IPON Phase 1 Decisions

by Natalia Fargasch Norman

in IPON

As I move to the next phase on the IPON project, and before I commit to a circuit to be implanted in the first plush object, I was considering the following:

In my last post I presented the circuit I’ll be implanting in the plush objects; it used a force sensor (FSR) to be placed on the plush animal’s nose, which when pressed, will trigger the behavior response to that. (By the way I connected the sensor to a digital input, which means that the force applied, an analog value, was translated to either a 0 or a 1; it would have been better to use an analog pin and calibrate it so that it wouldn’t require so strong a force. The cuttoff used on the digital pin requires too much force to be used.)

I’m thinking instead of a FSR to use a push-button, as it will represend a savings of over $5 per plush object (remember, this project’s intended goal is to serve as electronics teaching to high-school at-risk students. So price is an important design factor).

So given the prices below, I think I’m going to go with buttons instead:

Price consideration: FSR x pushbuttons

FSR: $6.26 x Pushbuttons $0.95 or maybe these cute pink ones from Sparfun!

Pushbuttons

Now onto where I’m still undecided:

Trying to decide what is easier: conductive thread or conductive tape?

First the price comparison:

Conductive thread

Cost: $5.95 for 85’ (I have no idea how much would be required per circuit).

Will also need “snappy thingies” (they’re called sew-on snaps) to connect the soldered wire ends to sewing points (have no idea how many would be necessary).

Why I’m reluctant: well… sewing! (Can you tell I’m afraid?) Also a lot of work with the soldering and sewing, and it requires lots of manual precision, AND it is hard to undo (remember, changes to the circuit may occur throughout the project’s life). Hmm… maybe if this turns out to be a better option, I could save it for the final project when circuits are not likely to change anymore…

Conductive tape (see: Ni/Cu/Co FABRIC TAPE down the page)

Cost: $19.95, 1” x 25’ which I think it’s plenty since the 1” width yelds four 1/4” strips of tape that are what the circuit connections requires.

Why this seems like a better option to me: the circuit is easier to build, no soldering required, and it’s easy to undo if changes to the circuit occur (which are likely).

Soft circuit options

Pictured above are the cross-stitching fabric (whose hole spacing diagonally is perfect to fit the Arduino socket, or I may just use the mini breadboard), along with the roll of conductive fabric, conductive thread and the sew-on snap fasteners.

Which direction do you think I should go? The easier tape route, the sewing route, or something else altogether?

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{ 5 comments… read them below or add one }

Tom Fangrow

Interesting project! Force sensors can be very inexpensive, especially if you make your own. You know how some IC chips come with a little piece of black foam on the bottom? Strip a couple of wires and push them into the foam, then cover with tape to hold everything together. Now you have a variable resistor force sensor! I made one yesterday and it works great. The resistance is 3K and goes down (fairly linearly) to around 1K when pressed hard. If you want, I can send you a video of my $0.00 force sensor controlling an LED bar graph.

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Natalia

That’s great to know! Thanks Tom!

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Steven Pearson

What a great idea!

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Steven Pearson

Hi Natalia, I have just discovered your site via twitter and love your project!
I think that you are right with the tape for the short term, but for the final more finished version using the conductive thread and snaps…

I am looking forward to see the next steps. Nice project!
Steven

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Ryan Hatfield

You could always just run two wires really close to the nose on the inside and use a capacitive touch type switch, that way no pressure is required just being near it. You can calibrate sensitivity in code. Android has the CapTouch library, but I’m a big TI fan and some of their chips with capacitive touch built-in are really cheap! They also recently came out with a WiFi chip that’s cheap http://tinyurl.com/ahmxcmo .. in case you wanted to add your Plushy’s to the Internet of things!

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