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Old May 14, 2009, 05:17 PM
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Joined Nov 2004
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Quote:
Originally Posted by MoFl
Agree.

Have a look at this post and this one (A note for modders...)

In order to improve efficiency, a switching regulator would be much better than a linear one (in this case you can also use 3s lipo with almost same efficiency). A suitable part for this mod would be this one, also avaliable at ebay
Thanks MoFl, that's exactly what I was thinking. In fact, I probably read those posts some weeks back, and lost track of them. Thanks!

Has anyone made these changes yet? Can the single switching reg. supply the 5V for both boards, or will that pose some problem?
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Old May 14, 2009, 05:24 PM
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United States, OH, Galena
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Quote:
Originally Posted by renns
What's the thoughts on running this unit from a 2s lipo?.....
Any comments from the electronics hackers in the crowd?
I say, do not bother with 5V regulators, run the whole thing directly from a 4.8V NiMh receiver pack, preferably Eneloop or equivalent (Precharged Kodak or Duracell). Replace R30 with a suitable zener diode (maybe decrase the value of R31?) and off you go.
What say you?
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Old May 14, 2009, 07:56 PM
Canadian Bacon
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Kingston, Canada
Joined Jun 2004
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Got my 4 channel in a couple of days ago with the long ant. wires. Haven't read all the posts yet but wondering if It would hurt to shorten to the standard length without the coaxial casing.? Also, for short range foamys etc., how about running it without the satellite ant.?

Gord.
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Old May 14, 2009, 08:39 PM
Argue for your limitations
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Lincoln, CA
Joined Oct 2006
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Quote:
Originally Posted by flypaper 2
Got my 4 channel in a couple of days ago with the long ant. wires. Haven't read all the posts yet but wondering if It would hurt to shorten to the standard length without the coaxial casing.? Also, for short range foamys etc., how about running it without the satellite ant.?

Gord.
Ok. But, make sure you range test it first. Also, desolder the antennas and save them in case something goes wrong.
AJ
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Old May 14, 2009, 09:02 PM
Team Wack-a-Mole
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Quote:
Originally Posted by JMP_blackfoot
I say, do not bother with 5V regulators, run the whole thing directly from a 4.8V NiMh receiver pack, preferably Eneloop or equivalent (Precharged Kodak or Duracell). Replace R30 with a suitable zener diode (maybe decrase the value of R31?) and off you go.
What say you?
Check out the specs on the particular 7805's they use.
Most generic 7805 require a 1.5V input voltage above the 5V. Meaning you need at least 6.5V for it to properly regulate the 5V output.
There are other 5V regulators (don't remember the specific number) that needs only .5V (5.5V) but a 4.8V rechargable battery I think won't be enough for the input to a 7805.
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Old May 15, 2009, 12:15 AM
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Quote:
Originally Posted by Melnic
Check out the specs on the particular 7805's they use.
Most generic 7805 require a 1.5V input voltage above the 5V. Meaning you need at least 6.5V for it to properly regulate the 5V output.
There are other 5V regulators (don't remember the specific number) that needs only .5V (5.5V) but a 4.8V rechargable battery I think won't be enough for the input to a 7805.
What I say is to bypass the 5V regulators, do away with them entirely.
Feed both the encoder end the RF board straight with 4.8V from the battery.
The CPU in the encoder is specified from 2.7V to 6V, I believe, and the RF board has its own 3V and 2.5V regulators which are specified up to 5.5V. Furthermore, the Analog to Digital converter in the CPU is used in ratiometric or relative mode (it measures the ratio of input voltage - stick pot cursor - to the supply voltage, not the absolute voltage, as indicated by the fact that the pots are connected between common and CPU supply), so encoding, servo positions and RF performance should not be affected by the actual supply voltage as long as it is within specifications and over say 3.5V.
I'll be testing tonight and report.
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Last edited by JMP_blackfoot; May 15, 2009 at 03:10 AM.
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Old May 15, 2009, 01:50 AM
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First tests are VERY encouraging indeed.
I used a Hobby City 4-channel transmitter and Turnigy 6-channel receiver, with Hitec HS-50 servo and 700 mAh Eneloop NiMh battery.
The transmitter was modified as shown in the photographs of the main PCB.
The bigger 5V regulator input and output were connected together and to the output of the smaller 5V regulator. I did not remove the regulators, but it could be done as well.
I first powered the transmitter off 4 cells. The voltage under load was 5.12V.
Binding to the receiver was performed as usual. Operation was quite normal. The position of the servo (connected to channel 1 receiver output) is shown.
Then I removed one cell. The voltage under load was now 3.82V.
Again everything operated normally.
The position of the servo is also shown.
I could not see any difference in servo position between 4 and 3 cell transmitter operation.
In fact, when changing back and forth between 3 and 4 cell at the transmitter, the servo would not even twitch at all.
I would say this opens up the option of a single Lipo transmitter power supply.?
Also, RF output as checked with a field strength meter was the same, as was the range with transmitter antenna removed.
Current drain with 4 cells was 80 mA at switch-on, rising to 170 mA after two seconds. With 3 cells, currents were 75 mA and 165 mA.
That means at least 10 hours of operation with the 2100 mAh Eneloop batteries.
I am definitely sold and will field test range and fly my model this weekend with the 4-cell transmitter supply.
After that, I'll tackle the voltage detection circuitry and report.
Then we'll see about the 6-channel transmitter, but i do not expect anything much different.
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Old May 15, 2009, 03:23 AM
The reviewer
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Tokoroa
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Now you can modify the battery holder so as to hold eight cells wired as two paralleled sets of four cells in series and get 20 hours continuous operation.

