I would recommend Spektrum - range can be a bit less reliable than Multiplex but much depends on good installation of the rx. I've had one flying a glider at 420 metres with no range issues, but then at low level/far out the range can be rather less.

A lemon RX without pins and a 200mAh 1S would be lightest - around 8g maybe.


Jon
« Last Edit: March 16, 2021, 07:32:28 AM by Yak 52 » Logged
billdennis747
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« Reply #5 on: March 16, 2021, 08:10:20 AM »

Is there, somewhere, an idiot's guide, starting from zero, to all the dsmx, oranges and lemons, regulator, range stuff? Every time I think I've got a handle on it, something else pops up to confuse.
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Kevin M
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« Reply #6 on: March 16, 2021, 08:22:02 AM »

Well I do this, but not necessarily the lightest way, or the cheapest. It depends how small you want to go, model-wise. I am a Multiplex user too, and I use uncased MPX RX 5 light receivers, JST plugs and 2S LiPo. A 150mAH LiPo can be down to 4.5g. All my newer MPX receivers can use 2S LiPo power without an external VR.

If all you are doing is using rudder control to prevent fly-aways you can move the receiver from model to model, using a single Tx memory provided there is no programming involved and control throws are set up mechanically and there is no servo reversing required.

I have replaced D/T with rudder control on my Lulu so I can fly it in smaller places, and the weight cost is very low, the Lipo and servo replacing some of the nose-weight and using a very light fishing-line closed-loop control circuit.
« Last Edit: March 16, 2021, 08:37:03 AM by Kevin M » Logged
Flyguy
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« Reply #7 on: March 16, 2021, 11:36:06 AM »

I've been doing this for about 10 years, the orange or lemon with a single battery is around 5 g, check out this video, https://www.youtube.com/watch?v=9V-bxTQrTdQ
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SP250
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« Reply #8 on: March 16, 2021, 12:06:23 PM »

Personally, I wouldn't trust an orange or lemon Rx (as well as Spectrum) as far as I could throw it into the rubbish bin, if it were for a model with value (either monitary or building time invested).  If you want a decent range (specking out vertically, or 2 fields away low down), like Kevin, I rely on Multiplex small 5 channel Rx's with the case taken off.  The only use of Spectrum DSMX or DSM2 I use is with an add on module to my older MPX 4000 Tx and for indoor models only where the range is not an issue.

Other Radio systems are available - Futaba, JR, Jeti, FR Sky /Taranis etc and I realise many people have various Spectrum sets and swear by them.  We have however lost too many models to unexplained crashes, brown outs and the like at our local clubs when people do poor installations or use aftermarket cloned Rx's with Spectrum for me to recommend using them with any confidence at all if you value your airframe.
Just my experience and opinion, which I realise will not be the same as other peoples' and I don't want to start a slanging match with it, but there it is.

John M
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Flyguy
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« Reply #9 on: March 16, 2021, 12:27:07 PM »

Not a problem to report your experience, it sounds like you've had problems them, I wonder why, and considering that it typically takes me at least 3 months to build a plane, I wouldn't risk it. I'm talking about using the lightest versions (around 2 g, maybe that's not what you are referring to) with a single battery and servo for rubber power, I can't comment on the situation with an electric motor. Also the orange isn't available anymore, only the lemon is. Anyway that certainly hasn't been my experience, I'd say I've had well over 2000 flights at this point and I haven't had a single brownout or crash due to the receiver, zero, so they've been reliable for me. I've even smacked a few trees and fences and the receiver still worked fine, the servo is another story, those break pretty easy.

Squirrelnet - someone else commented they were checking Banggood receivers (given that the orange is no longer available, but the lemon is), that might be worth looking into.
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Squirrelnet
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« Reply #10 on: March 16, 2021, 02:26:50 PM »

Thanks everyone for some great ideas and ways to go with this.

 I am a huge fan of Multiplex, despite it's higher costs and will continue using that in my larger RC gliders but I feel it's a bit limiting when the size of the model reduces. The only small RX available is the RX5 Light and I'm really after something that will allow me to go much smaller in the future.

Jon -Your voltage regulator sounds great, I use one in my current Multiplex RC Assist set up with a 2s LiPo

Flyguy - I've admired videos before and marvelled at your rubber models amongst the skyscrapers so very pleased you posted a link to your set up. That's exactly the sort of thing I was thinking so I'm going to go with that - albeit with UK suppliers in a pandemic, so some bits are slightly different.

