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Nancy Golden
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Platinum
Re: Reverse Polarity?
Nancy Golden   5/27/2013 1:23:49 PM
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Me too, tekochip - if the LED is forward biased, I haven't seen one go out as long as the LED is rated for the current level they are running at. Current limiting resistors usually prevent such issues. A friend of mine said he has seen LEDs put right across the secondary of a 16 volt transformer with a series resistor but no diode to block the reverse voltage - the company told the manufacturer that we don't recommend that and they said they have been doing it for years with no problems. Hard to believe!

Nancy Golden
User Rank
Platinum
Brought Back Memories
Nancy Golden   5/27/2013 1:05:20 PM
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Interesting article and nice fix. I enjoyed this article specifically because it brought back great memories. As a student, I had my own home-lab set up in my bedroom (my room- mate at the time had two girls so I needed to have it out of reach of curious fingers) and I had the same setup. I was fortunate enough to buy one of the Tektronix scopes that had been used in the labs at school when they remodeled one of the labs and did some upgrades that made a few become available at a price a poor student could afford. Being a faculty assistant at the time allowed me to call dibs on one of them. It was only 20MHz but I was so proud of it and it was my workhorse. When I entered industry the o'scopes that were available (digital storage scopes - wow!) blew me away. My function generator was bought at the sidewalk sale in Dallas - it was a prebuilt trainer that was easy to work on - just pull the top off when something quit working - pretty easy to troubleshoot. It also had AC and DC  power supplies. Love those home labs - they are so much fun!

a.saji
User Rank
Silver
Re: Reverse Polarity?
a.saji   5/27/2013 11:13:55 AM
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@tekochip: Is it ? I thought it consumes more power in such scenarios.                            

tekochip
User Rank
Platinum
Reverse Polarity?
tekochip   5/27/2013 9:18:41 AM
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The only other time I've seen LEDs short is from reverse bias.  It doesn't take much current to take them down, either.

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