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 DIY Mumford rotary table 
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Post DIY Mumford rotary table
About 140USD in parts. As you can see it only takes a small piece of wood to couple the stepper motor to the rotary table. The controller 'firmware' is quite complicated because it has a menu system etc. but I believe you could instead get a commercial stepper motor controller that will step (or even microstep) the motor when you simply send it a pulse (say, from a cheap timer gadget) - I don't honestly know. Half-stepping gives 0.025degree resolution, which yields smooth pans even with a moderate telephoto lens. As the rotary table is essentially a worm-drive I don't bother keeping the motor energized (to hold table in position, which it does by itself) between shots, and so the battery life is admirably long.

Regards,
Tom.

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Wed Jan 14, 2009 9:18 pm
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Post Re: DIY Mumford rotary table
Hi Tom and welcome here!
Very cool! Is it synchronized with the shutter? And the rotary table: Is it also DIY or can you buy that?

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Wed Jan 14, 2009 11:12 pm
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Post Re: DIY Mumford rotary table
Good job!

Here's a $15 microstepping (1/8th step) chopping controller with just step/dir inputs:

http://www.sparkfun.com/commerce/produc ... ts_id=8368

I use it in my projects, it's good for up to 30V and 750mA.

Here're some couplers for the motor to the table, ranging from $13-15: http://dumpstercnc.com/couplers.html

And here's a $100 rotary table to hook it all up to: http://www.harborfreight.com/cpi/ctaf/d ... mber=47052

FWIW, anaheimautomation.com sells inexpensive steppers from NEMA-14 sizes on up.

!c


Thu Jan 15, 2009 7:14 am
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Post Re: DIY Mumford rotary table
Michael wrote:
Hi Tom and welcome here!
Very cool! Is it synchronized with the shutter? And the rotary table: Is it also DIY or can you buy that?


Thankyou for the welcome, I was pleased to find this place. Yes, the controller is synchronized. The 4" rotary table was bought for 100USD from harbour freight and the 3" version is 65USD, but may not provide the same resolution. It's a very heavy thing, the quality is reasonable.

I can offer more info about the controller, if you wish to know how it works (but you may regret it)...

The controller employs an (Microchip 18F4520 8-bit) microcontroller programmed in C. This programmatic approach is very suitable given the sequential nature of firing a camera. The controller has an internal intervalometer or it can be triggered externally using, say, a Canon TC-80N3. Either way, when a trigger signal is received the rotary table turns the prescribed amount and then fires the camera. When firing the camera it first fires the camera's pretrigger (equivalent to shutter button pressed half-way), waits for a prescribed time, and then fires the shutter (equiv. to button pressed fully). This way it allows the camera to autofocus, if you so wish.

Here are some of the menu items you can access, but please note that the menu is adapted from another camera project, so I don't consider them all particularly vital. Most important come first.

Number of steps
Total angle to travel
Direction of rotation
-----------------
Internal intervalometer or external trigger
Pretrigger delay
Bulb duration (for >30sec exposures)
Num Outputs (for firing multiple cameras, flashes, pocket wizards etc, or triggering other gadgets e.g. taking a timelapse of your timelapse equipment and other insanity)
Output stagger (for staggering the output cameras, or manually synching a flash with shutter)
------------------
Save mode (saves your current setup, up to 3 of them - pressing buttons A,B or C invokes those presets)
Motor speed and stepping mode
Mirror-lock-up enable
beep and some other pointless stuff.

The latest prototype on my workbench (not fit for outdoor use) has special modes; 'trajectory mode' and 'time dilation mode.' I saw some discussion about ramping the motion, so I'll describe what they do.

New trajectory mode:
On my computer I draw a trajectory (a plot of angle vs time) which is broken into discrete steps. I download this data to a SD card - somewhat overkill - that I plug into the controller. The controller gets its shot-by-shot instructions from this file. This way it can do fancy pans, even change direction. I did this primarily so that I could do horizontal pans whilst keeping the Sun/moon in the same horizontal position in the frame. I was inspired by some timelapses I saw in Planet Earth - which might've been made using the Mumford device.

