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I kept the rotary encoders in mind when I positioned them, I thought the 7-segs needed more room than the encoders. I think there's enough room, it will depend on the dimensions of the encoders.Quote:
Originally Posted by AndyT
Next on the list :)Quote:
Originally Posted by AndyT
Nothing connecting it at the moment, all in my head.Quote:
Originally Posted by AndyT
If necessary that can be done. I'm concerned about separating the ring gears too far as it extends the length of the bug and RMI indicators which will give us grief in the end if they start to droop. Let's see if there's enough room as is, then revisit.Quote:
Originally Posted by cscotthendry
Coincidentally, I have worked using 3mm gears right from the start :)Quote:
Originally Posted by cscotthendry
Trying, but there is a limit to how hamfisted we'll be able to be :) This is quite a precision instrument! We could always scale up to a 4" model to give us more wiggle room, but that affects gearing and all sorts of things.Quote:
Originally Posted by cscotthendry
picked up a selection of these yesterday at Mr Toys :)Quote:
Originally Posted by cscotthendry
I think the hard part is in the mechanicals, the look of it can probably be easily modified to suit almost any model once we've got the basics down. I'm working on the F-16 HSI a) because it's what I know, and b) because I know there is a big community of people over at ViperPits just screaming for it!Quote:
Originally Posted by cscotthendry
In milimeters to 3 decimal places? I'm going to have to find my calipers...
Here is an encoder.
http://www3.alps.com/WebObjects/cata...1E15244B2.html
We may not always achieve accuracy, but when we stop trying we guarantee it won't be accurate :)
I sort of though this was going to be a 4" unit.
You'd have a lot more space to work with.
Cheers mate - BSAI uses the Bourns 3315Y-1-006 - dimensions for that one would be awesome too.Quote:
Originally Posted by AndyT
first snag:
http://mycockpit.org/forums/images/HSI/7segs.jpg
The rotary encoders work really well, but the 0.3" 7-segment displays are too big and occlude the compass ring. This is based on the DigiKey 67-1416-ND single digit module. Couple of options:
- Find a smaller commonly available 7-seg module, probably 0.2" or smaller, and preferably in a 3-digit block. Best option. There is a candidate here but they are $21.30 each!
- Redesign to 4" to make enough space. Not my favourite option due to the redesign work required.
- Dispense with the 7-segs altogether. Will piss off the F-16 community and leave you only analog displays of CRS and HDG BUG information. Workable option.
Whaddya think?
*EDIT*
OK I tried it with the Kingbright KCSA02-127 0.2" SMT single - and it JUST fits if I relocate the top mounting hardware. There's about 2mm or clearance to the opto flags with the relocated hardware, so it's all good.
http://mycockpit.org/forums/images/HSI/7segs2.jpg
So here's a challenge guys - find these or similar 0.2" 7 segs at a reasonable price for 6!
Ask and you shall receive:
http://www.bourns.com/pdfs/3315.pdf
Can I have a 3/4 side view of that last shot?
Ok, Try this:
Since the LEDs are SMDs (Surface Mount Devices for you non-electronics types reading this) we can put them on the face of the front plate and cut holes for them in the final faceplate. They fit and if the faceplate is 3mm thick, they will be flush with it. AND they will not be interferring with the rings behind them at all.
Another update, I'll explain later:
http://mycockpit.org/forums/images/HSI/hsi04.jpg
*EDIT* OK I've dispensed with the optointerrupters and the flags, they're just too big. It was suggested above that magnetic reed switches or the like would be better, I think that's a great idea. Any suggested items, with dimensions and/or datasheets would be awesome.
I've added another large gear for the CDI assembly, and shown how it fits together. I decided to do it this way as it's more rigid and precise then the folded-metal approach, but it is heavier. There will be a brush contact shaft running through the middle of the gear which also mounts it on a 608 skate bearing or similar, again to aid rigidity and ensure it rotates precisely in the centre of the assembly. The CDI servo control board will be mounted on the rear of the CDI gear. There's about 20mm of space between the gear and the plate behind it for the board.
PS dimensions on commonly available steppers would be sensational.
