Logo
Builders' Plan Gallery  |  Hip Pocket Web Site  |  Contact Forum Admin (Account/Technical Issues)  |  Contact Global Moderator
June 23, 2021, 02:36:37 PM *
Welcome, Guest. Please login or register.
Did you miss your activation email?

Login with email, password and session length
 
Home Help Search Login Register
Pages: [1]   Go Down
Print
Author Topic: Spektrum RDT  (Read 563 times)
0 Members and 1 Guest are viewing this topic.
Yak 52
Titanium Member
*******

Kudos: 77
Offline Offline

United Kingdom United Kingdom

Posts: 2,789


Topic starter
Jon Whitmore



Ignore
« on: May 30, 2021, 09:09:51 AM »

As I'm putting together an RDT for my 36" glider using a Spekrum transmitter I thought I'd share a few details.

It weighs 5.5g with a 70mAh lipo, linear servo and de-pinned REDCON 4 Channel DSMX receiver.

https://www.youtube.com/watch?v=NE-WHauRyRA


Jon
Attached files Thumbnail(s):
Spektrum RDT
Logged
Pit
Palladium Member
********

Kudos: 132
Offline Offline

Germany Germany

Posts: 5,565


aka staubkorb


WWW

Ignore
« Reply #1 on: May 31, 2021, 06:39:41 AM »

I've been thinking along those same lines.  Will you be using a mouse trap for the actual DT line release (those linear servos really do not have too much oompf, and will you be combining it with a timer?

Cheers, Pete
Logged

A Dedicated Convert to:
WWWoFF (Wonderfull Wacky World of Free Flight)

Comparing Spammers to a pile of organic waste is an insult to the organic waste!
Jez Wilkins
Silver Member
****

Kudos: 2
Offline Offline

United Kingdom United Kingdom

Posts: 199



Ignore
« Reply #2 on: May 31, 2021, 07:30:47 AM »

Hi Yak 52/Jon.

That is a neat idea.

Is the 'flying lead' from the receiver, which provides a socket for connection to the battery, an item that you have fitted yourself? If so, I would be very grateful if you could advise of either the name of this type of socket, or where you sourced the lead from.

I had a search, a little while back, for such a lead/socket, without success  - although I did, I think, find another very similar looking small (white) socket/plug connector - but it seemed to be for a battery that did not have the 'ridges' on the side of the 'plug'.   

Thanks very much, in advance.

Cheers,

Jez Wilkins

         
Logged
raggedflyer
Silver Member
****

Kudos: 3
Offline Offline

United Kingdom United Kingdom

Posts: 127



Ignore
« Reply #3 on: May 31, 2021, 07:46:39 AM »

Not my scene, but my suggestion would be to integrate the servo and Rx in one package and include the timing function within the Tx.
Logged
Yak 52
Titanium Member
*******

Kudos: 77
Offline Offline

United Kingdom United Kingdom

Posts: 2,789


Topic starter
Jon Whitmore



Ignore
« Reply #4 on: May 31, 2021, 10:31:56 AM »

Pete, yes I intend to use a mousetrap with the servo connected to a wire pushrod 'door bolt' to release it. The DT line is securely wrapped on a capstan that takes all the tension so it wouldn't be a lot of torque anyway.

I don't intend to add a timer on the model just yet but the TX has a good timer so I will monitor the flights with that and trigger the DT manually.


Jez, the connector is found on eBay from China or a UK reseller. Search for "Micro JST 1.25mm." There are not actually made by JST it's just the generic term. I understand that the actual lipo connector is 'molex picoblade' or sometime 'Eflite UM connectors' and some report this generic connector causes slight wear but I've never had an issue. You can get the genuine ones soldered up with leads but they are actually through hole sockets: http://www.micronradiocontrol.co.uk/conn_picoblade.html

I'll probably add a switch and charge socket so that I don't have to remove the battery between sessions.
Logged
RalphS
Platinum Member
******

Kudos: 27
Offline Offline

United Kingdom United Kingdom

Posts: 1,003



Ignore
« Reply #5 on: May 31, 2021, 01:15:36 PM »

My simple RDT is similar to Jon's and to the Bodnar type installations that I have seen. I mentioned it in the Bodnar thread but no-one seemed interested so I did not enlarge on my approach which was to see what I could use from my micro electrics box of bits.