New Time dilation mode:
This is slightly peculiar. I don't know the jargon timelapsers use, but I think of timelapses as simply rescaling our perception of time, and describe that by saying, '60x speed' Well, this mode allows this 'speed' to vary, not simply be a constant. It dilates the timebase. I draw on my computer a plot of 'timelapse speed vs real-time', or 'timelapse speed vs angle' or 'timelapse speed vs frame number'. In any case there's enough information to completely determine the interval between shots and the angle between shots.

Examples of use:
1) This arose as a generalization of my desire to do multi-day timelapses whilst skipping night-time. I just 'dilated time' such that I compressed night-time into one frame.
2) Imagine a panning timelapse that panned steadily at a constant speed but the action speed varied. I once saw a glossy commercial of people in a train station; the camera panned steadily but the people accelerated until they were blurs. It might've been done in postprocessing, but it got me thinking about how to get many timescales into one timelapse.

Cheers.

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Thu Jan 15, 2009 8:04 am
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Post Re: DIY Mumford rotary table
shutterdrone wrote:
Here're some couplers for the motor to the table, ranging from $13-15: http://dumpstercnc.com/couplers.html


I see we surf in similar places. The coupler link was new to me, thanks, I may have to get one of those. I looked for something like that for ages.

I'd love to know where I can get cheap but sturdy worm gearboxes with about 36 teeth or more. Somewhere here I saw someone using gears taken from a Meade mount - those looked ideal. Add it to a stepper and you could get some very fine motion The rotary table is sturdy and smooth, but not an ideal solution, especially for 2 axis motion, which is my ultimate goal.

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Thu Jan 15, 2009 8:21 am
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Post Re: DIY Mumford rotary table
astronomerroyal wrote:
I see we surf in similar places. The coupler link was new to me, thanks, I may have to get one of those. I looked for something like that for ages.

I'd love to know where I can get cheap but sturdy worm gearboxes with about 36 teeth or more. Somewhere here I saw someone using gears taken from a Meade mount - those looked ideal. Add it to a stepper and you could get some very fine motion The rotary table is sturdy and smooth, but not an ideal solution, especially for 2 axis motion, which is my ultimate goal.


Indeed - it looks like we've had a lot of similar ideas *grin* Here's a prototype I had made a while back, operates on similar principles, but lacks some of the complexity, option-wise, of yours, and used a standard spur gear train instead of the worm-based rotary table. viewtopic.php?f=24&t=370 (The remote isn't shown there, but it also has an LCD and a keypad in an enclosure. The remote and the motor control unit speak through i2c, both using Atmel chipsets rather than Microchip.)

I'm working on a new design using timing belt pulleys, that has the same resolution (~ 72,000 steps per rotation) but all-in-all fits in about a 7"x3"x3" container. Once my CNC router arrives, and I get it all setup and running to make the first prototype, I'll post some photos and specs on it. Given that it's a ground-up design and using tightly controlled components, it would run about $150-200 to build one axis, but it would both be light and flexible.

As for finding worm gears? I know lots of places to get the gears themselves (such as mcmaster-carr and stock drive products), but I have yet to find _anywhere_ that has reasonable (that is "hobbyist level") pricing on assembled gear boxes. About the only way to get a complete geartrain box inexpensively is to harvest it from used equipment - not a very repeatable activity. I see the benefit of worm gears through their built-in holding torque as you mention, but I'm moving towards timing belts for ease-of-use and sourcing at the moment -- not to mention, it lets me use similar components for all sorts of motion needs.

I like the work you've done, especially the adaptation of the inexpensive rotary table and the multi-camera control.

!c


Thu Jan 15, 2009 8:54 am
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Post Re: DIY Mumford rotary table
This is a really impressive project, astronomerroyal! Talk about mad scientist work at its best. :)

Something like this could also be used to drag a dolly down a track, I'm sure.

BTW, it's great to have you here. Welcome.


Thu Jan 15, 2009 3:37 pm
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Post Re: DIY Mumford rotary table
I realised last night that I could use my wimberley gimbal mount to add a second axis to the rotary table. Rummaging through my scraps I found a cork, a large bucket lid and some metal scraps. It all fitted together like a charm, albeit with the help of some duct tape.

The lid:cork gearing is surprisingly only 12:1, so the tilt rotation is a little coarser with a resolution of about 0.075degrees, still quite usable. This was only made to aid in the development of the controller software. In the video both motors are being fed the same drive signal, which, combined with the discrepancy in the gearing, leads to the ridiculous camera trajectory. The final software and hardware will of course enable graceful swoops over flowerbeds and such - that's the goal.

