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Old Mar 24, 2012, 07:57 PM
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Need help programming 7 channel glider on DX8

I have 2 v-tail, 2 ailerons, 2 flaps, and throttle.

I want the throttle on the throttle, flaps on the F Mode (normal 0, cruise 1, and brakes 2), I want crow on Gear 0. I want full wing reflex, full wing normal, and full wing camber on Rudd D/R. Full wing ailerons with flaps at half rate would be cool looking but I really don't think it's necessary. It doesn't have to be exactly how I want it as long as it has all the functions.

I managed to achieve everything accept full wing camber... But for what I did so far it's kind of a mess. Some functions, as I programmed it, require multiple switches and I think I need to redo it.

Thanks! -Joel

Ready mixed presets would be ok but I'd like to learn how to program it too.

I thought I'd post it here as well as in the general forum.
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Old Mar 24, 2012, 11:34 PM
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The DX8 isn't a good choice for full-house sailplanes. It lacks native sailplane features. Worse, there aren't enough Pmixes to create all of them yourself. Limitations in switches, mix triggers combined with no channel cascading and channel mapping create additional problems.

I've developed two full-house configurations for the DX8. One profile supports e-gliders, it lacks full trailing edge. However, you could add that by removing another feature. The other profile supports unpowered sailplanes, it lacks both full trailing edge and crow. Creating a launch camber feature consumes two of the DX8's six Pmixes. Spektrum TX/RX design choices force the throttle channel to be useful only for controlling a motor, even in unpowered applications.

Both profiles are complex (at first) to operate due to DX8's limited switch and mix trigger choices. However, they do work. I've used them for the last year for hundreds of flights.

I really wish I'd purchased an SD-10G or JR radio instead. The DX8 is fine for RE, RES, helis and most power planes.
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Old Mar 25, 2012, 12:57 AM
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Great. I got it in december. I don't suppose they'll give me a full refund?
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Old Mar 25, 2012, 03:22 AM
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WAIT!!! I got it ALL on only 4 p-mixes! (not counting the native flap and v-tail mixes) But of course it's 1 in the morning now!

I learned how to assign switches (it helps to know you can do that) via google and then I went through every little change, watching my bird, to note what it all does and I decided that the user manual is ****!

Starting with flaps, neutral, cruise, and full + crow and elevator throws (p-mix 1) on Gear 1, off Gear 2, then full wing camber, neutral, reflex (p-mix 2) + elevator throws (p-mix 3) all on Aux 3 via knob + on, off with mix 1 and 0 (when you turn it on it goes back to where you left it, granted you haven't moved the knob) and full wing ailerons (p-mix 4) with on and off on Ail D/R 0 and 1,2.

Throttle is still on the left stick. Just need to fly it again to trim it all up.

Now I need a 72 hour psych evaluation.
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Old Mar 25, 2012, 03:21 PM
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Here it all is:

http://www.youtube.com/watch?v=C06Ekl4vHgg
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Old Mar 25, 2012, 04:33 PM
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The DX8 features six Pmixes, and two predefined mixes depending on the model/wing type selected.

Creating cruise/reflex/camber selection consumes a three way switch (Aux2 is a good choice) and two Pmixes. One Pmix controls ailerons and the other flaps.

Tow launched models require launch camber mode (two Pmixes and a switch). This isn't required for e-gliders.

Crow requires a Pmix to control ailerons, and a switch.

Full trailing edge requires a Pmix linking Ail->Flap, and a switch depending on your requirements.

I use the Fmode switch to control AilDiff, three sets of trims (launch, normal, camber/special) and control/mask Pmixes.

Fmode0 (launch)
100% AilDiff to help retain aileron control in climb-out stalls.
Trims set in launch conditions: power or tow. (usually nose down trim)
Disable useless features during launch, eg. crow.