We can get the LEDs from mouser for $2 each which is about as cheap as we are going to find them I think.
I understand the 4th ring is the mount frame for the CDI Arrow plate. Nice. It will fit right thru the center of the others and is strong enough not to bounce around because it's ultimately held by the same mount gears. I might make it 5 or 6 mm in thickness though because it has to bear the weight of the servo along with all the rest of the hardware.
WOW! Steppers are costly. I'm looking...
This really gives me the irrits - same product, same manufacturer, 10 times the cost in Aust. That's economies of scale for you.Quote:
Originally Posted by AndyT
http://www.portescap.com/Repository/...r_01042007.pdf
And what it looks like...
When we are done, we can figure something out on parts and shipping and such...
mhmm... US$19 for a 20 steps/rev motor... this one is about the same price and 48 steps/rev?
This one is $17 US and 48 steps.
http://www.portescap.com/Repository/...r_01032007.pdf
Take your pick.
That's the one. Awesome. They don't ship outside the US, so we might need you to buy 12 and on-ship 4 each to me and scott!
For the electronically minded, here's a challenge: design a microcontroller circuit within the following constraints:
- fits on a circular circuit board < 60mm dia.
- has only 5 inputs: data ground, data +, data -, power ground, power (5 or 12V)
- ideally uses a PIC flash microcontroller (e.g. PIC16F648A)
- can control a micro servo through roughly 90 deg movement, plus three separately controlled LEDs
- MAY be a daughterboard with a larger separate motherboard, but must conform to the input limitation above
- is suitable for home fabrication (so keep the traces at a reasonable width) or consumer board shop (e.g. PCB123, ExpressPCB)
- please supply Eagle or PCB123/ExpressPCB layouts
*EDIT*
- Contains some sort of protection to ensure the servo does not move unpredictably at startup. Possibly prevent power being supplied to the servo until a stabilising pulse train is active?
- Has approx 10mm dia hole in the centre of the board for a shaft to pass through.
- has holes for 3 #4-40 mounting screws
- supports ICSP so we don't have to disassemble the whole instrument or pull the chip to update firmware
Who's up for the challenge? :)
Lets limit it to Express PCB since I have that one also.
Hmmm..... Check this out....
http://www.futurlec.com/Mini_SMCC.shtml
One for the stepper gurus: will the L293D bipolar H-bridge driver (600mA) be able to drive this stepper? (note the 12V bipolar version).
Hi guys,
Re - tubes, bushes, rollers, axles etc, I can make what you need to any size and post them over. This is a great project growing on our pages and it would be good to see a working prototype!
(Tip - break apart old printers, they are a great source of small mechanical parts).
Gwyn
OK my brain hurts - but the drive shafts are in. I had to change the gears because they wouldn't fit. 32 on the (48 steps/rev) stepper drives a 48 on the idler for 2:3, a 12 on the other end of the idler drives the 120 for 1:10. Total 1:15, 0.5deg/step for all 4 rings. You can see the dual-axle shaft on the left of the instrument drives the front two rings, and the other on the right drives the rear two.
I had to remove the glideslope servos as there's just no room. Maybe we could do it with LED bars? Can someone get me dimensions on a 5- or 10- LED bar?
Remaining is the axle and brushes for the CDI assembly and the circuit board. Then: over to you guys :)
If anybody has 3dsmax9 please let me know, I need you to inspect the model to pick up any errors. Where's Mr Powell when you need him :) Couldn't have done this without inspiration and information from your excellent book sir.
http://mycockpit.org/forums/images/HSI/render6.jpg
Looks good to me.Quote:
Originally Posted by ruprecht
VERY interesting project!
Please folks :) :) :) Upload the photos in the gallery and link them in the forum rather then outside of MyCockpit.org. Otherwise it takes forever to load up a page.
I've moved all the CAD drawings to MyCockpit.org. NOW LOADS INSTANTLY!!!! :) :) :)
Matt O.
Hi guys:
Sorry for my absence. I'm in the middle of selling my boat and there's work to be done that keeps me out all day. I'll be offline for the rest of the weekend probably.
Whew!!! I miss one day and you guys have filled three pages of stuff...GREAT WORK!!!
