Society of Robots - Robot Forum

Electronics => Electronics => Topic started by: Asellith on September 22, 2012, 10:33:46 PM

Title: EZ1 Sonar problems outside
Post by: Asellith on September 22, 2012, 10:33:46 PM

Ok I've been out of the robot scene for a bit and our new makerspace in Pensacola ECCMakers.com (http://ECCMakers.com) has pulled me back in. I don't have much time to work on stuff any more after starting my own company but I did do more work on an old project to showcase at a makerspace event today.

Here is a video of the bot working just fine in my house.

http://youtu.be/5AFr27_udME (http://youtu.be/5AFr27_udME)

It even worked in the space this morning.

The event was a sustainable concert that (with some makerspace help) built a solar and pedal powered PA system and had an all day concert and the PA system was off the grid the entire time.

We had a booth for showing off projects and I tried to get my bot to work in the parking lot.

I have 3 continuous rotation servos with Omni-Wheels, An Axon II, and 3 EZ1 Sonar sensors.

I didn't have time for full blown Omni-Movement so I compromised with just backing away from anything when a sensor read 25cm or less. Rotates for 0.5 secs if two sensors trip.

Works as planned inside but I take it outside and it just rotates. So the only explanation I can come up with is something is screwing with my sensors and they are tripping early.

It is really close to the ground so I put some spacers on the sensors and tried to get it off the ground more. It still just spins.

The parking lot was a bit rough but I found a small and level concrete slab. Still rotates.

So any ideas on what might have been screwing with my sensors?

Title: Re: EZ1 Sonar problems outside
Post by: sufendi on September 24, 2012, 08:32:50 AM

i think you need to read the sensor datasheet first. in normal situation an ultrasonic sensor will not send back his measured distance if the distance is too far ( max<5m  for normal ultrasonic sensor).
i hope my answer will help you.

Title: Re: EZ1 Sonar problems outside
Post by: Asellith on September 24, 2012, 11:04:18 AM

I'm using the analog output. So if anything the sensors should just read max range not 0 VDC. I don't see anything on the datasheet that would explain what the sensor does to the analog output if it doesn't get a bounce back. The PWM just holds high if no target is found. I'd guess that when it updates the analog output that it just sets it to max.

Title: Re: EZ1 Sonar problems outside
Post by: Admin on November 11, 2012, 08:23:18 AM

I'd try bending the brackets holding your sonar to aim the sonar slightly upwards.

The ground is probably within the detected cone after a few feet of range (which it isn't inside because the walls are so close).