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IanCanada's Latest RPi GB Goodies Impressions... and your tweaks, mods and hints...
IanCanada's Latest RPi GB Goodies Impressions... and your tweaks, mods and hints...
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Old 13th February 2020, 07:36 PM   #1251
3kes is offline 3kes  Netherlands
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Quote:
Originally Posted by wlowes View Post
I have seen much discussion re pre charging supercaps. FWIW I will share my simple approach. I use 50F caps on the 5v supply to the Rpi. So much smaller than some I see here, but still a serious pair of caps. The PS is a simple linear CRC filtered linear supply regulated with the high amp version of the 7805. I put a heat sync on the 7805 consisting of a simple strip of brass. No problem with heat dissipation and no pre-charging required. Just flip the switch and it charges up in a few seconds and runs for weeks/months without issue. Great sound.
A picture of this setup would be highly appreciated
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Old 13th February 2020, 07:41 PM   #1252
jimk04 is offline jimk04  United Kingdom
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How does one know you are listening to that supercap and not the 7805 in this case?
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Old 13th February 2020, 08:44 PM   #1253
randytsuch is offline randytsuch
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IanCanada's Latest RPi GB Goodies Impressions... and your tweaks, mods and hints...
Quote:
Originally Posted by jimk04 View Post
How does one know you are listening to that supercap and not the 7805 in this case?
Add a switch so you can disconnect the 7805 and decide if it makes a difference. But the caps need to be large enough to power your setup without help.
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Old 14th February 2020, 03:36 AM   #1254
wlowes is offline wlowes  Canada
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Quote:
Originally Posted by jimk04 View Post
How does one know you are listening to that supercap and not the 7805 in this case?
I like the quote... "everything counts". In this case it means you are listening to the 7805, the supercaps, the transformer, the diodes and the filtering caps. It is a good linear PS with a LM7805 and supercaps powering a computer. Beats a switching PS by a long shot, but certainly not perfect. Quite sufficient for the task. In an earlier life it powered a DAC that was well regarded on these forums and now it powers a computer. It is enough for me.
PS schematic below. Caps are now Panasonic. Smaller resistors. LM7805 follows, then 2x 50F supercaps feeding the Rpi.
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File Type: jpg Rpi PS.jpg (15.6 KB, 307 views)

Last edited by wlowes; 14th February 2020 at 03:39 AM.
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Old 14th February 2020, 06:04 AM   #1255
jimk04 is offline jimk04  United Kingdom
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Good information thankyou. Can I ask what 50F caps you use?
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Old 14th February 2020, 07:46 PM   #1256
wlowes is offline wlowes  Canada
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Quote:
Originally Posted by jimk04 View Post
Good information thankyou. Can I ask what 50F caps you use?
I use Nesscap ESHSR. 14mOhm.
ESHSR-0050C0-002R7 NessCap Co Ltd | Capacitors | DigiKey
Nesscap was one of the early innovators. I believe ultimately acquired by Maxwell. I worked for a tech startup that used millions of these in the PS for industrial wireless communications modules. So I had a bunch of these in my parts bin that have now found new life in my streamer. They are still available at Digikey. You will find the same thing with a Maxwell label as well.
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Old 15th February 2020, 04:46 AM   #1257
nano35 is offline nano35  Hong Kong
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So you simply parallel supercaps at the regulator’s output?
No special circuitry to control the caps?
2.7V supercaps for use at the RPi’s GPIO 5V pin?
I thought it will blow with lower than 5V voltage cap.

I did a similar thing with Two 2200uF/10V cape at the GPIO pin 4 and ground before; the improvement is quite noticeable. Harshness is greatly reduced and bass is more defined.
I really want to try supercaps if connection is simple.
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Old 15th February 2020, 10:18 AM   #1258
misterdog is offline misterdog  United Kingdom
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Quote:
Originally Posted by nano35 View Post
2.7V supercaps for use at the RPiís GPIO 5V pin?
I thought it will blow with lower than 5V voltage cap.


Ultracapacitor Example No1
A 5.5 volt, 1.5 farad ultracapacitor is required as an energy storage backup device for an electronic circuit. If the ultracapacitor is to be made from individual 2.75v, 0.5F cells, calculate the number of cells required and the layout of the array.

ultracapacitor voltage
The array will therefore have two capacitor cells of 2.75v each connected in series to provide the required 5.5v.

https://www.electronics-tutorials.ws...apacitors.html

2x 2.7V capacitors connected to each other in series then placed in parallel across the supply.
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Old 15th February 2020, 01:07 PM   #1259
nano35 is offline nano35  Hong Kong
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Thank you so much. Very clear explanation!
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Old 15th February 2020, 02:18 PM   #1260
wlowes is offline wlowes  Canada
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Quote:
Originally Posted by nano35 View Post
So you simply parallel supercaps at the regulatorís output?
No special circuitry to control the caps?
2.7V supercaps for use at the RPiís GPIO 5V pin?
Series connected yielding a 5.4v 25F cap. No additional circuitry. If you go beyond 2 series caps use balancing resistors to ensure even distribution across the caps.
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