What about using non-switched regulators? Any tricks there that can be exploited? What is the upper range/type of the filter cap value I should be considering, for example?
The new arduino Due board now uses a switch mode regulator to convert from Vin to +5vdc, but surprisingly they seem to still use a simple linear regulator for the +5vdc to +3.3vdc duty and 3.3 volts is the main current consumer, as the ARM chip is a 3.3 volt device. But in a way that makes sense as the biggest waste of power and heat is when users use a higher value of Vin, say 12-20, where there is much energy wasted in heat if wired straight to a linear regulator like most past arduino boards.Lefty
Bt what about the choice of the other components? Caps etc.? (I was thinking about taking a look at the Due schematic for some hints regarding "best practice", but then remembered the thread about the 16V caps on the Vin input stage, and though "maybe not".)
Output filter caps on switching mode regulators have a much more active role as they are part of a low pass output filter to help filter out the switching frequency being used to generate the regulated DC output voltage.
Quote from: retrolefty on Dec 06, 2012, 07:22 am Output filter caps on switching mode regulators have a much more active role as they are part of a low pass output filter to help filter out the switching frequency being used to generate the regulated DC output voltage.Yes, I was thinking that if the 5V regulation was doing its job, there wouldn't be much need for the output filter caps regarding ripple from the supply side. But then I was thinking that maybe I hadn't considered their role for smoothing out demand spikes, which occurs might be coming into play in some situations? What do you think? Significant or not?
The 1117 off the 5v rail should be working. You need to figure out why it's not...
Well then the answer is simple, the best case solution is a switch mode 5 volt to 3.3volt regulator. It will not waste 5 volt power just to turn it into heat, so the total wattage consumed from the 5 volt bus from any given 3.3 volt load will be less. Next question?
The noise from the switcher isn't an issue for digital designs and easily dealt with for 10 bit A/D conversion with a 5 V reference because even the fastest A/D conversion I did averaged several measurements for accuracy and external noise rejection.
In bread boarding I've found that those little breadboard jumpers are totally unsuitable for carrying any current above 100 mA or so, depending... As they are 30 Ga stranded and with the combination of jumpers and breadboard connections typical are lossy. I start with 5 V from an external PSU and after 6" of travel through jumpers and pins the voltage ends @ 4.5 to 4.75 V.
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