Spektrum DX7 Programming Notes

Introduction and brief review

The Spektrum DX7 is the first full-range ii.4 GHz radio control organisation for R/C modellers. I reviewed it in the April issue of RCMW, and found it to be a well featured arrangement (if non quite equally flexible as some other 7-aqueduct radios). It is nicely synthetic, and provides a stone solid radio link.

Downsides are the poor balance of the box, rather archaic programming (though past no means worse than some other Far Eastern radios), and the need to install two receivers in the model.

The spread spectrum information link is very robust even so, and equally a result the set has become very pop here in the UK.

Here are some programming notes which owners may find useful.

• Programming four-servo wings
• Throttle 'kill' function
• other data.

Programming 4-Servo Wings

The increasing popularity of 3D electric models and F3x sailplanes has made support for four-servo wings almost essential in mid-range radios. While the stock mixers on the DX-7 only support two servos, the other ii servos can be driven by means of a couple of PMIX's and a flake of effort.

And so, let's come across how to implement a basic 4-servo setup to support the following:

• 4-servo Aileron
• four-servo Camber
• four-servo Snapflap

Footstep 1: Configure Flapperons

in the System menu, set up the model type to ACRO, and the wing blazon to Flapperon (and optionally enable the V-tail mixer).

Step two: Connect the Servos

The table below shows the servo assignments. The wing servos are shown in royal - chs two and six are assigned to the inner surfaces ('flaps'), while chs 5 and vii are assigned to the outer surfaces ('ailerons').

Rx Channel		Connect this Servo
one	THRO	Throttle
2	AILE	Right Inner
iii	ELE	Elevator
iv	RUDD	Rudder
5	GEAR	Left Outer
vi	FLAP	Left Inner
7	AUX2	Correct Outer

Footstep 3: Disable the 'Gear' switch

The Gear part must be disabled, then it doesn't affect aqueduct v.

1. Enter the SERVO TRAVEL menu
2. Set the servo travel for 'Gear' to zippo/nothing.

Pace 4: Configure Flap system

The DX-7 provides a choice of activation method for flaps. The 'Organisation' selection volition arrange almost sailplane pilots. It provides a choice of iii flap presets, selectable via the flight-mode switch.

1. Enter the SYSTEM->INPUT SELECT menu.
2. Select 'system'.
3. Set FLAP TRIM=INH

Footstep 5: Configure the mixers

In the final step, nosotros'll set upwards the stock mixers for the inner surfaces, with PMIX'due south for the outer.

Function	Mixer Menu	Rate	Offset
Inner Snapflap	[ELEV->FLAP]	D=0/U=+10	n/a
Inner Slant	[FLAP SYS]	NORM=0 MID=10 LAND=15
Inner Aileron	[D/R] (to set travel)
Outer Snapflap	[PMIX3]: Elev->Gear	0/+x	0
	[PMIX4]: Elev->Aux2	0/+ten	0
Outer Camber	[PMIX1]: Flap->Gear	+100/+100	0
	[PMIX2]: Flap->Aux2	+100/+100	0
Outer Aileron	[PMIX5]: Aile->Gear	+100/+100	0
	[PMIX6]: Aile->Aux2	-100/-100	0

Notes

• PMIX5/6 must exist used for the outer-aileron mix in order for the aileron trim lever to work.
• Aileron travel is gear up in two places:
  1. Dual Rate. This aligning affects all four servos.
  2. PMIX5/6. This aligning affects outer surfaces just.
• Differential is adjusted differently for inner and outer surfaces:
  1. For inner surfaces, use the Diff menu.
  2. For the outer surfaces, set different up/down rates in PMIX-v and PMIX-6.

Crow Mixing

Owners of F3B/F/J sailplanes will exist wondering whether the DX-vii can be used for crow brakes. Well yep information technology can, but the programming is tricky. Actually it's actually pretty horrible especially if you lot're used to the flexibility of a Multiplex radio as I am.

The principal problems are:

1. insufficient PMIX'southward to support crow mixing in addition to the basic mixing described above. As a issue, two of the mixes above have to be dropped.
2. the unpredictable issue of the Outset parameter in the Throttle mixes. This makes it tricky to set the crow travel accurately on the outer surfaces (it's easy enough on the inner flaps).

