Voltage REG gettign even hotter :S

I made a post about this a while back, as to whether it made a difference powering my shield form the Vin pin, and plugging the power adapter into the arduino, or plugging the power adaptor into the shield and sending the power to the arduino.

Either way my voltage reg and the 2 silver capacitors? was getting hot driving 1.5M of SMD5050 RGB LED strip. Now I have a full 5M of stip connected and it's gettign really really hot after a few seconds.

But why is this? Surly the 12V line that runs to the shield via the Vin pin doesn't go through any of these components? I don't see why the shield drawing more current is making the arduino board hotter.

Whatever's going on - how can I stop it?

I am not familiar with the shield you are talking about... I don't even know what type of shield you are using. You are using a "LED strip" and the regulator is hotter... For me, it mean to much current being use by the shield and the leds strips, and also with a higher voltage into the regulator simply make things worse.

In my opinion, the solution is to use a separated supply --> one for the microcontroller and the other for the shield / leds strips. If possible and reduced the input voltage to between 7 to 9.

What shield are you talking about?

Are you sure your shield isn't drawing anything from the Arduino's 5V pin?

That's what I'm saying. I have a 12V DC supply connected to a socket on the shield. This supply is connected to some FETs that drive the LED strip. It's also connected to the Vin pin on the Arduino providing power to it.

So it shouldn't matter what is connected to the shield because the shield is providing the power to the arduino board. So why does the arduino board get hotter the more power the shield uses?

Tmp2k:
So it shouldn't matter what is connected to the shield because the shield is providing the power to the arduino board.

If that were the case, you wouldn't be asking the question, would you?

Tmp2k:
So why does the arduino board get hotter the more power the shield uses?

This implies you are drawing power from the 5V node.

What shield are you talking about?
If you want an usable answer, you probably need to provide some form of schematic or better hardware description than "the shield."

I dont have any schematics for the shield it's all in my head, but the finer details of how the board actually works aren't really relevent.

Here's a very brief description of the shield. It uses the 6 PWM channels to drive 6x P channel FETs via NPN transistors. The shield has it's own DC jack socket. The only connections to the arduino board are the 6 PWM channels, all of the GNDs and Vin. No other pins are connected. The FETs are good for 60A each, but 5M of LEDs only draws 6A on full white.

Here's a pic of it to give you a better idea, but this pic shows the shield UNFINISHED. It now has the other 3 channels on there adn of course the 12v socket.

With the power adaptor plugged into the shield, when you drive the LEDs on full brightness or connect up all 5M the arduino board gets hot.

I can't see how the current being drawn by the shield should have any impact on the arduino board when the power is connected to the shield.

I'll get the ammeter on it and find out exactly what's going on, but I just though someone on here might know what's going on as it all seems a little odd.

With out a schematic of your circuit, we can't look into your head and understand why there would be excessive current draw.

What is your 'shield' board doing/using the Vin pin for?
Where is the Arduino board getting it's operating power during these heat incidents?
What is the voltage value of your external DC source for your shield?

Lefty

I dont have any schematics for the shield it's all in my head, but the finer details of how the board actually works aren't really relevent.

The "shield" I see in the picture, it a DIY shield. It's solder into a Proto Shield. Therefore, anything can be wrong. Like : bad soldering, short, open, badly design circuit, no safe gard ( Arduino pins draw to much currents - pass or close to 40 mA per pins )

Therefore, the board actual circuit and the workmanship is relevant.

Here why -->

With the power adaptor plugged into the shield, when you drive the LEDs on full brightness or connect up all 5M the arduino board gets hot.

That one of the raison.

I can't see how the current being drawn by the shield should have any impact on the arduino board when the power is connected to the shield.

If each digital pins draw too much current ( close to 40 mA ), my answer would be ...YES...it is possible

but I just though someone on here might know what's going on as it all seems a little odd.

Well...without a schematic and how it is wire, it going to be hard to find out.

I can draw a schematic of all the components but it's going to take me a while. It's just an NPN (2N3904), with a 10K resistor on the base driving a P-Chan FET(FQP27P06) with a 10K resistor across the gate and source.

Here's how it's connected up. The only pins that are connected to teh arduino board are Vin, GND and 6 PWM outputs.

The shield uses the Vin pin to supply 12V to the arduino board.

The power is connected to the shield, which then supplies the arduino.

The PSU is outputting around 11.7V depending on load

I can draw a schematic of all the components but it's going to take me a while.

If you can show 1 output channel, that might be enough.

It's just an NPN (2N3904),

If there's no limiting resistor into the base of the transistor, that could be the problem.

Techone:

I can't see how the current being drawn by the shield should have any impact on the arduino board when the power is connected to the shield.

If each digital pins draw too much current ( close to 40 mA ), my answer would be ...YES...it is possible

But if the problem was on the low current side of things, why would it only get how when driving more LEDs? Say the outputs were drawing too much current, wouldn't the board get hot regardless of how much current the FETS were handling as the high current draw would be in the output>transistor circuit, not the +12V > FET > LED circuit.

DVDdoug:

I can draw a schematic of all the components but it's going to take me a while.

If you can show 1 output channel, that might be enough.
I'll get drawing tomorrow it's gone midnight here :slight_smile:

It's just an NPN (2N3904),

If there's no limiting resistor into the base of the transistor, that could be the problem.

It's just an NPN (2N3904), with a 10K resistor on the base

Would 10K not do the trick?

What are the small value resistors with the largest power rating you have? See if you have something around 50 ohms or so. Connect it between Vin and Gnd (only the resistor, no shield.) Ideally, put some in parallel, one at a time.

The idea is to draw current through the Vin pin through the simplest device possible: a resistor. If the regulator area isn’t getting hot, then you know it is something about your circuit.