Centrifuge PCB

[Giuvasco]

Hi, I am doing a science experiment to look at the behaviour of ball bearings in a centrifuge. I need to have a live video steam of what is happening to the ball bearings inside the centrifuge. This means I have to be able to stream live video from a rotating canister. I need to build a circuit board that would be housed inside the top lid of the centrifuge that can interface with a small video camera, transmit the video feed via wireless RF (or mechanical or optical slip ring). I also need to light the interior of the canister with a strobe light, whose frequency (Hz) can be remotely controlled. A strobe light can be tuned in real time to freeze the visual movement of the ball bearings.
I need help to identify the right electronic components and how to build this system. Ideally I am looking for an expert who is willing to walk this journey with me - via ongoing online correspondence. I would be willing to pay some $$ if I find the right (and technically capable) advisor. I can source the recommended components, build and configure. I just need a guide to keep me on the right path. I already have a Raspberry Pi2, if that is a good start.

Any suggestions about where to go to get this online consultancy? Is there an existing service? I would prefer someone who already does ongoing online consultancy, rather than just chatting with hobbyists who want to help. I know this sounds counterintuitive, but I want someone who will invest stakeholdership.

That said, if there are hobbyists out there who are passionate to assist, just for the fun of it, then that is ok as well. I don't want to sound too precious

Thanks Giuvasco.

 

[(*steve*)]

I would recommend you transmit the data wirelessly and make sure the antenna is axial to the rotation of the centrifuge. It's probably better to make it battery powered, but you're going to have to be *really* careful about balance and loading issues. Keeping everything as close as possible to the the axis of rotation will be the key,

Oh, another possibility for powering it is to use a wireless (Qi) type of charger to transmit power. Note that these only have a range of about 5mm, so you'll have to keep moving and stationary parts reasonably close, but not as close as if you were using contacts.

Do you need to alter the frequency while it's running, or could you set it for one run? Alternatively is the frequency based on rotational speed (which you could pick up from a sensor).

 

[Giuvasco]

Hi *steve* - thanks for that.

My default option will be to try transmit wirelessly and yes, the antenna will be axial to rotation. My only concern (I have spoken to a few techs) is that at higher RPMs (up to 3000) may cause RF noise, and degrade the video transmission. Thus, I need to build in contingency for slip ring option. That would mean that I need to allow enough space on the motor shaft to accommodate a slip ring if the RF option fails.

With power, I was not aware of wireless Qi charger - so that is a good tip from you - thanks. I will probably start with the battery option, and just ensure that I have a minimum of 2 batteries, on opposite sides of the housing, so that they balance out (counterweight each other).

Regarding the strobe frequency, I most definitely need to be able to adjust it in real time while observing the video stream - no way out there. So, this does mean I need a way to remotely control the frequency.

Where I am struggling - is to find someone who can recommend the correct components - PCB with required logic, best type of mini camera, leds or lights that work well as strobes, good tips for battery type, electric motors type etc etc...

I don't myself dabble in electronics day-to-day, so I am really looking for a source of expert advice.

Any ideas?

Giuvasco

 

[(*steve*)]

I don't myself dabble in electronics day-to-day, so I am really looking for a source of expert advice.

Is there a hackerspace near you?

 

[Alec_t]

Is the centrifuge lid static, or can it be modified to be static? If so, that would avoid the need for slip-rings/balancing.

 

[Giuvasco]

Is there a hackerspace near you?

Hi *steve* - I am not sure what a hackerspace is? Can you describe?

 

[(*steve*)]

Hi *steve* - I am not sure what a hackerspace is? Can you describe?

http://bfy.tw/60CM

 

[Giuvasco]

Is the centrifuge lid static, or can it be modified to be static? If so, that would avoid the need for slip-rings/balancing.

Alec_t, the lid spins with the centrifuge. It's really a spinning cylindrical canister, with a top half containing the electronics, camera & lights, and the bottom half being an empty chamber with ball bearings. It's not a centrifuge as we most commonly know them (ie in biology labs for separating liquids in test tubes). It's more like a washing machine drum, spinning in a horizontal axis. The camera needs to spin, otherwise, it would see the ball bearings in the lower chamber as just a spinning blur.

In this video of the inside of a centrifuge, the camera is fixed to an external point, so the details of the centrifugal effect on the contents is just a blur.

In this video of the inside of a centrifuge, the camera is fixed to the centrifuge chanber itself, so the details of the centrifugal effect on the contents is clearly visible (G-Force squashing).

My camera needs to be the latter.

 

[hevans1944]

You stated your centrifuge spins on an horizontal axis, yet refer to an upper chamber containing electronics and a lower chamber containing ball bearings. Does that mean the centrifuge is spun about a horizontal axis (like the propeller on a boat) and split horizontally into two tandem chambers rotating about a common axis? Or is the rotation axis really vertical so one chamber (with the electronics) can be considered the upper chamber "above" the other "lower" chamber?

How long does the experiment require the centrifuge to run at its operational speed?

In post #3 you mentioned needing a motor:

Where I am struggling - is to find someone who can recommend the correct components - PCB with required logic, best type of mini camera, leds or lights that work well as strobes, good tips for battery type, electric motors type etc etc...

is the centrifuge in the process of being constructed, or is it a commercial product you are adapting? What are its physical dimensions and what is its maximum rotational speed? Can you post some photos of your "centrifuge"?

Low-noise slip rings are available at truly outrageous prices, but you may be able to use batteries and wireless technology, or a rotating transformer-type coupling for both power and data, depending on how you construct the "upper chamber". Can it constructed with "RF friendly" plastic?

 

[(*steve*)]

Hop, a "like" on your post is insufficient.

note that Qi power us essentially via a transformer and the coils are (not surprisingly) circular. I see no particular reason why you couldn't have two concentric coils, one for power, the other for signal, however since your"centrifuge" has an exposed moving cover, there is no reason not to poke a short stiff antenna out along this axis.

your strobe light could be controlled by the relative angular position of a pair of magnets outside the centrifuge and detected by a hall effect device internally. Another option is to control it with an optical signal, but isolating it from your strobe may be an issue.

 

[hevans1944]

Yet another example of an OP telling us their "solution" rather than explaining what they are trying to DO. For all we know, this could be an example of ball-milling, and the OP wants to observe how the balls pulverize whatever substance is being milled. I think probably not, though, as ball-mills typically operate at slow speeds. But surely the OP wants to "freeze" each image with a strobe illumination to observe whatever process is occurring in the target chamber. Having the camera rotate with the chamber means the point-of-view is the same from one frame to the next, which will be helpful for analysis of the process.

Rotary transformers work pretty much the way you think: a cup and pot are used to hold two coils (one primary, one secondary) separated by a small air gap. The cup rotates and the pot remains stationary. You can couple power and data at the same time by adding modulation to the waveform used to couple power.

What really confuses me is why the OP is in charge of making this work... just saying. It is clear that the OP would prefer a turn-key solution from a contractor who knows how to build and integrate such a project in Australia. If I were there, I would probably make an offer of a cost-plus-fixed-fee contract after learning more details. Maybe you can do that for him, Steve. It is hard enough to make things like this work here, much less on the other side of the world, without being there in person. Oh, and thanks for the "like".