UBEC adversely affecting arduino

Projects General Guidance
1

Hi all

I'm working on a project which uses an arduino mega with a gsm unit and gps unit.

As the project will be powered by (9v) battery I bought a UBEC (this one here- http://www.hobbywing.com/uploadfiles/sx/file/manual/HW-03-6S.pdf) to save power (otherwise the linear regulator on the arduino will burn excess power off).

However, I seem to have run into a problem in that when the GSM unit starts it shuts down after a few seconds. It doesn't do this without the UBEC (directly powering from the battery to the arduino power jack).

I suspect that the GSM unit isnt getting enough power (I think startup uses the most power). The UBEC is rated for 3a which I thught would be enough.

Any ideas on how to resolve this?

Thanks

2

An average 9volt block battery is 300mAh, and you can drain maybe 50mA for a short time.
A Mega and gsm and gps and DC/DC converter will draw 250mA or more.
No match for a 9volt battery.

Even a string of AA batteries will have trouble with this.
Think 12volt car battery.
Or at least a 2C or 3C 5Ah LiPo pack.
Leo..

3

You didn't mean to use a PP3 battery, did you?

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4

Any ideas on how to resolve this?

Use your multimeter to monitor the output voltage of your 9v battery. That should give indication of what may be going on with your setup.

5

Paul__B:
You didn't mean to use a PP3 battery, did you?

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Sorry i wasn't very clear - not a pp3 but rather 9 x aa batteries (1.5v) = 9v.

6

Hi,
Have you tried what zoomkat asked in post #3?

Can you please post a copy of your circuit, in CAD or a picture of a hand drawn circuit in jpg, png?

Tom.... :slight_smile:

7

rather 9 x aa batteries (1.5v) = 9v.

Your calculator needs new batteries. 9 times 1.5 is not 9.

8

PaulS:
Your calculator needs new batteries. 9 times 1.5 is not 9.

eek... 6 aa batteries!

9

TomGeorge:
Hi,
Have you tried what zoomkat asked in post #3?

Can you please post a copy of your circuit, in CAD or a picture of a hand drawn circuit in jpg, png?

Tom.... :slight_smile:

I've got my multimeter out.

Without the UBEC the voltage supplied to the GSM unit is 4.9 - 5v

However when the UBEC is used the voltage supplied to the GSM unit is approx 3v.

What's going on here?

10

Any ideas why the 5v pin on the arduino is only giving 3v or so when the UBEC is used?

11

Hi,
Measure the voltage at your battery pack, see what it does when you run your project.

Can you please post a copy of your circuit, in CAD or a picture of a hand drawn circuit in jpg, png?

Tom.... :slight_smile:

12

GSM modules can use up to 1A of power. Your AA cells are rated for .2A. When the GSM module starts pulling a lot of current and the battery can't keep up you see the voltage drop.

13

I found that if I use the power jack on the arduino there is a voltage drop so if you are only supplying 5 volts then that would explain why the problem only occurs when using the ubec and not the battery pack.

I use a buck converter off ebay the output voltage can be adjusted and it can supply 2 amps without cooling or 3 amps with, so far it has not caused me any problems but I have only been using arduino for a few weeks so time will tell.

14

Chagrin:
GSM modules can use up to 1A of power. Your AA cells are rated for .2A. When the GSM module starts pulling a lot of current and the battery can't keep up you see the voltage drop.

ok but then why does it work fine without the UBEC?

15

Ifly4S:
I found that if I use the power jack on the arduino there is a voltage drop so if you are only supplying 5 volts then that would explain why the problem only occurs when using the ubec and not the battery pack.

I use a buck converter off ebay the output voltage can be adjusted and it can supply 2 amps without cooling or 3 amps with, so far it has not caused me any problems but I have only been using arduino for a few weeks so time will tell.

Do you get the same problem when connecting the battery to VIN?

16

As I am new to arduino I have only used usb and the power jack to supply the arduino I have not used VIN.

If you check the specs for the Mega on the arduino web site its states the recommended input voltage as 7-12 volts.

17

ah, so a UBEC going to 5v is pointless...

The board can operate on an external supply from 6 to 20 volts. If supplied with less than 7V, however, the 5V pin may supply less than five volts and the board may become unstable. If using more than 12V, the voltage regulator may overheat and damage the board. The recommended range is 7 to 12 volts.

18

So connect the UBEC to a USB socket?

19

Why cant you just connect the 9 volt battery pack to the Mega using the power jack?

20

Ifly4S:
Why cant you just connect the 9 volt battery pack to the Mega using the power jack?

Because that's pretty inefficient - the point of the UBEC is to save power.