October 03, 2006

Case Study: Effective Kiosk Design

A successful kiosk design isn’t only appealing and functional, but also reliable, secure, and easy to maintain. Nice writeup looking at it from an engineering perspective.

Source Link

by John Jedrzejewski, Neil Brashnyk, and Scott Vahlsing

From retail environments to airports to hotels, interactive kiosks are practically everywhere you turn in many public venues. Enabling users to conveniently perform a range of tasks, including retrieving information and buying tickets, these devices are only useful, however, when they’re working properly. When a kiosk malfunctions, which most of us have experienced, the failure is often due to overheating of electronic components inside the enclosure. That’s why anyone designing a kiosk containing such electronic devices must know the keys to keeping it functioning properly. Here’s a look at how to ensure reliability in your kiosk design, starting with an understanding of the basics of heat and airflow.

Inside the enclosure
Any system that requires power will generate heat. Electronic equipment is typically designed so that when it’s located in a relatively open space indoors at room temperature, heat dissipation through the air is sufficient to keep the equipment from overheating. However, when you place a piece of electronic equipment in an enclosure, you’re creating a local ecosystem for that equipment. The heat produced by the equipment must somehow be removed from this local environment to prevent failure.

Ambient and operating temperature
Ambient temperature is the temperature in the area immediately surrounding a piece of electronic equipment. When the device is sitting on a table in an open room, the ambient temperature is the room temperature. Inside an enclosure, the ambient temperature is likely to be significantly higher than the room temperature outside the enclosure.

If a device is operating in an ambient temperature above the operating temperature range specified for the device, it may overheat, reducing the life of the unit or causing it to fail. A typical operating temperature specification is 10 degrees C to 40 degrees C or 50 degrees F to 104 degrees F.

Types of heat transfer
Heat transfer takes place in three ways:
• Conduction takes place when heat travels through material.
• Convection takes place as air circulates and carries heat with it. Natural convection is the result of hot air rising. Forced convection occurs when air is blown across the surface of a device, moving heat away.
• Radiation occurs when heat is transferred electromagnetically away from a device such as a stovetop burner, for example. In an enclosure, radiation is typically not a significant heat transfer mechanism.

In most enclosures, the rate that heat is dissipated depends primarily on heat transfer by convection. Convection can be enhanced by increasing air circulation through appropriate placement of vents, and in some cases, by installing fans.

After getting a better grasp on the basics of heat and airflow, it’s necessary to consider how these factors should influence your initial design.

Estimating heat generation

Due to conservation of energy, all power used in a system is eventually converted to heat. Some energy is immediately converted to heat due to inefficiencies in the system, while the remaining power makes the transformation as it’s consumed by equipment in the system.

Therefore, an estimate of the power used in a system can be used to represent the amount of heat generated. Although an estimate based on the assumption that equipment is running at its maximum power rating will typically overestimate the amount of power that’s consumed, this allows for other variables that are more difficult to take into account.

Full article

Posted by keefner at October 3, 2006 07:52 AM