Bill - The range of DSMX's, Lemon , Oranges and AFHDS's is quite large , theres a thread on RC Groups which runs into several pages just explaining the different protocols https://www.rcgroups.com/forums/showthread.php?2301242-The-Beginners-Guide-to-RC-Protocols Hope Ratz is ok with me posting a link.

But I think the way to go is find a suitable receiver and supplier and work backwards from that as not all systems have small rx's available and - Flyguy has shown me the way :-)


So I'm going to get a DSMX set up

Receiver - Lemon DSM2/DSMX 6 Channel Receiver (LM0021S)
A small 6 channel DSM2/DSMX compatible receiver with JR/Futaba pins. Weight: 4.5gm, dimensions: 30mm x 18mm x 11mm. Voltage range: 3.45V - 8.4V.

http://www.micronradiocontrol.co.uk/rx_spektrum.html

I would go for the smaller ones but this is all I can find in stock in the Uk due to Covid

Servo - Micro Servo

Specification,
Size (LxWxH):   16 x 8 x 20 mm
Weight:   2.5 gm
Torque:   0.2 kg/cm @ 3.7V
Speed:   0.08 sec/60° @ 3.7V

http://www.micronradiocontrol.co.uk/servo.html

This is a bit bigger tha Flyguy's HK https://hobbyking.com/en_us/hk-282a-single-screw-ultra-micro-servo-2g-0-2kg-0-08sec.html?queryID=6fcb7a7ed08319bda8375c3bbf0e7e18&objectID=38896&indexName=hbk_live_magento_en_us_products but I think the larger surface area and larger weight of the scale models I have in mind will be better with the extra torque

Battery

100mAh Lithium Polymer cell with built-in protection circuit and 35mm wires.

Continuous Discharge Current: 1A

Size (l x w x h)   Weight
27 x 11.8 x 3.9 mm   2.05 gm

http://www.micronradiocontrol.co.uk/lipo_1s.html

This is slightly more than Flyguys recommended 70 Mah but I already have a charger that can charge Lipos at 100 Mah (1C) so that makes sense

 This set up comes in at 9g but no doubt once life settles down again, post pandemic and parts become more available, smaller lighter products will be available for future Rc guided ff models

Transmitter

To control all this I need a DSMX transmitter

Robmoffs offer a game style TX is lovely (PM sent) if we can work something out that would be great. it would be good to have something to play while I build the system into a model

The OrangeRX TX looks good on HK or there's the Spectrum range which are all DSM2/X

https://hobbyking.com/en_us/orangerx-tx6i-mode-2-eu-version-6ch-2-4ghz-dsmx-compatible-radio-system.html?queryID=&objectID=59920&indexName=hbk_live_magento_en_us_products

I think Ralph's idea of looking for S/H Spectrum is a good thought too

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Invader3
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« Reply #11 on: March 17, 2021, 11:50:49 AM »

Thanks for starting this thread, Chris - I've been thinking along these lines too, but like Bill I could do with a good tutorial so I can understand all the "new" technology Roll Eyes
(My R/C gear on the shelves is Sanwa and HiTec 35Mkz bricks Cheesy, although I've just bought a cheap Turnigy set from HK to play with in my electric trainer  Grin)

John
« Last Edit: March 17, 2021, 12:31:27 PM by Invader3 » Logged
Konrad
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« Reply #12 on: March 19, 2021, 11:14:53 AM »

+1 for the Multiplex radio. (I still fly a Profi 4000mc)

But as you have cheap in the search I think you might want to look into FrSky as an inexpensive radio. Many brands have light weight "park flier RX that are range limited. I avoid these at all cost as all my models need some kind of ballast to trim properly.

A main reason for this is that you already are somewhat familiar with the Multiplex mixing philosophy.

But the down side of this is that FrSky does not interface with Multiplex so you need a TX and RX to use FrSky. This is also true if you move to Spektrum.

Spektrum is a bit easier for a novice programer to understand. There is some baggage with Spektrum in that they were one of the first to bring 2.4 gHz to market. So while we early adopter did suffer some failures with Spektrum early on. The new DSMX protocols are solid. Ive had solid performance (no RF failures) with the Lemon brand of receivers using DSMX protocols. I've had over a  50% failure with the Orange brand of RX and 80% failure rate with the TX/modules.

