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ChrisLX200's DIY Projects


ChrisLX200

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I thought I may as well start a new thread for this rather than dumping on everyone else's threads like I usually do ;-)

My existing AllSky camera is fine and it's been in constant use (when it's clear) for over a year now. It makes use of a mono QHY5L-II (the newer one with MT034 sensor) contained inside a laboriously machined alloy cylinder and sealed optical perspex dome. The casing being made from aluminium alloy has its Pros and Cons - the heat from the camera is rapidly dispersed keeping the sensor cool but because it radiates heat so rapidly on cold nights it's difficult to keep the dome clear from dew/frost. There is some dessicant inside to keep it dry, and a dew-heater band to supply some warm air that was supposed to keep the dome just above ambient. However when it gets really cold the heater just can't keep up and it gets covered in frost. I suppose I could use more power to provide more heat...

Anyway, what I'm planning to do is avoid all the hard work of machining a casing out of metal and instead use my new 3D printer to simply print one (or more). I have some spare domes (proper optical ones - not cheap at £28 each but they provide an excellent undistorted image) and a few Altair GPCams (colour and mono) to play with. The other advantage of using a 3D printed case is that it's well insulated and will not lose heat anywhere near as fast. It won't cool the camera as efficiently of course but I'll have to live with it, and I find the use of dark frames is pretty effective at removing any hot pixels anyway.

I'm having to learn SketchUp as I go along, this is the program I use to generate the 3D print files and I'm finding it really stange to use after being familiar with 2D CAD software, however I'm starting to get to grips with it. It is a lot of work creating the STL print files but once completed then extra casings can just be printed as required. I actually bought a 3D Connexion SpaceNavigator gizmo which was delivered today and I'm finding that a big help for moving quickly around SketchUp screen.

This is the dsign as it stands so far - not final (probably) as there is no provision for the heating circuit yet. This time I will use a home-made affair with series connected resistors. The heater will be in the main compartment and the warm air will rise up through the ventillation holes into the lens compartment, and from there it will be able to keep the dome warm.

 

ChrisH

AllSky_Case3.jpg

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This is the second DIY project I have underway at the moment: a remote USB-controlled relay box. I needed this to switch the fans and internal heaters of my ODK12 remotely from the Warm Room some 15M away. The device is a simple affair, consisting of an inexpensive (£13) Sainsmart 4-Channel relay PCB, a suitable 3D printed case, and leads to connect to the scope. I had intended to use a 12V-powered PCB but somehow ended up with 5V-powered ones, I doubled-checked my order after they arrived (from China) and as far as I can tell I had ordered the 12V versions. Returning them to China for exchange was not a good option given the long delivery times so I'm going with the 5V version - if only because I do have a 5V supply on the pier already. The casing used was a customised version of one I found on Thingiverse, adjusted for size, together with an extension at one end to accept three 12v output sockets. This was printed in ABS on my Wanhao 3D printer.

So this is the little circuit board resting on top of the test print of the case:

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And with the relays being powered by 5v it needs 2 power inputs - 5v for the logic and 12v for the load. That's an extra lead that I would not have needed had I used the 12v version of the PCB. Oh well. The three output sockets are 2.5mm x 5mm, and all the necessary internal wiring means everything is a tight fit in the limited space inside the case. I wanted to keep the whole thing as small as possible because the control box will be attached directly to the OTA itself.

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It's all been tested and it works fine, the control software is a simple little app allowing either manual or timed switching of the relays and is all I need:

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The PCB offers 4 channels, I actually only need 2 of them right now but have wired up an extra one (so total 3 channels) in case I think of something else that needs remote switching.

ChrisH

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First rough print (medium quality and without some of the refinements - 20% infill to save filament, only 2 outer shells, no chamfers, plus some bits like the camera plate and dome retaining ring missing). I just wanted to check the dimensions were right and the dome fits perfectly. Looks OK and nice and light compared to the amour-plated alloy version!

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ChrisH

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This is a print of the working AllSky camera, all components fitted (apart from camera!). The lens will be pre-focussed before the retaining ring is screwed down using the 12 screws you can see in the photos below, there are two O-ring seals under the edge of the dome which are compressed by the ring so I expect it be fully watertight and weatherproof. There should be little need to remove the dome other than perhaps to replenish the desiccant (infrequently at that!) or even replae a scratched acrylic dome.

Power and USB leads enter case at the bottom, it might be better to use sealant here as it is a possible entry point for water vapour:

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Twin rubber seals are in the recess which the edge of the dome sits in:

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Dome attached to case:

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One addition I want to make is to add an Horizon Mask to the inside of the Dome to match the lens FOV (either 150 or 180 deg) but it's always possible to add a custom mask to the outside if necessary to blank out intrusive house or street lights.

