Modifying LED Schematic to Use 20mA LEDs Instead of 10mA for Star Trek Panel

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#31 21664282 24 Feb 2014 15:17

Steve Lawson Steve Lawson

Anonymous

Post #31
21664282 24 Feb 2014 15:17

Just in case someone hits on this discussion from a search (or something), the issue of how to "run" LEDs comes up so often, I decided to do a Blog on the subject. Here's the URL:

* http://www.sinistercircuits.com/Blog/LEDs_LightemWithoutSmokinem
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Topic summary

The discussion centers on modifying a simple LED driver schematic designed for 10mA LEDs to accommodate 20mA LEDs for a Star Trek: TOS style panel project. The key technical advice is to adjust the current-limiting resistor value according to Ohm's law, considering the LED forward voltage and desired current. For a 5V supply and 20mA LEDs with a forward voltage around 3.2-3.4V, resistor values between 250Ω and 500Ω are recommended to safely limit current and control brightness. The original schematic used a 1kΩ resistor for 10mA LEDs, which results in about 5mA current; lowering the resistor value increases current accordingly. The conversation also explores alternatives to the CMOS binary counter/divider circuit, suggesting microcontroller-based solutions like Arduino or PICAXE for more flexible and realistic LED flashing patterns using pseudo-random number generation. PIC microcontrollers (e.g., PIC16F877, PIC16F88) and development tools such as MikroElectronica IDE and Microchip MPLAB are discussed as cost-effective alternatives to Arduino, though Arduino is favored for beginner-friendly support and ease of use. Programming languages mentioned include BASIC (for PICAXE) and simplified C (for Arduino). The user eventually opts to switch to an Arduino kit after difficulties with the original board. Additional resources include online tutorials and blogs on LED driving techniques.
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