Teensy 3.2 output range

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razataz327

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Hi all I am planning to build a pixel mega tree with 20, 8 ft pixel strips ws2812b. They are 30 led per meter. I live in Alberta and we can get lots of snow 4 to 6 ft on the lawn. I want to put the tree on the roof, out of the snow and better visibility from the road. My questions are; what is the cold temp rating of the teensy 3.2, and how far can the output lines be from the teensy to the pixel strips?
Do I need to put it in an enclosed box with some heat as the temps can get to minus 40c here..
It appears I will need two teensy to run the tree. I wanted to add a mico sd card on the one teensy instead of connected to the pc. Will it work with multiple ones connected?
Thanks very much for your help.
Garnet
 
The crystal is rated down to -10C. The rest of the parts are rated to -40C, so it will very likely work all the way down to -40C but perhaps with slightly less timing accuracy.

However, those WS2812B LED chips and the SD card probably aren't rated for cold temperature. They might work too, but you might wish to test them, maybe in a cooler with a block of dry ice.

If you're going to add a SD card, maybe Teensy 3.5 would be a better choice. It has a SD socket built in.
 
The crystal is rated down to -10C. The rest of the parts are rated to -40C, so it will very likely work all the way down to -40C but perhaps with slightly less timing accuracy.

However, those WS2812B LED chips and the SD card probably aren't rated for cold temperature. They might work too, but you might wish to test them, maybe in a cooler with a block of dry ice.

If you're going to add a SD card, maybe Teensy 3.5 would be a better choice. It has a SD socket built in.

Thanks for the info. I will do some testing. I have the sd socket already and several teensy 3.2.
Can a wireless unit be added to the teensy so I won’t have to run a cable to it from the pc if I go that route instead?
Tha
Garnet
 
Hello.
I'm curious. What are you using the cable for. I didn't understand from the first post regarding "I wanted to add a mico sd card on the one teensy instead of connected to the pc"
 
Hi Gibbedy. The cable was referring to the connection from the teensy to the pc, USB connection. I don’t think that distance can be very long. My teensy will be about 40 ft , on the deck, from the pc, which is in the garage. The mega tree will be up on the roof about 30ft from teensy. I may need null pixels from teensy to tree. I saw that was done on by people on another topic.
Garnet
 
I see, but is the cable used for programming the teensy or are you using it to feed data to the teensy.
I was just going to say if it is used for programming only then I use a pi zero over wifi to remote program my teensy's, exept in my case it's to avoid the insects and not the cold.
 
I was going to program it but will want to change some patterns at times. It being in the garage where it will be warm is my best option. Not sure if I prefer cold over insects, all depends how big and how many. We can get to minus 40 plus windchill plus 5ft plus of snow.
 
Yikes. Yeah null pixels or rs485 to keep the teensy close. Post a pic when it’s all running.
 
RS-485 … web search ...
TIA-485-A, also known as ANSI/TIA/EIA-485, TIA/EIA-485, EIA-485 or RS-485, is a standard defining the electrical characteristics of drivers and receivers for use in balanced digital multipoint systems. The standard is published by the Telecommunications Industry Association/Electronic Industries Alliance (TIA/EIA).
RS-485 - Wikipedia
https://en.wikipedia.org/wiki/RS-485

… RS-485 is a serial wiring made to work over larger distances with adjusted electrical properties over standard serial
 
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RS485 is a way to send serial signals over a long distance. Each signal is meant to be sent over a twisted pair of wires. Usually a shielded cable is used, where the shield is connected to GND at both ends. Unsheilded cable can also be used, but it's a good idea to have at least 1 extra wire in the cable which you connect to GND on both sides.

Usually the chips which convert between ordinary signals and the pair of signals for RS485 have both a transmitter and a receiver in an 8 pin chip. 2 of the pins control whether the transmitter and receiver are active. The simplest way to use these chip is to wire the RE & DE pins high on the sending side, which turns off the receiver and keeps the transmitter always on. At the other side, you would connect RE & DE low, so the transmitter is disabled and the receiver is always on.

The other common use is to connect RE & DE to a pin, so you can sometimes transmit and other times receive. This requires a careful protocol, usually where one side is the "master" which asks questions and the other "slave" side only turns on its transmitter when replying. Teensyduino's has a special transmitEnable(pin) function in Serial1 to automatically control this signal, so you can just send and receive data by such a protocol and the control of the pin is done automatically.

RS485 is so effective over long distances because it transmits as a pair of opposite signals (called "differential pair"). The idea is interference which happens over the long line tends to do the same bad stuff to both signals. The receiver is designed to only look for the difference, even if it's very small, and ignore anything in common, even if it's very large. Most receivers chips are able to handle the signals becoming negative voltages or higher than 5V and still pick out the original signal. This lets you send signals many thousands of feet. But it does mean you need to add these chips, or small boards with these chips.

RS485 isn't commonly used for consumer products, but it's pretty much the standard for connecting industrial and commercial building control systems.
 
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