Pi-users July 2013

pi-users@socs.uoguelph.ca

2 participants
3 discussions

who is coming to July 18 meeting?
by Judi McCuaig 17 Jul '13

17 Jul '13

Hi folks, I'm unfortunately really busy this week and can't make the pi-users meeting on Thursday. That said, you don't really need me to have a meeting- if there are people who plan to be there- I will make sure you have access to meeting space. I think it would be really interesting to see what progress people have made on their robots. Reply to the list if you were planning on being at the meeting and I'll help you organize it. Judi

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Distance sensing for the Pi
by Rick Knoop 05 Jul '13

05 Jul '13

Hi Everyone, For those of you who are taking part in the car challenge we were talking last night about different approaches to get the car to detect the wall. I figured I would save you all some research if you chose to use a distance sensor; one of the cheapest sensors available on the market is the HC-SR04 arduino sensor . This sensor takes a 10 microsecond signal and responds with a signal detailing how long it took for the signal to bounce back; or the distance to the object is half the time divided by the conversion of microseconds to m/s such that : distance in cm = (duration/2) /29 There are two small problems with this sensor and the pi though: 1. It sends a 5V signal as output which since we are using the GPIO pins on the pi (3V3) has a chance of shorting the pi , this can be prevented by using voltage divison ; there are wiring diagrams available that are specific to the pi and this sensor but the math tells me the resistance given in the diagram will result in a 2V1 signal to the pi. 2. The sensor when interfacing directly with the pi has a standard deviation of around 8%; this is due to the nature of having the os able to interrupt your code, but if you are using an arduino to the distance sensing though it comes to a 1cm standard deviation up to 2 metres. I will probably end up getting an arduino uno as they are not too expensive and I prefer the more accurate sensing. The hyperlinks are just there to show how cheap it is possible to get them on ebay choose vendors as you wish. Rick Knoop

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Thursday night meeting
by Judi McCuaig 03 Jul '13

03 Jul '13

Its meeting-week again! This week we'll do our regular 'what has everyone been doing' round robin, and then we'll see who has robot plans so far. We'll spend a tiny bit of time planning out a few more parameters for the robot-race contest and maybe set some deadlines. Robots can be constructed in teams or by individuals- we don't care. Please let me know if you're planning on building one so that I can get an idea of how many judges I might need to conscript. Judi

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Pi-users July 2013