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Mechanically moveable mic

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Mechanically moveable mic

Postby Kizzer » Fri Aug 17, 2012 1:12 pm

Hi guys

Bit of a weird question, but here we go.

I'm looking to make a device for inside of an iso cab, which can move a mic stand left and right over a distance of about 7 inches to cover the centre to outer cone of a speaker. I would like it to be push button controlled, so that I could move it a 1/4 inch left or right over a distance of around 7 inches. Here's a terrible diagram I've just made up:

Image

There is a company that builds one that looks like a windscreen wiper:

http://www.youtube.com/watch?v=VPtYM3treFA

I was looking at making a camera slider like this:

Image

But I would need a way of motorizing it, and the only thing I could think of was a small DC motor with a dolly system.

Any ideas on a better way to do this?

Cheers for any ideas you can give me,
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Re: Mechanically moveable mic

Postby Kizzer » Fri Aug 17, 2012 2:38 pm

Here's a video of a mechanical camera slider in action:

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Re: Mechanically moveable mic

Postby zenguitar » Fri Aug 17, 2012 4:10 pm

How about using a micro controller like PICaxe or Arduino to control a stepper motor of some sort. A standard DC motor is harder to control to the degree you require whereas a stepper motor is very controllable.

You can try a stepper motor to power a loop of wire/string backwards and forwards. You can find stepper motors with a threaded shaft that moves backwards and forwards. And you can search for Linear Actuators which might also do the job.

All three would be capable of moving your mic backwards and forwards along the track. You can add limit switches to stop it going too far in either direction and a reset function. And should be easy to have a couple of buttons for left/right movement and maybe even a display that tells you in inches/cm how far you have moved the mic.

A few minutes thought comes up with loads of other ways you could do get a stepper motor to drive the dolly, how about having the dolly run up and down a threaded rod turned by the motor?

Hope that helps

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Re: Mechanically moveable mic

Postby Jack Ruston » Fri Aug 17, 2012 7:09 pm

The difficulty inside an isocab will be space I guess. I know Eric Valentine made something like this. I think it's mentioned in his SOS interview.

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Re: Mechanically moveable mic

Postby dmills » Fri Aug 17, 2012 7:09 pm

Yep, steppers are the way to go, but I would probably not bother with the linear slide rail (expensive).

How about reusing the guts of an old dot matrix printer? The carriage should be quite well suited to butchering to take a mic clip and the simple round bar guide rails and toothed belt will be quite man enough for the job.

Tiny micro, some microswitches and a not very butch driver chip and the job is a good one.

Regards, Dan.
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Re: Mechanically moveable mic

Postby ef37a » Fri Aug 17, 2012 9:16 pm

Low tech solution.

Slide rail. Hang it from some curtain track. Drive it via a length of studding (6mm gives you exactly 1mm movement for one rev, just need a counter!). Note you would need to buy a split 6mm die* and run the studding thru it to clean up the threads and make it run smoothly. There will be some backlash but we are not talking "Vorsprung..." here are we?

S or bust limit microswitches each end and you could have micro switches at intervals to light external LEDs but! Cameras are so cheap these days. Fit one and an LED floodlight and a graduated scale inside the box.

*Or saw 1/2 way thru a 6mm nut and squeeze it!

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Re: Mechanically moveable mic

Postby zenguitar » Fri Aug 17, 2012 11:53 pm

ef37a wrote:Low tech solution.

Slide rail. Hang it from some curtain track. Drive it via a length of studding (6mm gives you exactly 1mm movement for one rev, just need a counter!). Note you would need to buy a split 6mm die* and run the studding thru it to clean up the threads and make it run smoothly. There will be some backlash but we are not talking "Vorsprung..." here are we?

S or bust limit microswitches each end and you could have micro switches at intervals to light external LEDs but! Cameras are so cheap these days. Fit one and an LED floodlight and a graduated scale inside the box.

*Or saw 1/2 way thru a 6mm nut and squeeze it!

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Re: Mechanically moveable mic

Postby ef37a » Sat Aug 18, 2012 5:21 am

One acronym Andy...K.I.S.S. Bloody computers! Like Jezzer said, " Put a CPU in an assult rifle and we stop all war"!

