Blue pill current usage

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arpruss
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Joined: Sat Dec 21, 2019 10:06 pm

Blue pill current usage

Post by arpruss »

Does anyone have any rough figures on the amount of current a blue pill uses when running without any power saving modes? I am wondering how many I can safely run off a single 500ma supply.
ag123
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Re: Blue pill current usage

Post by ag123 »

well, i actually use a maple mini clone + an ili9341 powering the backlight from a maple mini gpio pin (bad idea but i'm lazy ;) ), i run it off 4xAA nimh 1.2v batteries (the ldo is a bipolar AMS1117 lousy cos it drops about 1.1v but the specs say it can supply 1A,

the total currents is about 60ma including that ili9341.
so my cells say is 2000 mAh, 2000 / 60 gives about 30 hours, i tend to get less than that so it lasts about a day.
i think the ili9341 consumes the bulk of all that power

i think it is literally possible to connect 2x1.5V AA batteries directly at 3v3 and run the stm32f103, i.e. no ldo. but i'm not sure how long it would last as around 2.5v or so i'd think stm32 may shutoff
arpruss
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Re: Blue pill current usage

Post by arpruss »

Does the Maple mini have LEDs on it (and if so, how many)?
ag123
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Re: Blue pill current usage

Post by ag123 »

1 led for blinking, and no power led
https://www.youtube.com/watch?v=rvNIeKuXsxM

i've not actually measured just the board without attachments, hence my inputs probably won't help much
hope some one who have done the measurements could comment.
my guess is it is less than 1/3 of that 60ma, but that's just a guess.
Last edited by ag123 on Tue Jan 21, 2020 3:28 am, edited 1 time in total.
arpruss
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Re: Blue pill current usage

Post by arpruss »

But in any case, it's quite safe to assume at most 100ma per device, plus more for any attachments, so that I can safely count on plugging two or three devices into a single unpowered USB 2.0 hub?
ag123
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Re: Blue pill current usage

Post by ag123 »

think so, but just be wary if it is connected to some things else, those may literally take more power than the chip alone
after all maple mini (clone) + that power hungry ili9341 lcd on throughout with backlight draw a mere 60ma
mrburnette
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Re: Blue pill current usage

Post by mrburnette »

arpruss wrote: Mon Jan 20, 2020 2:59 pm Does anyone have any rough figures on the amount of current a blue pill uses when running without any power saving modes? I am wondering how many I can safely run off a single 500ma supply.
Thoughts for non-PC port power:

Is the 500mA rated PS a wall-wart or batteries, if batteries, alkaline or lithium? There is more to a power budget than just taking 500 ÷ n = units.

Wall-warts are of two distinct types: simple transformers plus rectifier plus filter or switching supplies. Both of these classifications have numerous caveats but ultimately one can think about the power-supply from the output impedance of the design... for chemical cells, this would represent the internal resistance: remembering that the cell voltage drops as the battery depletes.

Use of high-quality, high value capacitance (close to or on the uC board) acts to minimize the source voltage fluctuations and counteracts the resistance of the wiring from the devboard to the powersupply. Additionally, quality capacitors such as tantalum have low ESR which helps keep the PS impedance low.

The average current consumed by a uC is made up of numerous digital loads including clocks, gates, and pull-up and pull-down resistances. The PS filtering and devboard capacitance helps "smooth" the digital loads, but there is still the imperfect impedance nature of the wiring and supply design proper.

EE's may worry about the details, but most technicians will simply "de-rate" the PS wattage by 20% or more. So, a 500mA wall-wart used for an old cellphone may be considered to be only 400mA (or less.) De-rating is extremely important if the dev-board or uC has RF capability (ESP8266 or ESP32 for example.)

One of my tricks is to use DC-DC converters to feed the uC board ... input of 5V with 3.3 output (buck == step down.) They are both efficient and cheap. For example:
https://www.aliexpress.com/item/3282654 ... 7547t6qqKT

Look around before selecting your DC-DC... tantalum capacitors vs electrolytic, multi-turn pots vs SMT pots, etc. For projects subject to vibration, multi-turn potentiometer is superior voltage adjustment. Of course, non-adjustable DC-DC with fixed voltage output is also available. I purchased 100 various models in a single shipment years ago and got free shipping and a really cheap unit price.

Ray
fredbox
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Re: Blue pill current usage

Post by fredbox »

Blue pill running blinky plugged into one of those inexpensive USB power displays shows about 20ma +/- 2ma as the led blinks every second. Power led is on solid.
GonzoG
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Location: Prudnik, Poland

Re: Blue pill current usage

Post by GonzoG »

It all depends on what peripherals you have enabled as each one of them uses power if enabled.
I get from about 30 to 50mA (with 1.3" OLED).

I've attached page from stm32f103x8 datasheet with graphs showing current consumption.
each LED on blue pill board uses about 2mA.
Attachments
stm32f103 current.jpg
stm32f103 current.jpg (66.93 KiB) Viewed 9220 times
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