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Old Apr 08, 2012, 12:54 PM
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How Potentiometers work, are built

Hi Mescaline.

Except for the pot, I'm still using the Walkera Factory settings, the same settings that are in the Owner's Manual. I plan on cranking everything up, and go "balls to the wall" once I start flipping out. We have 5 or more mph winds here almost always, and I have my hands full just trying to do up-right banked circles in my small backyard at the moment.

Have you had an opportunity to make a close look at the pot? Did you see the dark/black resistive "ring" under the Metal Tweak part? And notice that the dark/black ring isn't full circle? Also, 180* away from the Metal's Flat, there is a tiny metal "dimple" pointing downward toward the dark/black semi-ring?

After taking another look at the pot using a cheap magnifying glass, it looks like the "detents" I was trying to describe in the above post and barely feel when I reach the end of the Pot's travel is from the "dimple"/pointer" being stopped by the Pot's extreme Max and Min Solder Terminals. If this pot is like all the other pot's I've had, the Wiper's Solder Terminal is located in between the pot's two extreme terminals, and in this case it appears to be all the way on the other side of the pot (i.e. the two extremes are at what I call 11 and 1 O'Clock (toward the Rotor Head), and the Wiper's Solder Terminal is at what I call 6 O'Clock (toward the Landing Skid).

We've both "rolled" our own inductors, but have you laid a resistive line before?

If not, here's a tutorial video:
(NOTE: Variable Resistor = another name for POTentiometer)

Pencil Graphite as a Variable Resistor (1 min 38 sec)

(notice how the LED varies in brightness depending on where the "Wiper" is positioned along the dark/black track)

Here's a video showing the inside of round Pots, similar to what is being used on the RX:

Potentiometers - How They Work, Disassembly and Exploration (9 min 22 sec)

(don't bother watching past 5:30, unless you want to know how to "lay" non-linear resistive tracks)

Notice in the above video, how the Pot really wouldn't work at all if the Wiper is OFF the dark/black ring?

The reason why your's may be all over the place, may be because you have the wiper off the resistive "pad"/trace? Try re-adjusting the Pot so its "dimple"/wiper is not over the "white" non-conductive plastic, and instead is over the "dark" resistively conductive material.

Once again, IMO, the Pot's Metal's Flat spot is very misleading. If the location of the dimple/Wiper is too difficult for you to remember/see, then I recommend getting your favorite color fingernail polish and very carefully placing a microdot 180* away from the Metal's Flat, right above the "dimple"/wiper. WARNING: Don't get ANY polish under the dimple or on the dark resistive trace!

I've experimented having my Pot's "dimple"/Wiper all over the place between 1 and 11 O'Clock, and it is controllable anywhere in between; however, having the "dimple"/Wiper closer to 1 O'Clock (MIN? CCW) makes it more responsive to stick and "outside" influence; whereas having the "dimple"/Wiper closer to 11 O'Clock (MAX CW) makes it less responsive to stick and outside influence. IMO having the "dimple"/Wiper at 1 O'Clock would be like having a light virtual Flybar; whereas having the "dimple"/Wiper at 11 O'Clock would be like having a heavy virtual Flybar.
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Old Apr 08, 2012, 01:16 PM
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i812 :

If you really want to know the range as you turn pot. Put a multi meter from centre pin to Ground and measure the volts.
Being used as a voltage divider, so should see working range as you turn pot. Just mark it off.

Pity its not a simple idea to fit programmable pot, just put a number in till you find your own sweet spot.
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Old Apr 08, 2012, 05:18 PM
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i found my sweet spot with the flat at 7 oclock with mannys settings. I' like thinking the flat spot is the pointer. I unfortunately have my brushless esc glued/soldered to the board directly in front of the screw. i can barely turn it with a screw driver because the esc is blocking it. I cannot see the black part or the indent. I think the best way for me to even turn it is with hemostats from the side.

And I know what you mean about the wind. I tried flying today with huge gusts and the heli would pop 30 feet into the air. The wind also slammed the little heli down into the grass a few times with no damage. I had to reset the servo arms but that is second nature now. You should try some more settings, Just copy over the model you are using and tweak the new model. I noticed when I use tame settings that the heli is hard to fly, just wont turn when you need it to. When using those settings it would be hard to get out of trouble.
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Old Apr 08, 2012, 08:39 PM
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? Best way to replace/reposition Servo Gear?

