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Unread 01-14-2004, 12:55 PM
Dave Flowerday Dave Flowerday is offline
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Warning: Error in beacon assembly directions included in the kit!

Everyone,
While assembling our IR beacons we discovered that the "First Infrared Beacon" assembly sheet that was included in the kit is incorrect. The connections to pins 2 and 3 of the FET are reversed. FIRST has been notified, and I hope they'll release updated directions to address this. In the meantime, if you know your way around electronics you should be able to take care of this yourself (search for IRL3103 on Google if you'd like to look at the datasheet for the FET included with the kit). If you don't know exactly how to modify the circuit to be correct, I'd recommend that you just wait to assemble it until new directions are released.

For those interested, you can see where the error is by looking at the sheet included in the kit and examining the schematic that represents the internal "guts" of the FET and compare it to the schematic right at the top of the datasheet for the FET. You'll notice that the FIRST version has pin 3 connected to the "D" (for Drain) line of the FET, but if you look at the "Lead Assignments" on page 8 of that same datasheet that Drain is really pin 2.

P.S. Thanks to Kevin Watson for confirming this to make sure I wasn't making a fool of myself
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Unread 01-14-2004, 03:17 PM
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Re: Warning: Error in beacon assembly directions included in the kit!

Quote:
Originally Posted by Dave Flowerday
Everyone,
While assembling our IR beacons we discovered that the "First Infrared Beacon" assembly sheet that was included in the kit is incorrect. The connections to pins 2 and 3 of the FET are reversed. FIRST has been notified, and I hope they'll release updated directions to address this. In the meantime, if you know your way around electronics you should be able to take care of this yourself (search for IRL3103 on Google if you'd like to look at the datasheet for the FET included with the kit). If you don't know exactly how to modify the circuit to be correct, I'd recommend that you just wait to assemble it until new directions are released.

For those interested, you can see where the error is by looking at the sheet included in the kit and examining the schematic that represents the internal "guts" of the FET and compare it to the schematic right at the top of the datasheet for the FET. You'll notice that the FIRST version has pin 3 connected to the "D" (for Drain) line of the FET, but if you look at the "Lead Assignments" on page 8 of that same datasheet that Drain is really pin 2.
I've whipped-up a replacement schematic that can be found here: http://kevin.org/frc. The data sheet for the IRL3103 is also there. For those interested in electrical engineering terminology, this type of circuit is called a "low-side switch" because is switches the ground or current return side of a load as opposed to a "high-side switch", which switches the power or current source.

-Kevin
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Unread 01-15-2004, 07:23 PM
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Re: Warning: Error in beacon assembly directions included in the kit!

The resistors in the schematic should be 33 ohms, not 330 ohms. The 33 ohm color code is orange-orange-black; 330 ohm is orange-orange-brown.

-Kevin
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Unread 01-15-2004, 07:32 PM
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Re: Warning: Error in beacon assembly directions included in the kit!

Thanks for the update Dave. I'll make note of that when we start soldering that up tomorrow.
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Unread 01-16-2004, 07:14 PM
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Re: Warning: Error in beacon assembly directions included in the kit!

Is there an online version of the PDF that we can download? This would probably updated much earlier than they can distribute anything, and even if it is erroneous, our electronics lead could do whatever you just said =)
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Unread 01-16-2004, 07:22 PM
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Re: Warning: Error in beacon assembly directions included in the kit!

Quote:
Originally Posted by Eko
Is there an online version of the PDF that we can download? This would probably updated much earlier than they can distribute anything, and even if it is erroneous, our electronics lead could do whatever you just said =)
Yes, just use the schematic I mentioned above.

-Kevin
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Unread 01-17-2004, 02:31 PM
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Re: Warning: Error in beacon assembly directions included in the kit!

Thanks for the info. We were having some trouble figuring out what was going wrong.
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Unread 01-17-2004, 08:50 PM
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Re: Warning: Error in beacon assembly directions included in the kit!

Is the diagram FIRST posted yesterday correct?
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Unread 01-17-2004, 09:01 PM
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Re: Warning: Error in beacon assembly directions included in the kit!

Quote:
Originally Posted by Gary Bonner
Is the diagram FIRST posted yesterday correct?
Yep, it looks like the MOSFET drain and source are where they should be.

-Kevin
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Unread 01-17-2004, 10:34 PM
Dave Flowerday Dave Flowerday is offline
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Re: Warning: Error in beacon assembly directions included in the kit!

Quote:
Originally Posted by Kevin Watson
Yep, it looks like the MOSFET drain and source are where they should be.
But the connections TO the drain and source on the FET still look incorrect! The updated diagram only changed the little schematic inside the FET but they didn't update the connections from the LEDs and ground to match.
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Unread 01-17-2004, 10:58 PM
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Re: Warning: Error in beacon assembly directions included in the kit!

Quote:
Originally Posted by Dave Flowerday
But the connections TO the drain and source on the FET still look incorrect! The updated diagram only changed the little schematic inside the FET but they didn't update the connections from the LEDs and ground to match.
Yeah, I spoke too soon. The connection diagram is messed-up too.

-Kevin
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Unread 01-27-2004, 03:36 PM
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Re: Warning: Error in beacon assembly directions included in the kit!

Just FYI, The FIRST folks are about to post the corrected beacon construction document.

-Kevin
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