Electrical – How to connect LED driver to arduino

To drive LEDS, you have two options, each with their own pros and cons a) linear b) switching

a) linear, dissipates excess heat, simple (LM317) (or relatively simple)

b) switching, low dissipation, potential switching noise

To choose between these two, and then to choose which way to implement either, you need to look at your other constraints. Heat? Cost? Board area? Able to control finely? Design skills?

You can get integrated solutions for both methods. Maxim IC do a gazzillion drivers in both types, try sampling them for one or two.

Linear devices will always get hot. At 0.5A, with a few volts drop, you will always need to think about heatsinking, whether you use an integrated or discrete solution

FWIW, my personal preference for a linear multi-colour driver, and OK, it takes large board area, is a discrete solution. Each channel uses a TO-220 MOSFET, with a small resistor in the source to monitor sink current, driven by 1/4 of an LM324 op-amp, driving the gate to servo the source voltage to maintain the drain sink current, 3 channels uses 3 FETs and 3/4 of the LM324. The compare voltage to the 324 inputs allows you to set the currents. The heat dissiaption is spread over several big cheap devices. TO220s are good for 1 to 2 watts in free air, to 100watts on a heat sink, so it's scalable to many amps and higher voltages, still staying with cheap MOSFETs.

There are so many integrated LDO (low dropout) regulators available that can be configured as current sources that it would be futile for anybody other than you to start trawling through them. Look for voltage input range, heat dissipation, package size, AND ABILITY TO WORK WITH WHAT TECHNOLOGY STABILISATION CAPACITOR, ie ESR (ceramic, tant, alli elec), as you don't what them to oscillate in service.

To do without the heat, investigate integrated switching solutions.

You need to control the current going through the LED strip. You can control the Vgs of the MOSFET to turn the current on and off. You put the MOSFET on the low side because that way you can use the Arduino's low-voltage output to apply 0V or 3.3V (5V depending on the Arduino) to the gate of the MOSFET. Because the source of the MOSFET is grounded, that controls the MOSFET Vgs (the voltage between gate and source) turning it on and off.

^{simulate this circuit – Schematic created using CircuitLab}