Seriously here's some things I see.
I see that you've added a fourth gear and stepper. If we can get rid of it I think it would be better from a reliability/simplicity point of view. I agree with the guy who designed the blackbird "Simplicate and add lightness"
The washers for the retainers/stepper can be easily custom made. Also we can make them from delrin which will make them slippery and smooth.
Please let's don't go to 4". The only thing that I think would push us there is accomodating lots of steppers and I'v already aired my opinion on that.
Reed switches are 13mm long and 2mm diameter with axial leads. The exit of the leads is VERY fragile so allow about 20mm width total to keep the bend in the leads away from the body.
Sourcing parts from the US. I have a friend in Texas who is quite willing to source stuff and ship it for me. I'm sure that if we offered him an HSI, he'd fall all over himself to help.
I only have Protel99 for PCB, but I see Andy has put his hand up for that. Good one Andy.
Don't buy stuff from Futurlec. They are honest, but slow. Also they only seem to deal with runout stock so supply may not be guaranteed.
For stepper drivers for small steppers, it's hard to go past the FAN8200 from JAMECO. At 80 odd cents they're cheap as chips ;) They can drive unipolar or bipolar steppers so they're very versatile. Unfortunately, they're through hole devices so if we need 4 on a board, that's a lot of real estate. Another reason to get rid of that extra gear/stepper.
Ruprecht: What can I say about your drawings. Mate I'm just speechless in awe. I do have a suggestion though. You could squeeze some space out from between some of the gears and maybe bring back the glideslope servo. I think also that the GS could be done with one servo, we might just have to make a fiddly bit of metalwork for the arms. But that's OK. I really think the glideslope capability is essential.
*EDIT* Instead of squeezing space out from between the gear plates, maybe if you added just a little space forward of the plate in front of the steppers, the GS servo(s) could go there??
Finally, I just don't believe the work you guys have done on this. I can hardly wait to get started on the parts.
*EDIT* Ruprecht, I don't think we need the fourth gear. The course pointer will ride on the CDI plate.
*EDIT* I just had another idea for the GS pointers. mount them on cables and make them slide up and down. Put a pulley at the top and bottom and drive the cable from the servo. Then the servo can be mounted in any orientation.
http://www.mycockpit.org/photopost/data/500/render7.jpg
Guys, a quick explanation of a few things:
4 rotating elements are required. Compass card, heading bug, RMI needle, CDI assembly.
I could dispense with the fourth (CDI) gear, but what would I replace it with? In the end, the assembly must rotate. As it stands now, all 4 rotating elements work exactly the same way, same gearing, same everything. I agree with "simplicating" (did Dubbya work on the SR71? :) ) but IMHO making one rotator work differently is "complificating" :) Accept that it means more work for our esteemed gear cutter though :)
Re Delrin, mate do you have an Australian source? I've had no answer from Aircraft Spruce's local distributor.
Agree on avoiding 4" unless it becomes impossible otherwise. Not least because of the redesign work required!
re board space, the only circuit board that will be tight will be the swinging CDI board. the rest we can split over multiple 3"x3" boards if necessary. I'd prefer to use the RS422 architecture from MikesFlightDeck rather than depending on any specific manufacturer's control hardware, if that's at all possible?
I'll pick up some reed switches today hopefully, just so I have one handy for prototyping.
Referring to the numbered sections in the pic above, I agree we could probably save some space in sections 2, 3 and 4 now that we've dispensed with the optos. However until we've figured out the position sensing and are sure there's enough room, I'll leave it as is. I can always compress things later, but I'd hate to do it now and have to undo it because of unforseen requirements.
I think it's important to keep section 1 as shallow as possible to maintain the "look" of the instrument. Obviously there's a minimum depth dictated by the CDI needle, which in turn is related to the CDI indicator arc radius, dictated by how far back the CDI servo is. 3/8" will do for now :)
Sections 2,3,4 and 6 are 1/2" deep. Section 5 and 7 are 1" deep. Section 5 is reserved for the swinging circuitry mounted on the back of the CDI gear (gear 4), to be modelled when my mouse shoulder stops hurting!
