Voltage Regulator - Arduino pulling current

[Hodzilla]

Hello,

I need to power my Arduino MEGA2560 through the Vin port, and I'm using a 24V power supply. I read other forums for help on how to drop the voltage to 6-12V using a LM317T voltage regulator and i've successfully done that, I'm getting 7.4V on the output of the regulator.

Now, when I connect the output voltage into the Vin port, my power supply says its outputting 0.06-0.07 amps along with the 24V (i'm using a variable power supply for prototyping).

The regulator gets very hot even with a heat sink on it. I've tried dropping the voltage in stages using multiple regulators. Using two regulators lowers the output current to 0.03 amps, however three regulators brings it back up to around 0.07 amps. Currently I have the two regulator setup going where the output of the first regulator is the input of the second.

Is this normal, or should I consider another approach. My main concern is burning out the Arduino with the current.

I should add that I will have a large NEMA 34 stepper motor, the stepper motor driver, an HMI, and an 8V relay connected to the Arduino when it's all said and done. I'm not sure if that information will be useful.

[LarryD]

The power dissipated by the voltage regulator is = to the current being drawn X the voltage across the regulator (input to output).

The efficiency of a linear regulator is low.

Get a ‘Buck Converter’, many have 95% efficiency.

[SteveMann]

Hodzilla:
The regulator gets very hot even with a heat sink on it. I've tried dropping the voltage in stages using multiple regulators. Using two regulators lowers the output current to 0.03 amps, however three regulators brings it back up to around 0.07 amps. Currently I have the two regulator setup going where the output of the first regulator is the input of the second.

Is this normal, or should I consider another approach. My main concern is burning out the Arduino with the current.

That extra 16V has to go somewhere. It is being dissipated as heat.

See my post on a similar question.

[Hodzilla]

larryd:
The power dissipated by the voltage regulator is = to the current being drawn X the voltage across the regulator (input to output).

The efficiency of a linear regulator is low.

Get a ‘Buck Converter’, many have 95% efficiency.

Thank you. I was considering this but I was trying to stay away from potentiometers. I'll just glue the screw once it's set.

[LarryD]

These are 10 turn pots, they really do not need sealing.

However, a drop of Glyptal paint or glue will work if you think it is necessary.

[bluejets]

There are also "fixed output" versions but what I don't see the reason for is the 24v supply in the first place.

[wvmarle]

Hodzilla:
I need to power my Arduino MEGA2560 through the Vin port

Why must you use the Vin? Why not simply get a buck converter with 5V output and use the 5V pin?

Also interesting you have an 8V relay. That's a highly unusual voltage for a relay. If you have a 5V relay you can use the same buck converter that powers the Arduino for the relays. No worries about overheating regulators.