I have been using a Qwiic Shim and a Qwiic hub to connect 2 Sparkfun BME280 sensors to a hydroponics control system run by a Raspberry Pi. This system has been running fine for several months on a Pi3. I recently upgraded to a Pi 4… which also ran fine for about a month, and then for some reason the Pi suddenly started overheating… going from normal operating temp of 120F to 180F and getting stuck there no matter what I did… it even overheated when booted with no SD card, indicating internal damage. Also, some of the GPIO pins would no longer function. At first I thought it was a defective Pi since I had just unboxed it to install in this system. But after rechecking all my circuitry again for any shorts or other problems and finding none, I installed a spare Pi 4 into the system and it worked fine for a few days, and then that Pi started overheating and also lost functionality in some of it’s GPIO pins. I dismantled the system again and upon closer examination of the individual components I discovered that the Qwicc Shim I am using to connect the sensors to the Pi is burned… the voltage regulator got so hot it melted a hole in the shrink wrap it was touching!
Why would this happen? There are no shorts, the Qwiic Shim is connected to the proper pins, and the total cable length to my sensors is under 15 feet, so I can’t believe that line-capacitance would have caused this. If there were a short or some other problem I would think that I would have noticed some issues with data acquisition from the sensors, but the i2c seems to still be working, however I believe the failure of the Qwiic Shim voltage regulator is what caused the damage to the Pi and the GPIO bus… there is no other way this could have happened.
We move a lot of SHIMS and I can’t say I have ever seen them damage a customer’s Pi before in this manner. The SHIM also uses the same AP2112K SMD voltage regulator we have used on 100+ products in the SparkFun catalog. It is a solid little regulator that has been used for over 6+ years.
The SHIM is a very simple circuit. A voltage regulator and a couple capacitors. I highly doubt if used properly it would damage a Raspberry Pi 4 in this manner.
How certain are you that you are not running more power thought the SHIM than it can handle? Can you provide details on your power specifications for the project?
Have you considered using a heat sink for the voltage regulator? If ran close to maximum capacity it is highly recommended to add a heat sink for longevity. Our motor driver boards have the same heat dissipation considerations.
I am using the official raspberry pi power supply that came with the Pi4. As far as other power, I am using a separate 5V 3A regulated power supply to the low-side of a 4 channel relay that is attached to the Pi’s GPIO… the GPIO is only supplying high/low signal to the relay, the coils are powered by the separate 5V PSU to avoid current overload on the GPIO. The grounds between the separate 5V PSU, the relay board, and the Pi are all tied together as they should be. The relay is working fine and shows no signs of damage. There is also 12V in this system, but it is isolated from the rest of the circuit… it’s only supplying TX power to a couple of RF transmitters (which aren’t being used), and pass-through power to a couple of PWM fans. All input signals to the GPIO are protected with voltage dividers where needed. So I can’t see anywhere that over-voltage could have gotten into the GPIO except for the failed voltage regulator on the Qwiic Shim.
TS-John:
We move a lot of SHIMS and I can’t say I have ever seen them damage a customer’s Pi before in this manner. The SHIM also uses the same AP2112K SMD voltage regulator we have used on 100+ products in the SparkFun catalog. It is a solid little regulator that has been used for over 6+ years.
The SHIM is a very simple circuit. A voltage regulator and a couple capacitors. I highly doubt if used properly it would damage a Raspberry Pi 4 in this manner.
How certain are you that you are not running more power thought the SHIM than it can handle? Can you provide details on your power specifications for the project?
Have you considered using a heat sink for the voltage regulator? If ran close to maximum capacity it is highly recommended to add a heat sink for longevity. Our motor driver boards have the same heat dissipation considerations.
I don’t see how I can possibly attach a heat sink to that tiny voltage regulator, maybe they should use a higher rated VR on this product if it gets too hot under prolonged use. This is being used on a “production machine” that needs to run 24/7 for at least 6 months at a time.
Hmmm, Voltage regulators generally fail when over taxed. The BME280 board pulls micro amps so it would not have taxed the regulator to failure.
If the device did not fail early on and worked for some time, there must have been a reason for the eventual failure. I think you should recreate the circuit without the SHIM and the BME280 and see what kind of voltage and current output you get on a new Pi4 while operating under “standard conditions” without input from the BME280 sensors. I would think something would come up on the Pi GPIO pins 2/4 and 6. If you can’t see anything, introduce the SHIM and see what happens. We can send you a new one if you want to fill out a return ticket.
I honestly am not entirely sure how what happened happened at this point. My theory is something caused the regulator to defect, though, it is possible it is was inherently faulty in some way and something minor set it off.
It is hard to say without running some tests. Your circuit is unique and figuring out the root cause on my end is difficult.
I would love to “test the circuit” in another configuration… as soon as Sparkfun replaces BOTH of my damaged Raspberry Pi 4s and replaces the Qwiic Shim with a more robust component.
I tested this circuit thoroughly when designing and bread-boarding it. There is nothing wrong with my design. The Qwiic Shim is the only component in the entire system that shows physical signs of failure. Usually when a voltage regulator gets burned out due to a short or voltage reversal, it either just pops, or the package actually explodes… this regulator shows signs of prolonged overheating… the package is deformed the area around the component is burned, and the solder connections all show signs of extreme overheating… those are signs of long-term overheating. You component failed under “normal operating conditions” and caused damage to two Raspberry Pis… it also caused my hydroponics system to go down for several days while I tried to determine the cause of the problem. Stand behind your products and make this right… replace the qwiic shim and both of my damaged Raspberry Pi 4 2GB boards.