I had a small RX - Oversky R/C MA-RX-42, that claims "full range" depending on the signal strength of the Tx.  It is a 4 channel Rx but as I only need one channel to DT the model I chose the one that controls the throttle. It is self binding so no bind plugs are needed.  I made a "mousetrap" device from piano wire and put all the bits in a balsa box that could be banded onto the fuselage under the wing of my old P30 model.

To stop the Tx stick from unplanned movement I put a rubber band on the handle and looped it around the stick.  The stick can be moved against the resistance of the band to activate the servo and DT the model.

I had a few flights and the system worked without fail.  I don't know the range and from the above experience doubt that it is of importance to me.  Clubmates with the Bodnar unit mentioned a 4km range.  I don't need that.

I have been using a 160mah battery - the smallest one in my box of bits.  I had bought the Rx for little over £12 but the price varies week to week and I have seen them at £30. The servo is not as small as the Bodnar servo and cost about £4.  The Spektrum Dx6i can use the older DSM2 system as well as the newer DSMx and mine have never missed a beat.  The little connectors for the battery are available in the UK from Micron as mentioned by Jon. ( micronradiocontrol.co.uk )
This site gives a very good guide to the types/sizes and names of the the types of connectors.

Making the Rx/mousetrap/battery unit in one makes it a bit clunky.  I didn't shorten and rejoin leads, etc., to save weight.
If I was thinking of fitting the RDT to several models I would probably permanently fit the Servo/mousetrap to the fuselages and fit the Rx/battery unit as a plug-in unit. 




Attached files Thumbnail(s):
Re: Spektrum RDT
Re: Spektrum RDT
Re: Spektrum RDT
Re: Spektrum RDT
Logged
Jez Wilkins
Silver Member
****

Kudos: 2
Offline Offline

United Kingdom United Kingdom

Posts: 199



Ignore
« Reply #6 on: May 31, 2021, 01:42:56 PM »

Jez, the connector is found on eBay from China or a UK reseller. Search for "Micro JST 1.25mm." There are not actually made by JST it's just the generic term. I understand that the actual lipo connector is 'molex picoblade' or sometime 'Eflite UM connectors' and some report this generic connector causes slight wear but I've never had an issue. You can get the genuine ones soldered up with leads but they are actually through hole sockets: http://www.micronradiocontrol.co.uk/conn_picoblade.html

I'll probably add a switch and charge socket so that I don't have to remove the battery between sessions.

The little connectors for the battery are available in the UK from Micron as mentioned by Jon. ( micronradiocontrol.co.uk )
This site gives a very good guide to the types/sizes and names of the the types of connectors.

Thanks very much for the information, Yak 52/Jon and RalphS.   Smiley

My biggest fear is using too much 'brute strength' (ha!!) on these small connectors and thin wires and pulling everything to bits!! Grin

Cheers,

Jez Wilkins
Logged
Yak 52
Titanium Member
*******

Kudos: 77
Offline Offline

United Kingdom United Kingdom

Posts: 2,789


Topic starter
Jon Whitmore



Ignore
« Reply #7 on: June 01, 2021, 03:46:02 AM »

To stop the Tx stick from unplanned movement I put a rubber band on the handle and looped it around the stick.  The stick can be moved against the resistance of the band to activate the servo and DT the model.

This is a great idea!

In terms of range I've flown a glider at 420m with one of these but that was above me. I've occasionally had them drop out when low down and far away, possibly due to the installation in the model which seems to make a difference.

I'm also planning to mount the RDT as a unit on a little plate.
Logged
Yak 52
Titanium Member
*******

Kudos: 77
Offline Offline

United Kingdom United Kingdom

Posts: 2,789


Topic starter
Jon Whitmore



Ignore
« Reply #8 on: June 10, 2021, 04:40:27 PM »

I've now finished the RDT set up on my 36" glider. I mounted the whole lot on a removable ply plate - perhaps it would have been lighter if built-in from the start but this is a retro fit.

I added a simple on-off switch and changed to a more compact 70mAh Lipo. The bits weigh 5.9g and the ply plate and screws add another 2 grams - not an issue in a model that already has 20 odd grams of nose weight. The servo is mounted on balsa rails and secured with tooth pick 'pins' and CA. The RX and lipo are stuck onto double sided tape. The switch is a small through hole type mounted on a bit of copper clad board for easy soldering and mounting.

