TOMAPOWA

My Feedback: (1)

Hi capt17,
Funny you ask that. A while back, I was wondering how many people would use something like that... a stagger type circuit. I had that project on the backburner... as a few others asked in the past seeing Lado was no longer making them.

I then abandoned the project since there is an easier way to get around this... I use this idea on my 90-size electric pattern that uses two Hitec retract servos and two Robart mechnical retracts. The gadget you can use is a "servo slow-down unit"... like one of these:

http://www.hobby-lobby.com/servo_slo..._2157_prd1.htm
or
http://www.hobbycity.com/hobbycity/s...idProduct=8863 (one I used)

Using a Y connector, you would connect one of the retract servos and the input of the servo slow-down unit together (Y), then these connect to the receiver channel that will control the gear (say channel 5, which is the norm I think). The output of the servo slowdown unit is then connected to your other retract servo. Most retract servos only toggle position (up/down) when seeing a servo signal that is greater than 1/2 stick position (1.5ms, mid-way point). The retract servo that is directly connected to the receiver channel (via Y) is immediately controlled when the landing gear switch is thrown (signal goes from 1ms, immediately to 2ms). The retract servo that is connected through the servo slow-down unit does not see an immediate switch command (1ms to 2ms) since the output signal signal of the slow-down unit slowly goes from 1ms (off) to 2ms (on), and the control of this retract servo is delayed (or "staggered") as compared to the other retract servo. The delay time of the second retract servo can be altered by changing the servo delay on the servo-slow-down unit (most have a small rotating potentiometer/resistor that alters this delay setting).

Pretty simple eh? Been working great in my pattern ship for a few years now. Funny that I have not shared this idea of mine before....

capt17

Sounds easy enough to me! Thanks a ton!

wollins

Any updates?

TOMAPOWA

My Feedback: (1)

None yet unfortunately... (darn work has me very busy lately... can't wait for retirement!)
I'm still waiting on some 8mm flanged bearings to test some actuators with... (should had ordered a few from the states instead of China). The electronics are pretty much done and could use a few tweaks but without reliable actuators, you won't have a good "system". I'm trying to design the DIY actuators such that other tinkerers out there can not only easily obtain the parts, but also build/assemble. Hopefully in weeks time I'll have those bearings in hand to assemble a few actuators and test... then I'll post the results.

wollins

Tom, just wondering ... is your intention to actually sell these as plug and play "sets" as opposed to just DIY kits?

If so ... do you think you'll beat Eflite to the market for 60 size elecctric retracts?

Colin

TOMAPOWA

My Feedback: (1)

Hi Colin,
Sorry for the belated reply... darn work travel....

I really only planned to develop a set of DIY retracts for a few planes of mine, while documenting how I did it (like most of all my DIY projects @ http://www.diyrc.com ). I was hoping to just sell the controlling electronics or at least parts of it (like a pre-rogrammed PIC and maybe even a PCB). Other parts can easily be purchased either online (like the Pololu H-bridge board), at your local hobby shop and/or hardware store. I was hoping maybe some else would take on the fabrication of the actuators, and I have even contacted a few existing retract manufacturers re: retrofit kits for their existing mechanical gear... still got no response. I have a feeling they are either not considering the idea all together (since they have lots invested in their air systems) or they are in fact designing their own (if they use my notes/design... power to them!).

I just got in some new flanged bearing I hope to test this weekend, and will eventually update my [link=http://www.laureanno.com/RC/E-Retracts.htm]DIY Electric Retract webpage[/link] re: results of my test. Eventually, I will have specific details as to the building/fabricating of the DIY actuators... and then I should start selling parts for the electronics. Again, I doubt I'll get into building complete turn-key systems as I really do not have the time to do so (if I was about to retire, I'd jump head-first into this market!).

garfred-RCU

Hi You were wondering a few pages back, if anyone was making linear servos. A while back (a couple years ago) a company called JASKO( i think that was the name) made some that were advertized which look much like yours, and as being able to be used for retracts, flaps, and the like. But i have not seen an ad for them recently. I was going to get some for my 1/4 scale cessna , but didn't.[>:]
Your retracts are looking great!!!

