robjharrison
Posts: 19
Joined: Tue Sep 05, 2017 6:48 am

Sensehat unreliability, anyone else?

Thu Mar 28, 2019 4:23 pm

I have a project that uses the sensehat on pi3b. It's back and forth outdoors, but sits solidly on the pi gpio. However, it's so unreliable in terms of whether it gets recognised or not that it's jeopardising the entire project. Ironically, its also the most expensive single bit of kit in the project. I love the ease/interfacing of the hat(although i dont need the led screen) but are there any known issues? It's so frustrating that despite my love for it, i have come to despise it.

scenario
pi boots and loads scripts to run, some of which access the sensehat. Sense hat shows rainbow and never gets past this. i reboot it several times, no change. I take it with me and 40mins later switch on, this time with hdmi attached.... boots straight away. reboot it, and it works fine. Again...works fine. When i really need it to work fine.... doesn't get past the rainbow.

i have the usual
dtoverlay=rpi-sense

Is there anything else i can use to FORCE the sensehat/pi to perhaps clear any references that might be lingering or to check the gpio for issues before forcing some kind of clean up?

robjharrison
Posts: 19
Joined: Tue Sep 05, 2017 6:48 am

Re: Sensehat unreliability, anyone else?

Fri Mar 29, 2019 7:45 pm

Either a question that has been asked too often, or not one that anyone recognises or cares to comment on. :)

Either way, for others in the same boat.
I'm wondering if it has something to do with the undervoltage warnings i'm seeing quiet a lot off. It just got me wondering having reread the boot issues sticky. I'm booting from one of three differrent options with varying cables(Phone power bank, 2600 LiPo and mains via apple plug (3 different cables but all generic), but it seems to be a common, but inconsistent issue. Although the pi always boots when attached to a screen - although the senshat stays 'rainbow' .

I dont know what the additional power draw a sensehat might induce, if any at boot time but its not my scripts because it doesnt get that far.

mattmiller
Posts: 2106
Joined: Thu Feb 05, 2015 11:25 pm

Re: Sensehat unreliability, anyone else?

Sat Mar 30, 2019 9:56 am

I've got two sensehats and not noticed any unreliability and I suspect its not a common issue

You really have to test things like this out with a known reliable power supply.

I have one official Raspberry PSU that I use for this (I use other ones for real-world projects)

Until you've tried it out on a known good PSU designed for Pi , its all just speculation and guessing

User avatar
bensimmo
Posts: 4175
Joined: Sun Dec 28, 2014 3:02 pm
Location: East Yorkshire

Re: Sensehat unreliability, anyone else?

Sat Mar 30, 2019 11:20 am

powerdraw is quite high, it lights all the LEDs during the startup, assume it 20mA max per LED, probably don't drive them that high.
The specs are not available any more, but 20mA is the closest one
undervoltage is probably the cause...

As for working not working, it's usually a poor connection, take the black gpio cover off and check the contact with the pins.
does i2cdetect see the i2c address's ?

alphanumeric
Posts: 2066
Joined: Tue Jan 19, 2016 2:17 pm
Location: Sydney, Nova Scotia, Canada

Re: Sensehat unreliability, anyone else?

Sat Mar 30, 2019 5:14 pm

I have two sense hats here, neither of them exhibit your issue. Both are attached to Pi A+'s. A+'s not 3A+'s, shouldn't have to say that but some are confusing the two or just saying A+ when they mean 3A+. Anyway, one runs 24/7 displaying weather info on the LED matrix. Official Pi Foundation Power supply. The other is running from a powerboost 1000c and 6600 MAH battery displaying the same info on the LED matrix. A portable version of the first one. I have other issues with my sense hats but not being detected isn't one of them.

robjharrison
Posts: 19
Joined: Tue Sep 05, 2017 6:48 am

Re: Sensehat unreliability, anyone else?

Sun Apr 07, 2019 3:26 pm

thanks folks for the advice.

It does appear as though it's a power issue, although switching the sensehat to the PiZero seemed to resolve it.

Annoyingly, I have tried multiple batteries, both Lipo and phone charging blocks, even a car battery booster and so many cable variations i am finding making a portable project with the Pi 3 with such power issues, difficult.