Fmode1 (normal flight)
AilDiff setting in normal flight (exact % must be tuned to model)
Trim settings in normal flight
Enable full-house features created with Pmixes

Fmode2 (camber/special)
AilDiff for tight camber circling (exact % tuned to model and your style)
Trim setting to match wing camber used in camber mode

The special case (early trim flights, AilDiff testing, etc.) provides test trims and AilDiff with easy A vs B testing against your current "normal" settings. Simply flip between Fmode1 and Fmode2. Is this trim/AilDiff better than my normal settings? This is very helpful early on while fine tuning Pmixes and AilDiff.

Depending on power vs tow launch (creating launch camber consumes 1/3 of the available mixes) you might have unused Pmixes.

I have flaps/crow mapped to the throttle stick (switched). This is a great feature. However, it consumes Pmixes and a switch. One Pmix maps the throttle signal to flaps. The other Pmix provides Flap->Elev comp. I tried it without ele comp, it's possible but error prone.

The two predefined mixes offer:
Ail->Rud mix, likely will require a switch
SnapFlaps (Elev->Flaps) requires a switch (a little flap goes a long ways, be careful)

The DX8 includes two preset flap positions with ele comp and deployment speed adjustments. Two positions are nice and speed works well.

Flaps/crow on the stick is better, if you have Pmixes to create that feature. My config offers both preset and on the stick. I set predefined flaps to fairly mild flap deflections used during non-spot landings. On the stick offers full (~90 degree flaps) for steep landing approaches.

An unpowered full-house model is the most restricted due to the requirement for launch camber mode consuming 1/3 of the available Pmixes.

My powered profile includes another feature mapping the knob to flaps in Fmode2 to fine tune camber mode flap deflection. I could use that mix to provide full span ailerons, but the powered model's RX doesn't have enough channels.

These are the basic full-house features. Other TX with native sailplane features offer other nice features, plus a better selection of mapping switches to mixes/features than the DX8. The DX8 doesn't include a Pmix trigger for Fmode0. There are other switch choice limitations too.
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Old Mar 26, 2012, 12:53 AM
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I've been thinking about moving full trailing edge on a 3way switch so I can put crow on the knob. But I'm going to try it both ways and see what sticks.

So I guess there's a lot more sailplane mixes than I knew.

Can't you just turn off crow to get launch camber? What is launch camber on a sailplane?
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Old Mar 26, 2012, 02:37 AM
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Originally Posted by CrazyJB View Post
I've been thinking about moving full trailing edge on a 3way switch so I can put crow on the knob. But I'm going to try it both ways and see what sticks.

So I guess there's a lot more sailplane mixes than I knew.

Can't you just turn off crow to get launch camber? What is launch camber on a sailplane?
The DX8's knob is great for adjust it before flight (eg. launch camber) and adjust it rarely in flight (flap trim). However, it doesn't work well for adjustments made in real-time, because it's too difficult to reach and requires moving your right hand too far from the stick.

Launch camber is camber (beyond typical thermal camber deflections) used during the initial phase of a tow/high-start launch to increase launch height. Both aileron and flaps are usually deflected down more than thermal camber.

After the initial nearly vertical climb phase launch camber is removed, reducing drag allowing the model to increase airspeed. Reflex mode is often used to further increase airspeed prior to releasing the tow line and beginning a zoom climb.

The entire launch process (throw, climb with launch camber, arc over, enter reflex, leave tow line and zoom climb) occurs quickly. You wont have time to mess with that knob.

The knob is useful for fine tuning launch camber before launch. Changes in wind conditions, launch method (winch vs high-start) and winch battery power lead to increase/decrease launch camber.

Too much launch camber is a serious problem (nearly uncontrollable model, pop-offs, broken tow lines), not enough reduces launch height. The exact value varies with model, elevator trim, tow hook position, pilot skill and wind/launcher conditions.

The published settings for my tow launch model:
Thermal camber: ailerons down 5 degrees, flaps down 10 degrees (max values)
Launch camber: ailerons down 10 degrees, flaps down 15 degrees

I've noticed other designs use more launch camber deflection, with aileron and flap closer to matching values.

