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#1 2008-06-12 17:36:00

chalkmarrow
Scratcher
Registered: 2007-05-18
Posts: 100+

Resistance Values

I'm happy to see there's a forum just for sensor boards, and welcome to the forums, Lutz. We just received our board, and it works great.

FYI for anyone playing with the resistance values, we did some experiments and figured out that, for our board, the resistance sensor value (0-100) that the PicoBoard produces is related to the actual resistance (in KOhms) across the alligator clips by the something like the following equation:

sensor value = a*ln(bx+1) where, approximately:

a=19.5
b=0.9

BUT, if you are only interested in low resistance values between 0-10 KOhm, the following simple relation works real well:

sensor value = a*x, where a is approximately 5.57

Last edited by chalkmarrow (2008-06-16 12:38:46)

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#2 2008-06-12 20:50:53

Paddle2See
Scratch Team
Registered: 2007-10-27
Posts: 1000+

Re: Resistance Values

I've been thinking about getting a Scratchboard...have you done anything interesting with it yet?  Keep us posted!


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#3 2008-06-12 21:24:43

Cyclone103
Scratcher
Registered: 2008-03-20
Posts: 500+

Re: Resistance Values

chalkmarrow wrote:

I'm happy to see there's a forum just for Scratchboards, and welcome to the forums, Lutz. We just received our scratchboard, and it works great.

FYI for anyone playing with the resistance values, we did some experiments and figured out that the resistance sensor value (0-100) that the scratchboard outputs is related to the actual resistance (in Ohms) across the alligator clips by the something like the following equation:

Value = a + b*ln(Resistance)

where, approximately:

a=-8.264
b=1.450

This relation is more accurate for low resistance values than it is for high resistance values.

Who is "we"? Are you really a team of people that I thought was one person right until now??


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#4 2008-06-12 22:46:50

chalkmarrow
Scratcher
Registered: 2007-05-18
Posts: 100+

Re: Resistance Values

Paddle2See: Just playing with it now. It's pretty fun, really. I wish it could produce some form of output (rather than being exclusively input), but perhaps in some later rev. There's a project in progress that I'll post a prototype simulation for later this week.

Cyclone103: I'm old like Paddle2See (xD) , but this login is used by my kids as well, from time to time. We do projects together so I can teach them how to program.

Last edited by chalkmarrow (2008-06-12 22:48:43)

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#5 2008-06-12 22:54:46

Bluestribute
Scratcher
Registered: 2008-01-24
Posts: 1000+

Re: Resistance Values

chalkmarrow wrote:

Paddle2See: Just playing with it now. It's pretty fun, really. I wish it could produce some form of output (rather than being exclusively input), but perhaps in some later rev. There's a project in progress that I'll post a prototype simulation for later this week.

Cyclone103: I'm old like Paddle2See (xD) , but this login is used by my kids as well, from time to time. We do projects together so I can teach them how to program.

I also thought that you were like a high schooler or something. And would you recommend getting a Scratch or Pico board?


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#6 2008-06-12 23:57:39

chalkmarrow
Scratcher
Registered: 2007-05-18
Posts: 100+

Re: Resistance Values

Bluestribute: It looks to me like they are exactly the same, but the Scratch board is 10-20 dollars cheaper for some unknown reason.

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#7 2008-06-12 23:58:21

Bluestribute
Scratcher
Registered: 2008-01-24
Posts: 1000+

Re: Resistance Values

I might see if I can get one ("MOM!")


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#8 2008-06-13 00:01:14

Bluestribute
Scratcher
Registered: 2008-01-24
Posts: 1000+

Re: Resistance Values

Are thet easy to hook up?


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#9 2008-06-13 10:35:22

geckofreak
Scratcher
Registered: 2007-12-20
Posts: 100+

Re: Resistance Values

Bluestribute wrote:

Are thet easy to hook up?

They just fit in a usb slot. Of coarse their easy to hook up.


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#10 2008-06-13 13:36:25

Bluestribute
Scratcher
Registered: 2008-01-24
Posts: 1000+

Re: Resistance Values

geckofreak wrote:

Bluestribute wrote:

Are thet easy to hook up?

They just fit in a usb slot. Of coarse their easy to hook up.

But it says I need to download all of this hardware and stuff


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#11 2008-06-13 16:47:55

Cyclone103
Scratcher
Registered: 2008-03-20
Posts: 500+

Re: Resistance Values

chalkmarrow wrote:

Paddle2See: Just playing with it now. It's pretty fun, really. I wish it could produce some form of output (rather than being exclusively input), but perhaps in some later rev. There's a project in progress that I'll post a prototype simulation for later this week.

Cyclone103: I'm old like Paddle2See (xD) , but this login is used by my kids as well, from time to time. We do projects together so I can teach them how to program.

Thats nice! If I was old enough to have kids, I am sure I would be teaching them too. Most of your project scripting confuses me utterly  smile  but I try to figure out how it works.


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#12 2008-06-16 10:53:58

Lutz
Scratcher
Registered: 2007-05-18
Posts: 27

Re: Resistance Values

Bluestribute wrote:

geckofreak wrote:

Bluestribute wrote:

Are thet easy to hook up?

They just fit in a usb slot. Of coarse their easy to hook up.

But it says I need to download all of this hardware and stuff

They are quite easy to use. There is a driver for the Cable that hooks up the board to the computer, but that's it.

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#13 2008-06-16 12:23:17

chalkmarrow
Scratcher
Registered: 2007-05-18
Posts: 100+

Re: Resistance Values

I agree with Lutz: They made it really easy to set up. An 8-year old installed it and downloaded the drivers by himself on my PC (he was eager to use it, and I wasn't home at the time).

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#14 2008-06-16 12:23:55

Bluestribute
Scratcher
Registered: 2008-01-24
Posts: 1000+

Re: Resistance Values

chalkmarrow wrote:

I agree with Lutz: They made it really easy to set up. An 8-year old installed it and downloaded the drivers by himself on my PC (he was eager to use it, and I wasn't home at the time).

Alright. I'll ask my mom (or other relatives *wink wink*)


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#15 2008-06-16 14:02:08

terminator68
Scratcher
Registered: 2008-02-26
Posts: 1000+

Re: Resistance Values

Wat's a scratch board, Paddle?


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#16 2008-06-16 14:04:36

terminator68
Scratcher
Registered: 2008-02-26
Posts: 1000+

Re: Resistance Values

how much is a scratch board if ya have to buy it, chalkmarrow?


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#17 2008-06-16 15:42:21

chalkmarrow
Scratcher
Registered: 2007-05-18
Posts: 100+

Re: Resistance Values

terminator68: i think it's about $50:

http://www.picocricket.com/order-picoboard.php

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