My Brother MFC-7420 is playing silly buggers. Won't pick paper from the bottom tray or if it does it jams on the second sheet. I have replaced toner and drum and blasted it with a can of air but no joy. Will have to find a decent printer tech'.

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Re: Mechanically moveable mic

Postby Kizzer » Sun Aug 19, 2012 10:37 am

Cheers for all the replys guys! I'm busy looking through and trying to get get my novice head around your ideas! I should specify that the inside dimension of the iso will be around 20 inches, but the the mic only needs to be able to travel around 7 inches to cover the centre to speaker to outer edge.

dmills wrote:Yep, steppers are the way to go, but I would probably not bother with the linear slide rail (expensive).

How about reusing the guts of an old dot matrix printer? The carriage should be quite well suited to butchering to take a mic clip and the simple round bar guide rails and toothed belt will be quite man enough for the job.

Tiny micro, some microswitches and a not very butch driver chip and the job is a good one.

Regards, Dan.

Anymore details on Tiny micro, some microswitches and a not very butch driver chip What, where to buy, how to setup?

Cheers

Kieran
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Re: Mechanically moveable mic

Postby ef37a » Sun Aug 19, 2012 11:07 am

http://www.bizoner.com/pan-and-tilt-kit-with-hitec-hs311-servos-for-sensor-mount-p-223.html?zenid=qjs9ldoop821dkqa6isgmfrg82 ?

You only need "pan" and the mic describes a very shallow arc but 'tis only rock and roll!

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Re: Mechanically moveable mic

Postby zenguitar » Sun Aug 19, 2012 12:52 pm

Kieran...

Do you have any experience with micro-controllers or hobby robots/remote control cars/boats/planes? Or are you starting from scratch?

And are you in the UK, Europe, or USA? No point in recommending suppliers on the wrong continent.

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Re: Mechanically moveable mic

Postby ef37a » Sun Aug 19, 2012 1:22 pm

zenguitar wrote:Kieran...

Do you have any experience with micro-controllers or hobby robots/remote control cars/boats/planes? Or are you starting from scratch?

And are you in the UK, Europe, or USA? No point in recommending suppliers on the wrong continent.

Andy
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Re: Mechanically moveable mic

Postby Kizzer » Sun Aug 19, 2012 6:59 pm

zenguitar wrote:Kieran...

Do you have any experience with micro-controllers or hobby robots/remote control cars/boats/planes? Or are you starting from scratch?

And are you in the UK, Europe, or USA? No point in recommending suppliers on the wrong continent.

Andy

Total novice I'm afraid!

I'm based in Hampshire, south of England.

Loved the idea about butchering an old printer, just need to understand how to control the movement in 1/4 inch steps.
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Re: Mechanically moveable mic

Postby zenguitar » Sun Aug 19, 2012 8:27 pm

OK Keiran,

You have a couple of learning curves ahead if you want to proceed with your plan. The first is to build the mechanism to move the mic. The second is to build a device to power it and control it's movements so that they are accurate enough for you and repeatable. Although the idea is quite simple, it will be quite challenging to make it work effectively and reliably enough to make it worth while. If you keep having to open the iso-box because it isn't working properly you might as well just put in an access hatch, fit the mike on a gooseneck, and adjust it by hand.

The simplest mechanism would be a simple pan head operated by a servo. Select the correct angle of rotation and you could get that 7" range of movement. However, in the extreme positions the sound will be coming at the side of the mic which might be a problem. The device Dave linked to would do the job but is more complicated (and more expensive) than you need. You could knock up something with a door hinge and a basic servo. A slider would be more accurate, but breaking up an old printer isn't for the faint hearted. How you do it depends on what printer you have, and you will have to work out yourself how to make it work.

