Apologies if this is a trivial question.

I have an IoT project with a ESP32 processor and an array of LED matrix displays. I sometimes end up with too little available power (e.g. limitations of USB 500ma or limitations of a USB car charger adaptor.) The power hog is the LED display, and consumption depends mainly on the brightness settings of the LED display and the number of LEDs lit in the message which is being displayed.

I'd like to throttle the supply voltage or current draw on the LED matrix and prioritize keeping my processor alive and out of its "brownout" zone. The simpler my control mechanism, of course, the happier I'll be.

Is there a fairly common best-practice for ensuring some components get priority power over others?

Thanks
Peter

 

Is there a fairly common best-practice for ensuring some components get priority power over others?

Not that I'm aware of.
You could add a current sensor to the supply current and have the processor use that info to reduce the display power when the current draw gets near 500mA.

 

Thanks crutschow. The 500ma is a nominal USB spec, and I'm sure some of my ports deliver more, some perhaps less, and the car chargers tend to depend on whether the motor is running or not, etc. So my preference is to detect the falling supply voltage and use that to current-limit the draw. I've seen the pins on the LED matrix display dip to about 3.8v (from a nominal 5V USB supply on my laptop). Changing LED brightness on the fly is possible, but will be a slow response - we need to have software detect the falling voltage, then send some commands to the LED matrix controller.

In a complicated world one could even analyze the text before displaying it to tell how many dots will be lit, and then set the max brightness ahead of the text. (Scrolling the text is more complicated). But that starts to feel like serious overkill.

 

You could detect the voltage drop, but you may not be able to reduce the load fast enough to avoid a brown-out.
A large capacitor (say 10,000μf) from the input power to ground would give you more time to reduce the load as the voltage drops.

Note that if the voltage is dropping, you are overloading the supply, and prolonged operation at a lower voltage may damage the supply.