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by Huub
Sun Aug 17, 2014 1:40 pm
Forum: HATs and other add-ons
Topic: Safe shutdown circuit using a supercap
Replies: 29
Views: 14484

Re: Safe shutdown circuit using a supercap

I'm booting from a usb drive, and i modified the fstab to handle the sd card as a read only source. I found the tutorials online, but i can't find the one i used. Google "raspberry pi read only sd card" and make sure you boot from usb.
by Huub
Sat Aug 16, 2014 2:37 pm
Forum: HATs and other add-ons
Topic: Safe shutdown circuit using a supercap
Replies: 29
Views: 14484

Re: Safe shutdown circuit using a supercap

Thanks everyone. I made my sd card read only and this solved my corruption issues. I might look into a UPS in the future. I have a few buck converters that i can use.
by Huub
Fri Jun 27, 2014 9:02 pm
Forum: Other projects
Topic: Selfmade Case with dynamic-PWM driven Fan
Replies: 7
Views: 23378

Re: Selfmade Case with dynamic-PWM driven Fan

Last but not least: Sry for my bad english greets form Austria ;) Hello, I'm using your awesome mod, but I have a question. I'm using a PNP transistor, so the PWM need to be inverted. I'm looking over the code, but I'm not very good at raw code or C. Could you please tell me if there is an easy way...
by Huub
Tue Jun 17, 2014 8:01 pm
Forum: HATs and other add-ons
Topic: Safe shutdown circuit using a supercap
Replies: 29
Views: 14484

Re: Safe shutdown circuit using a supercap

Hello, I did consider that, however, i have a 8 year old hd ready tv with no such functionality. I found another solution though. I boot from a usb drive, and thus all read/write operations take place on the usb drive. I set my sd card to read only to prevent corruption (which was my reason to build...
by Huub
Tue Jun 17, 2014 11:57 am
Forum: HATs and other add-ons
Topic: Safe shutdown circuit using a supercap
Replies: 29
Views: 14484

Re: Safe shutdown circuit using a supercap

The LM317 doesn't have a shutdown circuit.. it's just a constant current source. Simple, less stuff to break. While NIMH doesn't like the high trickle charge levels of NICD, they work fine at C/30 to C/50 rates (Some manufactures quote C/30, some C/40). I settled on about C/40, which keeps the batt...
by Huub
Tue Jun 17, 2014 10:40 am
Forum: HATs and other add-ons
Topic: Safe shutdown circuit using a supercap
Replies: 29
Views: 14484

Re: Safe shutdown circuit using a supercap

Long charge times aren't a problem for me, but is there an overcharge protection?
by Huub
Tue Jun 17, 2014 10:00 am
Forum: HATs and other add-ons
Topic: Safe shutdown circuit using a supercap
Replies: 29
Views: 14484

Re: Safe shutdown circuit using a supercap

I might 3d print a casing when I'm sure what my setup will look like. One last question: you seem to use the LM317 as a charging regulator. It looks like a resistor is tied to the adjust port so that when the battery reaches a certatin voltage, the regulator shuts down and stops charging. Is that co...
by Huub
Tue Jun 17, 2014 9:25 am
Forum: HATs and other add-ons
Topic: Safe shutdown circuit using a supercap
Replies: 29
Views: 14484

Re: Safe shutdown circuit using a supercap

Hello Moses, Thank you for that extensive answer and explanation. Thank you for sharing your work with me. My inital idea was to create a supercap powered UPS that still fit inside my RPi casing. Looking over your project/product, that seems like less and less attainable. However, I found this: http...
by Huub
Tue Jun 17, 2014 7:16 am
Forum: HATs and other add-ons
Topic: Safe shutdown circuit using a supercap
Replies: 29
Views: 14484

Re: Safe shutdown circuit using a supercap

Thank you, that's very helpful. I'm on Raspbmc myself, and this requires about 10 seconds to shutdown. Which is still more than the 7 seconds you mention. I was afraid that that would be the case. May I ask what you are using? Are you using a 12v power supply and a normal voltage regulator to step d...
by Huub
Mon Jun 16, 2014 11:44 am
Forum: HATs and other add-ons
Topic: Safe shutdown circuit using a supercap
Replies: 29
Views: 14484

Re: Safe shutdown circuit using a supercap

I will have a look when I return home. Thank you for your advise. I'll keep updating this thread
by Huub
Mon Jun 16, 2014 11:32 am
Forum: HATs and other add-ons
Topic: Safe shutdown circuit using a supercap
Replies: 29
Views: 14484

Re: Safe shutdown circuit using a supercap

Ah I see. I did use "sudo crontab -e", after editing the standard "crontab -e" thescript still doesn't run at boot.
by Huub
Mon Jun 16, 2014 11:23 am
Forum: HATs and other add-ons
Topic: Safe shutdown circuit using a supercap
Replies: 29
Views: 14484

Re: Safe shutdown circuit using a supercap

I don't understand. I thought that that was what I did. I opened crintab using "sudo crontab -e" and added "@reboot sudo python /home/pi/shutdown.py" at the end of the cron file. Did I do something wrong?
by Huub
Mon Jun 16, 2014 10:48 am
Forum: HATs and other add-ons
Topic: Safe shutdown circuit using a supercap
Replies: 29
Views: 14484

Re: Safe shutdown circuit using a supercap

I did just now :) There are a few people doing similar things (like this guy: http://www.element14.com/community/community/raspberry-pi/blog/2012/09/11/raspberry-pi-lapdock-tricks ) I still can't find anyone that did exactly this, (initiating shutdown sequence when usb power goes down). I'm going to...
by Huub
Mon Jun 16, 2014 10:36 am
Forum: HATs and other add-ons
Topic: Safe shutdown circuit using a supercap
Replies: 29
Views: 14484

Re: Safe shutdown circuit using a supercap

I'm fairly sure this has been done with supercaps before. Might be worth a quick google. I'm sure it has, but I haven't been able to find one. There is a commercial UPS that's battery powered. I found people that did the same thing with batteries. But I can't find any documented project that does t...
by Huub
Mon Jun 16, 2014 10:13 am
Forum: HATs and other add-ons
Topic: Safe shutdown circuit using a supercap
Replies: 29
Views: 14484

Safe shutdown circuit using a supercap

Hello everyone, I'm new to the forum and to raspberry pi. I'm running my Pi with Raspbmc as a media centre. I shutdown my complete home entertainment system (TV, receiver and PI) every night. I know most will argue that powering down the Pi isn't neccesary, but I like it that way. As you all probabl...

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