To make it all work you'll then need to choose your micro-processor, get one, learn how to program it, and work out how to interface it with your stepper motor or servo. There are a few options out there, but the main candidates would be a PICaxe or an Arduino. Both have their advocates and there is plenty of info online about both of them. However, for a beginner the Arduino has a lot to commend it. It was designed for beginners but is capable of some very powerful things in the right hands. It is open source, so there are a lot of companies making compatible devices and you can even make your own from kits or even from parts. Most people start with an Arduino Uno which you can get here, here, or here. All of those are very good suppliers, and they also sell things like expansion boards for motor controllers, servos, stepper motors, robotics parts and so on.

I would suggest you spend some time reading the Arduino site and doing a little research there before you go any further. There are plenty of examples of what people have already achieved.

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Re: Mechanically moveable mic

Postby Folderol » Sun Aug 19, 2012 10:26 pm

What is your budget?

A fairly elegant solution is something like This
It is a stepper motor with built-in linear actuator. You only need to add a 'home' limit switch to be able to get repeatable and accurate results. Although the stroke length is only about 2 inches, you can either use a longer lead screw, or attach it part way along a lever, with the mic on the end.

Proper dedicated drives will set you back about £150, but as these are nice low voltage, low current devices, Andy's suggestion, a cheaper (and more interesting) option, is to go the Arduino route. There are articles on their home page about stepper driving.
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Re: Mechanically moveable mic

Postby Exalted Wombat » Sun Aug 19, 2012 10:48 pm

You might consider applying your ingenuity instead to a method of getting a simple mechanical control rod through the wall of the box. I think you'd spend less time mending this solution!
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Re: Mechanically moveable mic

Postby Goddard » Mon Aug 20, 2012 1:02 am

Heh, love this "mic-robotomy" stuff. Reminds me of my early studio days, where the studio couldn't afford the remotely controlled electro-mech damper adjustment option for the EMT plate and we had to settle for the basic manual handwheel, and then used to brainstorm endlessly on how to fit a motor of some sort and remotely control it. Got very Rube Golderg-esque (Heath Robinson-esque) at times. To this day I still think the hamster in a wheel idea had merit.

I mean, really, much more practical than that ridiculous donkey-carrot proposal.

Maybe time to hunt down that old Meccano (Erector) set gathering dust in the attic...
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Re: Mechanically moveable mic

Postby Kizzer » Mon Aug 20, 2012 9:42 am

Folderol wrote:What is your budget?

Not big I'm afraid.

I was looking to build the iso cab for around £150-£200. Its going to be a box within a box design, made with 3/4 inch mdf and filled with rockwool. I have most of the rockwool and acoustic foam, just need to get the mdf cut to size when i'm ready to build.

Funnily enough the "Rod through the box idea" was the first thing my Dad came up with when I mentioned the idea to him. This would be easier, but wouldn't drilling holes through the box compromise the isolation?
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Re: Mechanically moveable mic

Postby Exalted Wombat » Mon Aug 20, 2012 10:24 am

Kizzer wrote:Funnily enough the "Rod through the box idea" was the first thing my Dad came up with when I mentioned the idea to him. This would be easier, but wouldn't drilling holes through the box compromise the isolation?

You're not going to get perfect isolation anyway. If that's what you're after, put the whole thing in a distant room (in which case, why bother with the enclosure?).

Ships manage to feed a propellor shaft through the hull. Drive shafts get in and out of gear boxes without an oil leak. You should be able to make a gland for a control rod.
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Re: Mechanically moveable mic

Postby Kizzer » Mon Aug 20, 2012 11:01 am

Its not going to be silent, but with the box within a box idea I will achieve between a 35-40db decrease in sound level. I have neighbours next door and my recording is limited to nights due to work and travel commitments, so needed to find a way of recording at resonable levels without disturbing people.

