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mrfliboy

Mechanical HT help needed

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I have just picked up a 4channel Futaba radio which has a buddy cord plug also.

I'd like to figure out how to get 2 of the channels (1 gimball assembly) onto channels 5 and 6 in my Futaba 7C. Using my buddy cord. I believe similar to the manufactured HT. Or is a 6 channel donor radio needed?From there I'll be going mechanical for my Myvu glasses. Thanks for any and all suggestions.

Similar to http://rcexplorer.se/files/18a79546e6235d58e8acefae1eda83de-75.html He's using Ch 4 and 5, I'm hoping to find 5 & 6. Feasible at all??

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You'll need a 6CH donor radio indeed, or find a way to rewire one of the gimbals your 4CH radio to use CH 5-6 if possible.

What your 7C will do when enabling trainer on channels 5 and 6 is take the corresponding channels from the trainer port. So, the channel numbers need to match.

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Well I found a cheap Hitec 6 channel with trainer port. Started the disassembly last nite and so far not bad. As I've removed components I check after every step too make sure all still works.

The amount of throws with the stock 5 and 6 channel turning knobs was say 90 degrees or so. Now I went and removed the knob pots and hooked up to the gimbal pots and my movement is less than 30 degrees. The turning knob pot was 10ohm and I believe the gimbal pots are 5ohm.

Is my next step to change to 10ohm pots on the gimbals or am I missing something here. Thanks for any and all help.

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Those would be 10k ohm and 5k ohm. But (as transmitters and position measurements are usually made) changing the pot value might not change anything. The issue is simple, look at how much you rotate the CH5 and CH6 pots - usually around 270°. How much does the pot move in the gimbal? only about 90°...

Didn't actually think of that earlier, but indeed the transmitter might have circuitry (resistors) between the gimbal pots and the processor that doesn't exist on the CH5-6 inputs. You might want to check if you see something that could be replicated. Or, which is more likely, it's just software calibration, in which case you'd be out of luck...

Edited by Kilrah

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Thanks for the reply Kilrah,

I believe I saw where someone had adapted a gearing setup to the gimbals and pots, I believe I know why now. I'll check the mount of movement on the gimbal pots later today and compare. Thanks

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Here goes.... with the stock Channels 5 and 6 knobs i get around 90 deg of movement. With the gimbal setup down to 30 deg or so. With the gimbal pot removed, I'm back to 90 deg or so, so I could gear it but only to 90 deg. If I was to use a 10turn pot would that make a difference?? Thanks again.

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If I was to use a 10 turn pot would that make a difference??

A ten turn pot would make the problem ten times worse.

Time to see what can be hacked in the Tx. What Hitec Tx are you using? What is the FCC ID?

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Its a Hitec Focus 6

FCC ID IFH FOC456

Also I have no servo movement on either 5/6 unless a pot is hooked to both channels. When I hooked up the gimbals I removed all the trim tab stuff. I'm direct wiring to the gimbal pots.

The good news is I got my 5way splitter in today and all is fine with the ground station. 7' monitor, Myvu glasses, Sandisk recorder and MP5 player. All being powered from a 2200ma 3cell w/lipo monitor and only the DVR had to have a voltage regulator (20amp brushed esc with a heat sink)

Thanks

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Basic R/C Tx's from the 1990's era (like yours) are based on the NE5044 R/C encoder. The scaling for the stick pots is a simple electronic affair; usually three or four fixed resistors and occasionally an OPAmp will be involved. The best thing to do is to reverse engineer the channel for one of the sticks and then copy the components onto the new channel you want to use.

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Thanks again. I'm thinking just wiring it in between the pots and my donor TX board.

I also have found the mechanical gearing style:

More tinkering later today.

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Thanks again. I'm thinking just wiring it in between the pots and my donor TX board.

That wouldn't work. The module expects and outputs servo signal pulses, not an analog voltage like you're dealing with in the TX.

One of those modified with custom software for 3x gain instead of 2x (or even 6x, while we're at it, to get 180° servo movement) and put between the receiver and servo would indeed compensate for the loss of throw. However, resolution might be noticeably low.

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Well it was a thought anyway, Thanks Kilrah

I pretty much stripped the donor Tx board down already, meaning removed the excess stuff that did not affect the ch 5 and 6. Reverse engineering the existing ch 1 thru 4 will be tough. The gear setup looks feasible. Thanks again

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Mechanical gearing is doable. One side tested and all is well. Almost 90 deg throw and no stops needed. Gimbal assembly came from the donor 4 channel radio. Lower gear is from a 1/4 scale servo and I used the original pot shaft without the electronics. Upper gear is from a std servo and the pot is from the 6 channel radio. Tomorrow attempt the otherside and hopefully by the weekend at least have this part done. Thanks for the help.

With a Mechanical tracker is it better to have the gimbal return to center and install the springs again or leave it with a little friction and no centering? Thanks

post-5645-125427086558_thumb.jpg

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I don't think it matters much , the springs wouldn't be strong enough for you to feel them anyway. Maybe if you put them it would bring the camera to center instead of an uncomfortable position should the mechanical assembly disconnect in flight, but I see no other advantage...

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Thanks for the info Kilrah. The centering springs will take alittle extra work to reinstall. I'll give it a shot. I've heard a few stories of cameras getting jammed in unfortunate spots.

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In case you need to use an electronic solution: Looking at the two photos, I don't think it would be impossible to reverse engineer the board.

The NE5044's Pins1-4 are POT inputs for CH1-CH4, and Pins 5-6 are for CH5-CH6. I see that they scale the stick range with simple resistors. Just compare their values and see how they differ on the two upper channels. In this particular case, the POT's value will also impact range, so copy it too.

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No electronics whiz here but hear me out. On the NE5044 (I believe) The dot on the chip is #1 and on up th ladder. 1 thru 4 all have a 683 resistor and 5 and 6 have a 473 resistor (the actual numbers written on the resistor). Could it be just swap a pair of those around and give it a shot?? My mechanical geared setup is twice the size of the 6 channel gimbal. The smaller would be great to use. Thanks again

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I haven't been keeping up with resistor designations, but, the first two numbers are probably the value and the third number should be the number of zeros, so, for example 683 would probably be a 68,000 ohm resistor. Verify this with an ohm meter.

Rather than swapping would be better to just buy one resistor and swap only one to see what the outlook would be. Easier on the ckt board lands this way.

Another way would be to tack solder a 100,000 ohm resistor in parallel with one of the 68,000 ohm resistors which would give a resistance of around 47,000 (off the top of my head) and try that.

Edited by W3FJW-Ron

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It's hard to tell from the photo, but I think I see a total of three resistors for each channel. Did you check the other two?

My gut feeling is that changing the 47K / 68K will give you what you want. You are on the home stretch.

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Well I went ahead and soldered up a 100K resistor piggyback to the 47 resistor and no difference noted. I'll try and do some more reverse engineering later today. The red circle is where I soldered on to. Thanks

post-5645-125458034151_thumb.jpg

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