Sorry about the youtube quality - I never did learn how to upload videos without them getting mashed up.


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Sat Jan 17, 2009 7:11 pm
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Post Re: DIY Mumford rotary table
I'm following your project with interest, and noted that you are using wooden block motor couplers.

A machinist friend gave me a tip about mounting stepper motors to various drive mechanisms - which I use on all my gear.
He said that due to the "choppiness" of the step motor, it was always a good idea to avoid a "hard'' (straight) coupling and use flexible couplers.
He suggested using a spring coupler that would help absorb the transmission of the inherent vibrations from a step motor.(especially at high speed)
If you look closely you can see the cut-outs in the coupler that give it its "springiness".
(There is probably an official name for the type pictured, but I know them as spring couplers.)

cheers, m


Sun Jan 18, 2009 4:00 pm
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Post Re: DIY Mumford rotary table
matt b wrote:
(There is probably an official name for the type pictured, but I know them as spring couplers.)


I think they're called helical couplers, though I've never held one. My beloved wooden block is slipping a little - I think the rotary table has developed a stiff spot.

The problem is that I need to couple a 1/4" shaft with a 10mm shaft. Or rather, my problem is that I have no idea how to do this. Advice gratefully received.

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Mon Jan 19, 2009 10:39 am
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Post Re: DIY Mumford rotary table
Oddly enough, some peristaltic pumps I bought used a while back had a pretty simple coupling design for two different sized shafts. (And, .25 to .393 isn't _too_ big a difference =) It was a piece of clear, probably vinyl tubing, and some clamps. This also worked like a flexible couple to deal with mis-alignment. The tube was sized to fit the smaller tightly, and likely heated before placed on the larger side (as it had swollen compared to the other end) - then once both sides were on, tube clamps were applied to keep the coupling on the shafts.

!c


Mon Jan 19, 2009 2:31 pm
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Post Re: DIY Mumford rotary table
astronomerroyal wrote:
shutterdrone wrote:
Here're some couplers for the motor to the table, ranging from $13-15: http://dumpstercnc.com/couplers.html


I see we surf in similar places. The coupler link was new to me, thanks, I may have to get one of those. I looked for something like that for ages.

I'd love to know where I can get cheap but sturdy worm gearboxes with about 36 teeth or more. Somewhere here I saw someone using gears taken from a Meade mount - those looked ideal. Add it to a stepper and you could get some very fine motion The rotary table is sturdy and smooth, but not an ideal solution, especially for 2 axis motion, which is my ultimate goal.


What an awesome setup. Thanks for sharing. I'm loving this forum by the way. I've been looking for a place like this for the last 12 months.

Regarding the cheap worm gearbox. I have been looking for something similar for ages. Living in Australia has made it a bit tricky for me, but I've come this Queensland company TEA Transmissions If you go to Motors and Drive>Wormgear Motors and Reducers and downoad the PDF they have quite a range. I have just ordered a 10:1 WJA030. It's cost me $158.00 AUS. By far the cheapest thing I could find brand new that is light weight (1.2kg) enough for my needs. I will post some photos when it's all hooked up.

Here's my original design, but I think I will change it to be direct drive now instead of timing belt. It has an option of a hollow input shaft unlike the example in the picture.
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Sat Mar 21, 2009 1:53 am
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Post Re: DIY Mumford rotary table
That's a nice diagram. Are you going to drive a rotary table with the gearbox? If so then you'll have excellent resolution. If you're sticking the camera on the gearbox then a nominal 0.18' step resolution will probably restrict you to fairly wide angle lenses.

It is a pity that decent worm drives are so difficult to get cheaply. I have found that the worm drives from the autostar 492 motor kit have been a Godsend. Fraction of the price on ebay (~10dollars, if you can find them) but require some work to use, and not as beautifully engineered as the gearbox you have. Thus far I've used 4 of them in machines - bought a seller's entire inventory of eight.

I used a cheap NEMA23 stepper motor, but am thinking of getting another with more torque - it's difficult and irritating trying to determine if the motor is missing steps, especially when every step counts. It was only 0.4A per phase so maybe that should've given me a clue... If you have any expertise in this area, I'd love to hear about how to choose a stepper.

