DB1 Episode 15  

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DroneBot Workshop
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2019-09-08 9:47 pm  

Just published episode 15 in the DB1 series. This one is about some new modules I'm constructing to get the base unit working.

The modules are as follows:

  • An improved motor controller, based upon the ATmega328. I'm keeping it as compatible as possible with the Arduino Nano design for those of you who have already built that.
  • A sensor distribution board. This is the "other end" of our sensor cables, the board converts the buffered I2C back to "normal" I2C and also distributes the emergency stop and I/O signals. There will be two of these in the base, and additional ones on the upper layers of a similar design.
  • A corner sensor board, my favorite! It has two ultrasonic sensors, two infrared collision sensors and a big fat RGB LED.  There will be four of these, one on each bottom corner.

I'll also FINALLY be making the GitHub repository for eth DB1 base unit public later this week.

And now that summer is over and the basement has returned to normal temperatures I'm back in the workshop, so you'll be seeing a lot more video very soon.  At least until May!

😎

Bill

 

 

"Never trust a computer you can’t throw out a window." — Steve Wozniak


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byron
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2019-09-08 11:27 pm  

@DroneBot Workshop

Our UK summer has had a few days of over 30 Degrees and at that point I don't feel like doing anything but loafing in a chair and being cooled with a full pelt fan and a cool drink so I sympathise with your over toasty basement predicament.   But its good to see you are back and that DB1 is getting to a nice complicated stage. 😎 

I'm looking forward to your JST crimping tool recommendations and tutorial and I will probably follow your good example as I've been waiting to see what connectors you were going to plump for.


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Robo Pi
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2019-09-09 5:26 am  

I'm still looking for the detailed motor control and acceleration sketches.   I don't even have my robots moving yet.   I want to get to that point first and then worry about adding sensors from there.  I'm hoping the motor control sketches will be on the GitHub page.

DroneBot Workshop Robotics Engineer
James


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Pugwash
(@pugwash)
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2019-09-09 11:21 am  

Bill, it is good to see you back in your basement. We had record temperatures here too, up around 35°C, and as in common with most of Europe no aircon escape. Some days my brain just turned to mush!

Am looking forward to your review of the crimping tools, as I have bought a load of JST connectors, but haven't decided which crimping tool to buy.

Living in Germany means that the flavour of the month is always "Knippex", which are readily available at my local hardware and electrical suppliers, but have the downside of being prohibitively expensive. But Knippex was about the only brand available that would survive years in a toolbox on my boat without corroding. I am very reluctant to buy Chinese tools but when everybody else has ceased making them, then there is no other choice.

I recently bought a new Philips TV, that's got built-in YouTube, now I can watch DroneBot videos in full glorious format and you are much bigger 😀 than you were on my iPad. N.B. stature has nothing to do body height. 😎 On the back of the TV, it said "Assembled in Poland" but my guess is the most of the internal parts still came from China!

Anyway, keep up the good work and to quote GoT "Winter is coming"!

SteveC - I would never join a club that accepts people like me as members (Oscar Wilde).


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Bif99
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2019-09-10 7:40 pm  

I've been trying to locate the I2C cables and connectors Bill suggested in Ep15.  I found some M/M 8" long cable assemblies and some F/F 30 cm long cable assemblies but haven't located a supplier for the female connectors that get installed in the perfboard assemblies.  Anyone know where to find them?


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codecage
(@codecage)
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2019-09-10 9:37 pm  

@bif99

Try this from Digi-Key:  JST 2,3 & 4 Pin XH Kit

SteveG


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Bif99
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2019-09-11 6:44 pm  

Sorry for the confusion Steve.  I was referring to the I2C connectors Bill mentioned at the 14 min 50 second point in the Ep.15 video.  The connectors are black in color and have a security latch.  I was looking for the female connectors that are soldered to the perf boards.  Bill, maybe you could chime in here since you mentioned they are the closest thing we have to a standard connector for I2C.  BTW guys, I was late to the party but worked all summer to catch up.  Fortunately, I have AC so my shop was very comfortable.

Bif


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codecage
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2019-09-11 7:58 pm  

@bif99

OK, Bif, I'm clear now.  Seems as if I found those connectors, but at the moment have not purchased any, so I'm going to have to look them up again!  I do know which ones you are referring to, but the main reason I didn't buy them was that I was wondering couldn't these also be the JST-XH connectors (or XA which I will assume will be more expensive).

@dronebot-workshop

Maybe Bill will chime in.

SteveG


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Bif99
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2019-09-11 9:59 pm  

I found a JST kit that should work OK.  Check out https://www.ebay.com/itm/JST-XH-Connector-Terminal-Header-Assortment-Kit-Male-Female-RIGHT-ANGLE-90-Deg-/292219710596

I just ordered one.  You have to make your own cable assemblies but that is no problem.  It allows you to make the cables any length you want.  I'm ordered a kit but still looking for the one Bill suggested.