Quote:
Originally Posted by mescalinedream View Post
... The wind also slammed the little heli down into the grass a few times with no damage. I had to reset the servo arms but that is second nature now. You should try some ...
I recently stripped my first Servo!

No, I hadn't done the Servo Saver Mod, and Yes, I do know about the mod.

I chose to start off without the Servo Saver Mod, because I first wanted to get first hand knowledge on how it felt to fly with a "solid" Servo, didn't want to "cheat" myself out of the experience of stripping a Servo, and wanted an honest purpose to be given the opportunity to look inside my first Servo. Also, before doing the Servo Saver Mod, I wanted to have a "baseline", so I could compare how much better (if any) the Servo Saver Mod works. My Servo "game" plan, is to first ride them "raw" until they strip, then repair by repositioning the stripped Gear, and finalize the repair by doing the Servo Saver Mod.

Now that I have finally stripped a Servo and looked inside, Whoopie!! A few small gears with tiny teeth. Yeap, upon careful observation, I saw it indeed was that famous Gear that somehow managed to get a tooth broken off. I even found the missing hair-like tooth laying by itself about a 1/4-inch away.

As reported by others, that brass collar seems to be keeping the whole gear-train in-track, and I couldn't figure a way to easily remove it, so was clueless why I hadn't recalled anyone posting having problems replacing or repositioning the Gear that always seems to get damaged. I did a search for the terms "brass collar", and found that most people posted to simply sway open two gear posts apart so the damaged Gear could be repositioned/replaced; however a few others posted that forcing the Gear posts apart may result in prematurely weakening the Pot inside the Servo, and instead recommended doing the repair by either first heating the Brass Collar and then pulling it off its post, or driving one of the other Gear Posts out from their positions. I gently tried swaying apart the Gear Posts and was able to remove and reposition the damaged Gear with minimal effort. I was reluctant on using the "heat" method as a way of removing the Brass Collar for fear that the heat may inadvertently slightly deform any of the nearby fragile looking Gears, and decided to wait and try using that repair option as a last hope approach. The "pull out one of the other non-collared Gear Post" approach may be the best method, but I chose not to try it, because I was concerned I wouldn't know how to properly push the Gear Post back in to its correct depth, fearing that without taking the Servo further apart, I had no idea what the Gear Post mated into. I decided whenever I had no other choice, before tossing the Servo into the trash, I'd tear it further apart to see all off its inner workings. Until then, I rather use the better safe than sorry repair approach.

Has anyone had success pulling/pushing Gear Posts out/in? If so, what is the best procedure (i.e. pull or push from which end? and on reassembly how to know when to stop pushing?)?

Here is one of the posts that mentions this repair approach:
Quote:
Originally Posted by paul2pilot View Post
It's better to pull the little pin out of the stripped gear, then it falls right out. If you push that brass collar, you risk ruining the pot that it turns and you will have an erratic servo.
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Old Apr 08, 2012, 09:06 PM
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I have done the prying thing but you can just pull the post which holds the bad gear strait up and out. The only reason why you would need to remove the brass thing is to fix the gear under the brass thing. Both gears on my servo stripped teeth. The one that always strips and the one under the brass. The one that is the most common striped is held with a pushed in post that comes right out.


When I did heat the brass thing the gear under it melted. I didn't care cause it already had 2 teeth gone exactly where the usual stripped gear touches. Some people get lucky and only strip the easy to fix gear. I wasn't lucky but a guy on here helped me out with a gear set. It contained all the gears luckily.

So hurry and do the servo saver mod before you strip the gear under the brass thingy!