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Sat Mar 21, 2009 5:26 am
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Post Re: DIY Mumford rotary table
This would be in place of a rotary table. I'm hoping for this to be the first real piece of hardware for my long term DYI 6 axis Moco Rig project. What do you think would be the optimal ratio when using 1.8 degree full steps? I'm new to this and may have got the ratio wrong. I'm more interested in it's real time application, I was thinking about the top speed (in real time) went I decided on 10:1. My cheap steppers only go so fast so based my ratio choice from their top speed (about 1 rev per 0.85 seconds).

Sorry, not sure how to choose the right stepper. As you said, I guess it just a matter of carefully studying the data sheets. I'm still tinkering with sparkfun steppers and software design before I spend money I don't have;) But it looks like you are much further down the track than I am :)


Sat Mar 21, 2009 6:03 am
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Post Re: DIY Mumford rotary table
I just realised why you looked familiar - I'd been to your blog before. Real-time, I see - sounds like it'll be a beautiful setup. I actually know nothing about film-making, just still photography. This motion timelapse business is definitely 'in at the deep end.'

Regarding optimal gearing/driving methods etc., this could easily become an ongoing debate. I'll just say that I completely rebuilt my timelapse setup; 60:1 gear ratios, multiple steppers are 1.8' single-phase/full-step driven (for power reasons - makes a big difference to me). I therefore have 0.03' resolution which is enough for convincing ramps (hyperbolic tangent). I imagine you're more interested in smooth motion, and I'll further guess you are - being a sparkfun patron - using the EasyDriver microstepper. Sounds like you're onto a winning setup.

Does 6-axis mean x,y,z translation, and pan,tilt and roll rotation?

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Sat Mar 21, 2009 8:50 am
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Post Re: DIY Mumford rotary table
Yes, you are right. pan tilt roll and xyz translation. I'm basing it heavily on this design:
http://www.general-lift.com/GLMoCo/Products/genuflex/Prod_genuflex.html

I built a fully functioning virtual version of this rig in Maya (animation program). This taught me a lot about trigonometry and Pythagoras. The system I designed exported a 3D camera move to the real rig you see in the link above. The unique thing about this setup is it's virtual axis. It allows for any kind of camera move. That is to say you can move the virtual camera anywhere in 3D space and and translates motion into the rig.

Here's a video tutorial on how the software works.
http://www.veoh.com/collection/KuperToolsTutes/watch/v8383654yMZ6Wzn

And here's a video of the rig in action:
http://www.veoh.com/browse/videos/category/technology/watch/v65942418b4ZmEQQ

Here's another video. It's for my short film, but there is a section on motion control that shows off the rig.
http://www.veoh.com/browse/videos/category/animation/watch/v7010592PBJj9bNm

I'm beginning to think that I should choose my stepper motor first before I choose anymore ratios. Regardless of speed. I think increment resolution should come first. But to decide on resolution I need to know the motor's top speed. Torque is hugely important too. And I want to keep to full steps for mechanical repeatability. I guess I'm in the same situation as you. Researching for the right stepper. 60:1 sounds good I just need to find a motor small enough and fast enough to do quick real-time pan and tilts with this ratio.

Thanks for the info.


Sat Mar 21, 2009 3:43 pm
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Post Re: DIY Mumford rotary table
Daniel wrote:
I built a fully functioning virtual version of this rig in Maya (animation program). This taught me a lot about trigonometry and Pythagoras. The system I designed exported a 3D camera move to the real rig you see in the link above. The unique thing about this setup is it's virtual axis. It allows for any kind of camera move. That is to say you can move the virtual camera anywhere in 3D space and and translates motion into the rig.


That's hot! So do you think you could port this to MAx? seriously you're going to be so blown away with what shutterdrone is cooking up... You'll be able to work this into the system. I'm very psyched to see someone with your talent set here!!


Sat Mar 21, 2009 4:33 pm
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Post Re: DIY Mumford rotary table
milapse wrote:
seriously you're going to be so blown away with what shutterdrone is cooking up...


Do we get a clue? I'm expecting at least 3 axes, custom software, and several flashing LEDs ...

Daniel, I may ask about stepper motors at http://www.electro-tech-online.com/ which is where I usually go for advice, although maybe a CNC forum would be better. If I get any useful info I'll be sure to post it. Your project is very impressive and I wish you the best of luck in the interim.

