# Will house burn down enclosing camera in foam ball?

• Paul Uszak
In summary, the conversation discussed putting a web camera inside a foam ball and the potential for heat build-up and safety concerns. The camera runs on 5V DC and the sphere is made of expanded polystyrene. The question was posed about the temperature rise inside the sphere above ambient. Calculations were mentioned, resulting in a 7 degree rise, and the rated temperature range for the camera was unknown. The idea of using the camera for entropy was also brought up. Suggestions were made for conducting a trial with a thermometer and covering any holes for light. The conversation ended with discussing the possibility of a noise filter affecting the randomness of the data collected.
Paul Uszak

## Homework Statement

This is not exactly homework, but is homework level so this is probably the best place to ask rather than the more learned sections. However, I'm prepared to defer to your better judgement.

I want to put a web camera inside a foam ball. The camera is a retail product so it's passed relevant EU safety standards. My concern is will heat build up cause the foam to melt, or burn my house down by starting a fire.

The camera runs off 5V DC consuming approximately 500mA.
The hollow sphere is of outside diameter 300mm with a wall thickness of 20mm. I would characterise this as a thin walled vessel.
The sphere's made of expanded polystyrene /Styrofoam.
This is all the data I know for certain.

What will the temperature rise be inside the sphere above ambient?

## Homework Equations

As this is a safety issue, I'm not giving any equations that I have used. I do not want to influence /prejudice anyone's thinking. I'd very much welcome an independent assessment.

## The Attempt at a Solution

I've considered the thermal conductivity of the material, the power dissipation of the camera and the sphere's mean surface area. I've also assumed that the thermal conductance through the camera's mounting to the outside is negligible.

I've calculated a 7 degree rise inside the sphere. I deem this acceptable but what do you think?

Is the camera going in the centre of the hollow ball? If so how will the camera see out? Lens angle will determine the size of the hole needed?

Inside diameter is 260mm (0.26m).
Area 4piR^2 = 0.21 sqm

Thermal conductivity polystyrene (k) about 0.03 W/(mK)

Power = k * Area * T / thickness

T = Power * thickness / (k * area)

= 2.5 * 0.02 / (0.03 * 0.21)

= 8 degrees.

What's the rated temperature range for the camera?

If your house does burn down don't blame me!

CWatters said:
Is the camera going in the centre of the hollow ball? If so how will the camera see out? Lens angle will determine the size of the hole needed?

Mea culpa. It's difficult to write down all the things that aren't obvious to me.

Yes, the camera is at the centre of the sphere and the camera is totally enclosed. The camera does not need to see out of the sphere. I realize that there will be differential heating of the sphere due to convection currents within, but I don't have the resources to model that kind of heat flow. I'm really only looking for a non dynamic steady state approximation that I hope averages out to 7ish degrees.

The specification available to me only gives a storage temperature range (-20 to +60 degrees C). The apparatus will be operated at UK room temperature not likely to exceed 40 degrees. With a 7 degree thermal gain it should be okay I feel.

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Foam shells are cheap? Set up a trial with a thermometer inserted through a covered hole so you can retrieve it after 5 or 6 hrs to note the reading.

We are all curious to learn what will be revealed by filming the inside of a closed foam ball?

NascentOxygen said:
Foam shells are cheap? Set up a trial with a thermometer inserted through a covered hole so you can retrieve it after 5 or 6 hrs to note the reading.

We are all curious to learn what will be revealed by filming the inside of a closed foam ball?

I'm hoping random noise will be revealed. This will then be used as an entropy source for a true random number generator.

http://www.reallyreallyrandom.com if I may.

I suspect some light will get through 20mm of foam so there might be some sort of day/night cycle but that could easily be fixed with some paint.

Pretty sure web cams will have some sort of noise filter built in. Noise is the enemy of compression techniques. The filter won't eliminate all noise but it might remove some frequencies making it uncertain how random it is.

CWatters said:
I suspect some light will get through 20mm of foam so there might be some sort of day/night cycle but that could easily be fixed with some paint.

This may be getting off topic; however... Good call, but I've got that issue covered - get it?

As for the filter, I don't think that it's possible to substantially remove the noise I'm looking for. What's a PITA is the JPEG algorithm itself. It acts simultaneously as both an ersatz low pass filter reducing the entropy available to me for extraction, and increasing pseudo entropy due to it's coding specification making entropy characterisation problematic. I'll post my findings on the reallyreallyrandom website.

## 1. Can enclosing a camera in a foam ball prevent a house fire?

While enclosing a camera in a foam ball may seem like a good idea for fire prevention, it is not a reliable method. The foam ball may not be fire-resistant and could potentially catch fire itself, causing more damage. It is always best to follow proper fire safety protocols and not rely on unconventional methods.

## 2. Will a foam ball completely protect a camera from fire damage?

A foam ball may provide some level of protection for a camera, but it is not a foolproof solution. In the event of a fire, the foam ball may not be able to withstand high temperatures and could potentially melt or catch fire itself. It is always best to properly store and protect valuable items, such as cameras, in fire-resistant containers or safes.

## 3. How can I ensure my camera is safe from a house fire?

The best way to ensure your camera is safe from a house fire is to follow proper fire safety protocols. This includes keeping flammable materials away from potential fire hazards, installing smoke detectors, and having a fire escape plan. Additionally, storing valuable items in a fire-resistant container or safe can provide an extra layer of protection.

## 4. Will a foam ball make a camera more fire-resistant?

No, a foam ball will not make a camera more fire-resistant. While it may provide some level of protection, it is not designed to withstand high temperatures or flames. It is always best to properly store valuable items in fire-resistant containers or safes to ensure their safety in the event of a fire.

## 5. Is it safe to leave a camera enclosed in a foam ball unattended?

No, it is not safe to leave a camera enclosed in a foam ball unattended. If a fire were to occur, the foam ball could potentially catch fire and cause more damage. It is always best to properly store and protect valuable items, such as cameras, in a fire-resistant container or safe. It is also important to never leave potentially hazardous objects unattended, especially in the event of a fire.

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