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Arcing when plugging in LOR boxes...


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Is it just my boards, or does anyone else get a good arc (from plug to outlet) when plugging in their LOR boxes?

The happens to both of my Standard Kit boards, but not to my LOR1602W. I didn't notice this on the bench when I was testing them after soldering them up. But now that they are in place and hooked to lights it is happening.

I initially assumed I had something soldered in wrong, but both boards "look" correct. Then I thought, maybe the outputs are "on" when the board powers up. And sure enough, they are. A flood light plugged into one of the channels momentarily lights when I plug the board in.

I hooked an ammeter in line with the power feed and saw a pretty good current spike upon connection and then it dies right off. So it appears that the drivers that feed the Triacs are latched "on" at powerup, but then get reset to the off state.

Once powered up, the boards operate fine. My show was running all weekend without a problem (48 channels, 2 kit boards + 1 LOR1602W).

Could something still be wrong with my wiring on the board, or is this just a trait of the processor/registers used on this model of the board (green - kit - standard)?

Let me know if anyone has any ideas? It doesn't seem to be an issue, I just don't want any loose extension cords sizzling in their sockets!

Thanks!

Jim.

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Jim:

As an electronics engineer that works with microcontrollers every day, it is normal for them to power up in an undefined state (aka on). As soon as the firmware gets off reset the first thing that is done is to set the outputs to a known state (aka off). So it's like you are plugging in a lot of lights at one instant, an arc is normal. Different devices will respond differently, it's nothing to do with the board.

So in other words, it's normal and will not cause any problems.

Mike

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Mike,

Thanks for the input!

Other than the char marks on my extension cords I figured all would be fine once things got reset. It is just a little concerning if you had a loose extension cord and it was powering on/off at random intervals. One may end up with a lot of heat inside (and outside!) of that connection.

Still curious why the LOR1602W doesn't do it at all. I'll have to check to see if they are using the same chips.

BTW, it is possible for them to keep the outputs off during power-up, but since they are usually the only driver on the bus it probably doesn't matter - and they don't go to the effort to keep them from firing. When you start getting multiple output drivers on the same bus you can run into power supply problems trying to overcome the bus contention during powerup. So you need to be a little more careful on how the output latch/drivers are designed. Okay, enough work talk... back to Christmas lights!

Anyone else notice this with their boards?

Thanks, Jim.

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I've always had the initial "everything on" when i plug in my board. Ive never seen an arc though because i run mine throught a powerstrip and use the switch on that to turn them on and off. If you wanted to keep the board in its known off state there should be a way to wire a battery in to keep the processor running. That same method is used on computters to keep the clock ticking.

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