Raspberry Pi - $35 Linux computer

  • Thread starter Thread starter daz
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Amazon sell some kits with a range of devices fairly inexpensively. Cover both sensors but also simple displays, servos and motors. Sometimes looking for Arduino in the search throws up more results than just a Pi search
 
n30_mkii said:
Thinking of getting my 8 year old a Raspberry Pi for Christmas this year. I've been covering some basics of Python with him and he's a wiz at scratch. He loves building things, and I like the idea of trying to do some interesting projects with it based around the use of sensors and perhaps servos. Now I'm not very wise with all things in this space, but is there a good starting kit with a good amount of sensors bread board and servos? Or is there a better way to approach this? I did notice crowdpi which looks interesting, but pretty pricey.
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Take a look at the Pi400 as well as the Pi 4. The 400 is a Pi 4 (4GB) built into an official Raspberry Pi keyboard
 
Having a minor issue with my RPI 4 regarding power. I've noticed for a while now that when someone in the house switches a socket on or off, my TV screen goes blank for a second or two. I'm a long way from being an electrician (can wire a UK plug and that's about all I've ever tried), and at first I thought there might be a problem with the TV itself or the house wiring but I'm no longer convinced that's the problem at all. For info, the RPI 4 was bought as part of a bundle - LABISTS RPI 4 B 4GB Starter Kit. What I've noticed:
  • If I'm watching anything via the RPI 4 and someone turns sockets on or off, the screen goes blank
  • If I'm watching something on normal TV channels and turn sockets on or off, everything is fine
As I said I'm no electrician, but based on the above I'm inclined to think that the power supply itself may be the problem. I know most of you are probably more knowledgeable in this area than me, so looking for advice / confirmation of my suspicion.
 
It's got a Labists logo on the power supply, so I'm going to say no :). I didn't want to waste money on another power supply if it's not that, even if it is only ~£11. I have enough junk & spare computer parts that I had to buy a shed to put it all in. :D
 
Is the RPI4 on the same ring as the sockets being turned on/off? What happens if you plug the RPI4 into a different ring, if you have that? How long does the screen go blank for? A brief flicker or for a longer period?
 
It happens if someone turns a switch on or off up or downstairs. Presumably they're on different rings? I know very little about electrics unfortunately. It's only a brief (1 - 2 seconds) black screen, and it only seems to affect the RPI 4 upstairs. I've tested live TV and the Chromecast that's also plugged in and they don't seem to have any problem. I've also swapped HDMI ports for the RPI and the black screen follows. Never noticed it happen on my RPI 2 or 3 downstairs.

The only other thing I can't test at the moment is the HDMI cable as I don't have another micro to HDMI cable, though I will have to check my shed tomorrow as I 'think' I might have a HDMI converter I may be able to test another cable with.
 
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Should have added that before. I have tried 3 or 4 different sockets in the room with no difference. Can't seem to find the HDMI converter I thought I had (just a ton of USB converters) so it looks like I'll need to either buy another HDMI to micro cable or just a converter.
 
HDMI converter arrived today - no difference.

In a blinding flash of 'why didn't I think of that before' I remembered I had a spare RPI2 loafing around (I could have grabbed the one that's downstairs but it's more of a faff as I have it all cable tidied behind the unit the TV sits on), so I stuck OSMC on it and plugged that in. No black screen. So it would appear that it's the RPI4 itself that's the problem. Mildly irritating, but it's an intermittent issue that only really happens *if* I'm unlucky enough to be watching something when my housemate decides to do something that requires switching sockets on or off (which is usually in the kitchen).
 
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Just trying to get a 800x480 display to work on an old Pi I have and in the /boot/config.txt file I noticed

Code: 
# uncomment to increase signal to HDMI, if you have interference, blanking, or
# no display
#config_hdmi_boost=4

I wonder if this might help?
 
Thanks. It was certainly worth a try but unfortunately made no difference. I've since found the RPI Documentation for the config.txt here, which says:

config_hdmi_boost

Configures the signal strength of the HDMI interface. The minimum value is 0 and the maximum is 11.

The default value for the original Model B and A is 2. The default value for the Model B+ and all later models is 5.

If you are seeing HDMI issues (speckling, interference) then try 7. Very long HDMI cables may need up to 11, but values this high should not be used unless absolutely necessary.

This option is ignored on the Raspberry Pi 4.
 
Have you tried the RPi connected to a different TV, elsewhere in the house & confirm the fault follows the Pi?

Does it matter what is plugged into the other socket that's switched on/off? It could be voltage spike/drop from loads changing (especially if any of them are highly inductive/capacitive). This would normally be resolved by the PSU smoothing this ripple, but it sounds like it's more than what either of your PSUs are able to handle.

Can you try either of the PSUs on another Pi to see if it exhibits the same issue?
 
R.C.Anderson said:
Have you tried the RPi connected to a different TV, elsewhere in the house & confirm the fault follows the Pi?
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No, but I've plugged a different RPi into the TV and the problem goes away.

Does it matter what is plugged into the other socket that's switched on/off? It could be voltage spike/drop from loads changing (especially if any of them are highly inductive/capacitive). This would normally be resolved by the PSU smoothing this ripple, but it sounds like it's more than what either of your PSUs are able to handle.
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I can only guess for the downstairs, but it's likely the kettle or the microwave in the kitchen. Upstairs I've tested with a halogen heater. Both of these do cause the blank screen.

I've now tried a couple of other, lower powered devices (Amazon Echo and Logitech Steering Wheel), and neither of them seem to cause the problem so it would seem your assumption is correct.

Can you try either of the PSUs on another Pi to see if it exhibits the same issue?
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While I do have four RPi's, only one of them is an RPi 4 (which has a USB-C adapter); the others are all micro USB. I did however buy an official RPi 4 adapter to test last week (see above) but it made absolutely no difference.
 
Infidelus said:
No, but I've plugged a different RPi into the TV and the problem goes away.



I can only guess for the downstairs, but it's likely the kettle or the microwave in the kitchen. Upstairs I've tested with a halogen heater. Both of these do cause the blank screen.

I've now tried a couple of other, lower powered devices (Amazon Echo and Logitech Steering Wheel), and neither of them seem to cause the problem so it would seem your assumption is correct.



While I do have four RPi's, only one of them is an RPi 4 (which has a USB-C adapter); the others are all micro USB. I did however buy an official RPi 4 adapter to test last week (see above) but it made absolutely no difference.
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Does sound like a voltage transient issue. It's odd it's multiple devices that can cause it though. Normally it's when a device has poor transient suppression built in, or is dyeing & whatever suppression was built in initially has started to fail.
Unfortunately it sounds like a bad combination of something causing your mains voltage ripple to be outside of the nominal spec, and the RPi being overly sensitive to it. As your RPi isn't shutting down & restarting completely, it doesn't sound like the power is being completely lost, but it might be out of range for a short period, and the RPi disables the video out briefly to protect itself (either from damage due to over voltage, or to protect from shutdown, at an undervoltage).

One thing you could try, is adding a large capacitor between the 5V input pin & GND, which should help stabilise any voltage transients coming into the Pi. As it sounds like a fairly brief disruption, the capacitor shouldn't need to be too large to cater for it.
 
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