Also I was wondering if you would in your spare time,if you would explane some of the electrical terms that you use i.e. pic , h-bridge, pcb . I am not a electrical guy.[] But am enjoying the thread emencly!!!


Thanks , Gary

mark_d

@ Gary:
PIC is a micro controller, basically a computer in a chip that you upload a program to for sophisticated electronic controls. Microchip corp makes them; look to microchip.com or google it to find reams of information.
An H-bridge is a motor control circuit that allows a motor to be reversed, it is easily drawn in the shape of an 'H', hence the name.

PCB: Printed Circuit Board - usually made by applying a photo sensitive resist material to a fiberglass and copper sandwich that is covered with a negative and exposed to light. The parts not exposed to light are dissolve in a solution and the the board is submerged in a corrosive etching agent such as cupric acid that dissolves the exposed copper thereby leaving "traces" that act as conductors.

Hey Tom, I bought a gear motor and controller from Pololu to do the same with except the gear motor I bought was not the high power version you have since the amp draw looked to be a bit too high for the board I chose. The revs of the lower powered motor are a lot slower at 250 vs. 630 so I'm using 6-32. The torque is only 192 compared to your 400 but for one retract it's still overkill. My retract servos don't have that much torque and they raise 3 gear. The board I'm using is [link=http://www.pololu.com/catalog/product/713]this one[/link]. It's under 10 bucks and smaller than yours but lacks a current feedback so I'm planning to use the ADC on the pic to measure it. I've never tried this before what do you think of the idea?

TOMAPOWA

My Feedback: (1)

Hi Mark,
Thanks first for helping with some of those definitions on PIC stuff...

Re: that small H-bridge that Pololu sells... as you mentioned, it has smaller current handling capabilities but should still work with those gear motors (my HD gear motors, as measured, draw around 800mA when stalled using 6v input). As you mentioned, that small/cheaper H-bridge/motor controller lacks the current sensing capability of the larger board I am using. The ADC on the PIC is normally used to measure a voltage vice a current so you will need to convert that (either using a current shunt and some Opamp design... or you could use the current sensor Pololu sells... http://www.pololu.com/catalog/product/1185). Adding up the parts needed for controlling two actuators... it's probably better to just buy the larger $39 controller w/ current sensing built in... rather than worrying about the much needed integration efforts of cobbling something together... just my 2 cents worth...

I finally found a little time this weekend to put together some new actuators and tested them last night. Works excellently I must say... I tried and tried to get them stuck and/or break them ... but to no avail. I'm ultimately happy with them as is and will be putting them in my 1/4 scale Zero this week some time! Attached is a video of the new actuator design in action... enjoy!

More details on the construction, etc... will follow on my webpage:

http://www.e-retracts.com

[youtube]http://www.youtube.com/watch?v=Anp8lLKvF6s[/youtube]

Boeing314

I've got my gear motors installed in my Robart gear...now I just need a driver set for it. I was looking at the electric main gear offered by Eflight and wondering if it would be possible to 'cannibalize' one to borrow the guts for my gear. Any thoughts on this? My other option is to have an electronic timer built to lower and raise the gear....but at about $140, it wouldn't be a cheap option, but in the absence of driver boards with current limiters this would be another way to get me in the electric gear game.

booker-RCU

My Feedback: (43)

I'm sort of at the same place you are. I have some retracts I want to make electric and can easly mount the gear motor but lack the electronic expertise to make the controllers. When you suggested to 'cannibalize' the Eflight retracts I happen to have a set and took a look at them. It's possible to do that but the down side is they are programmed to stall on to light a pressure. They would probably not raise a 3" wheel. I keep hoping our friend TOMAPOWA will put together some kind of kit for the electrics or at least supply the pcb with a list of components. I’ll do some more experimenting with the EFlights and see exactly how much they will lift.
Galen

