News Raspberry Pi computer, is it rational?

Fabri91

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So, something more "Earthly" for now:

For a project the idea is to replace this array of separate and not-too-reliable timers



and so, after fiddling with Python, an RPi 3B and an Arduino UNO I keep around, here is a generic programmable timer relay controller (specifically, 8 relays with a maximum of 12 activations per day for now), controllable through a 3.5 inch resisitive touch display:



After some testing the idea is to use an Arduino Nano and eventually a Pi Zero to package everything decently in a more compact box.

Since this would be used without an internet connection, a thing I have to figure out how to do is how to attach a real-time clock without using the GPIO pins, currently used by the display.
 
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Fabri91

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Will take that into account, thanks!

Luckily the application would be checked in on daily and should it fail for a couple of days it's not a major problem, but better safe than sorry.

Regarding the real-time clock, I think that there are three viable solutions:

  • RTC directly connected to the Pi via USB - haven't really been able to find any, but it would be the easiest solution.
  • RTC connected to the Arduino - would need to communicate the time to the Pi via serial, but I'm not sure that a Python application can tell the system to set a specific time.
  • Different screen which enables the use of GPIO pins on the Pi, enabling the use of a miriad of clocks that are available.
 

Artlav

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Even if you install sysvinit and nuke systemd to the ground?
Even if i leave nothing but the Linux kernel and my program as init.
Best i can tell, it's some sort of a brownout issue - the only thing that had an effect was adding a capacitor to the 5V GPIO, but even that failed to stop the lockups completely.

And no, the watchdog timer on the thing does not do anything when it locks up.

In the end i made a board like that with a proper watchdog timer, an RTC and a capacitor -
 

Notebook

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The Pi will run on the battery(till its flat of course), if the mains power supply is interrupted.
That's as I understand its purpose.
 

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Ah, I see. I am messing around with ESP32's these days, trying to run apps for days on button cells. Compared to those boards, Raspberry's are big power hungry machines. :lol:

This was my eureka moment this week:
 

Notebook

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Yes, it has an app.
Quite versatile, rgb sliders for the HMS indicators. Five and fifteen minute markers, a "Pendulum" effect, an invert colour mode. Its quite...colourful!

Not much soldering, just the 60 shields between the RGB LEDs and the cable.

Next kit is a 6 digit Nixie tube clock. More my era, and no SMD, yeah!
 

Urwumpe

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Does anybody have experience in putting a SoC in place of a RC receiver? Like, how well does it work in driving servos, did anybody already use software defined radios?
 

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Does anybody have experience in putting a SoC in place of a RC receiver?
I do not. Do you have any doubts regarding the range, resolution and latency of the signal?

I've heard that Bluetooth5 allows to trade bandwidth for range which should increase the range to a few kilometers and also offer accurate positioning information. That's quite interesting.
 

Urwumpe

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I do not. Do you have any doubts regarding the range, resolution and latency of the signal?

I've heard that Bluetooth5 allows to trade bandwidth for range which should increase the range to a few kilometers and also offer accurate positioning information. That's quite interesting.

No, more about the power output of the GPIO pins for those boards - what can they drive directly? Also, I am sure there is a solution for any range (Even if its mobile phone technology).



The main feasibility question is for example, could a SoC drive a sail winch servo?
 

Notebook

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SMD.. Do you mean 'surface-mounted device' or 'smart device'?
Surface mounted devices.
They were starting to appear in equipment when I was finishing working in bench-maintenance and doing more operational stuff.

Very clever, and probably essential technology these days. I just couldn't get used to soldering all the pins together then using solder-wick to separate. Just felt bad.
Friend of mine who kept practising says its easy when you get used to it. He was a better technician than me anyway.

Besides, one good sneeze and you've lost £50 of components!
 

Urwumpe

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Surface mounted devices.
They were starting to appear in equipment when I was finishing working in bench-maintenance and doing more operational stuff.

Very clever, and probably essential technology these days. I just couldn't get used to soldering all the pins together then using solder-wick to separate. Just felt bad.
Friend of mine who kept practising says its easy when you get used to it. He was a better technician than me anyway.

Besides, one good sneeze and you've lost £50 of components!

The trick is to not solder. Better use the pan and sand method.
 

Notebook

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Pan and sand?
 

Urwumpe

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Pan and sand?

Yes, some smart guy found out, that with some small modding, you can use a standard electric pan (for cooking) with some sand to exactly get the necessary temperature for surface element soldering, similar like professionals do, with the sand ensuring a uniform temperature at the SMD elements.



That is a lot cheaper than even a cheap reflow oven - but requires some modding to ensure exact temperature to protect the ICs.
 
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