Motorola E-Field Sensor

Posted 8 Jun 2003 at 01:56 UTC by steve Share This

Motorola designed the MC33794 E-Field sensor for use in automotive applications but it's such an interesting sensor, experimenters are beginning to have fun with it. The chip generates a 3-D electrical field and detects the size and shape of objects within the field. The June issue of Circuit Cellar has an article describing the sensor and Motorola's development board. Back in April, Motorola announced an E-Field design contest for the part with prizes going to the most interesting use. The sensor costs about $3 and a $25 evaluation module is also available.

Nuts and Volts has a Contest going on too, posted 8 Jun 2003 at 12:32 UTC by earlwb » (Master)

Nuts and Volts has a contest using the chip that is starting up. They were giving away a limited number of evaluation boards and two extra chips as well.

I got my kit. What I wanted to determine is if the sensors would work for detecting empty soda cans for a DPRG Contest Can-Can robot or not.

he problem with the DPRG contest is you have a ambient daylight problem with the huge plate glass windows on the East side of the Dallas Science Place, then the course has 1/2" by 6" board walls painted white as well.

Infrared sensors get a lot of interference from the daylight that comes in from the EastSide of the building, even if it is shaded. Next the flouresecent lighting overhead causes IR problems as the lights work on a near 38.5k frequency too. Ultrasound works OK, but you have problems when you get up close to a Can. Then if a can is near one of the walls, you have a problem finding the can and not the wall.

My idea is to use the wire antennas to "look down" on the course, as you find a can you can then zero in on it to pick it up. Anyway, we'll see what happens.

Oops Sorry it's Circuit Cellar instead., posted 8 Jun 2003 at 12:42 UTC by earlwb » (Master)

Sorry it's actually Circuit Cellar hosting the E field uses contest.

Free? Did I hear FREE?, posted 8 Jun 2003 at 16:41 UTC by jeffkoenig » (Master)

Hey Earl,

Do you have a link for the free evaluation board?

I've got lots of free time...

It's right on the Circuit Cellar page., posted 9 Jun 2003 at 01:49 UTC by earlwb » (Master)

This was the link as i last remember looking for it.

It's pretty cool what they are putting into cars nowadays. You need to download all the software from the website, as the EVM kits don't have anything in them. They even use a little PIC MCU for the serial interface to the PC demo program.

links, posted 9 Jun 2003 at 01:55 UTC by steve » (Master)

Both of the links you're looking for are in the article. They're out of free boards but are still selling them for $25.

Why again are these things in cars?, posted 9 Jun 2003 at 02:55 UTC by The Swirling Brain » (Master)

Why again are they putting these things in cars? Beep, Beep, Beep... Slow down, deer hazard ahead... Beep, Beep, Beep... Slow down, Police officer ahead... Beep, Beep, Beep... Speed up, Grandma crossing street - 100 points.

Why in cars, posted 9 Jun 2003 at 11:21 UTC by earlwb » (Master)

The car can then identify whether a person is in a seat and can pass on that information to the computer that controls the air bag deployment. It could also maybe determine how large a person is or heavy and the airbag computer can determine whether it needs to more forcefully deploy or not. If you put in a heavy box in the seat, the chip should be able to determine that as well. Also it can light up the seat belt light on the dash. More expensive cars use them to help adjust the suspension system depending on how many people are in the ca..

The airbag computer is the little back box they can use for evidence should you ever get into an accident. It records the last few seconds just before the impact. Somebody recently had them use it against them, when they were DUI and going over 100mph in a residential neighborhood, and they hit another car.

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