Thermal – VoltLog

Voltlog #266 – How To Check If Your Raspberry Pi 4 Is Throttling CPU

Welcome to a new Voltlog, today my raspberry pi 4 is again in the spotlight because I want to show you the different scenarios where the board could be throttling down the CPU frequency and how you can identify those. Because it might be a case where your raspberry pi is running slow on a particular task and you don’t know why because there is no built-in mechanism to let you know when the board is throttling down. There are logs which you can check but let’s be honest, few people actually check the logs for something like this.

Throttling of the cpu frequency occurs for good reasons, to protect the board or the cpu from overheating or to prevent any errors from occurring in the case of an under-voltage scenario which may lead to data loss or corruption. Luckily there is a way to check if your system is under one of these conditions, you can run this command on your raspberry pi.

Voltlog #264 – Passive Heatsink Cooling For The Raspberry Pi 4

Welcome to a new Voltlog, here is my raspberry pi 4 which I got a few months ago when they released it and if you have one you might have noticed it gets quite hot especially when it has to do some processing. This newer processor, will get hot quick and the board alone cannot cope with all of this heat so what does it do? Well when the CPU temperature reaches 80 degrees Celsius it will start throttling down the CPU as a way of protecting itself from overheating and this will result in a loss of performance.

The Raspberry Pi 4 has a 1.5GHz quad-core 64-bit Arm Cortex-A72 CPU, that’s roughly three times the performance of the raspberry pi 3 cpu. That inevitably generates more heat. In the original plastic case just sitting idle, connected to a network, doing pretty much nothing, the raspberry pi4 when compared to a raspberry pi3 runs about 12 degrees hotter.

Voltlog #195 – Is Thermal Adhesive Tape Any Good?

Welcome to a new voltlog, today we’re gonna be testing and comparing thermally conductive double sided tape to other solutions like thermally conductive adhesive, silicone pads, or even regular double sided tape to see how effective these solutions are for transferring heat between an IC and the heatsink.

To produce the heat I’m gonna use a small analog electronic load circuit, which will be set for a certain current let’s say 200mA and in theory should produce the same amount of heat for each run. Then we’re going to insert the different type of materials between the heatsink and the IC and we’re gonna measure the temperature of the IC and the temperature of the heatsink. As you can see I have a thermocouple glued to one side of the heatsink with thermally conductive adhesive and another thermocouple glued to this TO247 style transistor that’s producing the heat.

I don’t have a particularly good way of testing this but my plan is to heat the transistor to a stable temperature while the heatsink is kept at room temperature. Then I’m gonna connect the two bodies and measure the time it takes for the heatsink to reach the same temperature or a certain value, close enough. Then repeat the test with a different material and compare the values. If that time span is shorter or longer will depend on the thermal resistance between the body of the transistor and the heatsink and that is highly dependent on the material used between them.

Voltlog #164 – Pirl USB Charger Review & Teardown

This is a review of the Pirl charger which has 4 independent USB ports each capable of up to 2.7A continuous output. The product will launch on kickstarter soon.

You get 4 ports each capable of 2.7A and we’ll put that to a test later. The 4 ports are independent so a fault on one of the ports is only gonna shut down that port. It has input reverse polarity protection, thermal protection and ESD protection. It can also detect and optimize the charging current based on the connected device so I expect to see one of those tiny chips which handles the usb data lines on each port.

Another interesting feature they mention on their website is voltage compensation such that each channel adjusts the output voltage according to the current drawn, if the current increases the voltage will increase slightly to compensate for the voltage drop that might occur in the cable up to your device.

They also have a wattmeter on the front of the device showing you how much power your device is pulling from the charger.

Voltlog #78 – 2x25W Bluetooth 4.1 Stereo Amplifier TDA7492P

In this episode we are going to build a bluetooth speaker amplifier based on the TDA7492P class D audio amplifier coupled with a Bluetooth 4 module. We are not actually going to build the amplifier module because we can get that from China, very affordable, it only costs around $12 shipped which is way less that it would cost us to buy the bluetooth module and the TDA7492P individually not to mention the cost of fabricating a PCB of this size.

So we are actually going to use this module and build the final product with a nice enclosure and a suitable external power supply

Here are some links for the parts used to build this project:

Wiring diagram below:

Upgrading Workbench Lights Using 7020 White LED Strips

Although the operating temperature of this LED might be up to 85 deg C, while looking through various datasheets, I couldn’t find a graph showing a plot of the expected life in hours vs temperature. If I were to guess I would say you need to run these at less than 50 degrees C to get some decent life out of them. There was a mention of a stress test in a datasheet and that meant for that particular led manufacturer running it at 60 degrees C full rated current for 1000 hours with no resulting damage.

If you have any info on these LED’s and what temperature they should be running at to get some decent life out of them, please leave a comment below.

So to finish up on this story I have to say that I learned some things about these LED strips. If I were to design something from scratch I would run some basic thermal calculations based on the figures from datasheets but in this case, with these chinese led strips, there is no datasheet, I can’t even easily compare to existing datasheet because these can’t be compared: the driving current is different, the LED only has one die in my case and so on.

The next thing I will try is to double my L shaped heatsink with another piece the same model and size this way I will be increasing my heatsink surface and hopefully cool the LED’s better, maybe shave another 5 degrees.

I will be posting an update with some measurements for comparison once I get the upgrade done. Links for the power supply, led dimmers as well as the light meter used in this video will be in the description of the video so do check them out.