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Dragon*Con
#1
I’m bringing R2-D2 to Dragon*Con this weekend (Thursday to Monday).  If anyone is going to be there I’d love to meet up and geek out on droid building. I think I’ll be hanging out on the Marriot main floor and the Hyatt lobby mostly.  Send me a message or respond here. 

Eebel
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#2
Lots of pics - or it didn't happen!
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#3
R2 was the star of the show!

   
   
   
   
   
   
   
   
   
   

Eebel
2
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#4
(09-05-2018, 07:47 PM)Eebel Wrote: R2 was the star of the show!

Looks like R2 makes a terrible wing man.
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#5
   
   
   
   
   
   
   
   
   
   

Eebel

So after four days of intense R2ing, I have some observations.

First, I am happy to report that my updated drive units did not overheat and R2 was able to navigate the hard surface of the con very well.  However, he HATES carpet.  I will work on making him more carpet friendly.  I talked to another R2 build who had "foot Locks" (these are in Mr. Baddeley's design but I did not know what they were for).  These locks prevent the feet from twisting when you accelerate and allow better performance on carpet.  Also, I am going to wire my six 8000mHr LiPos so they provide more capacity.  I was able to go over six hours with three of them.  (One 12V and two in series for 24 V).  So I will bridge them so I have 16000mHr in 12V and 24V. I had them wired so I could switch to a backup.  However, I found that I could go all day with three.  I figure I could get more available amps if I merged them.

Second, I burned out three of my cheap Amazon SG90 clone servos.  I will replace them all with MG90s.  They are metal geared versions of the same servo.  Hopefully, they will be more robust.  The SG90s cost about $2 a piece and the replacement MG90s are about $4 a piece.  I hope I don't need to upgrade to $10 a servo as my droid has 15 of micro servos. The bigger servos worked fine (there are four of them).

Third, I found I needed more interaction commands.  I tended to hide in the crowd and Have R2 approach people who called out to him(which happened a LOT).  Since I use the SHADOW-MD system, they had NO IDEA who was in control of the droid and to them he seems to be alive. They would ask questions and the only sure-fire response was shaking his head back and both for a "NO" answer.  I did not have a good "YES" response.  So, I will be working on a "YES" and some more ambiguous "magic 8-Ball" type answers to questions.  One of my favorite moments was when a little boy asked R2 a question and I hit a generic bleep-bloop response and he turned to his mom and exclaimed "What did he say!?"

I cannot not adequately describe how much FUN it was to make R2 come alive in a crowd of people.  I would stand next to someone for five minutes and talk to them about how alive he seemed as he was interacting with other people/kids and debate as to who or how he was being controlled. Then, I would reveal it was me the whole time!  People were literally looking overhead for drones or trying to peer inside to see if someone was inside.  This never got old!

Eebel

(09-05-2018, 08:04 PM)LarryJ Wrote:
(09-05-2018, 07:47 PM)Eebel Wrote: R2 was the star of the show!

Looks like R2 makes a terrible wing man.
Yeah, he is an attention hog!

Eebel
2
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#6
I must have missed this post when you put it up. Looks like you had heaps of fun with R2 and lots of people enjoyed seeing him.

I didn't think it possible but one of those droids was possibly too weathered!? I'm surprised he didn't have Dagobah swamp dripping off him onto the carpet.

Do you think the ankle control bars that are part of the 2-3-2 system would fix the ankle twisting on carpet problem, or is it his front foot that is the problem?
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#7
(09-18-2018, 01:50 AM)Martyman Wrote: I must have missed this post when you put it up. Looks like you had heaps of fun with R2 and lots of people enjoyed seeing him.

I didn't think it possible but one of those droids was possibly too weathered!? I'm surprised he didn't have Dagobah swamp dripping off him onto the carpet.

Do you think the ankle control bars that are part of the 2-3-2 system would fix the ankle twisting on carpet problem, or is it his front foot that is the problem?

I am not sure.  My first stab at addressing this issue will be to double my battery capacity so I can have more of total amps available for the spike caused be starting the motors.  I am going to wire up four 8000mAh 100C batteries to produce 24V.  At Dragon*Con I only had two of these batteries producing 24V.  I had the second set of batteries installed but not attached as backup power to get me back to my hotel room.   I did find that I could go for ten hours with just the two battery setup on hard surfaces.  

Eebel
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#8
If you add some large capacitors at the power input terminals of the motor controller, you can get the power boost you need for starting.
You will need to make sure the capacitor is rated well above the max charge voltage and also if possible has a very low Equivalent Series Resistance (ESR)
Most of the voltage drop you get when starting motors is caused by having too small a size wire between the batteries and the controllers or between the controllers and the motors themselves, So increasing the wire size can also help with starting the motors.
The resistance internal to the batteries is a bit harder to overcome, and is why the use of large capacitors can work to help with the startup surge.
As a general rule of thumb, a motor will draw between 5 and 10 times its nominal rated current when starting.
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#9
(09-24-2018, 09:09 PM)Cyber_One Wrote: If you add some large capacitors at the power input terminals of the motor controller, you can get the power boost you need for starting.
You will need to make sure the capacitor is rated well above the max charge voltage and also if possible has a very low Equivalent Series Resistance (ESR)
Most of the voltage drop you get when starting motors is caused by having too small a size wire between the batteries and the controllers or between the controllers and the motors themselves, So increasing the wire size can also help with starting the motors.
The resistance internal to the batteries is a bit harder to overcome, and is why the use of large capacitors can work to help with the startup surge.
As a general rule of thumb, a motor will draw between 5 and  10 times its nominal rated current when starting.

Good info as always!  However, I've never bought a capacitor on my own before. So if I understand correctly, I would need one capacitor ahead of the power input to my Sabertooth 2x32, since this single controller runs both foot motors. I am using 12 gauge wire for all of the battery and motor connections tp the 24V, 100W motors from Amazon.com.  So, since I=P/V, this means a nominal 4.167 Amps.  This is where things get fuzzy for me.  I see lots of different styles of capacitors and am not sure how the specs translate to this application. Do you have a suggestion on a suitable model of capacitor?

Eebel
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#10
Ok, this is a tricky one to explain, however the rule of thumb is the bigger the better.

Typically a motor starting DOL (Direct On Line) will draw between 5 and 10 times it full rated load current.
This however is not for very long, in these small motors a second or two

It can however cause power issues for anything else using the same power source.
A large capacitor is a small power reservoir that will supply the surge while the motor is starting and help the get the motor going.
The startup draw shouldn't be quite that big with the motor controller, but the capacitor will help with the starting torque.
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