Hi Mark
Not quite what Olivia means I don’t think. The regulator might be able to output 1A ut the input has to supply that. It does not come out of thin air by some magical means.
Some arithmetic:
5V output @ 1A = 5W
5W at 3.3V (your input from Pico) = about 1.7A
Allow for a worst case conversion factor of 85%
(1.7/85)*100 = 2A
So you can see that the 5V @ 1A output could require 2A @ 3.3V input.
I point out that the above is just an example. You would have to plug your own number in for real world figures.
Cheers Bob
PS: Boy it is a very long time since I have heard of Visio. I had forgotten it existed. Used to be the go to package for engineers to do their own drawings before all the CAD packages like AutoCad were common.
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I assume I’ve somehow damaged the regulator in my mucking around.
The SENS0208 spec say the working load is 40mA. This I assume peaks when there’s a trigger event and that would be too short a time for me to see with the AT085 or the Fluke 77.
Following on from Olivia’s post and Bob’s maths:
VOUT is 5v with a load of 40mA = 200mW
VIN is 3.3v at 200mW = 61mA
The regulators efficiency is VIN/VOUT = 66%. Their chart shows ~ 80% but their words state VIN/VOUT.
So the load on VIN = 61mA / 66% = 92mA which is well within the Pico’s available 300mA.
As an aside I set VIN to 5v using VSYS and got the same result, being the SENS0208 runs but does not return a valid read.
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Hi Mark
Should be 0.061A (not mA)
Which you have corrected here
Cheers Bob
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I installed a 47µf cap on the regulator’s VIN as per instructions. Same result.
I converted the test code from M’Python to Python and ran it on a Pi5 and then on a Pi Zero 2 W using the same GPIO assignments, same breadboard with the SENS0208 and regulator in play.
Works fine. Regulator turns on, 3.3v stepped up to 5v, code runs through 10 cycles reading distance as required.
So it seems the issue in the end is the Pico W itself. I tried two Pico. I don’t have the test equipment to look into this (using the Pico) further so I’ll leave this be.
An educational and interesting, if long-winded, investigation.