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Sat Mar 21, 2009 7:50 pm
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Post Re: DIY Mumford rotary table
Daniel wrote:

I'm beginning to think that I should choose my stepper motor first before I choose anymore ratios. Regardless of speed. I think increment resolution should come first. But to decide on resolution I need to know the motor's top speed. Torque is hugely important too. And I want to keep to full steps for mechanical repeatability. I guess I'm in the same situation as you. Researching for the right stepper. 60:1 sounds good I just need to find a motor small enough and fast enough to do quick real-time pan and tilts with this ratio.

Thanks for the info.


Hi Daniel, a range of stepper motors to suit your application once
could be found in the Pacific Scientific catalogue. These are the 'royal red' coloured ones mounted on the early General Lift gear.
I believe the Pacific Scientific section is now buried somewhere in http://www.DanaherMotion.com

Its been several years since I last purchased any but the Powerpac and PowerMakII range were my favourite for a good mix between speed and grunt.

ps I'm actually in SA on a job - fly out tonight!


Sat Mar 21, 2009 8:43 pm
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Post Re: DIY Mumford rotary table
Hi Matt, you are probably on the plane by now. But just wanted to say thanks for the link. They have motors on there that can go up to 3000rpm! currently the cheapo steppers that I own have a top speed of... wait for it... 70.5rpm, Weak!

It's good to know that they can go that fast. This means I can choose a higher ratio gear box anywhere from 60:1 to 100:1 and not worry about it. Then when I save my pennies I can buy a motor to suit :-)

Now if I can just change my order before it's too late!

Enjoy Adelaide. And good luck with your job!


Sun Mar 22, 2009 2:53 am
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Post Re: DIY Mumford rotary table
Stepper rpm is largely a factor of driver. You can probably quadruple the top speed of your stepper by simply increasing the voltage and adding a power resistor to keep the current within spec. It's largely about inductance, which limits how quickly the current rises to its max value. This time limits how fast you can switch the coils on and off. If you get a suitably sophisticated driver you'll be able to go faster. It's a massive subject.

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Sun Mar 22, 2009 11:00 am
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Post Re: DIY Mumford rotary table
astronomerroyal wrote:


I can offer more info about the controller, if you wish to know how it works (but you may regret it)...


Sorry for my english i'm french timelapser !
It will be cool to share your design. I'm actually working on a 18F877 board but time is missing !...
Regards
Raph :lol:


Tue Apr 28, 2009 4:24 am
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Post Re: DIY Mumford rotary table
Dear Raph,

I abandoned this project in order to build some better machines. Those machines are approaching completion and I'll be happy to share the software. However, I fear that between now and then a lot more time will go missing...

What sort of machine are you making? I love hearing about people's inventions.

Regards
Tom.

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Thu Apr 30, 2009 4:00 am
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Post Re: DIY Mumford rotary table
it's a motorized head for night timelapses. First i' worked with a PIC (intevallometer is fine now) then with arduino platform and EasyStep + bipolar stepper (H bridges) to move photographic head (mini rotary table). Machining part is not a problem, but develloping software and electronics is so painful for me :lol: no time enought ! :lol:
Planning to move the camera at defined angle , stop, shoot 30s max with a Sigma 30mm@1.8 move and so on .
Regards


Sat May 02, 2009 3:43 am
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Post Re: DIY Mumford rotary table
Arduino + EasyDriver + single axis machine is a very good way to start. Although I don't use my machine, I'm pleased I made it - very educational, although I found the hardware part difficult. Perhaps you should start a thread, giving updates on your progress. This (project) is the sort of thing shutterdrone does over breakfast, and he may have precisely the code you want.

In my experience it's best to do timing using a 'timer interrupt' (ideally generated by a 32kHz crystal) rather than using purely software timing routines, especially if you're doing both intervalometry and timing the camera exposure (e.g. using Bulb mode) on the same microcontroller. I assume you're also using optocouplers to fire the camera. As for a user-interface on small projects I quite like DIL switches. Very easy to include. These are the most fundamental things to consider, I believe.

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Sat May 02, 2009 5:24 am
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Post Re: DIY Mumford rotary table
oh yes ! have not seen the open moco projet !
Okay thanks ! :shock:


Mon May 04, 2009 5:20 am
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Post Re: DIY Mumford rotary table
In general, I use a mix of standard timing functions (checking how much time has passed), interrupt timers, and flag evaluation for time-lapse apps.

