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alexeames
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Gertboard proximity sensor

Sat Sep 22, 2012 10:08 am

Anyone else noticed this effect? When set up to mess about with the LEDs, when I put my hand near the straps, the LEDs light up. It's controllable and predictable. I hope it doesn't mean I've messed something up. :lol:

There's a little video clip here to show what I mean...
http://raspi.tv/2012/gertboard-is-a-proximity-sensor

Does yours do this too?
Alex Eames RasPi.TV, RasP.iO

el10t
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Re: Gertboard proximity sensor

Sat Sep 22, 2012 11:09 am

Phew! I thought that was just me! I thought I had duffed it up somewhere - glad to see you get the same effect.

(Alex - looks like you've lost one of your motor connector grub screws)

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alexeames
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Re: Gertboard proximity sensor

Sat Sep 22, 2012 11:19 am

el10t wrote:Phew! I thought that was just me! I thought I had duffed it up somewhere - glad to see you get the same effect.
We can't both have made the same assembly mistake, so it must be an "undocumented feature" :D Well it's documented now. Loving it.
el10t wrote:(Alex - looks like you've lost one of your motor connector grub screws)
All four grub screws are there, but the leftmost one is a bit deeper set than the others. ;)
Alex Eames RasPi.TV, RasP.iO

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Tandy
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Re: Gertboard proximity sensor

Sat Sep 22, 2012 11:26 am

Haven't had time to look at it in any detail but I think the reason is probably because the Gertboard has no pull-up/down resistors on it so the inputs to the buffers are floating. Try either setting those IOs low or turning on the pull down resistors on the Pi and I suspect it will not happen.
Tandy - The home of electronics - www.tandyonline.co.uk

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alexeames
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Re: Gertboard proximity sensor

Sat Sep 22, 2012 11:41 am

Tandy wrote:Haven't had time to look at it in any detail but I think the reason is probably because the Gertboard has no pull-up/down resistors on it so the inputs to the buffers are floating. Try either setting those IOs low or turning on the pull down resistors on the Pi and I suspect it will not happen.
Thanks. Will have a play with that.
As long as it doesn't mean anything's broken, I think it's quite cool. 8-) :lol:
Although it was a bit alarming at first...
"Where's the short?"
"Did I put the board down on a piece of metal?" :shock:

I think I'll be making a balsa wood base pretty soon anyway. I've toasted a board before by putting it down on coins. :cry:
Alex Eames RasPi.TV, RasP.iO

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Gert van Loo
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Re: Gertboard proximity sensor

Sat Sep 22, 2012 5:44 pm

so it must be an "undocumented feature"
It is mentioned in the manual.
I was hesitating adding pull ups to the Gertboard as that would mean even more parts to solder.
Also there as no easy place to put the pull-up resistors unless I made them SMD and I tried to keep the number of SMD parts to a minimum.
So in the end... no pull-ups.

pygmy_giant
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Re: Gertboard proximity sensor

Sat Sep 22, 2012 6:00 pm

...and there was me bending my brain to design such a thing on purpose: http://www.raspberrypi.org/phpBB3/viewt ... in#p139918

Should just get a Gertboard!
Ostendo ignarus addo scientia.

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alexeames
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Re: Gertboard proximity sensor

Sat Sep 22, 2012 7:30 pm

Gert van Loo wrote:
so it must be an "undocumented feature"
It is mentioned in the manual.
Oops :oops: sorry.
Gert van Loo wrote:I was hesitating adding pull ups to the Gertboard as that would mean even more parts to solder.
Also there as no easy place to put the pull-up resistors unless I made them SMD and I tried to keep the number of SMD parts to a minimum.
So in the end... no pull-ups.
I probably wouldn't have understood what a pull up resistor was, to be honest. I'm still grinning that this board works at all after I put it together. :D I'm about half way through the tests and it's all OK so far.

I think it's an excellent product Gert. :D Looking forward to some "real computing" with my Y5 group later in the year. And I'm having lots of fun with it too. 8-)
Alex Eames RasPi.TV, RasP.iO

add1ct3dd
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Re: Gertboard proximity sensor

Thu Oct 18, 2012 2:24 pm

Oh my god I'm such an idiot, this is what is causing my random LED issues as well!

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