Warning: Error in beacon assembly directions included in the kit!

[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.

P.S. Thanks to Kevin Watson for confirming this to make sure I wasn't making a fool of myself

[Kevin Watson]

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

[Kevin Watson]

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

[ChrisA]

Thanks for the update Dave. I'll make note of that when we start soldering that up tomorrow.

[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 =)

[Kevin Watson]

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

[KBMSora]

Thanks for the info. We were having some trouble figuring out what was going wrong.

[Gary Bonner]

Is the diagram FIRST posted yesterday correct?

[Kevin Watson]

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

[Dave Flowerday]

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.

[Kevin Watson]

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

[Kevin Watson]

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

-Kevin