Bif


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codecage
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2019-09-11 10:42 pm  

@bif99

What is the max number of pins in that kit?  I think Bill was referring to 6 wires in his cables.  If you got 6 pin JST-XH connectors those should work instead of the ones Bill actually mentioned.  I still need to search for the black one though.

And to get his input on using the JST connectors for that purpose.

SteveG


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DroneBot Workshop
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2019-09-12 2:10 pm  

By the "black" connector I assume you are referring to the I2C connector.  It's a Molex 0705530003 (WM4902-ND) that I purchased at Digikey   The male connector for the cable is the Molex 0050579404 (WM2902-ND), and it uses Molex 0016020086 pins (WM2510CT-ND).

I actually ordered a few kits of JST connectors (including one that I got "accidentally " as it was misrepresented on Amazon, but it's too much trouble to send it back).

The first kit I got (from RobotShop) was a nice kit of 2 to 4-pin connectors. Then I ordered a set of them from Amazon, one with 2 to 5-pin devices and another with 6 to 9-pin devices.

For DB1 I will be using 3, 4, 5 and 6-pin cables, at least on the base unit. Some examples:

  • 3-pin connectors from the Cytron motor controllers to the Motor Control board. Only one end (on the Motor Controller) is actually a JST-XH connector. Cytron provides the 3-pin connector for the other end.
  • 4-pin connectors from the motor rotary encoders to the Motor Controller board.
  • 5-pin connectors for the I/O connection between the I2C distribution board and the Arduino Mega.  Each I/O connection has one pin, plus ground.
  • 5-pin connectors for the Emergency Stop connection between the I2C distribution board and the Motor Controller board. One pin for each emergency stop line, plus ground.
  • 5-pin connectors for the cables from my "smart sensors" (i.e. the corner sensor) and the Sensor Distribution boards.  Two pins for I2C, one for Emergency stop, one for the I/O line and ground. Note that in some cases. like the corner sensors, a 4-pin connector will be used at the other end as these sensors don't use the additional I/O line. Plus, I have to confess, I don't have room for the extra pin on my corner sensors!
  • 6-pin connector from the Arduino Mega to the Motor Controller board.  This will have the two I2C lines, ground, one emergency stop lines, and two additional I/O "status" lines, one from each processor on the Motor Controller board.
  • 6-pin connector on the Sensor Distribution boards. These cables have the 6-pin aviation connector on the other end.

 

As for replacing those aviation connectors with JST-XH, I don't see any real problem with that electrically. However, I think aviation connectors are more rugged and would survive more disconnections and reconnections.  And as the base and tower of DB1 will be disconnected and reconnected about a thousand times before the project is finished that's an important consideration.

Also, as a "heads up", I am currently wiring and testing the I2C distribution and Sensor Distribution boards right now, so that will be the subject of the next installment of the DB1 series.  I'll provide a parts list and a schematic as well.

And finally, I purchased an excellent set of crimpers for the JST connectors, the Engineer PA-09.  It's a bit expensive (about 50 US dollars), but considering the number of connectors, I need to crimp I think it will pay for itself very quickly.  And, as the "official" JST hand crimper retails for over 2000 US dollars it's a bargain!

If you're a follower of my (currently) "secret Patreon" I put out a short video a couple of days ago showing off my new crimpers, as well as all of those JST connector kits.

I like the little kits a lot, eventually, I'll find an eBay supplier who sells the connectors by the hundreds and order a pile of the ones I use the most. The same thing I did with the Dupont connectors a few years ago.

Hope that helps!

😎

Bill

P.S the RobotShop, Digikey and Amazon links are all to their Canadian sites, but you'll find the equivalent devices on RobotShops and Digikeys US site and on most of the Amazon sites as well.

 

This post was modified 2 months ago by DroneBot Workshop

"Never trust a computer you can’t throw out a window." — Steve Wozniak


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Robo Pi
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2019-09-12 8:42 pm  

@dronebot-workshop

Bill, have you posted the motor controller code on GitHub yet?

I'd like to see the acceleration routines in more detail using the motor encoder sensors along with how the Arduino Mega controls the two ATmega328 chips.

Thanks.

DroneBot Workshop Robotics Engineer
James


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DroneBot Workshop
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2019-09-12 10:00 pm  
Posted by: @robo-pi

Bill, have you posted the motor controller code on GitHub yet?

Hi James. As I already said in the video I still have the DB1 repository set private as I still need to do some work on both the code and wiki. And that particular code is going to need a bit of rework, as I've added a few components to the motor controller (however the base code, which is what you want, wil stay the same)

Once it is public you'll be able to grab all the code, however, right now I'm working on this weeks DroneBot Workshop video and article so I won't be getting around to the DB1 stuff until after that's finished.  

Keep your eye on my GitHub, it will all be there soon!

😎

Bill

 

"Never trust a computer you can’t throw out a window." — Steve Wozniak


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Bif99
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2019-09-13 1:57 am  

@codecage

The Molex kit I sent the link on has 2,3,4 & 5 pin connectors and the pins are on a 2.54 mm pitch.  I saw Bill's detailed post about the connectors so I will be buying what I need for the I2C cables.

Bif


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