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|23rd January 2019, 07:36 PM||#1|
Join Date: Nov 2018
Please help with powering Rpi
I'm new here.
Have been reading this forum for some time but I have registered now because I really need your help.
For many months I had Rpi + Allo Kali reclocker combo and had no problem with powering it via linear psu.
Now for a while I have put Ian's Isolator in between these two and since then I have problem powering Rpi because I can't use Kali(SBC jumper) to give a bit more extra power to Rpi.
As I have read (and tested also) :
1.Kali(just for itself) need more than 100 mA
2.Ian's isolator about 300 mA
3.HDMI I2S module about 500 mA
I can power all these bords with 5V/1A with no problem.
Now about Rpi.
I have 3 b+ model...I know it is rated to power it with 5V/3A but have read
many people said that it needs just more than 1.5 A
And friend of mine from Italy powers it with 5V 1A without a problem.
For powering all my boards I use two O type transformers rated 30W with
2 x 8V out.
I have used cheap LDO LT3042 5V 1A like you can see in pictures...but it was
not enough for Rpi.
At the and I have ordered Linear psu like this
Supper Ultra Low Noise linear power supply LPS PSU KIT 5V 9V 12V 15V 18V 24V | eBay
to get more current.
At the end I have managed couple of times to start RPi with it but actually in 9 of 10 when booting it does not start. If I manage to start it...while playing music for some time it just powers of and tries to start again but can't boot.
Any time when I use smartphone charger rated 5V/2A it works for days without any problem.
My music is on SSD with it own power.
Please know I am totally new in DIY and electronics and I have just some cheap multimeter at home.
But I have measured some things again today.
Since AC at my home is a bit more than 240 each transformer gives about 8.8 V AC on output.
LT3042 Power modules on output give 5V DC and from 1.19 to 1.2 A current.
And bigger psu gives 2.73 A.
I have measured current on bigger psu while all other modules working and powering boards but I did not put Rpi in the circuit...so that 2.7A is measured on out of psu without powering Rpi.
Logic tells me that for booting Rpi draws much more current that my 2.7 A so that is why it can't work.
So another solution that I tried...when I put two LT3042 Power modules in parallel(1 +1 =2A) it works perfectly again. So solution for me would be like that.
How come now 2A is enough and on scenario with PSU 2.7A it is not!?
I have also noticed while paralleling them one of modules gets hot on small heatsink. No to crazy hot...I can keep my finger on it for 5-6 sec.
But it is hot comparing to others heatsinks that are dead cold.
I think I have read it is not good to use it just like that.
Can you please help me to maybe do some easy solution so I can make these 2 boards in parallel give equal current...so one of them don't go so hot?
Third solution would be that I connect two and two outs on transformer to double the current but I would like not to mess with AC and transformers.
Is it just mine Rpi strangely current hungry?
What would be best soluton?
Sorry for so long post and for so many questions.
Last edited by nikolacigo; 24th January 2019 at 09:48 AM.
|24th January 2019, 09:25 AM||#2|
Join Date: Jan 2007
Available current is not everything. First step is to check with a meter that your PSU is not dropping below 5V when the Pi is powering up.
|24th January 2019, 11:28 PM||#3|
Join Date: Nov 2018
You were right jooners!
Did not have time today till now but I have measured PSU and while booting starts from 5.2V and then drops down even to 4.3V and goes up and down like that all the time
Now I need to think some solution what to do next.
|25th January 2019, 10:18 AM||#5|
Join Date: Nov 2018
Yes..thank you again!
I don't now how I didi not check that thing earlier.
Been also reading yesterday a lot about Rpi's.
Latest version that I have consumes is some tasks almost double power than version before so I got answer why some people don't have any problem with 1A current powernig Pi for audio.
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