Throw a solar cell on the top and you might never need to go near a charger again! :-)
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Old May 15, 2009, 03:39 AM
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Quote:
Originally Posted by XJet
Now you can modify the battery holder so as to hold eight cells wired as two paralleled sets of four cells in series and get 20 hours continuous operation.
Thanks XJet, I hadn't thought of that one
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Old May 15, 2009, 04:35 AM
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Originally Posted by Lead Wings
I see HC are now selling the 6 channels for US$33. Can't see who will buy the 4 channel when you can get a 6 channel with more functionality for only $3 more:

For many of us the problem with buying the 6CH from Hobbyking is the $30 shipping if you want the PC cable as well (not much use without it).
R2 Hobbies only charge $17 shipping so they work out quite a bit cheaper.

In any case there seems to be yet another new kid on the block here.
6 CH computer TX with display and no PC required. So far it's Heli only but no doubt an Aero version will follow. Looks interesting.
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Old May 15, 2009, 04:45 AM
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Tokoroa
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The price is way-steep though.

55 quid is nearly US$84 or more than the Turnigy 9X and even once you include another US$40 for module/receiver, the 9X only comes to $110.

Are the extra channels, memories etc of the 9X worth the additional $36?

I don't know.
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Old May 15, 2009, 05:07 AM
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Yep, prices are always sky high in UK.
If a US distributor or HobbyKing got hold if this it would be a lot cheaper. It's another step in the right direction so hopefully we will soon have the functionality of a DX6i at a fraction of the price.

How may flyers actually need 9 channels anyway? 6 is plenty for the vast majority. What we want is more model memories.
The ideal would be a 6CH TX with a SD card slot for unlimited memories. It would be cheap enough to make but they won't do it 'cos then we'd never have to buy another TX again!
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Old May 15, 2009, 05:25 AM
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Tokoroa
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Yes, it's a shame that so few of the Chinese manufacturers seem to have Western model fliers on their design team.

A well designed, tested and documented set out of china that had features people wanted and which undercut the big-brand pricing would do very well.

Unfortunately it seems that right now, the typical lack of QC and product consistency, combined with some very oddball decisions in the design process mean that most Chinese products are still a bit short of the mark -- but they still sell because they're so damned cheap.
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Old May 15, 2009, 08:27 AM
Team Wack-a-Mole
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Maryland
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JMP,
What about the voltage to the RF module?
What happens when that goes below 5V

I noticed that they put 2 regulators and it looks like one is dedicated for the RF module.
Possibly to keep the voltage regulation "quiet" that is going to the RF module.

Let us know how a range test goes w/ the battery down to 1/4 or 1/2 capacity.
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Old May 15, 2009, 08:33 AM
Dan Thompson (MP8K developer)
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USA, KY, Paris
Joined Dec 2002
329 Posts
Quote:
Originally Posted by Melnic
JMP,
I noticed that they put 2 regulators and it looks like one is dedicated for the RF module.
Possibly to keep the voltage regulation "quiet" that is going to the RF module.
capacity.
Quite to the contrary. The dual regulators are to keep the voltage quite to the encoder. Most of the 2.4 Ghz RF decks transmit intermittently, so the voltage supply to them fluctuates and this can play havoc with the encoder in some cases.
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