The linear servo has a short bit of carbon rod CA'ed into the control horn. This captures the long end of the mousetrap. All pretty simple: https://photos.app.goo.gl/U7S9HHebJTqMV4Y36


Attached files Thumbnail(s):
Re: Spektrum RDT
Re: Spektrum RDT
Re: Spektrum RDT
Re: Spektrum RDT
Re: Spektrum RDT
Logged
Russ Lister
Free Flight Modeller .... sub 250g!
Palladium Member
********

Kudos: 75
Offline Offline

United Kingdom United Kingdom

Posts: 4,929


Russ Lister



Ignore
« Reply #9 on: June 11, 2021, 10:12:04 AM »

I been thinking about a RDT conversion myself, Jon .... you've saved me a fair bit of thinking, thanks! Smiley
Logged
Tapio Linkosalo
Platinum Member
******

Kudos: 35
Offline Offline

Finland Finland

Posts: 1,331



Ignore
« Reply #10 on: June 11, 2021, 10:36:21 AM »

One thing worth checking - does the RX support failsafe? I've found that depending on the RX software, even the sub-one-gram receivers may have this feature (at least some AFHDS 2 -protocol ones as used by FlySky radios). Now with the failsafe, you can make a feature that if the model flies out of radio range, it will always DT, thus preventing fly-aways. Or, if you are afraid of such action in a competition, you can program it other way, not to DT if loses signal.

Reminds me of my very first attempt on RDT, like 30 years ago. Using FM radios back then, the micro RXs had really short range, like 200 meters. As I used the RDT together with my timer in small fields trimming, I wanted to be sure that the RDT always works when needed. Thus I programmed the timer so that if it looses RX signal, it DT's. In effect I created a 200 meter radius "bubble" around my flying spot. The model was never able to fly beyond that!  Grin
Logged
RalphS
Platinum Member
******

Kudos: 27
Offline Offline

United Kingdom United Kingdom

Posts: 1,003



Ignore
« Reply #11 on: June 11, 2021, 11:20:59 AM »

The small Rx in my post#5 above has failsafe.  Turn the Tx off and the D/T releases.
Logged
SP250
Gold Member
*****

Kudos: 13
Offline Offline

United Kingdom United Kingdom

Posts: 522



Ignore
« Reply #12 on: June 11, 2021, 12:07:50 PM »

I believe that all 2.4gHz radios now have to have a failsafe function if they are CE marked for sale/use in Europe.

John M
Logged
Yak 52
Titanium Member
*******

Kudos: 77
Offline Offline

United Kingdom United Kingdom

Posts: 2,789


Topic starter
Jon Whitmore



Ignore
« Reply #13 on: June 12, 2021, 03:03:25 AM »

One thing worth checking - does the RX support failsafe?

Hi Tapio, yes - it's in the video in my first post. Only on the throttle channel on this RX which is one reason to use it (throttle cut button is the other reason)

I flew the model successfully today but still managed a couple of 'DT failure' flights  Roll Eyes one where I forgot to switch it on despite consciously trying to establish good habits. The other was when the slightly tacky rubber band hung up on the mousetrap after release - I've replaced it with a plastic washer on the end and had no further issues.

The linear servo with carbon cross bar worked really well. Capturing and releasing the mousetrap perfectly.

After one heavier landing the battery had popped itself off the plug with inertia so it could do with a better method of securing it than the double sided tape.

I did find it mildly awkward carrying a transmitter round with me everywhere - I must get a lanyard. It also takes a second or two to locate the throttle cut button by feel with eyes on the model, but you can reach the actual throttle stick with the left hand anyway.
Logged
Tapio Linkosalo
Platinum Member
******

Kudos: 35
Offline Offline

Finland Finland

Posts: 1,331



Ignore
« Reply #14 on: June 12, 2021, 07:55:08 AM »

Ah, ok. I did not watch the video, I seldom do. I prefer written text over videos.
Logged
Pages: [1]   Go Up
Print
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.21 | SMF © 2015, Simple Machines Valid XHTML 1.0! Valid CSS!