Reeds Emulation Encoder for 2.4ghz modules
Phil Green, 22/04/2011
Following on from the Single Channel Emulation Encoder which was an up-to-the-minute take on 1960s S/C radio
control, I’ve now completed the Reeds encoder which emulates a typical 1960s reed set such as the Orbit, Remcon
12, RCS Comp 10 etc. Every conceivable aspect of the old technology is reproduced in a small, reliable
microprocessor controlled unit. A standard Futaba-fit or DIY 2.4g module and receiver are used for the RF link.
Spektrum, Corona, Frsky and Futaba FASST have all been used successfully. JR modules are not directly supported
due to the battery-level inverted PPM they require.
The encoder features:
 Accurate emulation of up to 12 channel reed sets
 Functions include Aileron, Elevator, Rudder, Throttle, Auxiliary
 Standard reeds elevator trim, plus trim on all other channels too including throttle & aux
 Audible and visual trim change pips
 Fully simultaneous operation of all channels
 Servo reversing on all channels
 All reverse and trim settings are saved to flash and are retained during power off
 Range test sweep mode for single-handed range checking
 Simultaneous variable servo slow on all channels matching the transit speed of the old Bonner Duramites
 Master reset back to no reverse & central trims
 Trainer port output for Sim or Buddy use
 Schottky-isolated output for DIY or Futaba-style modules
 Reverse-polarity protected power input
All connections are made via standard 3-way servo connectors onto PCB header plugs.
Headers are provided for the battery, switch and RF module, and from 1 to 6 toggle switches.
Please note that reversal of any of these connectors could damage the encoder or RF module, or both.
The toggle switches are wired with red & black to the outer contacts and white to the centre.
If using JR leads this equates to red & brown to the outer contacts and orange to the centre.
Please note that it is essential to orient all the connectors properly or a short will occur. The toggle feed is shortprotected but its best to get it right in the first place. The encoder can be damaged by inserting the plugs wrongly.
The 8-cell nimh battery connects to the battery header on red & black. White is unused.
The power on-off switch is wired across the red and white of a servo lead, black is unused.
The module header connects neg on black, battery voltage on red, and the PPM stream on white.
The trainer header uses black for common ground and red for PPM.
The bi-colour LED may be extended to make it panel-mounted if desired.
Controls:
All controls accurately replicate those of the old reed sets, with the exception that we have trim on all channels.
Aileron, elevator and rudder are self-neutralising channels.
All trims, throttle and auxiliary are progressive (they stay where you leave them)
To reverse a function, simply hold that function toggle briefly during power up – for example to reverse the elevator
channel, briefly hold up or down elevator and switch on. You can reverse as many channels at once as you have
fingers, or do them one at a time.
To ‘un-reverse’ a channel, just repeat the operation to reverse it back to normal again.
To clear all the reverse settings, and to centre all trims, briefly hold down-trim on power up. Three pips confirm
To enter range-test mode, briefly hold up-trim during power up. This will cycle the surfaces so that you can walk away
from the transmitter watching for any loss of movement or stuttering. To exit range-test mode, flip low throttle or cycle
the power. If your RF module has a range-test low-power setting, power cycling is a good habit to get into.
Elevator trim is used exactly like an old reed set – simply nudged up or down - with the exception that there’s an
audio-visual signal of trim changes.
Aileron trim is invoked by simultaneously holding elevator trim (either up or down) and aileron at the same time.
Practise making this combination so that both switches operate at exactly the same time.
Similarly with trimming the other channels – simultaneously hold elevator trim and the required channel in the
appropriate direction. Again theres an audio-visual signal of trim changes. This is a modern luxury as period reed
sets didn’t generally have aileron, rudder or throttle trim – only elevator trim, and that used a separate servo
mechanically linked to the elevator.
Throttle trim can be used as an ‘engine cut’ by running with the trim towards ‘high’. Applying ‘low’ trim at tickover will
further close the throttle which can be made to cut the engine by adjusting the linkage or throttle lever.
Servo transit speed can be set in 4 steps from very slow to fast. Period reed servos were quite slow – speed 3 is the
most realistic.
‘Three pips’ occur whilst saving trims and reverse settings to flash – please do not switch off during the pips – wait for
them to stop.
The current software revision is ‘S’ but please be patient if at some stage I need to ask you to fit an updated chip. This
ensures we’re all on the current revision and that no-one misses out on new facilities. The prototype has been flown
extensively and although the software is mature, some enhancements may come to light as the reeds encoder is
taken up by more people. Version ‘S’ has been in use for several months flying and no further revisions have been
found necessary.
Connecting up:
All connections are made with standard servo-wire connectors to the headers on the board.
Note that the transit speed pot has red/black to the outers and white to the centre wiper.
The switch connections and the battery connections use two of the three wires each.
The encoder features a schottky ppm isolating diode so remove the inline diode from your module if there is one.
All the reed toggle switches (from one to six toggle switches for the full 12 channel emulation) are wired in a similar
way. The outer contacts used for up/down/left/right/high/low etc are wired to pos & neg, ie red & black. The white wire
(what would be the servo signal wire) is the common centre contact. Pressing the toggel switch off neutral connects
the white to either red or black. Releasing the toggle disconnects the white. This diagram shows a switch at neutral:
Centre-off toggle switch
Black
Red
White
The built-in Servo Slow function, which emulates the transit speed of the old Bonner servos, is controlled by a 10k
potentiometer. It isn’t continuously variable but rather has 4 positions from very slow, slow, medium to fast.
The medium speed most accurately represents a true reeds servo.
Note that the PCB connector is wired neg, pos, wiper but of course at the pot end, the wiper is the centre connection.
Pot value = 10k
If you use JR leads, then the colours are different. Futaba leads are preferable as the red/black is more logical for
pos/neg. Here is a comparison:
Futaba
Black
Red
White
JR / Spektrum
Brown
Red
Orange
Circuit diagram:
As usual, any photos of builds or conversions, and especially any flight pics & videos would be much appreciated.
Please keep an eye on http://www.singlechannel.co.uk as further photos and videos will be added as time permits.
Good luck!
Phil
philg@talk21.com
Phil_G on all the R/C forums