Pressure Sensitive Wall that triggers alarm

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JoshO76
 
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Pressure Sensitive Wall that triggers alarm

Post by JoshO76 »

My daughter is working on a science project. She decided to choose the option to solve a problem using electronics. When asked about a problem at her school, she said people writing on the bathroom stalls. This is what brings me here. What we dreamed up to do was a prototype was a pressure sensitive wall covering. When someone puts pressure on it, it would set off an alarm. I've never used Adafruit before, but my daughter and I read through the forums and put together the following supplied list. I saw a similar post and ADA_Support_Bill had an excellent response. Could someone please look over this list, and make any suggestions
Supplies:
1 - Flora: https://www.adafruit.com/product/659
1 - Pressure Sensitive Conductive Sheet: https://www.adafruit.com/product/1361
1 - Rotating LED Alarm light - https://www.adafruit.com/product/5134
1- 3 AAA battery enclosure: https://www.adafruit.com/product/727
I appreciate any assistance and direction.

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adafruit_support_bill
 
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Re: Pressure Sensitive Wall that triggers alarm

Post by adafruit_support_bill »

I saw a similar post and ADA_Support_Bill had an excellent response.
Can you post a link to the post you are referring to?

The conductive sheeting in your link can be used for home-made pressure sensors. This requires adding some conductive material to both sides of the sheet. It will probably require some experimentation to design something that can detect the pressure of writing.

The Flora will not be able to control the LED Alarm Light directly, you will need something like a transistor to switch the current.
https://learn.adafruit.com/transistors-101/example-uses

Another option (although more expensive) would be to replace the Flora with a Feather and add a Crickit board. The Crickit has built in drive circuitry that can handle the LED. It also has capacitive touch sensors built-in which might be an alternative to the pressure sensing sheet.
https://www.adafruit.com/product/3403
https://www.adafruit.com/product/3343

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JoshO76
 
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Re: Pressure Sensitive Wall that triggers alarm

Post by JoshO76 »

Thanks for the reply. Here's the original thread. viewtopic.php?t=192515
I was trying to make it a little fancier with the LED Buzzer. The original thread we found, you suggested the Gemma and a Piezo buzzer. If we were to stick with the Pressure sensor conductive sheet do you think putting aluminum foil in the back and front would be sufficient to send a signal to the Gemma to trigger the Piezo?
The revised supply list might look like this:
1 - Gemma https://www.adafruit.com/product/3501
1 - Conductive Sheet: https://www.adafruit.com/product/1361
1 - Piezo - https://www.adafruit.com/product/160
1- Power Supply - https://www.adafruit.com/product/727
Thanks again for your reply. I think my daughter will really have a fun time building this if we can get the right parts list.

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adafruit_support_bill
 
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Re: Pressure Sensitive Wall that triggers alarm

Post by adafruit_support_bill »

Aluminum foil might work.

First you need to attach it to the conductive sheet in a way that doesn't interfere with the electrical conductivity. Taping it around the edges should work. That way there is nothing between the foil and the conductive sheet.

You also need to connect wires to the foil. This can be tricky since the foil tears easily and there is no practical way to solder to it. But it you strip a long piece of wire and tape it along the edge of the foil, it should make good enough contact for your pressure sensor.

So a couple more things to add to your shopping list: Some wire https://www.adafruit.com/product/288
And some tape (blue 'painters tape' is easy to work with and would be a good choice for this)

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JoshO76
 
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Re: Pressure Sensitive Wall that triggers alarm

Post by JoshO76 »

Excellent. I appreciate your direction. I'll get that all added. Any other suggestions to make this project engaging? Would this be able to trigger a simple LED light or something?

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JoshO76
 
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Re: Pressure Sensitive Wall that triggers alarm

Post by JoshO76 »

Dought... Gemma is out of stock now.
Is there another comparable unit we could go with?

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adafruit_support_bill
 
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Re: Pressure Sensitive Wall that triggers alarm

Post by adafruit_support_bill »

A lot of chips are in short supply these days, so there are quite a few out-of-stock items. But we still have a lot of processor boards that would work. To narrow down the selection, first it would be helpful to know if you can manage soldered connections, or if you need a board where you can make connections without any soldering.

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JoshO76
 
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Re: Pressure Sensitive Wall that triggers alarm

Post by JoshO76 »

I do have a solder iron, but it wouldn't be a very high quality one. So if there's one that is very forgiving, and has large solder points I could manage.

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Re: Pressure Sensitive Wall that triggers alarm

Post by adafruit_support_bill »

Boards like the Gemma have large holes that can be used with alligator clips as in the image below, so no soldering is necessary. Other boards with the large holes include the Flora and the CircuitPlayground boards.
We do have the Flora in stock: https://www.adafruit.com/product/659
We also have the Circuit Playground Express and the Circuit playground Bluefruit:
https://www.adafruit.com/product/3333
https://www.adafruit.com/product/4333

Any of those boards are capable of doing what you need. The Flora is the simplest and least expensive. But the CircuitPlayground boards have a lot of additional features built in, including LEDs and a small speaker. So going that way, you could eliminate some of the other external parts.

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