ChrisH

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I have a heater element which is ideal for this job, max output is 10w (will be reduced with PWM output from an Arduino NANO). Also shown with GPCAM installed with 2.1mm f/l (150deg FOV) lens. This lens is not a fisheye 180deg horizon-horizon lens (1.8mm f/l) but it does make better use of the available sensor area - plus it eliminates peripheral house/street lights. The 180deg lens produces a circular image which is a bit wastefull of the available pixel resolution.

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ChrisH

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I had to think about how I was going to get a USB cable connection to the camera inside the casing. I didn't want to use a female USB socket attached to the outside of the case because it's not weatherproof. So I came up with this idea: There is a rectangular aperture in the side which is large enough to accept the USB 'B' plug (which fits the rear of the GPCam), and I made a pair of tapered wedges (keyed together) with a hole which was a tight fit on the cable. On the inside I attach a small cable tie to the cable to prevent it pulling out, the wedges grip the cable and when pushed home into the rectangular aperture securely lock everything in place - and it prevents water ingress. The disgram below includes one of the pair of wedges, and the photo shows it installed. The 2.5 x 5mm socket is for the 12V supply to the heater.

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ChrisH

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This is cool stuff for 3D printing - flexible TPE filament. I've had it on the shelf for a month or so but never tried it so I thought I;d have a go at printing some seals to use in place of the O-rings in the AllSky cam. I found it tricky to load the filament into the extruder because it tends to not feed in straight, however with a bit a fiddling I persueded it through to the nozzle. No problems after that, print temperature I'm using is 220deg, bed is set at 80deg. I use a glass bed and so gave it a spray with laquer - a mistake as nothing is needed to make this stuff stick to clean glass! So I had to cut the first print off with a blade but the second one peeled off easily enough. I tried printing one part with 20% infill and that was useless with no strength at all, so after that I used 100% infill (that for the AllSky case seals) but it would be worth experimenting with, say, 50-80% infill to see how it affects compressibility.

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ChrisH

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  • 2 weeks later...

I've been having problems with the (useless) Baader SteelTrack focuser on my ODK12, it simply cannot lift the camera without slipping and/or the motor stalling. Really frustrating when you cannot focus your scope!

Solution is courtesy of FLO:

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A 3" FeatherTouch (rack and Pinion of course). I think that will fix it... ;-)

Had to order some 4-1/2" O.D. x 4" I.D. alloy tube to make an extension to connect the focuser to the visual back. The focus stepper motor is a NEMA17-PG5 (5:1 planetary gearbox) - which at 0.5kg in weight I don't really want hanging off the focuser itself so I'll need to machine a bracket of some sort so I can attach it elsewhere then use a toothed belt to drive it. I will include a slip-clutch arrangement (and/or limit micro-switches) so that the powerful motor does not try to drive the rack and pinion mechanism past the hard stops at either end.

ChrisH

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So I need to attach the stepper motor to the focuser - not an easy task with the FeatherTouch. I'm in the process of designing a 3D-printed bracket but finding it tricky to get the angles right. This is not final by any means, a rough print, and there are parts not yet added, but you can see the idea... It will be held in place by the two screws usually used to attach the finder bracket.

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ChrisH

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Well the bracket is working OK... not enthusiastic about the design but I suppose it does work - and I can use the focuser now which is the main thing ;-) Just have to attach it to the scope now, and make an adapter for the camera.

IMG_0734_zpsutrt30tv.jpg

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Tonight I machined the necessary adapter to connect the focuser to the ODK12 visual back. Here I'm using a physically smaller NEMA11 motor but with a 19:1 planetary gearbox it has plenty of torque available, and the extra gearing means higher resolution (3800 steps/rev full-stepping, or double that if I choose to use half-stepping). Full-stepping offers more torque, and the resoltion is good enough to get within the critical focus position, so I'll probably stay with that. To the left in the image below is the Baader SteelTrack (POS) focuser which this FeatherTouch replaces.

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The NEMA17 5:1 motor had an issue - it runs off 12v and if I left the coils energised when not actually moving (which is needed to provide the holding torque) then both the motor and driving chip (L293D) get very hot indeed - so hot in fact that the 3D printed motor bracket started to go soft! (I used PLA for the print - ABS would have been a better choice for thermal stability but I didn't expect the motor to get too hot to handle...). Anyway, the NEMA11 motor runs off 5V and doesn't even get warm with the coils left energised so it's not a problem.