The problem with a single arm for both glideslope indicators is that the arm must, at some point, stretch horizontally across the width of the instrument with some range of vertical movement. I'd welcome suggestions, but I can't figure out where to fit it unless you move it right back beyond section 8, in which case flexion in the armature will give us accuracy problems. A LED bar is a "simplicated" solution and not one for the purist, but it's an option. Possibly as you say Scott, extending section 5 to 2" might give us enough room. The pulley idea is an interesting one, I had thought along similar lines with a toothed belt and worm gear, but dismissed it as too complex. Maybe you could sketch something and I can then model it?
Thanks for the kind words. I am trying very hard to accommodate all suggestions, I understand this is a community project and am resisting the temptation to just design it the way I want! Part of the reason for doing CAD is that it reveals things that just won't physically work, and much of the trial and error I go through when modelling isn't visible in the end result, but many lessons are being learned and I'm trying to document them here. Please be patient with me, I'm doing this around my day job and my young family :)
Matt, thanks for the tip on the images. I was hosting them on my own Apache server hanging off my broadband, so no wonder it was slow for y'all! And no wonder my bandwidth got hammered last night when you featured the post on the front page :D
Cheers
I would like to introduce you to the Power of MyCockpit.org LMAO.. :mrgreen:Quote:
Originally Posted by ruprecht
WHOA! I get a few hours sleep and we lose the optical sensors! How did that happen? And why?
They are too big (causing sect 2,3,4 to be deeper than necessary) and the interrupter flags conflict with the driver shaft. Reed switches and magnets are a neater solution I reckon?
Ok, so we get rid of the interupter flags and drill a hole in the gears, then straddle the sensors over the gears themselves. Uses less room between gears than the flags, is more accurate, and we can test for an 'open' instead of a 'close' to get our reading.
Its the simplest solution. If we have to lengthen the case by an inch, then so be it. We knew going in this would be a larger than normal instrument, and we NEED some kind of sensors. Mounting magnets and reed switches while it sounds cool, is needlessly complex to my thinking. There is the issue of mounting the magnets on the gears themselves in a way that over time they do not get dislodged or even fall off completly. Drilling the hole is easy and simple.
Try putting them in the way I suggest and see what we get.
By the way, Stagger the sensors slightly. Do not put the one right behind the other. That way they take less room. I meant to add that above.
I'm not sure mate, here's my thinking. Overall length is not a worry, the thing that worries me is the distance from gear 3 to the faceplate. That is the length of the RMI flags, which are thin strips of metal. That distance is currently about 30mm.
Mounting the optos between the gears will add, I'm estimating, at least another 10-15mm. that takes the RMI flag length to 40-45mm. if those flags sag, or suffer repetitive bending stresses during stepping, they will eventually conflict with the heading bug flag and tear each other apart, necessitating a quite difficult repair. remember that the steppers don't move the flags smoothly (in an analog way) they move them digitally, one half-degree step at a time. The longer the flag, the longer the intertial moment of the flag head and the more repetitive stress it encounters.
My thinking is that we need to *reduce* the gear 3 - faceplate distance as much as possible, not be thinking about making it bigger. I'm all ears, but I think the above is a valid concern given the tolerances involved?
I can see that there is no room in the housing for this, but many HSI's use a rotating drum with the CDI needle fixed to the drum rather than the needle swing back and forth across the dial face.
That's probably not an option at this point.
BSW, I think I know what you mean and yes all I have to do is quickly model it. I've just been focused on the gear train so hadn't done it yet. I really need to do an animation to show people how it all hangs together :)
Ok, I'm not sure we are on the same thought here, so let me add in a simple sketch and this:
What is the strength of aluminum versus the weight of the bugs that will have to be held? Inconsequential. The shaft of the flag mounts can be larger than what you have drawn because it will all be hidden behind the faceplate and CDI plate. This is not a problem we need to put that much worry into.
What are the measurements I have question marked in the sketch? These are your sizes for the plate distances.
Sorry, I did not label my sketch very well....
ah, you're a genius. Let me measure up the opto for you and see if it will work.