BTW, I noticed your e-glider build at the last meeting. Nice job!
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Old Mar 26, 2012, 02:54 AM
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I've been thinking about moving full trailing edge on a 3way switch so I can put crow on the knob. But I'm going to try it both ways and see what sticks.
In my profiles, Aux2 selects overall wing camber. Up is reflex (ail/flap up slightly), center is normal/cruise, down is thermal camber (ail/flap down slightly).

My e-glider profile uses gear switch to enable/disable crow (ailerons up flaps down), with aileron deflection tracking flap deflection as throttle stick is moved. Spektrum's profile has crow on the same switch, but it's fixed deflection and active only in preset flap position two. I used that configuration, before I adding flaps/crow on the stick.
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Old Mar 26, 2012, 05:50 PM
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I am beginning to be disappointed with the DX8's positioning of the knob and the lack of more variable controls like it.
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Old Mar 26, 2012, 07:31 PM
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I know how you feel. At first, I really liked my DX8.

It works great with helis with nice features like active gyro trim and throttle activated flight timer. Three sets of trims and two preset flap selections are nice with planes. The back lit LCD is nice, but they waste too much of its space with their name across the top and a large picture of a heli/plane.

With sailplanes it comes up lacking. However, they don't promote it as a sailplane radio. JR offers TXs that properly support sailplanes and work with Spektrum RX and their BnF/RTF products.

Spektrum announced a $800 model (DX18) that supports sailplanes, but it's not available. I don't know when it will ship. Don't put too much stock in their ship dates, because they often push them back a few months at a time. Once it actually ships, you'd be smart to wait several months for bugs to get worked out.

I purchased an early production DX8. I ended up being their unpaid Q/A dept. The crashes due to their bugs and lack of Q/A cost me too much money, which they refuse to cover. They ended up recalling* their first six months of production to fix several really nasty problems. My radio still needs this service. They should have discovered these issues long before they shipped to customers.

BTW, be careful with the included charging system. It's not safe to leave it plugged in charging for more that a few hours. Using the included NiMH pack their charging system doesn't stop charging automatically. It automatically stops charging when full, if you upgrade to their $80 LiPo pack.

HK offers a LiPo pack for the DX8 for much less. I don't have one, but I hear they work fine.

The stock NiMH pack works fine, but their charger will over-heat and kill it if you're not careful. To help avoid damaging the NiMH pack I remove the back cover and tilt the pack out away from the TX and foam while charging it. When the pack starts to warm up it's done charging. Leaving it on longer will slowly kill the pack, because it become too warm. Not removing the cover and tilting the pack away from the foam allows heat to build up faster.

* Many early customers consider it a recall. For legal reasons Spektrum calls it a "service bulletin". Either way, you must send your DX8 to them for repair. Tough luck, you can't fly while it's crawling its way to them and back via UPS Ground. Some thanks for functioning as their unpaid Q/A lab, where we supply the TX and crashed models.
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Old Mar 26, 2012, 10:37 PM
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BTW, be careful with the included charging system. It's not safe to leave it plugged in charging for more that a few hours. Using the included NiMH pack their charging system doesn't stop charging automatically. It automatically stops charging when full, if you upgrade to their $80 LiPo pack.

HK offers a LiPo pack for the DX8 for much less. I don't have one, but I hear they work fine.

The stock NiMH pack works fine, but their charger will over-heat and kill it if you're not careful. To help avoid damaging the NiMH pack I remove the back cover and tilt the pack out away from the TX and foam while charging it. When the pack starts to warm up it's done charging. Leaving it on longer will slowly kill the pack, because it become too warm. Not removing the cover and tilting the pack away from the foam allows heat to build up faster.
I am only using a smart charger for the NiMH until I get the HK Turnigy Lipo. Then I will only use the smart charger once in a while for balancing... Anyways I might try my hand at a refund. If that doesn't work, I'm going to take it apart and move the knob.
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Old Mar 27, 2012, 03:10 AM
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I am only using a smart charger for the NiMH until I get the HK Turnigy Lipo. Then I will only use the smart charger once in a while for balancing... Anyways I might try my hand at a refund. If that doesn't work, I'm going to take it apart and move the knob.
The provided charger works. It isn't a fast charger or stop charging automatically, but it works. The NiMH cells aren't low self-discharge, but function well. You just can't plug it in and walk away. This was safe with some older radios, but it's not for DX8 using NiMH packs.

