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Topic: What kind of adapter should I get? (Read 504 times) previous topic - next topic

niss3

So I was thinking of getting an adapter to my Arduino.

I've been using 9V batteries with this thing:


It's max 0,7mA.

So if I get a wall-socket adapter, what kind should I get?

If I get a 9V one, it can at most be P = 9 * 0.7 = 6,3 W
Am I right?

When I check the stores around here there's a gap between 3,6 and 7,2. So if I get the 3,6W I could run it at U = P / I = 3,6 / 0,7 = 5.1 V


So I guess I should get the 3-12V variable 3,6W adapter. It says when it's set to 5V it will deliver with 0.6mA.

Is my thinking correct?

CtrlAltElite

Has there been an outbreak of the stupid virus, and I didn't get the memo?

niss3

600uA?
Are you serious?
Probably not. That's why I'm asking for help.

Where is the 600 u A from?

CtrlAltElite

Probably not. That's why I'm asking for help.

Where is the 600 u A from?

Here
Quote
It says when it's set to 5V it will deliver with 0.6mA.
Has there been an outbreak of the stupid virus, and I didn't get the memo?

niss3



Levererar upp till 600 mA (vid 3/4,5/5 V)

^

Delivers up to 600 mA ( at 3/4,5/5 V)

That's where I got it from.

CtrlAltElite

0.6 mA is NOT 600mA.
So, no, you didn't get it there.
Has there been an outbreak of the stupid virus, and I didn't get the memo?

thomasbommel

A power supply like this one
https://www.amazon.de/dp/B01MS5ZQH5/ref=sspa_dk_detail_4?psc=1
works fine... it is capable of delivering 2A, so way more than you need (which is no problem) and it's really cheap.


niss3



This is what I'm looking to power with the adapter. The 8 relay COM will share the same 5V as the Arduino UNO board. But the relay VCC itself needs another 5V power source.


JohnRob

I would suggest you get an adapter that is at least capable of 1 amp (1000 ma).

Reasons:

  • They are relatively common
  • It will be capable of any new types of circuitry you might like to power in the future.
  • I don't think there is much of a cost difference.

I'm not sure you realize this and if you don't I will state it:

You circuit will only draw the current it needs from the power supply.   Having a power supply that is only slightly more capable than what the circuit needs will likely cause problems.  You want to have power to spare.

Stated differently, If you circuit requires 60 ma at 9V then that is all it will draw from the power supply even if the power supply was capable of 100A.



Please do not PM me with thread based messages.  If your thoughts are worth responding,  the group should benefit from your insight.

Wawa

It's max 0,7mA.

If I get a 9V one, it can at most be P = 9 * 0.7 = 6,3 W
Am I right?
Did you mean 700mA. That's sales talk.
9volt in and 5volt out is a 4volt drop.
With 700mA current draw, the linear regulator on that board would dissipate 4volt*0.7A= 2.8watt.
About three times the power it can handle.
700mA can only be drawn with a 6volt supply (less voltage difference is less heat).

With a 9volt power supply, that breadboard supply can only deliver ~250mA.
That's 200mA if you subtract 50mA for the Uno.
No more than two relays can be  active.
If you want more, then forget about that breadboard supply.

You need a 5volt supply capable of delivering at least 8*80mA= 640mA for the relay coils.
Plus 50mA if you also want to power the Uno with it.
A 5volt/1Amp tablet charger is common/cheap.

If you want opto isolation, then you need a separate relay coil supply and a separate Uno supply.
In that case, grounds of the two should not be shared.
Opto isolation could be wise if the relays are used for switching mains power.
Leo..

Wawa

The 8 relay COM will share the same 5V as the Arduino UNO board...
So what is it used for.
If you're using low voltage devices (motors, LEDs), then switching with logic level mosfets might be easier.
They don't draw the current a relay does (~80mA each), and they don't make noise.
Leo..

niss3

#11
Feb 26, 2018, 07:40 pm Last Edit: Feb 26, 2018, 07:45 pm by niss3
I got myself a 5V 1,2A adapter (it's adjustable).


And just when I got it, I noticed my board module I'm splitting the power with requires at least 6.5V to properly function. I  switched up my adapter to 9V, It delivers 0.65A with 9V.

Something weird that happens is that my relay "flickers" when I use the adapter. This does not happen with USB power.

Is this because the adapter is too weak?

Video: (most of the wires aren't connected yet, as I were just testing the first relay)
http://puu.sh/zwcZs/37d44f1f5e.webm

niss3

I tried wirering the 5V from the Arduino UNO to both the COM and VCC on the relay just to see if my wireing/grounding could have been the problem. But I experience the same issue.

I guess it's leaning towards my power adapter not beeing up to the task since it can't even get one single relay to function?

niss3

So what is it used for.
If you're using low voltage devices (motors, LEDs), then switching with logic level mosfets might be easier.
They don't draw the current a relay does (~80mA each), and they don't make noise.
Leo..

I'm just using the relays to open/close 5V circuits.

niss3

If I skip the whole idea with using relays and go for transistors instead. What kind of transistor do I need to simply pass through 5V? It got to be a super small one, right?

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