PCB Heat Management

[Dave]

Hi, this is my first full eletronics project so this truly is a
beginner question. I'm making a device that uses a PCB to power 6
loads that will equal a maximum of 100 watts. And I'm wondering,
assuming the loads can go either way, should I go with 12 or 24 volts
for my power source.

Based on the I=P/V equation, a 12 volt power supply would result in
about 8 Amps on the board, and a 24 volt power supply would result in
just over 4 Amps on the board. Which is best? Would it make sense to
use a 24 volt power supply instead of a 12 volt one? How do you
compare the dangers of higher amps vs higher volts and what would I do
to make a 100 watt device like this safe?

 

[John Popelish]

Hi, this is my first full eletronics project so this truly is a
beginner question. I'm making a device that uses a PCB to power 6
loads that will equal a maximum of 100 watts. And I'm wondering,
assuming the loads can go either way, should I go with 12 or 24 volts
for my power source.

Based on the I=P/V equation, a 12 volt power supply would result in
about 8 Amps on the board, and a 24 volt power supply would result in
just over 4 Amps on the board. Which is best? Would it make sense to
use a 24 volt power supply instead of a 12 volt one? How do you
compare the dangers of higher amps vs higher volts and what would I do
to make a 100 watt device like this safe?

Amps need copper to carry them. Volts need space between
copper to keep them apart. But the minimum board space for
24 volts is a lot less than the copper width generally
needed to carry 8 amps. So, just from a board design
standpoint, I would prefer a 24 volt system.

Then you have to look into the cost, efficiency and
availability of control devices and interconnects for the
two cases. I am pretty confident that you will find that in
almost every respect, the 24 volt system comes out ahead.

But don't take my word for it. Do a rough design for both
cases and compare them.

 

[David L. Jones]

Hi, this is my first full eletronics project so this truly is a
beginner question. I'm making a device that uses a PCB to power 6
loads that will equal a maximum of 100 watts. And I'm wondering,
assuming the loads can go either way, should I go with 12 or 24 volts
for my power source.

Based on the I=P/V equation, a 12 volt power supply would result in
about 8 Amps on the board, and a 24 volt power supply would result in
just over 4 Amps on the board. Which is best? Would it make sense to
use a 24 volt power supply instead of a 12 volt one? How do you
compare the dangers of higher amps vs higher volts and what would I do
to make a 100 watt device like this safe?

Generally speaking, the 24V system would be preferable, as the less
current through your PCB, connectors and wiring etc the better. e.g.
you might find that the lower current gives you more options with
regards to what connectors you can use, and how long you can run the
cabling to your load etc.

From a practical design point of view there is not much difference in

voltage between 12V and 24V, so unless there is something specific
(some component spec perhaps) that prohibits 24V operation, I would go
with 24V.

You'll need to provide further details if you want more detailed help.

Dave.

 

[Dave]

Amps need copper to carry them. Volts need space between
copper to keep them apart. But the minimum board space for
24 volts is a lot less than the copper width generally
needed to carry 8 amps. So, just from a board design
standpoint, I would prefer a 24 volt system.

Then you have to look into the cost, efficiency and
availability of control devices and interconnects for the
two cases. I am pretty confident that you will find that in
almost every respect, the 24 volt system comes out ahead.

But don't take my word for it. Do a rough design for both
cases and compare them.

Thanks, I have been preparing to convert my project from 12 to 24
volts for a while. It seems to make sense... I just wanted to run it
by someone first.