LSM303 Overheating

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robbgodshaw
 
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LSM303 Overheating

Post by robbgodshaw »

Hello,
I am using an Adafruit LSM303 Accel/Magnetometer combo and a Tennsy 2.0.
As of tonight, it gets hot enough to burn my finger within a second of being plugged in.
I am using only 4 of the pins on the breakout, SCL, SDA, Vin, GND. My voltage source is stable (computer USB) my wiring in not faulty. Despite the fact that it is about 200°F, it is giving me accurate data. (It is transmitting true heading over Serial to my Mac.) I have only dared 6 seconds of use, as I cannot imagine it is going to last long like this.
I have been using the sensor in a nearly identical set up for the past 40 days with no issues whatsoever. Direct wired to a Teensy.

It gets a bit weirder-
6 months ago, working on a similar project, I had an identical experience with the LSM303 FLORA module. The difference there was I was using a rPi in place of the teensy. I was running it at 3V3, and I found no wiring faults. In that case, I got a very square burn on my index finger tip. Again, it was working fine, for several weeks, with no issues. No change, and then sizzle.

I have no Google results for "LSM303 Overheating", which makes me think I am doing something wrong. I cannot imagine what could cause my luck on this sensor, twice, and on totally different setups.

At this point, It starts heating when 5v is applied, even with the SDA and SCL floating.

I'd love some insight.

Best,
-Robb http://robb.cc

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adafruit_support_bill
 
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Re: LSM303 Overheating

Post by adafruit_support_bill »

We haven't had any reports of these overheating before. Is there a specific component on the board that is getting hot?

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robbgodshaw
 
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Re: LSM303 Overheating

Post by robbgodshaw »

Hi Bill,
The bit that is getting hot is the actual compass module. The rest of the components feel fine.

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adafruit_support_bill
 
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Re: LSM303 Overheating

Post by adafruit_support_bill »

The LASM 303 chip normally draws only about 110 uA. It barely heats up at all. (The on-board temperature sensor would be pretty worthless if it did).

Can you post a photo of your setup? It might give us a clue as to what is going on.

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robbgodshaw
 
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Re: LSM303 Overheating

Post by robbgodshaw »

Well, It is acting normal again.
I had it connected to the i2c bus with a slightly messy set of wires.
I replaced it when I was prepping the board for the photo for clarity. I should always work as if there is an audience, it seems to cure bugs.
I replaced them and it is no longer hot and still gives good data.
Thanks Bill!

waltr
 
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Re: LSM303 Overheating

Post by waltr »

Possibly the power was oscillating?
Ensure that there is proper de-coupling caps on the PS lines.
Was the I2C lines only pulled up to 3.3V?
Only one set of pull-up resistors on the I2C lines?

I've been using one of these on an Adafruit breakout with no trouble. It has been powered from an R-Pi continuously for a few months.

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robbgodshaw
 
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Re: LSM303 Overheating

Post by robbgodshaw »

I don't see why it would be oscillating, it was powered by my Mac. I know very little about analog electronics.
Should I add caps? I thought all the needed circuitry was on the Adafruit breakout board.
My teensy is a 5V device, so that is what it was pulling the bus to. The board is said to be 5V safe
(https://www.adafruit.com/products/1120)

I hope to make this robot robust enough for a straight month of continuous operation.
It is behaving normally again with a new wire harness. I figure there was a crossed connection, though i was unable to find one.

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