Quarryman

Safe voltage for powering EV3 from external power supply

Recommended Posts

I guess the title says enough, but anyway; I've been looking into powering an EV3 brick from external power supply and have bought one that was supposed to be 9V. Unsurprisingly when measuring the output with my multimeter I got a different voltage at 9.48V (that's what you get for buying cheap from China..).

Obviously I don't want to fry my EV3 brick which is why I turn to you excellent people. Is 9.48V too much or not? And what is the safe range of voltages the EV3 can take anyway?

Share this post


Link to post
Share on other sites

Interesting question.

I am totally NOT sure, but I would be surprised if the EV3 can't handle 9.48V. But I would love to hear the experts opinion as well.

Share this post


Link to post
Share on other sites

The electronics are 5V or 3.3V.  There would be voltage regulators on the circuit board dropping the supplied voltage from batteries or power adapter to 5V / 3.3V. 

Unless it's a laboratory test bench power supply, you are not going to get precisely 9V out of any wall wart adapter.  I don't think an extra 0.48V is going to cause it to self-destruct.  Supplying 48V on the other hand...

 

Share this post


Link to post
Share on other sites

It should be fine, a set of brand new batteries can deliver 9.6v (1.6v x 6) or higher for a short time, so I'm sure you won't hurt it with an extra 0.48v.

Saying that though, I would still add some extra protection (something like what was used here), just in case... :wink:

Share this post


Link to post
Share on other sites
11 hours ago, Quarryman said:

I guess the title says enough, but anyway; I've been looking into powering an EV3 brick from external power supply and have bought one that was supposed to be 9V. Unsurprisingly when measuring the output with my multimeter I got a different voltage at 9.48V (that's what you get for buying cheap from China..).

9.48V, this is not bad, this is normal. May we have a link to see what do you mean about "external power supply".

Share this post


Link to post
Share on other sites

Thanks for the feedback everyone, it's been very helpful. I knew some variation was to be expected, just not sure how much, so it's a relief to learn that 0.48V is normal and not something to worry about. I'll post a link later to the power supply I got, on my phone now so getting a link is a bit too much work.

EDIT: this is the one I bought, but obviously there are dozens more like it available: https://www.aliexpress.com/item/9V5A-45W-AC-DC-Adapter-Charger-9V-5A-POS-machine-credit-card-machine-Switch-Power-Supply/32838762644.html

Share this post


Link to post
Share on other sites
Posted (edited)

Hi,
I just stumbled into this topic and took a look at your powersupply.
First thing that took my attention was the symbol after DC9V
You see there an = symbol with a lower broken line wich means this supply is not stabilised.
This means the output will be somewhere around 9V and will have some leftover of AC in it and for sure is NOT exactly 9V
(aka an unregulated PS)
When the symbol was an = it would.
 

Edited by coinoperator

Share this post


Link to post
Share on other sites
On 1/3/2019 at 2:44 PM, coinoperator said:

Hi,
I just stumbled into this topic and took a look at your powersupply.
First thing that took my attention was the symbol after DC9V
You see there an = symbol with a lower broken line wich means this supply is not stabilised.
This means the output will be somewhere around 9V and will have some leftover of AC in it and for sure is NOT exactly 9V
(aka an unregulated PS)
When the symbol was an = it would.
 

Thank you! That is very useful to know, my knowledge about these things are, as I'm sure you understand, rather limited, so learning more is always good! Guess I'll have to at least check the power supply I bought closely, I wouldn't be surprised if the image on AliExpress doesn't match the one I got. 

Share this post


Link to post
Share on other sites
On ‎1‎/‎6‎/‎2019 at 12:39 PM, Jim said:

I have ordered this one for my robot. It's awesome!

https://nl.aliexpress.com/store/product/15000mAH-DC-5V-9V-12V-USB-High-Capacity-Rechargeable-Li-ion-Battery-Pack-Charger/3871001_32867193291.html

Rechargeable, 12V, 9V and 5V! Granted, it's not the cheapest solution, but it sure fits my needs.

I am not very clever about LiPo charger, but are you sure this is a LiPo charger ?

Look at this one, I have the same, https://fr.aliexpress.com/item/IMAX-B3AC-Compact-Charger-Pro-Lipo-Battery-Adapter-2S-3S-7-4V-11-1V-Professional-Balance/32752543289.html?spm=a2g0w.10010108.1000016.1.227d4c94pauvNh&isOrigTitle=true

As you can see, there are two connectors. One for 2S battery and one for 3S battery.

When you charge a battery, the 2 or 3 led lights red, then green. This is very important. My research is "charger lipo rc".

Be careful, a LiPo battery have to be charged by a LiPo charger.

Share this post


Link to post
Share on other sites
5 hours ago, Quarryman said:

Thank you! That is very useful to know, my knowledge about these things are, as I'm sure you understand, rather limited, so learning more is always good! Guess I'll have to at least check the power supply I bought closely, I wouldn't be surprised if the image on AliExpress doesn't match the one I got. 

Best thing you do is buy a powersupply in a local store, these things cost peanuts but are considerably SAFER than the ali stuff..
Yes safer, the ali PS's have a know habit to cause fire because of there "good construction".

Just ask for a regulated PS

I buy lots of stuff on Ali, usually nothing wrong with it but please do not buy any loader, charger, powersupply or similar equipment there cause these have not even the slightest safety and there's no control over it at all.
The Lego PS is ridiculous in price but an universal loader should not cost more than 10 $€& orso

Share this post


Link to post
Share on other sites
6 hours ago, oracid said:

I am not very clever about LiPo charger, but are you sure this is a LiPo charger ?

I think I posted this in the wrong topic. I was browsing mobile and I wasn't aware I was in your EV3 battery topic. I don't think my battery is a proper solution :wink: 

Share this post


Link to post
Share on other sites

the voltage of your powersupply will drop if you attach a load to it (such as an ev3,nxt or whatever) however i dont think this would be a problem since the ev3 and nxt have voltage regulators built in. 

XGBC

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

  • Recently Browsing   0 members

    No registered users viewing this page.