We were definitely not on the same page, I'm a visual person :D
-- rup
*edit* Ok it appears there IS room to do it like that, depending on distance x in the attached diagram. So long as x < about 3.5mm, we're gold with 3mm gears. the tolerances are quite tight (1/8 mm either side of the gear) which worries me a little, but the optos could probably stand some grinding out without dying.
The H21A1 optos are near as dammit a half-inch wide, so the existing spacers can stay! sweet as. Little bit of rework to position the gears in the longtitudinal axis, but that's no biggie.
One more scribble for you to address your concerns about the bending of the shafts.
The shafts have the same curve as the inside of the gear. The shape is triangular to increase the strength and durability. With this design, no bending should be possible under normal use.
We can always move the index hole closer to the edge of the gear.
Hi, guys. I have just found this thread, and it’s very interesting to me, since I have just started to design an instrument panel for my own (steam gauge of course) IFR procedures training simpit, based on stepper motors and PICs.
I started with the altimeter because it seemed to have all the nasties in there that I would encounter in many other instruments - like multiple 360 degree rotation, a knob for tweaking, a subscale, a couple of high-res needles. No CDI of course, which is an additional complication, but I decided I could get to that later when I came to VOR / ILS design. I hadn’t planned on HSI!
Then I found this thread, and started (prematurely) thinking about the problem.
For what it’s worth, I have taken a different approach to you guys (maybe because I don’t have “The Book” that you all rave about, so I’m on my own there, which I hope you will believe is not necessarily a bad thing, since I’m not constrained or influenced by the ideas in there, whatever they are).
I’m intending to use needles visibly up front, combined with clear plastic disks on to which I’ll paste cards, subscales and the like, and I’ll also use these for zero location behind the visible faces. So the problem recently announced here about having no room for the various LED zero point indicators does not exist in my design. I just use one pair of IR devices, shining through all of the discs, behind the visible instrument face, each with its own mask (a bit of tape, probably) to blank out the IR, and I can program the pics to zero each disk in turn.
There’s plenty of room for that (using a 3" instrument face), and my 3-D design mockup using Cinema 4D XL 7 shows that this will work. For the altimeter I use three small stepper motors at $3 each (Futurlec, whom I hate just like you, and Sayal in Toronto, whom I also hate, but what’s a guy to do?), and some plastic worm gears and gear wheels for the drives, which I obtained at very low cost on eBay, so no machining of gears is required (although I do have a lathe and a mill, just in case).
However, the reason I’m posting this is in response to the problem of having a rotating card on which must be mounted a motor which controls the position of the CDI, and the resultant need for brushes to overcome the problem of twisted wires.
Nonsense, he cried! :D The design you guys are working on already involves PIC microcontrollers, and so you can solve your issues entirely in software. Remember, write once, use everywhere (to paraphrase the Java launch blurb). If you require a design with complex hardware requirements, everyone suffers and output is reduced to a quality-threatened crawl. Create a design where the software does the work on a (relatively) simple hardware platform, then write the software once, and you can produce hundreds of accurate gauges. And each simpit requires quite a lot of these devices.
If you drive the CDI by means of the angular position of a cog wheel, probably then driving a pulley arrangement (a bit of thread around a shaft :cool:) then of course whenever the carrier card rotates, the CDI will move because its driver cog will rotate too. But not if you program the CDI cog to compensate. After all, you do know what the new position of the carrier card is going to be, right?
So the carrying card moves, and the CDI is commanded to compensate, so that it stays fixed in its commanded position.
Now, what happens if the carrying card rotates through say 100 times 360 degrees? It doesn’t matter, and your software will not crash through the limitations of an 8-bit microcontroller, because the delta values you feed in to the CDI will not actually be part of its control structure. You are just re-adjusting the zero position of the CDI continually.
Sorry for the lengthy post! :oops:
Hi P1IC, welcome to the thread. I'm very interested in your suggestions, but as stated above I'm a dumb helo pilot and need pictures to understand things :) Can you sketch how you think you could design an independently rotating CDI assembly without the use of a brush contact rotor? The problem as I see it is not rotating the assembly itself to match rotation of the compass card (easily done in firmware as you say) but mounting a servo on that rotating assembly to give you a localiser bar. That is what requires the brush contacts in my book.