Just want to make sure I have PS pins understood, before

Official Hardware Nano Family Classic Nano
1

I have a Nano programmed to turn on a heater and a pump. I need 5V power for a DS18B20 temp sensor. So I'm creating a separate PCB with a 12V regulator to power two relays and to send 12v to the Nano on the Vin pin. Then I plan on getting 5V out back to the separate PCB for the DS18B20.
Is that the proper way to use the Vin and 5V pins?
I added a preliminary drawing, may sprinkle a cap here or there.
PS. I may drop the 12v a little with a few series diodes.

Arduino Sprouter Schematic
Arduino Sprouter Schematic1716×800 105 KB

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if pump drop too much 12V line ....

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How much current does the pump draw, it could easily overload the 12V regulator. You will need to dissipate 7 watts per amp from the regulator. I would seriously consider using a buck converter. Also you need capacitors close to the 12V regulator if you use it. You can get a converter for about the price of the parts.

4

Yes, that is a good point, the pump only draws 0.335amps and each relay about 0.03 amps. So, about 400ma plus whatever the Nano and DS18B20 use. I suspect I'm under 500ma. I can heat add a heat sink to the regulator mount it on a copper pour, so I think it is fine. The pump has a pretty limited runtime ten seconds every few hours. The heater, I'm still trying to figure out but plan on running it off the 19v input voltage.
I could even use a couple diodes before the regulator to shave of a little voltage, but with my 500ma load, it would only reduce heat by a little over a 1/2 a watt.

But my question still stands, am I correct I can input 12V on Vin and takeout 5v on the +5v pin?
Thanks, Douger

5

I would consider doing the thermal calculations. You can use about 62C rise per watt on a TO220. A 500mA load is is about 3.5 watts with a 19V power source. Multiply that by 62 gives you 217 watts to get rid of then add ambient which would take you to just over 240C. Here is a link that will help.

Rough approximation, assume the Junction of the regulator is 25C now add 62C for 1 watt load, the die is not at 62+25 or 87C, 188F. What is the data sheet rating.

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Could you expound on that?
Douger

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place capacitors on 12v Line, before diodes and after

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You can take out maybe 50mA but that is a guess as I do not know the environment. A simple rule: "A Power Supply the Arduino is NOT!"

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