Stop pushing when you cannot push anymore! I opened another servo and that rod was stuck to the cover of the servo, so don't be worried.
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Old Apr 08, 2012, 10:33 PM
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On my genius I have had more servos go bad due to malfunctioning pots than stripped gears. The symptom is a slight bobble of the heli back and forth or side to side. Still flyable, but it will only get worse. At first it's tempting to figure vibes are the cause or the Rx settings need to be adjusted. But, if you hold the heli while it's spinning up at full rotor rpm and you move the cyclic stick, and you see one of the servo arms twitch up and down slightly as it moves, that means there's a flat spot developing on the pot and it just has to be swapped for new. Unfortunately, this speaks to the quality of these servos and since I only seem to get 30 to 40 flights before needing a servo swap, that's not a very good indication of quality.

Crashes probably don't help the pots any, but I won't be able to do a crash free test any time soon . My crashes are usually light smacks that don't need repairs, but I do wonder if light sport flying would prolong the life of the servo pots. Walkera needs to step up their game with these servos, but I know I'm preaching to the choir on this. I have only owned Walkera helis, so perhaps someone else can tell me if other micro servo pots last a lot longer that these. Those were cool videos about pots i812.
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Old Apr 09, 2012, 05:21 AM
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Quote:
Originally Posted by i812 View Post
Mine drifts a few feet per second in one direction or the other; however, if I give it the tiniest TX stick "nudge" (or Trim) in the opposite direction, then it will drift in the other direction, so as best as I can figure out, even after numerous crashes mine has always been able to automatically "zero" itself into a level hover without requiring any Servo Arm, Link, Trim, and/or SubTrim adjustments, and the small drift of a few feet per second is just the nature of the "beast".

Are you stating you're unable to make the drift change direction by using either TX Trim and/or AIL/EL Stick movement?

Have you verified the Mini's CoG is along the Main Shaft in both the AIL and EL directions? Mine is still stock configuration, and I've verified the AIL CoG is OK; however, noticed that the EL CoG can easily be changed a large amount by LiPo positioning. If you've modified yours, and are using heavier/lighter Motor (or anything else), then that also may be skewing the CoG?

Also, I haven't completely understood how the Walkera FBL AIL/EL Gyro stabilization functions; however, I'm fairly certain they have a "memory" of what "zero" is. If so, and maybe if the heli is binded/initialized from a "skewed" angle such as on one side of a sloped "hill" and/or bent Landing Skid, then maybe once binding/initialization is complete the Gyro's will determine the "skewed" tilt as the "zero" and try to maintain the Swash in that "skewed" position, regardless of how the Servo's and/or Links are adjusted? After numerous crashes, out of curiosity, I've inspected the "squareness"/plumbness of my Landing Skid by placing the heli on a horizontally "plumb" surface, and verifying the Main Gear is also parallel with a horizontal plumb surface, and so far as close as I can tell the Landing Skid appears to still be "square" (i.e. the Main Gear is horizontally level, and Main Shaft is vertically plumb when the Landing Skid is placed and the Mini takes off from a horizontally level surface).

BTW, my stock Mini will only hands off hover from the center of my draft free living room before reaching one of the walls about 10 feet away within about 5 seconds.
i had this same problem i traced it to vibrations.
The screws holding the board to the frame came loose i tightened them up and it just sat there in a hover.

I also experimented with the screw on the board and found it is similar to the cyclic gain pot on the beastx. when you turn it clockwise you increase the cyclic gain.

In general the higher the gain the harder the helicopter will stop after cyclic moves and the helicopter will feel more stable in the air. If the gain is too high the helicopter feels spongy and tends to oscillate especially on the elevator axis.

If the gain is too low the helicopter does not stop precisely after a cyclic movement and feels unstable in fast forward flight.

i increased the cyclic gain until i had head wobble then backed it off as i found the tail held better when i increased it. I settled on the pot at about 1oclock position.

I have tried several brushless motors 1015 c05 hp03s hp05s.

I didnt like the 1015 motor much as other people had reported it heats up very quickly and was lacking a little in power,

The c05 is quite powerful however not overly smooth, bogs a little if you are not perfect with your pitch management and
The 1mm shaft bends and breaks easily after a few crashes.

The HP03s is more powerful than the c05, Smoother has about the same amount of bog but is very light only 3g! it is very efficient efficient i was getting 3m flight time on stock battery with 8t and about 5min with rcecho 350mah. It has a 1.5mm shaft so stronger in a crash.

