Question on $50 robot tutorial

[corp]

I'm building your $50 robot when I came upon this note:

"Note for those using the 4.8 battery holder: Remember that the battery + end of the capacitor should not connect to the servo power bus. Instead, connect the capacitor to the sensor power bus on the left of the board. Click here to see a graphical representation. If you are using a 6V battery pack, you can ignore this note."\

This is the picture it links to:


And now I'm lost. I'm using the battery holder and up until this point, I've been following the instructions. Is the green "x" on the image telling me NOT to solder there? Also, if the picture shows the a connection from the capacitor's positive end to the middle row of the motor control, where would I connect the 5v regulator to?

Any insight provided would be extremely helpful!

[Admin]

Is the green "x" on the image telling me NOT to solder there?

Yeap, dont solder that. You want the power from the 9V only going to the electronics, and the power from your battery holder going only to the servos. They both share ground, but the + voltages are different and so shouldnt be connected.

So Im glad you brought this up because it appears you found a big mistake in my tutorial that I should fix . . .

Ill have to go and fix this . . .

In the meantime . . . ignore the red line in that image and connect the output of the regulator to the sensor power bus. Its the same as the purple wire in the very next step.

Make sure there is no connection where the green X is. Solder the battery holder power lead to the servo bus.

With this modification the big capacitor becomes mostly useless, but wont hurt anything if you just leave it there. Ideally you would want the capacitor to connect between ground and the servo power bus only.

Hmmmm this I think is a bit too confusing, I think I need to go over the tutorial and fix it up a bit

Let me know if you still have problems!

[corp]

Ok! I desoldered the area where there shouldn't have been any solder and am now ready to add the battery pack to the unit. Now...since there are so many areas where the unit is grounded, can I just solder the black wire to any of those? Or does there have to be a specific place? Unfortunately, I can't really reason without a visual aid so I'm afraid to move on any further. If anyone can post a picture as to where they soldered the battery holders to...it'd be extremely helpful

[Admin]

Now...since there are so many areas where the unit is grounded, can I just solder the black wire to any of those?

In theory, anywhere is fine. In reality however the closer you solder it the less resistance the electronics will see. If you solder ground directly to the servo ground bus, thats the best place.

[Admin]

Ok I fixed the tutorial. If you still arent sure, go check it out.

[corp]

So I don't connect the positive terminal of the capacitor to the regulator?

[Admin]

So what the capacitor does is creates a buffer against power surges/drains.

If you connect it between the output of the regulator and ground, then it will stop surges going through your electronics. If you connect it between power and ground of your servo bus, then it will reduce surges across your servos.

If you use the 6V battery pack, the capacitor helps both since they share the same power source.

But with the 9V and AA holder setup, you have a choice on where the capacitor goes . . . or you can get a second capacitor and do it for both. For the $50 robot it doesnt really matter which you choose (it will work without the capacitor just fine), but in other future cases it might (in which case you can always add a capacitor).

Let me know if Im being confusing . . .

[corp]

Okay! I've done what the tutorial said and finally, after countless hours of soldering (@___@) I think I've got it. I've uploaded it to the robot and (surprisingly enough) it worked! I'm so happy . Now...can I pull out the battery or does it need to be in?

[Admin]

I've uploaded it to the robot and (surprisingly enough) it worked! I'm so happy . Now...can I pull out the battery or does it need to be in?

You mean you uploaded the software and the robot works? Excellent!

But I dont entirely understand your question, you mean, will your robot work without one of the batteries? Both are required . . .

[NOOBinDistress]

ok I was just flipping through the form.And I followed the tutorial to make my board. It is not going to be wrong because I followed the unmodified version.PLEASE dont tell me its wrong.

[Admin]

If you used the 6V battery pack directions, you can ignore this post - no errors. But if you did the 9V/AA holder method, then there is one mistake I made. You only need to change one wire though, so no need to panic

[NOOBinDistress]

Ok thanks. I need help in another post about the battery though. Thanks.