Boeing314

Sounds good, Booker. I did come up with an alternate way to do things on my timer idea. I had planned to make my gearset operate off one circuit. So, paralleling off the tri gear arrangement would be a fourth motor/gearscrew assembly...only this one would be separate and simply control a jack screw driving a bellcrank. On either side of the bellcrank would be adjustable limit switches. If all the motors could lift their gear at the same time, it would be possible to have this helper motor control the on/off timing of the entire retract sequence. Any discrepancy in battery voltage over time would also make the helper motor run slower as well. Of course if there is any mechanical binding, there's a problem in that when the gear was lowered, the affected gear would not extend properly. I plan to build a prototype timer in the next few days and will share my results with video if possible.

booker-RCU

My Feedback: (43)

I disassembled The EFlight Retracts and found that except for the output shaft , they are using the same motor as we are. The electronics could easily be transferred to the motor we are using and I'm sure it would work great. The motor terminals have a small capacitor (I think) across the terminals but otherwise it would be a simple matter of just soldering the wire leads to the new motor. I tested the retract before I took it apart and found it would raise a Robart 3" wheel with power to spare, so this would be a real easy conversion. The retracts I'm wanting to convert over will need a U milled out of the trunion for the jack screw to pass thru but otherwise should be easy to do. I have to wait till I get to where my lathe and mill are so I can to the modifications. Other than being a little costly this should work great.

booker-RCU

My Feedback: (43)

I connected the controller directly to the motor and gear set and found that it works real well. I cannot stall the motor with finger pressure. The only drawback is the controller is set for a 3 1/2 - 4 sec. time limit. Then it shuts off. Hopefully that will be enough time. Now to get to work with the mill and lathe.

Boeing314

Booker: thanks for doing the test and posting the pix! What voltage can we work with to be within the time limit of the board? I tested my motor retract time with 6v and got a 6 sec retract time (3.25" foam wheel). With 7.5v I got 4 sec. Can we run the controller at 7.5v (or more) to get the faster retract time? Or does the increasing the voltage to the board change the timing? I checked out the tri gear set online and it looks like it's going for about $119. Pricey, yes, but I've already spent $300 for the gear, so...

Boeing314

I just checked online and it looks like we can bump up the voltage to 7.4v on the board. This is from the E-flight site:

Application: Aircraft 10–15 size
Speed: 4.8V (1.25 sec), 6.0V (1.0 sec), 7.4V (.80 sec)
Weight: 5.0 oz (complete set)
Motor Type: Electric brushed can
Connector Type: JR, universal
Gear Type: Metal
Current Draw Idle: 5mA
Current Draw Stall: 200mA
Voltage: 4.8–7.4

booker-RCU

My Feedback: (43)

I ran the test with an A123 Battery and a Spektrum AR9000 receiver. The voltage is at 6.78. The EFlights raise the Robart 3" wheel at a length of 6" in about 1.5 sec. The geared motor keeps running for an additional 3.0 sec. probably because of a faster gear ratio. The times are taken using my wrist watch and are only estimates. Since it's going to be a while before I get the motor mounted on the retract and you already have yours set up I can ship you the controller and you can try it or you can ship me the gear and I can try it. What do you think? Of course we would return them when finished.

Galen

Boeing314

Since it sounds like the actual times are close to 4.5 seconds and this is pretty much spot on to what I need, I may just pull the trigger on this one and order the 3 gear setup for myself. If it does not work I can use it in the Eflite Beech Bonanza I may be getting in the future. But this sounds so promising it may be worth a try. I'll call my hobby shop to see if they have a set in stock.

OK, I'm back from the hobby shop with an Eflite tri-gear set and 7.4v lipo for the 2.4ghz receiver. If my testing goes well tomorrow I'll post a video of the gear operating. It looks like I'll be running a two receiver setup, one for the servos and the other for the retracts. I'll try the gear with the 6v first to see how far up they'll raise the gear.

Boeing314

OK, got the gear out today and had a go at it. In a nutshell, this won't work for us, guys. In the video I watched, they showed with great enthusiasm the ability of the Eflite gear to lock when stalled, like an H bridge circuit would do. The gear I have bought does not act that way at all. If you bind the gear, it will scream and slow down, but will not stall. The reason, I found out after cracking the case open, is that the gear uses very tiny limit switches surface mounted to the circuit board. A slider moves underneath the cam holding the landing leg and hits a switch at either end. I removed the board and wired it to my retract for a test. As mentioned in the previous posts, it runs for 4 seconds and stops, which even powering it with 7v is not quite long enough to work as a gear controller. And without an H bridge feature, it wouldn't have been suitable anyway. Unfortunately it also looks as though taking the gear apart this way has rendered it as DOA...it's too hard to put back together again and have it work properly. I'll try again tomorrow, but don't hold out too much hope for resuscitating it. I'm going to try going a simpler route tomorrow: setting up the gear to activate a super bright LED on the wingtip to let me know when the stop has been reached, maybe one color each for up and down.

Boeing314

I bit the bullet today and ordered 2 boards from Polulo to try the H bridge idea. My roommate says he can program the thing for me, so I should have them by next Monday to test.

By the way, the analog controller I build yesterday had too much drift: after 4 iterations, it was so far out of timing that it would be too impractical to use in the field.

Larry3215

My Feedback: (2)

Im thinking of trying this idea for a wing folding setup.

What all is involved in programming the Pololu boards? Keep in mind I have never done ANY board programming at all and have no equipment or experience.

Larry3215

My Feedback: (2)

I was just looking at the Pololu site again. It looks like they have programed controllers but Im not well enough informed to know if one of them would do what I want without needing special porograming.

Is there one thats ready to go - plug-n-play more or less?

I can handle the motor, gearing and drive components fine. Just need to be able to controll the unit from my Tx - easily

Boeing314

You have to write some programming for the controller to know what to do. I have no knowledge of boards that are plug and play for our purposes. I'm lucky in the fact that I have a friend who knows how to string the code together, otherwise there's no way I could tackle the project myself.

Jag Fan

I would be interested in these electric gear for my Sepecat Jaguar build. I don't want to go with air, but there really aren't any electric gear out there for 10+LB planes. I've checked out your website and now I'm thirsty for more information. LOL. I can do the mechanical work, but I have no idea about electronics. hopefully you can sell the elctronics only if you don't have the ability to mass produce full retracts. maybe Larry can help you out with that part. he makes some great looking gear and might be a good partnership. he's LJE4357 on RCGroups and his company is SouthEast Model Products. I believe his email is  [email protected]. worth a try at least.

Rich

TOMAPOWA

My Feedback: (1)

Hey Folks,
Sorry I have not been on in a while... I've just been swamped with real work lately...

Now for the good/bad news... !

I can no longer discuss my electric retract designs of any sort seeing I've recently been contacted/contracted by a manufacturer, possibly selling them my complete design for the jackscrew actuators & controller. I owe them a complete kit by the end of this month for evaluation and they will take it from there, continuing to use me as a design consultant (mainly firmware dev). This is certianly good news for me but bad news for you DIY'ers... but heck, at least I gave you folks some ideas to ponder...

One important thing I can say though is that I have recently come up with a novel mechanical design which fixes the mechanical issues evident with the Lado design (YES!... there is a major mechanical issue which no one, including Lado, will fess up to... oh well, they/customers will learn the hard way I guess... unless Lado took the last 3-4 months to fix the known issues). This actuator design of mine has been 100% reliable so far during all my tests (and they are pretty extensive), more than I can say for other actuator designs I've tested. I hinted at these design deficiency in previous posts... but can't say more than that!

That said, I'm sorry to inform that I will not be able to offer control boards or any other info pertaining to my e-retracts... (unless this deal drops through, which I don't think will happen from the looks of it). Under the current agreement, I'm able to leave my http://www.e-retracts.com webpage up seeing that it displays a working DIY design, but not the final, highly-reliable design... so have at it.

Use the information here how ever you want... I'm sure some one else out their with some microcontroller experience can develop some code to control an H-bridge/current sensor to do what I was doing.

Sorry folks...