user20413: I'm doing an rfid project that requires a read range of at least 5 inches or about 13cm.  I'm using a nano with a usb port, a rfid reader from priority 1 design and a large antenna. The problem I'm running in to is that when I power the project from the usb port I get a pretty decent read range of 11-13cm. But when I power the project from a DC power supply the read range drops considerably.
After a lot of testing with various power supplies I believe that all my power adaptors are dirty enough to cause rf interference and reduce the range.  Powering the project with a 9v battery and a 5v power regulator gives me really good range: 18cm with the largest antenna.  But I need plug in power.
So how can I power this project in a way that gives me ultra clean power?

I tried that same 5v regulator with a 5v adaptor and still had short read range.
Someone suggested adding a smoothing capacitor between V+ and Gnd but I wouldn't know what size.  I'm not an EE - I'm just a coder with a soldering iron.
Is there a better power supply I can get?

[EDIT] Also just FYI, when I connect even only the ground wire the the computers USB port I get a much farther read range. So..

Could it be a case of needing to ground the circut better as the switching power supplies only have 2 prongs and probably no real "ground". (Or am I making stuff up?)

[EDIT 2] What about a rechargable situation where my wall adaptor keeps a litium charged and the litium supplies clean power to the circuit?
Also I now know that I can charge my whole circuit with anything from 5 to 12 volts. In fact it would be better to have more in the 7 to 12 range than strictly 5v.
[UPDATE 3] Since this project is in my wall I was able to ground essentially to "earth" and that cleared up the noise. See this question as well: https://electronics.stackexchange.com/questions/230024/grounding-dc-project-to-clean-rf-noise

user521: This is what I use, although admittedly not in your application. I run it from a 12V wall adaptor and adjust the output voltage to suit my requirements. The input should ideally be at least a couple of volts above the output(depends on current and temperature at 25degC and 20mA it's > 1.6V and 1.5A at the same temp it's > 2.7V).

Another alternative if you want to really go to town would be to repurpose an old computer ATX or similar PSU. There are plenty of guides out there and it's a straightforward job.

20413: <p>I'm doing an rfid project that requires a read range of at least 5 inches or about 13cm.  I'm using a nano with a usb port, a rfid reader from priority 1 design and a large antenna. The problem I'm running in to is that when I power the project from the usb port I get a pretty decent read range of 11-13cm. But when I power the project from a DC power supply the read range drops considerably.</p>

<p>After a lot of testing with various power supplies I believe that all my power adaptors are dirty enough to cause rf interference and reduce the range.  Powering the project with a 9v battery and a 5v power regulator gives me really good range: 18cm with the largest antenna.  But I need plug in power.</p>

<p>So how can I power this project in a way that gives me ultra clean power?</p>

<ol>
<li><p>I tried that same 5v regulator with a 5v adaptor and still had short read range.</p></li>
<li><p>Someone suggested adding a smoothing capacitor between V+ and Gnd but I wouldn't know what size.  I'm not an EE - I'm just a coder with a soldering iron.</p></li>
<li><p>Is there a better power supply I can get?</p></li>
</ol>

<p>[EDIT] Also just FYI, when I connect even only the ground wire the the computers USB port I get a much farther read range. So..</p>

<ol start="4">
<li>Could it be a case of needing to ground the circut better as the switching power supplies only have 2 prongs and probably no real "ground". (Or am I making stuff up?)</li>
</ol>

<p>[EDIT 2] What about a rechargable situation where my wall adaptor keeps a litium charged and the litium supplies clean power to the circuit?</p>

<p>Also I now know that I can charge my whole circuit with anything from 5 to 12 volts. In fact it would be better to have more in the 7 to 12 range than strictly 5v.</p>

<p>[UPDATE 3] Since this project is in my wall I was able to ground essentially to "earth" and that cleared up the noise. See this question as well: <a href="https://electronics.stackexchange.com/questions/230024/grounding-dc-project-to-clean-rf-noise">https://electronics.stackexchange.com/questions/230024/grounding-dc-project-to-clean-rf-noise</a></p>
 521: <p>This is what I use, although admittedly not in your application. I run it from a 12V wall adaptor and adjust the output voltage to suit my requirements. The input should ideally be at least a couple of volts above the output(depends on current and temperature at 25degC and 20mA it's > 1.6V and 1.5A at the same temp it's > 2.7V).</p>

<p><a href="https://i.stack.imgur.com/qfyen.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/qfyen.jpg" alt="Circuit Diagram"></a></p>

<p>Another alternative if you want to really go to town would be to repurpose an old computer ATX or similar PSU. There are plenty of guides out there and it's a straightforward job.</p>