The HP05S is my personal favourite plenty of power and minimal bog however it has more torque so you have to run a low pitch setting (50%) otherwise the tail will blowout.

I had a spare 4g3 7mm tail motor lying around so modified the motor holder and glued it in i was able to run 75% pitch travel using a kbdd tail blade with no blowout.

I gave this setup to a sponsored pilot and he had no trouble performing any 3D manouver, was quite impressive to watch! He was so impressed by the mini cp he bought it off me there and then.
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Old Apr 09, 2012, 05:53 AM
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Thanks for the post achogg, I havent hear much of the hp03 power compared to the c05. I also thank you for mentioning the different feel of the gain. I couldn't seem to convey the feeling of trying to stop the heli but it wanted to keep going.


Paul2pilot , that's unfortunate news about the servo pots failing. I had thought i would be ok once I kept the gears from stripping with the servo saver mod. Now you are saying my minis servos are still going to fail? I do not have the money for more servos! I ask to buy some servos from Livonia bob and then found out I had no cash now that I think about it. Poor guy, I never pmed him back that I have no idea when I will!?!
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Old Apr 09, 2012, 08:43 AM
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Quote:
Originally Posted by achogg33 View Post
I also experimented with the screw on the board and found it is similar to the cyclic gain pot on the beastx. when you turn it clockwise you increase the cyclic gain.

In general the higher the gain the harder the helicopter will stop after cyclic moves and the helicopter will feel more stable in the air. If the gain is too high the helicopter feels spongy and tends to oscillate especially on the elevator axis.

If the gain is too low the helicopter does not stop precisely after a cyclic movement and feels unstable in fast forward flight.

i increased the cyclic gain until i had head wobble then backed it off as i found the tail held better when i increased it. I settled on the pot at about 1oclock position.
is that 1 o'clock on the same turn as stock or a full turn past stock? i am not sure the limits of the pot but seems like it can be turned at least 2 full turns.

Quote:
Originally Posted by achogg33 View Post
The c05 is quite powerful however not overly smooth, bogs a little if you are not perfect with your pitch management and
The 1mm shaft bends and breaks easily after a few crashes.
the C05 comes in both 1mm and 1.5mm shaft.

Quote:
Originally Posted by achogg33 View Post
The HP05S is my personal favourite plenty of power and minimal bog however it has more torque so you have to run a low pitch setting (50%) otherwise the tail will blowout.
but how efficient is it on battery compared to the c05/hp03? both hp03/05 are also a lot more expensive.. ($40 for hp05 vs $15 for c05).
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Old Apr 09, 2012, 09:00 AM
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Scub it doesn't matter if you turn the screw 1 time or twenty. The heli will respond the same way. If you want the heli really loose feeling, move the stick and the heli immediately moves in that direction, let off the stick and the heli will continue to move in that direction then put the flat spot at 6 o'clock. If you want the heli to be slow in movements and self correct then put the flat spot at 4 o'clock. Do not keep spinning the screw, it will probably wear the pot out.
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Old Apr 09, 2012, 09:20 AM
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i see, that is what i was curious about. so basically anything more than 1 turn just starts over.
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Old Apr 09, 2012, 02:09 PM
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If you already have a c05 and It's working well I wouldn't change unless you want more power. Matt bockman is bringing out a new motor a little heavier but more powerful si that will be one to try when it comes back in stock. It is fairly cheap too 19.95.
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Old Apr 09, 2012, 06:56 PM
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I had read about Matt Bockmans motor being 13,500kv . Sounds good. I wonder what it looks like.
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Old Apr 09, 2012, 07:14 PM
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Yeah 13,500 think it is black in colour and similar dimensions to the c05m but a tad heavier because of thicker windings.
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Old Apr 10, 2012, 12:33 PM
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I was too careless, didn't take note of battery polarity & plug in Turnigy nano Lipo into Mini CP.
Too late when I saw smoke came off from the Main receiver board.
Aileron servo won't move & main motor won't spin, but still have control over tail, elevator & pitch servo.
Anyone know how to repair the main receiver board?
Cost $60 for main board, rather order ARF MiniCP set if can't repair.
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