Deployment

[Penri]

Within the model town, not including the river system, there are 4 independent main supplies with associated 12V PSUs:

• 12V 25A PSU located in a IP rated box next to fence on south side of the site near the Methodist Chapel, this is currently on 24/7. This feeds the Methodist Chapel, the High Street and King Street, currently only used for lighting but will power TinyTVs when I get around to installing them in Wimborne Radio (High Street) and Holmans (King Street).

• 12V 25A PSU located in a IP rated box installed in the Minsters West Tower, this is currently on 24/7. Powering minster lighting and Music / Bells box.

• 12V 6A? (ex-laptop) PSU located in Kings Head, switched on and off daily via a remote control by the duty manager. Powers Kings Head lighting and TinyTV.

• 12V 6A? (ex-laptop) PSU located in Crown Hotel, switched on and off daily via a remote control by the duty manager. Powers Crown and Lloyds bank lighting plus Crown TinyTV.

I can fairly easily remove the remote on/off from the Kings Head and Crown without impacting anything much.

I do have an issue to face with Dacombes (which has a TinyTV installed) but no ready source of 12V as present! I'm toying with using a 12V battery but have not face up to the logistic challenge quite yet,


Penri

[TerryJC]

Penri,

It seems we have several choices:

1. Leave things as they are and risk SD Card corruption if the Pi is writing to it when the power is removed. This isn't as likely as it once was because the Pi has a journaling file system, but it's still a risk. Also the TV software is not logging anything and OS logging activities are fairly infrequent with a system that is only doing one thing.
2. Change the power arrangement so that the Pis are on 24/7. This risks losing the WiFi connection, but it should be no worse than the current situation with the Minster. It should be noted that this would mean that the screens would be on all night.

With hindsight, the ideal solution would be to have the power on 24/7 with a read-only filesystem, but I don't think that could be done remotely. It should be relatively easy to re-use the timing code from the Minster system to write black images to the screens at 1700 and restart the cycle at 1000.

[Penri]

Good morning

The last of the TinyTV shop fronts was re-installed this morning, after correcting a fault in the 12V supply. There was a short in the splice in the feed to the TinyTV electronics box, no damage was caused to the Pi, display module or supporting circuits.
The shop front, Dacombe, is powered from a sealed lead acid battery as there is currently no ready supply of mains derived 12V to its location. Battery charge, with the currently fitted battery, should last around a day. In due course I'll come up with a more appropriately sized battery and a change / re-charge process but in the meantime I'll take care of it but cannot guarantee that the supply will always be up.

So for completeness, in addition to the two hotels we have TinyTVs up and working at the following locations:

Holmans - screen1 - 192.168.0.71
Dacombe - screen 1 - 192.168.0.72
Wimborne Radio - screen 1 - 192.168.0.73

Penri

[TerryJC]

I have just successfully logged in to all five Tiny-TVs and checked their operating temperature (all ~40 deg C).

It will be interesting to see how the battery solution evolves.

Also. Is there perceived to be a problem with the permanently powered Pis running all night?

[Penri]

I hope the battery solution will need to last no longer that the end of this season, so don't want to waste too much money or time on it but also want to allow other to be able to support it without risk of damage to themselves (mainly) or the electronics.

The 12V circuits which include Holmans and Wimborne Radio and currently not switched so the associated lighting is always on during the open season, each circuits protected with a fuse link to try to offer some rudimentary form of protection but the total power draw is very low.

Would I like to minimise energy usage?, yes. Is there a perceived problem?, no.

Penri

[TerryJC]

Would I like to minimise energy usage?, yes. Is there a perceived problem?, no.

Penri, I wasn't really thinking about energy usage, which isn't a huge amount. I was thinking of the nuisance factor. We turned the Minster Bells off outside opening hours to avoid complaints from the neighbours and I wondered if anyone thought the screens being on 24/7 might be a similar problem.

As I say, I could look into blanking the screens overnight by reusing the code from the Minster system, but I'd like to be around when it is deployed, just in case. It should be possible to make modifications to the code over VPN, but it would be better to do it on site.