I've charged and tested my stock pack with another charger. However, almost always use their charger, after removing the cover and tilting the pack out. Unplugging the pack from the TX stresses the PCB connector. Basically, you end up pulling on the wires at an angle across the PCB connector.

If you plan to continue using an external charger, place a jumper between the PCB and pack to protect the PCB connector. Others have made jumpers with multiple connectors, and external charging jacks in the cover.

What would you like to control with the knob? It's not too difficult to mask the throttle output (stop the motor) and use the stick as input to a mix. My e-glider profile uses this to allow flap/crow (variable) on the stick, a feature I find valuable.
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Old Mar 27, 2012, 04:22 PM
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United States, CA, San Jose
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Originally Posted by LizardMan View Post
The provided charger works. It isn't a fast charger or stop charging automatically, but it works. The NiMH cells aren't low self-discharge, but function well. You just can't plug it in and walk away. This was safe with some older radios, but it's not for DX8 using NiMH packs.

I've charged and tested my stock pack with another charger. However, almost always use their charger, after removing the cover and tilting the pack out. Unplugging the pack from the TX stresses the PCB connector. Basically, you end up pulling on the wires at an angle across the PCB connector.

If you plan to continue using an external charger, place a jumper between the PCB and pack to protect the PCB connector. Others have made jumpers with multiple connectors, and external charging jacks in the cover.

What would you like to control with the knob? It's not too difficult to mask the throttle output (stop the motor) and use the stick as input to a mix. My e-glider profile uses this to allow flap/crow (variable) on the stick, a feature I find valuable.
I added in a set of plug savers (servo connectors) between the battery and the battery plug, when I got it, so it won't wear out. I recognized that right away.

The DX8's charger is really meant for Lipos, it will work for NiMH but, as for battery warmth, you really have no idea when, exactly, it reaches delta peak like a smart changer does. The Tx charger also does not discharge the remainder of the battery so, for NiCD's and NiMH's, the charge capacity will slowly shrink (Ni-memory) until you cycle it. A smart charger can take advantage of maximum capacity and longevity of the battery... but smart chargers are a pain to learn as you have to learn all about batteries voltage, current, tolerances and capacities, you have to do the math, everything just to use them without it canceling out on a charge or a discharge and they can easily trash a battery if you don't know what you're doing or enter the wrong values. Smart chargers are definitely for the techies (I'm not sure if there are any "automatic" smart chargers).
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Old Mar 27, 2012, 08:47 PM
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As far as I'm concerned, normal NiMH packs aren't worth bothering with any more. The DX8 came with an unmarked (LSD wise) NiMH pack, so I use it. However, I purchased a custom made Sanyo Eneloop LSD pack within weeks of the DX8. I tested it, charged it and carry it out to the field with me. It's my back-up/spare pack. I don't worry about having the DX8's stock pack at 100% at all times. If it comes up short, the spare is ready to take over.

The nice thing about LSD cells is they're safe to leave fully charged for long periods of time. Exactly what you want in a spare pack. Mine has sat unused, but fully charged for a long time. I'll test it soon, and expect to find it healthy, and retained at least 85% of its actual capacity.

Normal NiMH (non-LSD) aren't safe to leave fully charged. Over time they develop a high internal resistance (crystal growth) that renders the cell useless. Between their high self-discharge rate and problems if left charged I stopped purchasing them several years ago. I have several matched sets of AA Eneloop cells, purchased in 2007, that still function. The non-LSD cells I purchased at the same time all went Hi-Z long ago.
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