12v 3a power issue - arduino restarting

To start, my project consists of (not really important, but gives tad more context):

  • Arduino Mega R3 2560
  • 3-5v Realtime Clock
  • 3-5v SD Card Reader
  • 16 channel relay board
  • #10 - 12v-1a perstaltic pumps hooked up to relay board (only 1 is ever powered on at any given time)
  • #2 - 5v flow meters

So I recently switched my project from a 12v-1a power supply to a 12v-3a power transformer found here:

SEE 12V-3A Power Supply Here

When using my 12v-1a power supply, things were “stable” and everything worked… I would just get some LCD screen brightness dimming flickering when using one of the 12v peristaltic pump motors, but never did the actual arduino restart / crash.

However once I hooked up this 12v-3a power supply, everything loads up, but with LCD screen barley readable. The readability of the LCD continues to get harder and harder to read over say 10 seconds, then boom Arduino restarts. I know this is not correct, and have only been done quick tests and not leaving it on continuously restarting out of fear I could be harming stuff.

If I had to take a guess, I think what is going on is that with my 12v-1a power supply the voltage that would ultimately be reaching the micro controller was down to about 5v-7v… however now with this 12v-3a supply, I think the micro controller is getting a full 12v and it might be over powering it? Any feedback on my hypothesis and possible solution would really be appreciated!

Thanks in advance.

Have you measured the supply voltage under load?

I have, and under load I'm getting a reading of 11.1v but slowly climbs up to 11.45v and boom Arduino resets / voltage settles at 11.55v. Without load I'm getting a reading of 12.3v.

I'm also getting a reading of .3amps but that also climbs up to about .4amps and boom resets and settles at .5amps.

I meant Vcc (5V?). If the regulator is going into thermal shutdown you will see it there. The regulator may not like dissipating that much power (on the order of 0.3A x 6.5V I guess). Can you provide a schematic of your project?

That 16-channel relay board.
Is that the one with onboard 5volt buck converter, that also provides the Arduino with 5volt.
Diagram, code, pictures, and links to parts.
Need all if you want proper answers.

Sorry for delay, hectic work day.

So that essentially is my schematic when using the 12v 1a transformer power supply, but is the same thing with this new 12v 3a transformer.
The flow meters mentioned above are not in the schematic, but are powered form the 5V out source of ardunio.

As you can see I have the opportunity to completely remove the relay / pumps from my power supply to eliminate it from the source of the problem, and indeed I did and results were the same.

Here are the parts in question:
GEREE AC DC Power Module Supply
SainSmart 16-Channel Relay Module
12V DC Peristaltic Liquid Pump
Real time clock memory module Arduino
Micro SD Storage Board
Kuman 1602 Shield Module LCD Display V3

I meant Vcc (5V?). If the regulator is going into thermal shutdown you will see it there.

Sorry I'm not sure what you mean (sorry, kinda noob still). I power my arduino through the power jack, and other than hooking my multi-meter into the positive side of the power going to my arduino, I don't know how to measure the its Vcc in that way.

Now that said, I think what I might want to try next is a L7805 or L7806 resistor with 1uF capacitors to limit the current going to the arduino to 5v or 6v 1.5a and go from there to make sure the onboard regulator isn't pooping out as suggested above.

The 12volt supply should NOT connect to the DC socket of the Aduino.

VCC and GND of the pinstrip on the relay board should be connected to 5volt and ground of the Mega.
That relay board has a 5volt buck converter that powers the relays as well as the Mega.

That board has a serious design flaw. Optos, but no opto isolation.
Not a big issue as used here for low voltage LED applications.

Looking at your "circuit" picture, although you label the LED + and -, the symbol is back to front.

Tom... :slight_smile:

Thous are not LEDs they are 1N4007 1A diodes across the terminals of the pump motors.

Looking at your "circuit" picture, although you label the LED + and -, the symbol is back to front.

Tom... :slight_smile:

Cathodes are commonly labelled + on rectifier diodes, but should not be labelled on LEDs, since
they are not being used to generate a voltage rail.

Parts arrive in the morning (sadly I live in the worst spot to be able to drive and just pick up electronics parts) but in the mean time I went ahead and hooked up the power to the arduino from the relay's 5v and ground instead, however soon as I plugged it in all the relays on the board went on and off so fast it sounded like a rattle snake was in my project box and arduino / LCD sheild just flashed.. Scarred the crap out of me so didn't let it last for more than 2 seconds or try further.

So now I'm more convinced than ever that with the 12v 1a transformer, I was getting down stepped to a suitable voltage for the arduino + LCD sheild by sheer luck because of all the devices before it were also consuming power. Now however, a full 12v can reach the arduino and thus I get my results form my first post. My required voltage however must be slightly higher than what the relay board can output (with both transformers; yes I went ahead and tried both) and results in the rapid shut down and relay to turning into a "rattle snake" (should be a real electronics term btw).

So we will see what happens with the 5v or 6v resistors (with optional capacitors) between arduino and new power source and see if we can get this sorted.

Thanks you all, seriously! I should have more results soon.

Can you post a complete circuit diagram, a hand drawn one would be fine.
Please include ALL your components, including.

  • Arduino Mega R3 2650
  • 3-5v Realtime Clock
  • 3-5v SD Card Reader
  • 16 channel relay board
  • #10 - 12v-1a perstaltic pumps hooked up to relay board (only 1 is ever powered on at any given time)
  • #2 - 5v flow meters

Thanks… Tom… :slight_smile:
A picture of your project would allow us to see to see your component layout.

Sorry I honestly forgot to reply back here!
I was indeed able to solve my power issue(s) by using a L7812cv regulator between this 12v-3a power transformer and the Mega2560. I of course had to use a pretty beefy heat sink (is a must!) to keep the regulator nice and cool, but so far doing good.

I also (due to read, write and file create issues) had to stop powering my micro SD reader directly off the Mega2560, but instead use a L7805cv between the L7812cv mentioned above and Mega2560 (no heat sink) to break out a dedicated 5v for the SD reader (micro SD reader is a 3v-5v chip btw).

So far everything is working great!

Did you put the datasheet prescribed capacitors around the L7812cv and L7805cv regulators?

Tom... :slight_smile:

I did, sorry box is closed up now, and forgot to mention that.
Although things ran find without them, I as prescribed used two 1UF capacitors for both L7812 and L7805 (4 total). One capacitor on regulator's "out" pin / center ground pin, the capacitor on the regulator's "in" pin / center ground pin.

Thanks again Tom!

I think you are experiencing electrical noise. Try soldering 0.1 uF ceramic capacitors across your pumps. These protect your digital circuits from electrical noise from the motors and voltage dips.