Does anyone have a cable that they use that doesnt give the under voltage warning but is hooked to a battery not the official PSU? I'm on my 7th

Short(pref) or longer, dont mind.

thx

alphanumeric
Posts: 2066
Joined: Tue Jan 19, 2016 2:17 pm
Location: Sydney, Nova Scotia, Canada

Re: Sensehat unreliability, anyone else?

Sun Apr 07, 2019 3:42 pm

I have a Sense Hat mounted to an A+ (not 3A+) powered by a powerboost 1000c and 6600 MAH LIPO battery. No undervolt issues that I am aware of. It runs headless most of the time. The only time I hook up a monitor is to tweak my python code. My powerboost feeds the +5V to the Pi and sense hat via a Proto Hat. Basically right into the GPIO +5V and ground pins. Yes, I know this bypasses the poly fuse, I'm fine with that.
Pictures are here, https://1drv.ms/f/s!AjOYwiwlwDtpgsVkNRFKrcQ8HARM0Q

EDIT: 22 AWG wire from the powerboost to the proto hat.
Last edited by alphanumeric on Sun Apr 07, 2019 3:52 pm, edited 1 time in total.

User avatar
bensimmo
Posts: 4175
Joined: Sun Dec 28, 2014 3:02 pm
Location: East Yorkshire

Re: Sensehat unreliability, anyone else?

Sun Apr 07, 2019 3:49 pm

The A+ uses the same power draw as the Zero though.

It's the initial draw of the 3B+ that may be the problem here?

alphanumeric
Posts: 2066
Joined: Tue Jan 19, 2016 2:17 pm
Location: Sydney, Nova Scotia, Canada

Re: Sensehat unreliability, anyone else?

Sun Apr 07, 2019 3:58 pm

bensimmo wrote:
Sun Apr 07, 2019 3:49 pm
The A+ uses the same power draw as the Zero though.

It's the initial draw of the 3B+ that may be the problem here?
Totally agree, just posting what is actually working for me. I originally went with the A+ because the powerboost can only supply a max of 1 A. That and I wanted as small a foot print as possible. And the Pi Zero did not exist when I built it. ;)

There is this https://shop.pimoroni.com/products/mp26 ... er-module Which is good for 2A out. I may end up switching to one at some point. Not liking the no enable pin on that one though. There are times I turn off the powerboosts boost section and just leave the charger running.

User avatar
bensimmo
Posts: 4175
Joined: Sun Dec 28, 2014 3:02 pm
Location: East Yorkshire

Re: Sensehat unreliability, anyone else?

Mon Apr 08, 2019 4:08 pm

same reason i ran mine on A+

and now have a 3A+, i do like the shape.

robjharrison
Posts: 19
Joined: Tue Sep 05, 2017 6:48 am

Re: Sensehat unreliability, anyone else?

Wed Apr 10, 2019 10:55 pm

alphanumeric wrote:
Sun Apr 07, 2019 3:58 pm
bensimmo wrote:
Sun Apr 07, 2019 3:49 pm
There is this https://shop.pimoroni.com/products/mp26 ... er-module Which is good for 2A out. I may end up switching to one at some point.
Just to mention, ive had two of these module boards and neither work with the pi3b, i dont think that they can provide the power needed.

Actually now im saying this, despite my testing of them.... i never tried them with the zero. Ive not posted them back yet, so might just run a quick test on whether they do work for that model.

alphanumeric
Posts: 2066
Joined: Tue Jan 19, 2016 2:17 pm
Location: Sydney, Nova Scotia, Canada

Re: Sensehat unreliability, anyone else?

Thu Apr 11, 2019 8:20 am

robjharrison wrote:
Wed Apr 10, 2019 10:55 pm
alphanumeric wrote:
Sun Apr 07, 2019 3:58 pm
bensimmo wrote:
Sun Apr 07, 2019 3:49 pm
There is this https://shop.pimoroni.com/products/mp26 ... er-module Which is good for 2A out. I may end up switching to one at some point.
Just to mention, ive had two of these module boards and neither work with the pi3b, i dont think that they can provide the power needed.

Actually now im saying this, despite my testing of them.... i never tried them with the zero. Ive not posted them back yet, so might just run a quick test on whether they do work for that model.
What size battery are you using with them? Doing some quick math you'll need a LIPO that can supply almost 3A out to get 2A @ 5V.
But I wouldn't think you'd need the full 2A out? Maybe half that? Idle current for a 3B+ is ~500ma.

Return to “Troubleshooting”