How do I protect LED from reverse polarity?
How do I protect LED from reverse polarity?
(OP)
I need some help with a simple LED application.
I want to be able to switch one of two strips of LEDs on and off to indicate rotation of a gear. The gear has a cam that moves a lever arm on a switch. That part is simple.
The gear is driven by a 24 VDC motor that can rotate forwards or backwards depending on the polarity of the external connection when the device is placed in a station. The polarity of the station is reversed at every other station.
With this in mind, I have one strip wired opposite the other, and controlled by the same switch. The strips are about 12 VDC at 100 ma.
1. How do I reduce the voltage to the strips?
2. How do I protect each strip from reverse polarity?
Hopefully there is a simple answer for this newby.
Thanks for any help.
I want to be able to switch one of two strips of LEDs on and off to indicate rotation of a gear. The gear has a cam that moves a lever arm on a switch. That part is simple.
The gear is driven by a 24 VDC motor that can rotate forwards or backwards depending on the polarity of the external connection when the device is placed in a station. The polarity of the station is reversed at every other station.
With this in mind, I have one strip wired opposite the other, and controlled by the same switch. The strips are about 12 VDC at 100 ma.
1. How do I reduce the voltage to the strips?
2. How do I protect each strip from reverse polarity?
Hopefully there is a simple answer for this newby.
Thanks for any help.





RE: How do I protect LED from reverse polarity?
RE: How do I protect LED from reverse polarity?
Sorry for my stupidity, but I'm a newby.
RE: How do I protect LED from reverse polarity?
Next calculate the power using P=V*I. This resistor will be dissipating 12 volts times 100mA = 1.2 watts, so you should use a resistor of at least 3 watts, or perhaps even 5 watts (to be conservative since the duty cycle seems like it may be 100%).
The schematic is so simple that it can be derived from a careful reading of my previous post.
RE: How do I protect LED from reverse polarity?
If the image doen't show up, here is the link to it, and thank you for your help.
RE: How do I protect LED from reverse polarity?
http:/
RE: How do I protect LED from reverse polarity?
Don't forget to double-check the panel current because 100ma sounds suspiciously nominal. Be prepared to slightly adjust the resistor value if you're not seeing the normal brightness. But perhaps it is not critical anyway...
RE: How do I protect LED from reverse polarity?
I am still confused about what type and size of diode to use. Would something like this rectifier diode that I saw on the Allied Electonics web site work?
DIODE; 1 A (MAX.) @ 25C IF; 1.1 V (MAX.) @ 25C; 5 UADC (MAX.) @ 25C IR
RE: How do I protect LED from reverse polarity?
Keith Cress
kcress - http://www.flaminsystems.com
RE: How do I protect LED from reverse polarity?
RE: How do I protect LED from reverse polarity?
Thanks again for all your help and for putting up with my questions.
Paul