[Penri]

Terry

I'm not aware of any complaints and am fairly confident that if there were any I'd be told about them.

Blanking the screens overnight, however, would be good idea, particularly for Dacombe as it is at the moment, to eke a little more time out of the battery but that can wait until you're back from your gaunt.

Interestingly I ran the Dacombe shop front on a lower capacity battery yesterday evening, while monitoring the battery voltage, to see what would happen. There are three power consuming items, the shop lights (12V LED strips), lit radio dials (LEDs with dropper resistors) and the TinyTV.
When I went to check on it, the battery voltage was around 3.5V, the 12V LED strip were off but the radio dials and the TinyTV were on.
When I say the TinyTV was on I need to clarify; the screen was still displaying a clear, distinct picture although the Pi, by the point, was not changing the image. I should have been monitoring the current flow too but didn't.

By the way I didn't connect the 12V LED strips when I installed the shop front, to minimise battery drain.

Penri

[TerryJC]

I'm not aware of any complaints and am fairly confident that if there were any I'd be told about them.

Blanking the screens overnight, however, would be good idea, particularly for Dacombe as it is at the moment, to eke a little more time out of the battery but that can wait until you're back from your gaunt.

I'll look in to what's needed while I'm away and if I have spare time, I'll prepare some code ready for (fairly) instant deployment on my return.

Interestingly I ran the Dacombe shop front on a lower capacity battery yesterday evening, while monitoring the battery voltage, to see what would happen. There are three power consuming items, the shop lights (12V LED strips), lit radio dials (LEDs with dropper resistors) and the TinyTV.

When I went to check on it, the battery voltage was around 3.5V, the 12V LED strip were off but the radio dials and the TinyTV were on.
When I say the TinyTV was on I need to clarify; the screen was still displaying a clear, distinct picture although the Pi, by the point, was not changing the image. I should have been monitoring the current flow too but didn't.

I can see why that would would be. The Multi-screen Interfaces need 5 V +/- 0.1 V at the Pis and 3.3 V +/- <some unspecified tolerance> at the Screens to work. As the battery dies, the input voltage will fall below 5 V plus the headroom needed by the DC/DC Converter to keep 4.9 V at the input to the Pi. At this point, the Pi will start complaining and ultimately switch off. The Screens on the other hand only need 3.3 V or so to maintain the displayed image so the individual DC / DC Converters for the Screens will therefore stay up until the output of the main DC / DC Converter drops below the minimum needed.

This wouldn't work with the Single-screen Interfaces, because the 3.3 V display is powered by the Pi.

[TerryJC]

I have a possible software solution for the under voltage problem. Someone on the Raspberry Pi forums pointed me at vcgencmd, see https://www.raspberrypi.org/documentati ... cgencmd.md. I'm already using this from the command line to measure temperature, but it can also provide status information, eg, from the link

get_throttled
Returns the throttled state of the system. This is a bit pattern - a bit being set indicates the following meanings:

Bit Hex value Meaning
0 0x1 Under-voltage detected
1 0x2 Arm frequency capped
2 0x4 Currently throttled
3 0x8 Soft temperature limit active
16 0x10000 Under-voltage has occurred
17 0x20000 Arm frequency capping has occurred
18 0x40000 Throttling has occurred
19 0x80000 Soft temperature limit has occurred

I just ran this on the Dacombe Pi and got:

Code: Select all

pi@Tiny-TV3:~ $ vcgencmd get_throttled
throttled=0x0

If an undervoltage had been detected the result would have been 0x1 and 0x1000 if an undervoltage has previously occurred. I'm sure this could be built in to the software or run as an external script to shut down the system if an undervoltage is detected.

BTW. The screens would continue to display the last image because they have been programmed and the power hasn't been removed completely.

[Penri]

Terry

I’m is the process of trying to scrounge some reasonable capacity batteries to extend Dacombe’s up time. I’ll keep you informed on how I get on.

Penri