Having only a 1/2V of headroom is not good. I'm surprised that you're
getting your 3.3V. Anything else operating from that 5V supply could be
real iffy.
Ira
On 11/21/2024 10:50 PM, gregebert wrote:
So I checked my supply voltages, and that opened an unexpected can of
worms. The PIR sensor has it's own onboard linear regulator, and it's
pumping-out the expected 3.3VDC. The weird thing is the main 5V supply
was only putting out 3.8V. Despite that, the Raspberry Pi also had the
correct internal 3.3V supply (it also has it's own onboard supply).
So, the first mystery is why a DCDC converter rated for 1amp, and
typically supplying 400mA conked-out when it's not getting warm or
overloaded. I confirmed the RasPi typically uses around 200mA, and
occasionally peaks around 280mA.
I have to dig further into the regulators on the RasPi and PIR sensor
to understand why they still produce 3.3V when their input is
way-below 5.0VDC. I'm glad that they do, but I want to confirm why.
I'll see what I have laying around for replacing the 5V DCDC
converter, and if they beefier ones I have will fit on the PCB.
Once I get this thing back together, I'll see if the PIR sensor is
back to normal. I have some replacement PIR sensors on the way.
Why the DCDC converter failed is another mystery; I use these on all
my projects, and seeing one fail is disturbing, especially because
many of my gizmos dont have onboard A/D converters to monitor the
power supplies.
On Thursday, November 21, 2024 at 5:08:19 PM UTC-8 Max Di Noi wrote:
I had that problem once and it was due to a faulty capacitor on
the high voltage power supply creating instability on the HV
circuitry and affecting the PIR circuitry, which was odd as that
itself had its own capacitors located close to the chip and the
main power supply had plenty of stabilised power.
Now I'm trying to stabilise a microwave motion sensor that I
designed based on one of those commercially available. It's
embedded in the pcb, works OK but I need to figure out how to
calibrate it more easily. It depends on temperature and material
of the pcb. I purchased a frequency receiver up to 6gHz and I can
see the signal on the screen. So that's a good start! Sorry, got
sidetracked, slightly off topic :-)
-------- Original message --------
From: newxito <[email protected]>
Date: 21/11/2024 17:04 (GMT+00:00)
To: neonixie-l <[email protected]>
Subject: [neonixie-l] Re: PIR sensor got very sensitive
Maybe you have to clean the trimmer resistors or there is a little
bug inside, I had that problem but it was with an outside PIR :-)
gregebert schrieb am Donnerstag, 21. November 2024 um 07:50:38 UTC+1:
Here's a strange story....a few weeks ago, I noticed my 7971
clock was running a lot more than it was a few years ago.
After some experimenting, I found out the PIR sensor is
getting a lot of false triggers (no movement in room, even
covering-up the sensor didn't keep it off). Turning-back the
sensitivity 1/4 turn did nothing, so I put it at minimum
sensitivity and it seems to stop the false triggering. It
still detects motion.
Anyone else see this happen ? The sensor has been in-use for
about 6 years; it's one of those cheap 5V units that cost
about 1 USD and worked fine for many years.
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