I’m building a Bluetooth adapter. It’ll be powered off an automotive alternator and or battery so 12 to 15V max. I’ve got most everything prototyped but now need a power supply that’ll convert the as much as 15V down to 3.3V for the board. I need to figure out what will work best for a power supply. Thought I’d just snag one of these and try it:
One thing is FOR CERTAIN, it has to run COOOOOOL. The load isn’t too much (I need to measure it yet). It will be powering some IS2 chips, SD card and ESP32.
I think that chipset on breakout board will work but I’m not a Electrical Engineer so unsure what else might be worth considering. Looking at ESP32 Thing Plus Schematic there’s some pretty snazzy battery charging circuitry but I don’t think I’ll need that for my project nor would it drive my circuitry? FYI ~ This forum has been awesome. Thanks for your help.
12 years ago I helped design a battery controller. I was in charge of firmware. It was an aircraft battery. We implemented a Buck Boost regulator but my EE counterpart next to me designed that part of the system. I’m not even sure of what types of power supplies are out there otherwise (aside from voltage regulators like the 7805). I’m basically cutting my chops again catching up with a somewhat simple design. Will serve as a inline BT & SD MP3 adapter for an automobile but have other designs in mind which will need more complex and cleaner power supply. Eventually I’ll need a highly accurate voltage reference as I want to build a instrument to measure various signals on automobile.
Cool… I had wondered if OpAmps get used in power supplies. I suppose they work well when Voltage needs increased / boosted?
I’ve got a few more parts of the circuit design need figured out… I’ll make separate posts but think I can get most of it figured out either way. I’ll eventually have a board with I2S chips, SD card slot, buck regulator (this post). It won’t have a serial chip on it for programming. I want to have that on a separate board and leave just a small header on it. My thoughts are to use the FTDI chip that Espressif uses for JTAG debugging / Programming. Then in future designs I can do JTAG debugging as well as program the microcontroller.
Anyways, most of the software is working… I need to catch up on C++ though, a lot seems to have changed / evolved since I quit around 2012. Lots of new programming techniques centered around classes. Need to find a good YouTube course to catch up there.
For clean power you could do something like buck to 3.4V, then LDO the 3.4V to 3.3V.
For a stable voltage reference there are simple discrete IC’s available. Some components like ADCs will have the voltage reference built in, you just need to search around.
@cberman thanks for the tip! Cascading LDO’s is an interesting idea. For now I just need power and was confused by the 3.8V reading (was reading scope wrong). The design I’m working on above will have a 32V to 5V buck, then brought down to 3.3V via LDO so I can get 5V, and 3.3V. I will probably add a 1.8V as well but don’t really have any need for 1.8V yet.
I may need a really clean reference in the future. A couple of my upcoming projects require I take measurements. Not sure how the ESP32 handles ADC readings, if it has an internal reference? I’d not looked into it that far yet.
Oh cool! It’s been so long since I played around with this stuff. I’ll take a look into them. Back when I was doing that, they still came as DIPs Dang cool, you still have one in a DIP package…
I found this ADS1115 which I’ve added to my list to study. It maybe easier than configuring the ESP and more accurate in the end. I’m going to give it a try.
Dang cool, you still have one in a DIP package…