Powering multiple devices via a microcontroller

Hello again, I am in need of some help regarding electronics.
What I am trying to accomplish is using multiple sensors as well as an
ADC as a Shield.

I am also trying to reduce the noise in the system by using a switching
power supply step up from 5V to around 6V and then use a linear voltage
regulator to return to 5V as well as 3.3V.

Is it possible to reliably power all of these devices via
the micro-controller? or should I look for an external solution?

I am trying to use multiple copies of the device on a powered USB hub.
Also, should all of the sensors be connected to the same power supply or
should they have individual voltage regulators?

I apologize in advance since I am a beginner in this kind of thing.

Is it possible to reliably power all of these devices via
the micro-controller? or should I look for an external solution?

You said you're using an external linear regulator (or a USB powered hub), so you what do you mean power via the microcontroller?

And what "sensors"? Most sensors don't require much power (current).

What I am trying to accomplish is using multiple sensors as well as an
ADC as a Shield.

Is there some reason you can't use the "Aruino's built-in ADC?

I am also trying to reduce the noise in the system by using a switching
power supply step up from 5V to around 6V and then use a linear voltage
regulator to return to 5V as well as 3.3V.

That kinda' seems like a horrible idea... What kind of noise problems do you have? Are you sure the noise is coming from the power supply?

It would be better to start-out with a better power supply, or at least start-out with a higher power supply do you don't have to use a boost-circuit. (A regulator will help to reduce noise.)

The Arduino already has a 5V regulator and it can provide enough current for most "sensors". There is also a 3.3V regulator but it's only rated for 50mA.

I am trying to use multiple copies of the device on a powered USB hub.
Also, should all of the sensors be connected to the same power supply or
should they have individual voltage regulators?

You should be able to power a handful of Arduinos from a hub but it depends on what else is connected and what else is connected to your Arduino. If you want to make sure, measure the current draw for your actual Arduino circuit, check the specs for your hub, and leave some safety margin. (Be careful with current measurement... It's tricky!)

Klagemauer:
I apologize in advance since I am a beginner in this kind of thing.

Everyone has to start somewhere.

The usual formal process is to first identify the specific sensors/peripherals for your project. With this you can construct a power budget wherein you list the specific voltage and maximum current requirements for each item as taken from a data sheet or direct measurement. From this you can tally up the various current requirements which gives the minimum required performance for the power source.

I am also trying to reduce the noise in the system by using a switching
power supply step up from 5V to around 6V and then use a linear voltage
regulator to return to 5V as well as 3.3V.

Almost guaranteed to increase the power supply noise.
Just use decoupling techniques if you want to reduce noise on the power line.

http://www.thebox.myzen.co.uk/Tutorial/De-coupling.html

Thank you all for your responses. To answer some of your questions,
I am currently using a blue pill stm32 with a 12 bit ADC and I would like to
have a greater resolution that is why I am using a MCP3903 ADC in 24bit mode.

I thought about using the MU’s supply to power the adc, however I fear that it
may be too noisy and/or unreliable due to the varying load of the MU and since I
also want to use the supply as an external reference input I thought that there would be a better solution.

So my Idea was to connect the power supply of the shield to the power supply of the MU at the
USB interface to the hub. Not yet considering the external reference, my goal was to reach a steady
5V & 3.3V output as the ADC requires both and to ensure that, even when connecting the contraption to
a different computer, the Voltage would not fall below 5V. That’s why I wanted to use the hybrid power solution but it is good to know that it would most likely be useless. Just to note, I got the idea from here:
https://www.digikey.com/en/articles/techzone/2012/may/hybrid-power-supplies-deliver-noise-free-voltages-for-sensitive-circuitry

The sensors are supposed to use 3.9 mA each in at their peak consumption and require 3.3V.
The ADC on the other hand requires 20.2 mA at its peak and uses 5V for its analogue supply and
3.3V for its Digital supply.

I have attached the concept that I would like to use next to this post. Would this be sufficient
to reduce the noise?

Also, I am a bit confused how to connect the analog and digital ground. Should I just connect them
to their respective shielding plane and connect both planes via a narrow path? There are so many
opinions on this topic that I am not sure how it really works.

Thanks again for your responses.

Klagemauer:
I thought about using the MU's supply to power the ADC, however I fear that it may be too noisy and/or unreliable due to the varying load of the MU and since I also want to use the supply as an external reference input I thought that there would be a better solution.

You have just shot yourself in the foot. There is no way you would want to use a supply voltage as an analog reference in the context of high resolution and noise. It is the stability and cleanliness of the analog reference that matters, not noise on the supply rail. You are using a microprocessor which is the major generator of pseudo-random noise in the system, not externally supplied noise. As has been explained to you, bypassing is what is most relevant.

Klagemauer:
I have attached the concept that I would like to use next to this post. Would this be sufficient to reduce the noise?


I see nothing meaningful.

Klagemauer:
Also, I am a bit confused how to connect the analog and digital ground. Should I just connect them to their respective shielding plane and connect both planes via a narrow path? There are so many opinions on this topic that I am not sure how it really works.

A "narrow path" if of no relevance. Your analog ground must be the star grounding point for all the analog devices including of course, the analog reference itself. That star ground then connects to a digital ground close to the main (multi-microfarad) supply bypass at the microcontroller or ADC. You may choose to connect it by a small inductor though the value of this is dubious as the analog and digital grounds are generally connected inside the microcontroller or ADC.

Grumpy_Mike:
Almost guaranteed to increase the power supply noise.
Just use decoupling techniques if you want to reduce noise on the power line.

De-coupling

Thank you for your post. The information was very helpful.

Paul__B:
You have just shot yourself in the foot. There is no way you would want to use a supply voltage as an analog reference in the context of high resolution and noise. It is the stability and cleanliness of the analog reference that matters, not noise on the supply rail. You are using a microprocessor which is the major generator of pseudo-random noise in the system, not externally supplied noise. As has been explained to you, bypassing is what is most relevant.

I was planning on using it in combination with a Zener diode but to be honest the ADC's internal reference is already sufficient for me. So if its complete nonsence, I can leave it out.

Paul__B:
I see nothing meaningful.

Alright. Would you mind elaborating? I am fairly new to this so any input would be helpful.

Paul__B:
A "narrow path" if of no relevance. Your analog ground must be the star grounding point for all the analog devices including of course, the analog reference itself. That star ground then connects to a digital ground close to the main (multi-microfarad) supply bypass at the microcontroller or ADC. You may choose to connect it by a small inductor though the value of this is dubious as the analog and digital grounds are generally connected inside the microcontroller or ADC.

Thanks, I'll try to implement that.

Paul__B:


I see nothing meaningful.

Klagemauer:
Alright. Would you mind elaborating? I am fairly new to this so any input would be helpful.

The point that I had made was that stabilising the analog reference was more critical than the power rails and in regard to your diagram of the power rails, the number of components was less important than the layout of connections and the placement of the bypass capacitors. :grinning: