📋 Overview
The Envistia 20mA LED Driver is a constant current regulator (CCR) module that delivers a steady 20mA to your LEDs — no resistor calculations required. When you apply a DC voltage (2V to 45V) across the module and your LED circuit, the driver actively adjusts its own internal resistance to maintain a constant 20mA of current flowing through the circuit, regardless of voltage fluctuations.
Think of it as a smart, self-adjusting resistor. Instead of calculating and sourcing the correct resistor value for your specific LED and voltage combination, you simply wire this module in series with your LEDs and it handles the rest. If your supply voltage changes — as it does in automotive systems where battery voltage can swing from 11V to 14.5V — the driver compensates automatically, keeping your LEDs at a consistent brightness.
The module is built on a small PCB with through-hole pins spaced at 0.4 inches (10.16mm), making it easy to solder into a circuit or plug into a breadboard. Multiple modules are provided on a scored circuit board that can be snapped apart by hand.
⭐ Key Features
- Constant 20mA Output — Delivers a regulated 20mA (±2mA) regardless of input voltage, eliminating the need for current-limiting resistors
- Wide Input Voltage Range — Operates from 2V to 45V DC across the module (recommended maximum 20V for long-term reliability)
- Tight Current Tolerance — ±2mA accuracy, tighter than many competing products that only offer ±3mA, ensuring more consistent LED brightness across multiple circuits
- No Calculations Required — Drop-in replacement for current-limiting resistors; no need to calculate resistor values for different LED and voltage combinations
- Voltage Fluctuation Immunity — Automatically compensates for voltage changes, perfect for automotive and solar systems where supply voltage varies
- Series LED Support — Can drive multiple LEDs wired in series, as long as the total voltage overhead requirement is met
- Breadboard and PCB Friendly — Through-hole pins with 0.4-inch (10.16mm) spacing fit standard breadboards and are easy to solder
- Parallel Stacking — Wire multiple modules in parallel to increase current (40mA, 60mA, etc.) for higher-current LED applications
- Compact Module Format — Mounted on a PCB for easier handling and soldering compared to bare surface-mount components
- Scored Panel — Modules are provided on a scored circuit board that snaps apart easily
📊 Specifications
| Output Current | 20mA ±2mA |
| Input Voltage (Vak) | 2V to 45V DC (across the module) |
| Recommended Maximum Input Voltage | 20V * |
| Voltage Overhead | ~1.8V (minimum voltage drop across the module for regulation) |
| Module Dimensions (excluding pins) | Approx. 15.75 × 5.6 × 2.8 mm (0.62 × 0.22 × 0.11 inches) L × W × H |
| Pin-to-Pin Spacing | 10.16 mm (0.4 inches) |
| Pin Type | Through-hole |
| Form Factor | PCB module on scored panel |
* Note on Maximum Voltage: While the driver IC is rated for up to 45V, we recommend a maximum of 20V across the module for long-term reliability. At higher voltages, the module must dissipate more power as heat, which reduces its lifespan. For most LED applications — including 12V automotive — you'll be well within this recommended range. See the Power Dissipation and Heat section below for details.
🔧 How It Works
The 20mA LED Driver uses a constant current source IC — a two-terminal device that behaves like a self-adjusting resistor. Here's what happens when you wire it into a circuit:
- You apply a DC voltage to the circuit — for example, 12V from a car battery.
- The LEDs consume their forward voltage — for example, a red LED might use about 2V.
- The remaining voltage drops across the driver module — in this example, about 10V.
- The driver actively regulates its internal resistance so that exactly 20mA flows through the entire series circuit.
- If the supply voltage changes (say the car battery goes from 12V to 14.4V while the alternator is charging), the driver absorbs the extra voltage and keeps the current at 20mA. Your LED brightness stays constant.
This is fundamentally different from a fixed resistor. A resistor is calculated for one specific voltage — if the voltage changes, the current changes, and your LED gets brighter or dimmer (or burns out). The CCR driver eliminates that problem entirely.
The Overhead Voltage Requirement
The driver needs a minimum of approximately 1.8V across itself to regulate properly. This is called the "overhead voltage" or "dropout voltage." If the voltage across the driver drops below 1.8V, it can no longer maintain 20mA and the current will decrease.
This means your minimum supply voltage must be:
Minimum Supply Voltage = LED Forward Voltage(s) + 1.8V (overhead)
💡 Example: If you're driving a single blue LED with a forward voltage of 3.2V, your minimum supply voltage is 3.2V + 1.8V = 5.0V. A 5V USB supply would work, but just barely. A 9V or 12V supply gives plenty of headroom.
🔌 Wiring and Connections
Basic Single-LED Circuit
The simplest circuit is one LED and one driver module in series:
(+) Power Supply ──── Anode(+) LED Cathode(-) ──── Driver Module ──── (-) Power Supply
OR
(+) Power Supply ──── Driver Module ──── Anode(+) LED Cathode(-) ──── (-) Power Supply
⚠️ Important: The driver module is polarity-sensitive. It must be wired in the correct orientation or it (and your LEDs) could be damaged. Check the markings on the module PCB for the correct direction of current flow. The module can be placed anywhere in the series loop — before the LED, after the LED, or between LEDs — with the module’s anode (the tail end of the arrow silkscreened onto the board) toward the +V power supply, and the module’s cathode (arrow end) toward the ground/-V as shown in the figures below.
Multiple LEDs in Series
You can drive multiple LEDs in series with a single driver module. The LEDs and the driver are all wired in one loop:
Schematic showing the typical circuit configuration driving one or more LEDs with the Envistia 20mA LED Driver placed in the circuit before the LEDs
Schematic showing an alternate circuit configuration driving one or more LEDs with the Envistia 20mA LED Driver placed in the circuit after the LEDs
The number of LEDs you can drive in series depends on your supply voltage. Add up the forward voltages of all the LEDs, then add the 1.8V overhead:
Minimum Supply Voltage = (LED1 Vf + LED2 Vf + LED3 Vf + ...) + 1.8V
Series LED Calculation Examples
| Supply Voltage | LED Type (Typical Vf) | Max LEDs in Series | Calculation |
|---|---|---|---|
| 5V | Red (2.0V) | 1 | 2.0 + 1.8 = 3.8V needed (room for 1 LED) |
| 9V | Red (2.0V) | 3 | (3 × 2.0) + 1.8 = 7.8V needed |
| 12V | Red (2.0V) | 5 | (5 × 2.0) + 1.8 = 11.8V needed |
| 12V | White (3.2V) | 3 | (3 × 3.2) + 1.8 = 11.4V needed |
| 12V | Blue (3.2V) | 3 | (3 × 3.2) + 1.8 = 11.4V needed |
| 12V | Green (3.0V) | 3 | (3 × 3.0) + 1.8 = 10.8V needed |
| 24V | White (3.2V) | 6 | (6 × 3.2) + 1.8 = 21.0V needed |
💡 Tip: Always leave some voltage headroom above the minimum. For automotive 12V systems, the actual battery voltage can dip to 11V during cranking and rise to 14.5V while charging. Design your series string so that the minimum supply voltage (11V) still exceeds the total LED forward voltage plus 1.8V overhead.
Increasing Current with Parallel Modules
If you need more than 20mA — for example, to drive a high-brightness LED rated at 40mA or 60mA — you can wire multiple driver modules in parallel:
Two 20mA LED Driver Modules in parallel to provide ~40mA current to the LED string
Result: 20mA + 20mA = 40mA through the LED
Each module independently regulates its own 20mA, so the total current through the LED is the sum of all parallel modules. Three modules in parallel = 60mA, and so on.
⚠️ Important: Make sure your LED is rated for the total current. A standard 5mm LED is typically rated for 20mA. High-brightness LEDs may be rated for 30mA, 60mA, or more — check your LED's datasheet.
🔋 Power Dissipation and Heat
The driver module regulates current by converting excess voltage into heat. The more voltage the module has to "absorb," the more heat it generates. This is why we recommend a maximum of 20V across the module, even though the IC is rated for 45V.
Calculating Power Dissipation
The power dissipated by the driver module is:
Power (Watts) = Voltage across the module × 0.020A
The voltage across the module is whatever is left over after the LEDs take their share:
Voltage across module = Supply Voltage − Total LED Forward Voltage
| Supply Voltage | LED Vf Total | Voltage Across Module | Power Dissipated |
|---|---|---|---|
| 5V | 2.0V (1 red) | 3.0V | 60mW |
| 12V | 6.0V (3 red) | 6.0V | 120mW |
| 12V | 9.6V (3 white) | 2.4V | 48mW |
| 24V | 6.0V (3 red) | 18.0V | 360mW |
| 45V | 6.0V (3 red) | 39.0V | 780mW |
💡 Tip: For the best efficiency and longest module life, design your series LED string to use as much of the supply voltage as possible, leaving only the minimum ~2V overhead for the driver. This minimizes the power the driver has to dissipate as heat. For example, on a 12V supply, three white LEDs (9.6V total) leave only 2.4V across the driver — very efficient. One red LED (2V) leaves 10V across the driver — it works fine, but the driver runs warmer.
📌 Pinout and Orientation
The module has two pins — it's a simple two-terminal device wired in series with your LED circuit. However, polarity matters. The module must be oriented correctly in the circuit for proper operation.
- Check the markings on the PCB for the directional arrow showing current flow direction. The module’s anode (the tail end of the arrow silkscreened onto the board) goes toward the +V power supply, and the module’s cathode (arrow end) toward the ground/-V.
- The module goes in series with the LED(s) — it can be placed before or after the LEDs in the loop, as long as the polarity is correct relative to the direction of current flow.
- Current flows from the positive terminal of your power supply, through the LED(s), through the driver module, and back to the negative terminal.
20mA LED Driver PCB showing the current flow direction
⚠️ Warning: Incorrect polarity can damage both the driver module and your LEDs. If your LEDs don't light up, the first thing to check is whether the driver module is oriented correctly.
🧪 Installing the Driver on a Prototyping Breadboard
The LED Driver has 0.032″ solder holes which can accommodate wire down to 22AWG or standard 0.1″ header pins. The pin-to-pin spacing is 0.4 inches, designed to fit standard proto board hole spacing, as shown in the figure below.
Alternately, instead of using the pins, wires can be soldered directly to the plated-through holes. For electrical and environmental protection, it can be covered with heat-shrink tubing.
📏 Dimensions and Mechanical Information
The modules are provided on a scored circuit board that can easily be broken apart. Two 0.1″ header pins are included with each module.
🎯 Common Applications
- 12V Automotive LED Lighting — Dash indicators, accent lighting, interior lights, and custom LED installations in cars, trucks, motorcycles, and ATVs. The driver handles the 11V–14.5V voltage swings automatically.
- Model Railroad and Scale Models — Consistent LED lighting for buildings, signals, and rolling stock powered from variable DC track power or dedicated supplies.
- LED Indicator Circuits — Status indicators on custom electronics, control panels, and enclosures where you want consistent brightness without calculating resistor values.
- Hobby and Maker Projects — Arduino, Raspberry Pi, and breadboard projects where you want a simple, reliable way to drive LEDs from various voltage sources.
- Marine and RV Lighting — 12V LED installations on boats and recreational vehicles where battery voltage fluctuates.
- Solar-Powered LED Systems — LED lighting powered from solar battery banks where voltage varies with charge state.
- Replacement for Resistors — Any circuit where you'd normally use a current-limiting resistor for a 20mA LED. The driver is a direct drop-in replacement that's more tolerant of voltage changes.
🔌 12V Automotive Applications
This is one of the most popular uses for the 20mA LED Driver, so let's cover it in detail.
Why Use a CCR Instead of a Resistor in a Car?
A car's "12V" electrical system isn't really 12V. The actual voltage varies significantly:
- Engine off: ~12.6V (fully charged battery)
- Engine running (alternator charging): 13.8V – 14.5V
- During cranking: Can dip to 10V – 11V
- Load dump spikes: Brief spikes up to 40V+ (rare but possible)
A fixed resistor calculated for 12V will under-drive your LED at 11V (dim) and over-drive it at 14.5V (brighter, shorter life). The CCR driver handles all of these variations and keeps your LED at a constant 20mA and consistent brightness.
Recommended Series Configurations for 12V Automotive
| LED Color | Typical Vf | Recommended Series Count | Min Voltage Needed | Headroom at 14.5V |
|---|---|---|---|---|
| Red | 2.0V | 4 LEDs | 9.8V | 4.7V |
| Yellow/Amber | 2.1V | 4 LEDs | 10.2V | 4.3V |
| Green | 3.0V | 3 LEDs | 10.8V | 3.7V |
| Blue | 3.2V | 3 LEDs | 11.4V | 3.1V |
| White | 3.2V | 3 LEDs | 11.4V | 3.1V |
💡 Tip: For automotive use, we recommend designing for a minimum supply voltage of 11V (engine cranking) to ensure your LEDs stay lit even during starting. The table above accounts for this. If you only need the LEDs to work with the engine running (13.8V+), you can fit one more LED in the series string.
💡 Tips for Best Results
- Maximize your series LED count. The more LEDs you put in series (within your voltage budget), the less power the driver has to dissipate as heat, and the more efficient your circuit will be.
- Use series, not parallel, for multiple LEDs. Wiring LEDs in series with one driver ensures they all get exactly 20mA. If you wire LEDs in parallel, each LED needs its own driver module.
- Leave headroom for voltage dips. Especially in automotive and solar applications, design your circuit so the minimum expected voltage still exceeds the total LED Vf + 1.8V overhead.
- Use heat shrink tubing. After soldering, slide heat shrink over the module and connections for insulation and mechanical protection. This is especially important in automotive and marine environments.
- Test on a breadboard first. The 0.4-inch pin spacing fits standard breadboards, so you can prototype your circuit before committing to solder.
- Match LED forward voltages in a series string. For the most uniform brightness, use LEDs of the same type and color in a series string. Mixing colors (with different forward voltages) works electrically but may result in different brightness levels.
🛠️ Troubleshooting
| Problem | Possible Cause | Solution |
|---|---|---|
| LED doesn't light up at all | Driver module installed backwards | Reverse the orientation of the driver module. Check PCB markings for correct polarity. |
| LED doesn't light up at all | LED installed backwards | Check LED polarity — the longer leg (anode) goes toward the positive supply. |
| LED doesn't light up at all | Supply voltage too low | Verify that supply voltage exceeds total LED Vf + 1.8V overhead. Measure with a multimeter. |
| LED is dim | Supply voltage barely meets minimum | The driver needs at least 1.8V across itself. If the supply is marginal, the current will be less than 20mA. Increase supply voltage or reduce the number of series LEDs. |
| LED flickers in a vehicle | Voltage dipping below minimum during cranking | Reduce the number of series LEDs to lower the minimum voltage requirement, giving more headroom for voltage dips. |
| Driver module is very hot | Too much voltage across the module | Add more LEDs in series to use up more of the supply voltage, reducing the voltage (and heat) the driver must absorb. Or use a lower supply voltage. |
| LED burned out | Driver installed backwards, sending unregulated current through LED | Replace the LED and driver module. Verify correct polarity before powering on. |
| Inconsistent brightness across multiple circuits | Using drivers with wider tolerance | The Envistia driver is rated at ±2mA, which is tighter than many alternatives. If you're seeing inconsistency, verify all drivers are from the same source and batch. |
⚠️ Important Notes
- Polarity-sensitive. The driver module must be wired in the correct orientation. Reversed polarity can damage the module and your LEDs.
- DC only. This module is designed for DC (direct current) circuits only. Do not use with AC power.
- Not a voltage regulator. This module regulates current, not voltage. It does not convert or step down voltage — it simply limits the current flowing through the circuit to 20mA.
- Recommended maximum 20V. While the IC is rated for 45V, we recommend keeping the voltage across the module below 20V for long-term reliability and reduced heat generation.
- Not suitable for high-power LEDs. This driver provides 20mA, which is the standard current for indicator-type LEDs (3mm, 5mm, SMD). High-power LEDs (1W, 3W, 5W) require significantly more current and a different type of driver.
- One driver per series string. Each series string of LEDs needs only one driver module. Do not place multiple drivers in series — place them in parallel if you need more current.
- Breaking apart the scored panel. The modules are provided on a scored PCB panel. To separate them, gently bend along the score line. Pliers can help for a clean break. Be careful not to stress the solder joints on the module you're keeping.
🏪 Where to Buy the 20mA LED Driver Constant Current Source Regulator
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This guide is provided by Envistia Mall for educational and technical reference purposes. The manufacturer and Envistia LLC (dba Envistia Mall) are not responsible for any damages or losses resulting from the use of this product. Always follow proper electrical safety practices when working with electronic components. Specifications are based on manufacturer data and are subject to change without notice.