New answers tagged hardware
2
Before you go looking into additional hardware, please read up on what's called a "watchdog timer". The Raspberry Pi has a hardware watchdog built in that will power cycle it if the chip is not refreshed within a certain interval.
I have setup the watchdog on a Raspberry Pi 3 and a new'ish version of Raspbian with very little configuration. The first ...
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If you have wi-fi and just need to power off / power on, you could also consider using a smart plug. Amazon makes one for ~$25, you can power it on / off remotely and also set up timer routines if that's preferable. I've had a few for several months and they're quite reliable. You don't actually need an Echo or any other dedicated device. I use my smart ...
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I have quite a few Pis. All of them, except one ran flawlessly. The problem child would crash periodically and would never recover after a power outage without being power cycled again. I had it reboot itself every night via cron and that helped somewhat.
What fixed it though was taking the SD card and sensor hardware and putting them into another Pi. It ...
2
Question
Remote Rpi's freeze from time to time. How to wake them up?
Answer
2019jun17 Updates
So I tried the fork bomb. The system rebooted after executing the program, in about 15 seconds.
2019jun16 Updates
I found @berto's fork bomb program is a bit newbie scary. So I am learning Bash to find out what that fork bomb is doing. Basically it is just ...
4
Cutting power is a brute force method and has risks.
The conventional solution to lock-up problems is to use a watchdog.
There is a BCM hardware watchdog; If you want to start the hardware watchdog include dtparam=watchdog=on in /boot/config.txt
In and of itself this does little, although it should restart the system if not "kicked" regularly. You can ...
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Raspberry Pi is probably the easiest to build this with (plenty of hardware and software options available), but you could probably find a cheap microcontroller that is capable.
I'd suggest you build one with a Pi, consider it a prototype and then cost up variations for scaling up. Pi Zero WH may work out cheap enough once you add a networking board to an ...
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Your relay module is advertised as 5V, so it won't directly work with RPi GPIO which are only 3.3V. They seem to have a picture of their modules connected to the RPi, which doesn't help. You can complain to Amazon about this, and return the module for a refund (but considering the price, I wouldn't bother).
You can try providing 3.3V as VCC and 5V as RY-VCC ...
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I don't know how many amps Raspberry Pis can output on their GPIO pins, but the Songle SRD-05VDC-SL-C (the cheap blue electromechanical relay everybody seems to use these days) has a coil that needs 70 mA to latch... That could be the source of your problem...
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Question
Use MCP3008 to measure voltage of range 0V to 4.2V.
Use a voltage divider with 2.7MΩ / 8.2MΩ to step down value for Rpi but not working.
Resistor values too high?
How to calculate the resistor values?
Short Answer
MCP3008 ADC operation is indeed very complicated. You need to go through the long answer below a couple of times, ...
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Those resistors are in fact too high. Section 4.1 "Analog Inputs" (p. 17) and figures 4-1 and 4-2 (p. 18) of the datasheet are of special interest:
For the A/D converter to meet specification, the charge holding capacitor (CSAMPLE) must be given enough time to acquire a 10-bit accurate voltage level during the 1.5 clock cycle sampling ...
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I can't find a clear statement in the MCP3008 spec regarding input current.
Personally I suggest trying 27k, 82k and going up from there if it works.
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Question
How to connect a 24 pin BLDC motor plug to Rpi?
Answer
Well, I have been playing with various kinds of BLDC motors, mostly 24V to 30V. BLDC motors usually have 3 to 5 connecting wires, and many more with speed encoders.
There is no standard colour codes for the red, black, yellow, white, blue wires, so you need to very carefully read the ...
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Question
Would that be appropriate to power the Raspberry Pi Zero W directly from a 12 volt car battery?
Answer
Well, all these years I have been using a "12VDC source" to INDIRECTLY power the Rpi. I emphasize the word "INDIRECTLY", because of course I do not directly feed 12V to Rpi. I use a fixed or adjustable step down regulator to convert 12VDC to ...
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