So get a TX you are comfortable with. I like* the X-light S for it small size. A Archer R4 if you want to use the new ACCeSS protocol. Are you willing to go use S-Bus servos? if so there are real light weight  RX in the FrSky line.

The short of it is look at FrSky. Most RX will work fine down to 3.4V so a fully charged single cell Lipo at 4.2 volts is practical for RC assist FF.

X Lite-S
https://alofthobbies.com/taranis-x-lite-s-1.html

Low cost TX
https://alofthobbies.com/taranis-x9-lite.html

A must for any FrSky TX purchase
https://alofthobbies.com/radio/tx-gear/opentx-manuals.html

Archer M+ (ACCeSS S-Bus  RX [you will have to add your own connector])
https://alofthobbies.com/frsky-archer-m-access.html

MX+ ACCST S-Bus full range S-Bus RX)
https://alofthobbies.com/xm-plus.html

Small 6 gram S-bus servo.
https://alofthobbies.com/corona-sb6033-servo-95-kg-13-19-oz-in-0-10-sec-6-2g.html

* I like the full size tray style of radio. But if back packing or doing DLG work the X-lite S is almost perfect.

All the best,
Konrad

P.S.
Aloft Hobbies is my local hobby shop. They are a nice reference, as their site is exclusively FrSky for the radios. They know what they are selling!
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« Reply #13 on: March 19, 2021, 08:41:42 PM »

Another +1 for Multiplex. I have been using MPX sets since 1988- F3b, thermal and now F5J, and they have never let me down. My first set- a Royal MC is still operating on 36mHz.

The MPX 2.4 rcvrs should work down to 3.5v as per their specs and I have read of DLG's being flown with a 1S battery. This should also be enough for a small servo as you would not be using it much and again it is common in DLG's.

Having said this - Flyguy's system has been working well for him for a few years now and is worth a detailed look as well as the other comments from Jon and Konrad.

I think what you are considering as a safety emergency device, may well become a requirement.

John

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« Reply #14 on: March 20, 2021, 12:57:59 AM »

Another possible servo - wide voltage tolerance - 3.8-8.4v and 9 gms.

https://alofthobbies.com/kst-x08h-servo-2-8kg-38-oz-in-09-sec-8-grams-wide-voltage.html

John
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Konrad
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« Reply #15 on: March 20, 2021, 08:32:09 PM »

I've been getting real good performance from the X0-6. But this is not a cheap servo.
https://alofthobbies.com/kst-x06-1-8kg-24-99-oz-in-07-sec-wide-voltage.html

For FF assist the BMS 101 on a single cell might work fine. I have these in a few on my small single cell slope ships with questionable results. That is there is too much slop in the output shaft. Other than centering they appear to work fine on a single cell lipo.
https://alofthobbies.com/blue-bird-bms-101dmg.html

Some detail as to the BMS 101 short comings.
https://forum.alofthobbies.com/index.php?threads/blue-bird-servos-at-aloft-hobbies.1459/page-2#post-17110
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« Reply #16 on: March 21, 2021, 11:57:04 AM »

I see you are on the other side of the pond.

I can't recommend Hyperflight enough! Neil really knows his stuff, and is will to help with any and all your RC needs.
https://www.hyperflight.co.uk/products.asp?code=BMS-101DMG&name=blue-bird-bms-101dmg-servo-1kg-cm-0-07s-4-5g-7-6mm
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Squirrelnet
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« Reply #17 on: March 21, 2021, 02:38:02 PM »

Thanks Konrad

 I've used Hyperflight before and agree Neil offers an excellent service. Some servos I ordered for a DLG came the next day

It's good to see lots of suggestions for possible gear on here, hopefully this will a be help to others on here too.

My gear arrived the other day from Micron Radio Control another company I would recommend.

Again very quick turn round and exactly what I was looking for .... see post 10

Some of their receivers are tiny weighing just 0.25g, buying a DSMX set up will allow the use of these on future models which unfortunately my trusty Multiplex Royal tx won't .

http://www.micronradiocontrol.co.uk/rx_dt.html

The Multiplex is not going anyway though, that is still my favoured system for bigger gliders and despite being quite old, mine's a 35Mhz Royal Evo with a software upgrade to a Pro and conversion to 2.4 Ghz but it does everything (and possibly a bit more) that I need for a DLG with camber changing flaps and 4 flight modes including a launch preset. That it's still giving great service is a testament to their build quality

.. Anyway here's a pic of the bits from Micron, 9g in all





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