Below is a photo of the focuser with the Atik490EX + filterwheel, and a extra 2 x 1Kg printer filament spools. It can easily lift that weight and hold it in position.

IMG_0746_zpsw0qw2a5s.jpg

 

ChrisH

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Thanks Derrick, I just completed installing the focuser and Moravian G4-16000 camera on the my ODK12. That was quite a job, and needed some custom adapters making so t all went together. Focuser tested and appears to work OK (slight issue with SGPro but there's an easy work-around). Final job was making up a new wiring loom, being careful to make this one more flexible than the last!

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ChrisH

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I had chance to try out the new rig on Sunday night, the focuser worked perfectly apart from the fact I couldn't reach focus! Slight problem with my calculations somewhere... to cut a long story short - I had to shorten the alloy extension tube and also shave off metal from the threaded connector that goes between camera and tube. Now I could just about get focus ;-)

(pictures before the shortening exercise...)

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Another issue was actually loading the OTA onto the mount - I usually slide the OTA onto the dovetail and push it upwards into position, then test for balance and make further small adjustments sliding the scope up/down along the dovetail until it's balanced correctly. The problem here was the weight of this OTA and the fact it just won't slide freely in the dovetail due to friction. Yes, I could slot the OTA into the dovetail with the clamps wide open (thus avoiding the sliding) but that is fraught with danger because at some point the scope is not supported - I'm holding the weight of the OTA with one hand and trying to tighten the clamp knobs with the other. If it should shift/slip there is no way I could hold it and prevent a disaster. Hence, I feel it's more secure sliding upwards into the dovetail - because then the only way it can move is to slide out backwards and I can prevent that happening with just one hand. Anyway, after initially securing the OTA a further issue becomes making small adjustments to position where the scope simply doesn't want to move due to high friction. It's very difficult (i.e., impossible) to make small precise adjustments. Because of that I didn't obtain good balance and my mount model was way out (25" instead of the expected <5") which resulted in trailed stars.

So I modded the dovetail clamp by adding jacking screws to provide this functionality:

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Two push-pull thumb screws allow an easy method of moving the scope, the front one (to the left) additionally allows for setting an end-stop for repeat positioning. The one on the right is just rotated out of the way and the OTA slid onto the dovetail as normal, then the bracket is rotated into position and clamped in place with the smaller thumbscrew. the larger jackscrew can them be used to push the scope along the dovetail or the one at the other end to push it backwards.

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Incidentally, the thumbscrews are conveniently made with the help of the 3D printer to produce the large diamter caps. They are made a press-fit onto cap-head Allen screws (pressed on using the vice - they don't easily come off...).

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ChrisH

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Modded the brackets a little to avoid the possibility of the things sliding off the rod entirely. I machined some rounded grooves at 1/2" intervals, and rounded the ends of the clamp screws so they engage the grooves. No chance of them slipping once tightened. Here I'm just trying the adjustment out - the dovetail bar is my dual rig bar and much longer than the dovetail bar on the ODK12. I only need it to work with the ODK12.

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ChrisH

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These NEMA 14 motors from StepperOnline are fine motors - except there is very little protection for the wires where they enter the motor casing. I happened to notice the insulation is already damaged on the one which is on the scope at the moment so I decided to add some protection in the form of a little cover which snaps onto the end. As seen in the pic below, the cover holds a rubber grommet  which prevents the wires scuffing on any sharp edges. A length of cable sheath will complete the job. It took about 30mins to knock the design up in SketchUp and about an hour to print 2 of them. This 3D Printer is proving to be a very useful tool!

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ChrisH

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With all this messing about with electronics recently I decided I need a separate PSU to work with instead of using various random power bricks I had lying around. The best (cheapest!) option appears to be making use of one of the spare ATX computer PSUs I have, so I'm trying to 3D print a case to hold the connectors. The front panel printed fine (in ABS) but the main part of the case has warped and lifted from the bed ;-( I have quite a bit of time invested in this print so far so will continue and see if it's still usable, if not then next time I'll definitely be using PLA!

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ChrisH

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Hi Chris, good collection of stuff on here, really like those knobs you did...nice idea.

The 3D printer you are using, how much fettling/fiddling does it require? The reason I ask is that we have got a "proper" i.e. industrial machine at work that just does what it is intended to do with no quibbles but that cost about £10k plus the ABS is specific to the machine obviously not for hobby/home use.

I'd like to get one one day but don't want to be messing about with it too much.

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The little UP Plus 2 I use pretty much worked straight out of the box but the standard price is around £1200 - £1400.  The Velleman kit I bought, which was more than many RepRap style printers caused me no end of trouble.  But that was several years ago now and I expect things have improved.

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