Newbie questions

[Nos_reef]

Hi all, this is my first pi project and had a few questions before ordering everything to make the power bar.

1. Is the uln2803 needed if you are using a power relay?
2. Is the 12v power needed if it is not used by the 8 channel power relay? I know it potentially needed for dosing pumps... what else requires 12v? Can i skip it for now?
3. Is there a 120v to 5v step down module? I am in Canada, Would be the same as USA mains. I want to make a 3d printed power bar that only requires a inlet for db9 and mains.

Using pi zero 2

Thank you so much in advance!

 

[KrisReef]

Welcome to Reef2Reef!

Bump for pi ?

 

[robsworld78]

Hi, you do need the ULN2803 or similar to drive the relays, the GPIO's can supply enough current. If you don't have anything 12v then you don't need it, you can use any AC wall adapter as a power supply. Get a 5v adapter, cut the end off and power up your system.

 

[Ranjib]

Hi all, this is my first pi project and had a few questions before ordering everything to make the power bar.

1. Is the uln2803 needed if you are using a power relay?
2. Is the 12v power needed if it is not used by the 8 channel power relay? I know it potentially needed for dosing pumps... what else requires 12v? Can i skip it for now?
3. Is there a 120v to 5v step down module? I am in Canada, Would be the same as USA mains. I want to make a 3d printed power bar that only requires a inlet for db9 and mains.

Using pi zero 2

Thank you so much in advance!

its for safety. you may get away without it, but it can fail. It is used to ensure we dont draw more than 20ma current from any single GPIO or 80 overall. If you are just controlling one to two relays, then it might be ok.
12v power is also used for kessil control where we need a 10v power source. You can definitely skip it if your are not using any of those. I'll recommend to skip as much as you can and only do the bare minimal thing you need for your target automation, and test it before using it.
You can use a common phone chargers (5v ,2.4A) Micro USB base wall adapters.

There are also barrel jack based 5v, 3A/4A power adapters.
I have used PCB based 120V AC to 5vDC module as well, long ago.