Being able to set the mic on the centre of the speaker and move it in 1/4 inch steps to the outer edge of the speaker, while being able to listen to the results in real time over the monitors would be yet another way to use my time more effectively. The only other method would be going to the iso, opening two lids, resetting the mic position, shutting both lids and returning to listen to the results. I'm just trying to make the most of what time I have.
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Re: Mechanically moveable mic

Postby Kizzer » Mon Aug 20, 2012 11:20 am

A fairly elegant solution is something like This
It is a stepper motor with built-in linear actuator. [/quote]

That looks great! When you say stroke length, do you mean it will only move 2 inches, or that the length of the rod that moves is only 2 inches?
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Re: Mechanically moveable mic

Postby Kizzer » Mon Aug 20, 2012 11:27 am

Just found this:

http://www.youtube.com/watch?v=uewMphsBamk&feature=fvwrel

Something like this would be great!
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Re: Mechanically moveable mic

Postby zenguitar » Mon Aug 20, 2012 12:04 pm

Kizzer wrote:Just found this:

http://www.youtube.com/watch?v=uewMphsBamk&feature=fvwrel

Something like this would be great!

And about $770 (£490) which is more than twice your entire budget. However, it is essentially a stepper motor driving a lead screw which is something I mentioned earlier. You could make something similar with a couple of drawer slides, a stepper motor, and a long screw.

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Re: Mechanically moveable mic

Postby Kizzer » Mon Aug 20, 2012 12:17 pm

Yeah, the price is too high. But it was along the same lines as my original idea. I like your idea! Would it be controlled in the same way with Arduino?
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Re: Mechanically moveable mic

Postby ef37a » Mon Aug 20, 2012 12:28 pm

Exalted Wombat wrote:
Kizzer wrote:Funnily enough the "Rod through the box idea" was the first thing my Dad came up with when I mentioned the idea to him. This would be easier, but wouldn't drilling holes through the box compromise the isolation?

You're not going to get perfect isolation anyway. If that's what you're after, put the whole thing in a distant room (in which case, why bother with the enclosure?).

Ships manage to feed a propellor shaft through the hull. Drive shafts get in and out of gear boxes without an oil leak. You should be able to make a gland for a control rod.

Yes, get a cable gland from Maplin and grease the inner cable grip with silicone grease then nip it up on the shaft to get the right seal but with motion.

Dave.
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Re: Mechanically moveable mic

Postby Goddard » Mon Aug 20, 2012 1:00 pm

Maybe no need for any holes (except for passing the cables of course, which could be easily sealed airtight with a bit of silicone sealant).

How about using a pair of magnets, one at the upper inside of the inner box, fixed to an adjuster rod carried in a couple of blocks fixed to the inner top and suspending the mic below, and one positioned above it on the top of the outside box to move the inside one about?
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Re: Mechanically moveable mic

Postby Hugh Robjohns » Mon Aug 20, 2012 1:14 pm

Suddenly guitar rig plugins seem so much easier!

H
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Re: Mechanically moveable mic

Postby Kizzer » Mon Aug 20, 2012 1:23 pm

Hugh Robjohns wrote:Suddenly guitar rig plugins seem so much easier!

H

HA HA! Exactly!
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Re: Mechanically moveable mic

Postby Exalted Wombat » Mon Aug 20, 2012 3:57 pm

Kizzer wrote:Its not going to be silent, but with the box within a box idea I will achieve between a 35-40db decrease in sound level. I have neighbours next door and my recording is limited to nights due to work and travel commitments, so needed to find a way of recording at resonable levels without disturbing people.

Being able to set the mic on the centre of the speaker and move it in 1/4 inch steps to the outer edge of the speaker, while being able to listen to the results in real time over the monitors would be yet another way to use my time more effectively. The only other method would be going to the iso, opening two lids, resetting the mic position, shutting both lids and returning to listen to the results. I'm just trying to make the most of what time I have.

Use the time you would have spent fitting up this complicated (and, I suspect, unreliable) mechanism in making some test recordings with the mic in different positions. Then you'll know where it needs to be for the sound you want. Also, design some quick-release catches for the lids!

I've got a sneaky feeling that DI, maybe through some speaker emulation, is likely to sound better than a boxed-in cabinet.
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Re: Mechanically moveable mic

Postby grab » Mon Aug 20, 2012 4:44 pm

zenguitar wrote:You could make something similar with a couple of drawer slides, a stepper motor, and a long screw.

A couple of drawer slides and a bit of string would be fine for me.

I'll happily have a long screw as well, although I don't know how it would help with the project.
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