I haven't found a specific need to use a hardware-based solution, mostly because the skew is largely irrelevant to most uses (3s skew over a 24 hour period on average using an Atmega168/328P with a 16MHz crystal) we'd encounter in time-lapse. That is to say, we're not building pace-makers, nuclear power-plants, or real-time guided missile systems - if your timer is off by a microsecond every ten calls, you'll most likely never even notice. =)

So, when I talk about that combination of behaviors, what I mean to say is this:

* When you're designing a shoot-move-shoot system, you [shouldn't|can't] fire the camera when a motor is moving, and vice-versa
* The technique you employ should be capable of handling the numerous variances in your different program (today I run three axes, tomorrow one; today I have a 1s delay between shots, so I don't have to do anything special, but tomorrow I use a 10s delay and my camera goes into a soft-sleep mode at 5s, meaning I have to wake it up before I fire it.)

So, here's what I've come up with as my preferred method for handling these sorts of things -- I won't say it's better or worse than any other technique, just that I like it and it hasn't failed me yet:

* Use a standard timing loop for shot interval.

E.g.: measure time-elapsed, and compare it to interval time.

Code:

if( elapsedTime >= intervalTime ) {

  fire_camera();
  elapsedTime = 0;
}
else {
   elapsedTime += millis() - last_time;
   last_time = millis();
}


The benefits of this technique means you don't have to worry if you've created an unrealistic combination of factors, i.e.: (camera_exposure_time + camera_exp_post_delay + time_needed_to_move_motors ) > intervalTime. The reason is, you can add flag checks, e.g.:

Code:
if( elapsedTime >= intervalTime && camera_exposing == false && some_other == false ) {


... in that way you never trigger the camera when something else is happening. Now, there are draw-backs, primarily that you'll almost never be _exactly perfect_ in your timing, you'll usually be off by one or two milliseconds, but then again, I've never found that to be a noticeable problem in actual use. (Can you tell the timing difference between two shots taken 1 second apart, and two taken 999 mS apart?)

* Use an interrupt timer for camera exposure

This is mostly because it's easy, and more accurate than doing the measurement yourself. The MsTimer2 library taps into the PWM interrupts for providing millisecond-level timing interrupt. You say, for example:

Code:
void fire_camera() {

  camera_exposing = true; // set the flag for the interval loop

  digitalWrite(camera_pin, HIGH);

  MsTimer2::set(camera_exp_tm, stop_camera);
  MsTimer2::start();
}

void stop_camera() {

  digitalWrite(camera_pin, LOW);

  MsTimer2::stop();

  camera_exposing = false;
}



This also allows you to do many other things, such as handle user interface interaction on the same microcontroller while your camera is exposing, do other tasks, etc. External real-time clocks, 555 timers, external crystals, etc. will all provide more accurate timing, but the difference is so minimal, that I've never found them worth the effort for _run of the mill_ time-lapse shooting.

Here're some files from the openmoco code base that'll help to illuminate this more:

Camera control: http://openmoco.svn.sourceforge.net/vie ... iew=markup

Main application pde (loop timing, etc.): http://openmoco.svn.sourceforge.net/vie ... iew=markup

You can kind of see from the main .pde file that I use a very complex set of chained timers, flag checks, and delay()s where appropriate to allow for a very flexible workflow (allowing keyframing, numerous modifications to interaction, triggering flashes, etc.). This hasn't failed me yet =)

!c


Tue May 05, 2009 9:28 am
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Joined: Tue Apr 14, 2009 5:57 am
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Location: Denmark, Elsinore
Post Re: DIY Mumford rotary table
Hi gang,

so if I were to build a dolly with only horizontal movement, could I get a working set up buying these parts:
EasyDriver
Stepper motor
Ardunio Duemilanove
some sort of power source.

I plan to use the motor to pull a cart with the camera via a simple wire setup?

I have no experience with electronics, so can I program the motor/driver to do step, pause, step loops?

Thx.


Sat May 09, 2009 12:29 pm
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Location: Troutdale, OR http://www.vimeo.com/ac
Post Re: DIY Mumford rotary table
deepseas wrote:
so if I were to build a dolly with only horizontal movement, could I get a working set up buying these parts:
EasyDriver
Stepper motor
Ardunio Duemilanove
some sort of power source.

