Trinket Altimeter

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tozian
 
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Trinket Altimeter

Post by tozian »

I'm trying to make an altimeter for a model rocket using a trinket and a barometric pressure sensor (it has to be real small.) I have two questions.
  • What is the best (as well as most inexpensive) way to power it?
  • What is the best way to store a recorded altitude?

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adafruit_support_mike
 
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Re: Trinket Altimeter

Post by adafruit_support_mike »

A model rocket will make short flights, so you probably don't have to worry about battery life.

LiPo cells have the best energy density on the consumer market, and these are pretty small:
https://www.adafruit.com/products/1570 - 100mAh
https://www.adafruit.com/products/1317 - 150mAh

All our pressure/altitude sensors are small:
https://www.adafruit.com/categories/114

Whichever one you choose, you'll need some kind of microcontroller to run it, and for sheer lack of size, it's hard to beat the Teensy:
https://www.adafruit.com/products/199

That uses the same microcontroller as the Arduino Leonardo or Micro, so it's generally compatible with Arduino code.

For storage, it's a toss-up..

The WS25Q80BV Flash chip is small, but you have to read and write the data directly. You'd need a separate sketch to pull the data out of the chip and move it to a computer:
https://www.adafruit.com/products/1564

A Micro-SD card is also small, though our breakout adds some size to it. The advantage is that you can pull the card out of the connector and plug it directly into a computer:
https://www.adafruit.com/products/254

tozian
 
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Re: Trinket Altimeter

Post by tozian »

I can't use an Adafruit Trinket? I can power a 3.3v one with one of these, right? Is there a definitive tutorial for the tiny flash library?

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adafruit_support_mike
 
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Re: Trinket Altimeter

Post by adafruit_support_mike »

The Trinket can talk to the Flash chip (barely), but doesn't have enough memory to work with an SD card.

The only code we have for the Flash chip is here: https://github.com/adafruit/Adafruit_TinyFlash, and it has an 'advanced hacking' challenge rating. One 256-byte page of Flash is half the Trinket's total SRAM, so almost everything is written in low-level code.

tozian
 
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Re: Trinket Altimeter

Post by tozian »

Okay, I have an Adafruit OLED screen laying around that I'm not using. I think I'll use that to display the highest altitude reached. Using a barometric sensor and an oled together won't be a problem right?

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adafruit_support_mike
 
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Re: Trinket Altimeter

Post by adafruit_support_mike »

The OLED and sensor shouldn't interfere with each other, but a Trinket doesn't have enough memory to run an OLED.

The smallest OLED we have has a 128x32 display area. The display buffer for that would consume 512 bytes of RAM, and a Trinket only has 512 bytes of RAM. There wouldn't be any memory left for anything else.

tozian
 
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Re: Trinket Altimeter

Post by tozian »

I'm postponing this project in favor of a different one for now. It's windy this season anyway. Thanks for all your help.

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adafruit_support_mike
 
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Re: Trinket Altimeter

Post by adafruit_support_mike »

Fair enough.

Putting a project on hold is always a good excuse to look for other small projects that use bits of the same hardware, or just to tinker with things when you have a few minutes. You can pick up a lot of background knowledge from a batch of 15-minute "let's see what this does" experiments.

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