Let's Make Robots!

Bench Power Supply - Linear or Switching?

I am looking for a bench power supply.  I want a general purpose power supply for testing purposes, motors, circuits etc.  I am debating between two units but am open to other ideas as well.  There seems to be quite a debate about whether a switching power supply is as good as a linear power supply.  I will not be using it for ham radio, so I don't know that the higher noise will be an issue with the switching supply for robotics and other electronics and I like the size and weight reduction provided by the switching power supplies.

Which one would you recommend?

Linear - http://www.mastechpowersupply.com/dc-power-supply/linear-power-supply/mastech-variable-linear-power-supply-30v-10a-hy3010d/prod_11.html

Switching - http://www.mastechpowersupply.com/dc-power-supply/switching-power-supply/mastech-power-supply-hy3010ex-30v-10a-over-voltage-over-current-protection/prod_70.html

I am open to recommendations for other supplies, trying to keep the cost down but I could raise my budget if necessary.

 

 

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I've looked at that.  My current project is going to use 7.2v and the atx power supplies supply something like 3.3v, 5.v and 12v.  Could an ATX power supply be used for 7.2v?  I took electronics in high school (many years ago) and am just now getting back into it.

No ATX does not provide 7.2 only 3.3, 5, 12 and a low power -12 for biasing. A linear regulator or switching regulator could drop the 12 volt to 7.2 These components can be purchased for 15$ or so to build a circuit and be able to handle about 5 amps if you use proper cooling.

Go for the switching. It's cheaper and has over current and over voltage protection, a very very important feature. Not sure if the linear comes with that.

At a glance the difference is;

Linear Ripple noise: CV <= 10 mV RMS, CC <= 10 mA RMS
Switching Ripple noise: CV <= 1%

Nothing you build at home should be so sensitive that 1% ripple be an issue. So the switching ripple is acceptable.

As for switching noise it exists but is not a large problem unless you have a circuit running at very high frequencies (if you are really concerned email the manufacturer and ask them what the switching frequency range is. If it is beyond what your circuits will run at then don't even worry about it). Either way this noise can be filtered with an EMI filter, band pass/band stop filter or a bridge rectifier if it ever does become an issue.

So in closing, go for switching, if you ever outgrow it's capabilities (probably master level research in electrical eng.) then by that point you will easily be able to  build circuits to solve the problem.

On a side note an ATX power supply or a universal variable power adapter can provide similar functionality for a third of the price. Consider those if you are just starting out.

PS One advantage to linear is that they use less components and are more robust. If you plan to lug this thing everywhere you go consider that it takes talent (ie shorting the main coil windings) to break a linear regulator.

Wow those are fancy... If it were me I would use an old ATX power supply for free... then spend the $160 on some cool sensors...
It's worked for me well so far.