DIYDrones Magnetometer issue resolution

It's a long story that I will try to summarize. The latest revision of the magnetometer that had some design improvements including making it easier to manufacture to boost production using the pick and place machine, but that also came with a weird issue.

When I was developing the APM Oilpan we had some noise issues on the 3.3V line caused by a missing 200K resistor on the Voltage Reference pin on the 5V side of the I2C translator (obviously this board never saw the light), if you don't populate this resistor it will introduce terrible noise on the line and cause the analog sensors to fail, this bug was found by Jose Julio (Thanks!).

A curious thing is that the first version of the magnetometer didn't have this resistor (it worked fine anyway), in the second revision i tried to do the right thing and follow what the datasheet suggested so I added the 200K resistor (same that caused terrible issues on the Oilpan because we didn't use it), expecting some improvement.

When the boards arrived from the fab, we assemble some and they appeared to be fine, Cindy (our testing lady) added the observation that the sensors were slightly noisier, but we didn't listen (Sorry Cindy!). For the pressure of months of long waits we just released the boards. In just matter of days we received tons of complains.

After days trying to solve the problem we finally discover that the 200K was the issue. The 2nd issue we have discovered but is not critical is that the voltage regulator will not perform well if you don't suck enough current from it, the magnetometer uses very, very low power and the best practice to solve this is to add a 200 ohms resistor from the 3.3V to GND to add enough load to it (Thanks to Nathan Siedle for this trick), we are not doing this right now, so you will see a power supply output of 3.7V, but the performance is perfect.

All new boards have this fix, but for those who already got affected boards I would like to give a sincere apology to all our custumers and I would like to offer two resolutions to this problem:

1.- Send it back and we will repair it for you. We will cover all the shipping expenses. Please contact custumer support for more info: help[@]storediydrones.com

2.-Repair it yourself (DIY) quickly and safely by following the following instructions.

NOTE: Before you repair your board, check if your board has a resistor marked "204". This means it has not been fixed (see the first two photos of the repair steps for reference), and if you see instead a resistor marked "0" your board is fine.

If you choose to repair it yourself and something gets messed up, you cannot then return the board. If you are unwilling to take this risk or are feeling a little uncertain about your soldering ability, do not do this. Just return the board for replacement.

1- Locate the 200k resistor, it is marked with "204."

2- With a soldering iron, heat either of the resistor's solder points
and wait a few seconds for the heat to reach both solder points. Weak solder irons may not work very well.

3- Without applying too much force as no not damage the pads, gently
nudge the resistor with the tip of the soldering iron.

4-The resistor

should stick to the tip, so just lift the tip off the board to remove
the resistor.

5- Make sure you the pad are still there.

6- To create the solder bridge place the tip of the soldering iron
over both pads and apply enough solder to brigde the pads.

7- If the solder ball is touching both pads then your are done.

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Comments

Sam Kelly January 19, 2011 at 8:26am

@ Gary H: There is a way of knowing if your board has been fixed. As mentioned in the instructions and on one of my previous comments, if your board has a resistor marked "204" it has not been fixed (see the first two photos of the repair steps for reference), and if you see instead a resistor marked "0" your board is fine.

Also, all magnetometers in stock and in production right now have this fix.
3D Robotics

Lorenzo@StoreDIYDrones January 19, 2011 at 8:20am

Gary we posted a schematic for the board, it is the same board as the old magneto,we only changed one resistor ( 200k for 0 ohms)... It is earlier in this post.
Gary H January 18, 2011 at 8:31pm

Chris is there a schematic for the new board. That way since the pads are not viable I can place a jumper across the trace at a level I can get such exposed for soldering?
Gary H January 18, 2011 at 7:22pm

Chris there is no way of knowing if this board was fixed or not based on Jordi's post. Whether I eat the cost of this mod or not, I would like to see Jordi post to this thread and let everyone know that all new boards shipping as of X date are fixed and not leave this to us to guess. if indeed all units shipping are fixed then this post needs to clearly reflect that or remove the post to avoid confusion.
3D Robotics

Chris Anderson January 18, 2011 at 7:01pm

Gary, I don't know what to say. Jordi could not have been more clear in his post: if you attempt to modify the board yourself and fail, you cannot return it. In addition, as I mentioned above, you board was probably fine to begin with. I really wish you'd consulted with us *before* you attempted the modification, rather than afterwards. We offered free returns specifically to avoid this, and in your case no modification may have been necessary at all.
Gary H January 18, 2011 at 6:50pm

Ok.. Will be good to know for sure since I am sure others will make note of Jordi's post like I did, receive the unti, notice the resistor is there and attempt to remove it prior to installation. Hence this is what I did since I assumed any new units would have been fixed and noted in this posting of Jordi's. As such I removed the resistor but what should be noted is the pad were so minuscule that they cannot be bridged with solder or a wire as that pads were not viable. I now have a useless unit which I am going to coordinate with Rebeca to get returned and replaced.

Regardless we need Jordi to update this thread so all of us understand why units are shipping with the resistor still in place.
3D Robotics

Chris Anderson January 18, 2011 at 6:35pm

Hmm. That's the day after Jordi's post, so maybe an older one was in the ship queue. I'm checking with production, but it was my understanding that all were fixed after that. BTW, I'm not sure what the fix consisted of. It may be that he's simply replaced with resister with a better value, in which case it might be difficult for you to visually tell if is fixed. It may well indeed be an updated mag that simply looks the same.

(This is Jordi's post, so I'm hoping he'll give you the word straight from the source--I'm in Spain on travel).
Gary H January 18, 2011 at 6:27pm

Ordered on January 13th and shipped the same day.
3D Robotics

Chris Anderson January 18, 2011 at 6:20pm

Gary: When was it shipped?
Gary H January 18, 2011 at 6:08pm

The reason I ask is that the board I just did receive today did not have the fix in place.

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