About Silicone Elastomer

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ferite
 
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About Silicone Elastomer

Post by ferite »

I bought a couple of Silicone Elastomers (https://www.adafruit.com/product/1611), and now have a couple of questions:

In the Item description is said: "On the bottom of each button is a conductive pad ring which can close a properly design contact underneath". However our measures on the black ring is in order of hundreds of kilo-ohms. Are something wrong with my keypads?.

Is it posible to paint some letter or symbol on the buttons. If so, what kind of paint should be used.

Thanks for your help!.

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adafruit_support_rick
 
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Re: About Silicone Elastomer

Post by adafruit_support_rick »

Are your buttons not working?

I'll check on the paint...

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adafruit_support_bill
 
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Re: About Silicone Elastomer

Post by adafruit_support_bill »

Check out the design of our Trellis board: https://learn.adafruit.com/adafruit-tre ... led-keypad
It is designed so that there are multiple points of contact. And the button-sensing is handled by the HT16K33 chip.

ferite
 
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Re: About Silicone Elastomer

Post by ferite »

Hi.
Actually, my plan was to make a custom board, basing the contacts on Trellis board, but controlling them with the GPIOs of a dev board. Is it necessary a special controller like HT16K33?

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Re: About Silicone Elastomer

Post by adafruit_support_bill »

It should be possible via GPIO. The HTK16K33 just simplifies things a bit because it has the row/column scanning logic built-in.

ferite
 
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Re: About Silicone Elastomer

Post by ferite »

I have my software application working with a standard 4x4 Matrix Keypad already. My concern is if the same electronic design, will work with a keypad based on the elastomer, because the current keypad makes a perfect bridge (short) between columns and rows when a key is pressed, whereas the elastomer based keypad would not make a 0 ohm bridge, but a hundreds of kilo-ohms one. I don't know if this resistance is not going to let the MCU detect the High level that is raised whenever a key is pressed.

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adafruit_support_bill
 
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Re: About Silicone Elastomer

Post by adafruit_support_bill »

With multiple points of contact over a wide area, it will like several resistors in parallel and the effective resistance should be less.

ferite
 
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Re: About Silicone Elastomer

Post by ferite »

Thanks for the clarification. By the way. Do you have a recommendation on the kind of paint to be used on the elastomer?.

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adafruit_support_bill
 
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Re: About Silicone Elastomer

Post by adafruit_support_bill »

I don't have any first-hand experience with it, but this looks promising: http://www.inkcups.com/inks-thinners/sc ... icone-ink/

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latigidon
 
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Re: About Silicone Elastomer

Post by latigidon »

Hi, I'm wondering about the dimensions of the conductive ring of the silicone button set, and whether I could fit a 1206 LED underneath the button. I have the EAGLE file and I see there will probably be a conflict with the top track of the Trellis board. I would therefore need to reshape the pad.

Thanks!

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adafruit_support_bill
 
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Re: About Silicone Elastomer

Post by adafruit_support_bill »

The 3D CAD files will have all the dimensions. They are located in the Github repository: https://github.com/adafruit/Adafruit_Trellis

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latigidon
 
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Re: About Silicone Elastomer

Post by latigidon »

Many thanks, I have the hole dimensions now (I couldn't see the conductive pad) which is close enough to what I need.

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