Nevertheless, here's my solution for crow. In gild to costless upwards PMIX's for crow, I've dropped two of the mixes, namely snapflap and camber on the outer surfaces.

Function	Ch	Mixer Menu	Charge per unit	Offset
Inner Snapflap		[ELEV->FLAP]	D=0/U=+10	n/a
Inner Camber		[FLAP SYS]	NORM=0 MID=10 LAND=fifteen
Inner Aileron		[D/R] (to set travel)
Inner Crow		[PMIX3]: Thro->Flap	+50/+50	+100
Outer Crow		[PMIX1]: Thro->Gear	+l/+fifty	-100
		[PMIX2]: Thro->Aux2	+50/+l	-100
Crow/Elev Compensation		[PMIX4]: Thro->Elev	0/+25	0
Outer Aileron		[PMIX5]: Aile->Aux2	+100/+100	0
		[PMIX6]: Aile->Gear	-100/-100	0

Summary

We've seen how it is possible to program a bones 4-servo wing up quite easily if you don't need crow brakes.

Crow brakes are possible only with some compromises and difficulties.

It'south worth remembering that the DX-7 too lacks flight modes and curves, and in that location may be installation issues arising from the twin receivers. While some modellers get around the latter by using the AR6100 park-fly receiver, this do is non recommended for full-range applications.

Implementing a Throttle Kill part

There is no throttle kill part provided with the DX-7, instead at that place'due south 'Throttle Idle Recovery'.

For those who prefer a traditional Kill function, hither's a solution which works off the MIX switch:

• Use PMIX-five or PMIX-half dozen
• mix THRO->THRO
• SW=MIX
• Charge per unit = -100 / -100 (annotation both negative)
• Offset = -125 (note negative)

Note ane: employ only PMIX-five or half dozen, otherwise the kill setting will vary with idle trim.

Notation 2: The kill position is adjusted via Offse t.

Channel Assignments

Table below shows channel assignments of the DX-7.

	Wing Blazon
Ch #	Normal	Flapperon	V-tail	Delta	Notes
1	Throttle
2	Aileron	Flapperon		Elevon
3	Elevator		Vtail	Elevon
4	Rudder		Vtail
5	Gear
6	FLAP	Flapperon			labeled as 'AUX1' on AR7000
seven	AUX2

Mixing Architecture

The mixing architecture is quite unproblematic.

Mixers: Simple case

Consider a mixer C1 -> C2, e.grand. THRO -> ELEV

In the unproblematic case (east.thou. for Normal wing blazon), moving stick C1 will effect just the aqueduct corresponding to C2. So with THRO -> ELEV mixer, moving the throttle stick volition change the signal to servo #three .

Mixer: special cases

Things are only a little more than complicated for the special wing types. Once again, consider a mixer C1->C2. The table below shows the effect of different C2 and wing types:

Wing Blazon	C2	Output Channels	Relative sense
Flapperon	AILE	#five, #six	opposite sense
	FLAP	#5, #6	same sense
Delta	AILE	#two, #three	opposite
	ELEV	#2, #three	same
Five-tail	RUDD	#3, #4	reverse
	ELEV	#3, #4	same

Examples for wing type = Flapperon

Rudd -> Aileron

Here, C2= Aileron, so the mix drivers flapperons in opposite directions (i.east. as ailerons). Possible applications include:
1. Coupling of ailerons to rudder, where the rudder is the primary turn command.
2. Curl correction during knife edge.

Elev -> Flap

Here, C2=Flap. Displacing the elevator stick causes flapperons to move in the same direction. Use this to implement 'snapflap'.

Pulse Widths

Measured on aileron channel, trim at centre, all settings at default values (measured using servosim).

Servo Travel	Min (mS)	Max (mS)
+l/+50	1.three	one.7
+100/+100	i.ane	1.ix
+125/+125	1.0	2.0
+150/+150	0.9	two.1

Interestingly, the DX-vii outputs eight (not 7) channels at the DSC interface.