I plan to use the motor to pull a cart with the camera via a simple wire setup?


I want to do the same thing, but I'm suffering from severe incompetence here. Some of the stuff being concocted here is genius, but way too overcomplicated for my needs. I just want a single axis moco with adjustable speeds (maybe even ramping) to replace my hacked apart meade mounts, which are too unreliable and take forever to set up. Then I can pull the plug on building a solid dolly track. I don't even know where to start with the electronics.

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Sat May 09, 2009 5:16 pm
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Posts: 626
Post Re: DIY Mumford rotary table
EasyDriver
Stepper motor
Arduino Duemilanove

That sounds good to me, at least for the motor driving part. When choosing a (ideally bipolar) stepper motor be sure to note that the EasyDriver supplies a limited (but quite respectable) current. For the camera firing part you'd just add a couple of optocouplers.

It's trite to say, but the electronics is only as complicated as you want it to be. Put another way; the equivalent of the "Hello World" program in the world of microcontrollers is to simply flash an LED. Replace that LED with an optocoupler (a light activated switch) and you have a camera intervalometer. The intervalometer I placed in the woods does things that I believe no commercial device does, yet it only has 5 components - just the bare essentials.

I'm sure all the code is somewhere in OpenMoco (the engine?), ready to dump onto an Arduino. What i think would be is good is to see a 'simplest possible solution' consisting of Arduino + simplest code (intervalometer and EasyDriver stepper) + plain-English tutorial, just so that you can synch a camera with a motor, and do so in a weekend. With that you can do almost anything, not just panheads and dollies.

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Sun May 10, 2009 6:09 am
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Post Re: DIY Mumford rotary table
astronomerroyal wrote:
It's trite to say, but the electronics is only as complicated as you want it to be. Put another way; the equivalent of the "Hello World" program in the world of microcontrollers is to simply flash an LED. Replace that LED with an optocoupler (a light activated switch) and you have a camera intervalometer. The intervalometer I placed in the woods does things that I believe no commercial device does, yet it only has 5 components - just the bare essentials.


Agreed, if you look at the plethora of intervalometer code shared for the arduino, most of it is as simple as "delay 1s, bring pin high, delay 70ms, bring pin low."

If you want to learn to write the code, this is the starting point. It's very simple. As Astronomerroyal has pointed out, the circuit is as simple as an arduino and an opto-coupler.

astronomerroyal wrote:
I'm sure all the code is somewhere in OpenMoco (the engine?), ready to dump onto an Arduino. What i think would be is good is to see a 'simplest possible solution' consisting of Arduino + simplest code (intervalometer and EasyDriver stepper) + plain-English tutorial, just so that you can synch a camera with a motor, and do so in a weekend. With that you can do almost anything, not just panheads and dollies.


Indeed! You can upload the existing engine to an arduino, install the perl library on your computer, run the example script (and presuming the hardware is already wired), be doing all sorts of moco in about 3 minutes. There are zip files and instructions on the website.

That being said, it is like a cadillac vs. a go-kart if you're starting out very simple. There's a rich set of functionality that takes some time to get familiar with. But all of that is unnecessary for simple use-cases, and you don't need to pay any mind to it when you're getting started.

It wouldn't be hard to write a "up and running with the complete basics in five minutes" tutorial. I'll put it on the list of tasks for this coming week.

I strongly suggest just diving in. Between Dan Thompson's easydriver tutorial, and what's been said in this thread alone, you could be up and running in about an hour or two with no prior experience.

!c


Sun May 10, 2009 7:14 am

Joined: Fri Jul 25, 2008 6:15 am
Posts: 20
Post Re: DIY Mumford rotary table
Shutterdrone it's true , I' ve uploaded your code in 1h (installing arduino, wiring etc ...). Your code is simply clear !
Learning Perl quite cool too !
It works, a complet set of functions are available inside the engine, just be careful with "path=c:\myengine\mymoco\" at the install !
What you've done is just amazing...
Now I'm planning to buy a smallest (3") rotary table (RDGtools UK) and a CNC bipolar stepper : any idea for the stepper ? Vexta, Sanyo Denki , Portescape, or just @stock ?
:D
Thanks !


Mon May 11, 2009 12:23 am
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