Hack to get 5V for keyboard

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Paul
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Re: Hack to get 5V for keyboard

Post by Paul » Thu Oct 10, 2019 3:02 pm

mrtinb wrote:
Thu Oct 10, 2019 7:50 am
As SMD I didn’t find electrolyte capacitors
In your use case it's not necessary to use a polarized capacitor. Any 4u7 capacitor will do. In SMD you find larger non polarized capacitors than in through hole.
Kind regards Paul
P. S.
https://m.reichelt.de/Elkos-SMD-Low-ESR ... OUPID=4001
In theory, there is no difference between theory and practice. But, in practice, there is.

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mrtinb
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Re: Hack to get 5V for keyboard

Post by mrtinb » Thu Oct 10, 2019 3:14 pm

When I'm using SMDs it will be from these 30,000 parts. As they will assemble them cheaply.

https://jlcpcb.com/client/index.html#/parts
Martin
ZX81, Lambda 8300, Commodore 64, Mac G4 Cube

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1024MAK
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Re: Hack to get 5V for keyboard

Post by 1024MAK » Thu Oct 10, 2019 3:19 pm

If you are going via the SMD route, there are also 4.7uF multilayer ceramic capacitors. The bonus being, then you only need a single capacitor (no need for a 100nF capacitor).

One thing to watch out for with tantalum capacitors, is the voltage rating of the capacitor needs to be at least twice the maximum voltage that it will experience.

Mark

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1024MAK
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Re: Hack to get 5V for keyboard

Post by 1024MAK » Thu Oct 10, 2019 3:27 pm

Enter part number CL05A475MP5NRNC in the search box at this link. This capacitor may be a suitable SMD multilayer 4.7uF capacitor.
I’ve not fully checked the specs, as I’m on a train... but the capacity and voltage rating should be okay.

Mark

Note: edited, as the original link was not very helpful :(

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mrtinb
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Re: Hack to get 5V for keyboard

Post by mrtinb » Thu Oct 10, 2019 3:52 pm

1024MAK wrote:
Thu Oct 10, 2019 3:27 pm
This may be a suitable SMD multilayer 4.7uF capacitor.
I’ve not fully checked the specs, as I’m on a train...
Looking at the search-result you sent, they don't show up as polarized capacitors, when I import the component in EasyEDA, that is connected to this database.
Martin
ZX81, Lambda 8300, Commodore 64, Mac G4 Cube

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1024MAK
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Re: Hack to get 5V for keyboard

Post by 1024MAK » Thu Oct 10, 2019 4:09 pm

Sorry, I should have said. Multilateral ceramic capacitors are not polarised, so you will have to change the symbol / type.

The only reason that some types of capacitor are polarised, is due to the limitations of the practical construction of the capacitor. In any circuit, if there is an equivalent value of non-polarised capacitor, it can normally be used to replace a polarised capacitor.

Over the past twenty years or so, the improvements in the technology of multilayer ceramic capacitors has pushed them into the area where electrolytic and tantalum capacitors were the normal type to use. And at the same time, low ESR electrolytic capacitors have been pushing tantalum capacitor out as well. Hence tantalum capacitors are used less often these days. As the cheapest normally wins.

Note my post above has been edited.

Mark

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