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RogerL
(@rogerl)
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Posts: 26
2019-07-12 9:03 pm  

@rcomito

Thanks Rick, I haven't seen that type before and they look interesting.  Do you know if they do a bulkhead-type connector, or is it just the line connector type?  On Amazon.co.uk they only have the line connectors.

Roger


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DroneBot Workshop
(@dronebot-workshop)
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Joined: 12 months ago
Posts: 536
2019-07-12 9:27 pm  

One other suggestion for alternate connectors.

On my DB1 I am only using the 6-pin aviation connectors in certain places, not always on both ends of the cable.   As I stated in both the video and article I found the male connectors to be challenging to solder so I wanted to minimize the use of them.

On the OTHER end of the cable, I haven't figured out what to use, but am leaning towards using two connectors - the Molex 0705530003 connector for the I2C connections and a 2-pin JST connector for the GPIO and Emergency Stop signals.

There is no reason why you couldn't use that arrangement on BOTH ends of the cables. I'm sure it would be more lightweight.  A 4-pin JST could also be used instead of the Molex connector, as the "I2C" connections on the cables are actually the buffered I2C connections so you wouldn't want to accidentally connect then to an I2c-level signal.

Really any 6-pin connector that can lock into place would do the job. I used the aviation connectors for three reasons:

  1. They do a good job of securing connections.
  2. They fit perfectly into the holes in the Actobotics channel.
  3. They were inexpensive.

Actually, there is also a fourth reason - I had already purchased them for another DB1-related task that I changed my mind on, so I had them anyways!

?

Bill

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


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rcomito
(@rcomito)
New Member
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Posts: 3
2019-07-12 11:18 pm  

@rogerl

Hi Roger - That particular connector is line type only.  That was just what I needed for my project.  They have several flavors of bulkhead though, like:

MUYI 10 Kit 6 Pin Way Waterproof Electrical Connector

 

Let us know how you make out.

 

Rick Comito


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ShaneO
(@shaneo)
Active Member
Joined: 12 months ago
Posts: 10
2019-07-13 5:36 am  

Hello Bill,

I notice you're now using the chassis as a signal ground.  On Cara-2 I've gone to the level of the chassis being a common earth.  Just one issue I've found is the Actobotics hardware appears to be very lightly covered with a substance, probably some kind of machine oil, but you might be surprised to discover that it's enough to create a highly resistive connection, particularly if you're just relying on a bolt.

I've checked all bolt connections on my chassis and found resistances as high as 30 ohms.

To overcome any issue I use a rotating wire brush on the end of my Dremel which cuts through whatever is on the surface.  In addition, I am using Star-Washers which help to bite into the metal and now all connection points show no resistance at all.

 

 

image

 

Just something you might want to look out for.

Shane.

 

There are 10 types of people - those who understand Binary and those who don't


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DroneBot Workshop
(@dronebot-workshop)
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Joined: 12 months ago
Posts: 536
2019-07-13 10:31 am  

@shaneo

Hi Shane

That is a very good point, I actually hadn't measured resistance but I suspect you are correct. The idea with the Dremel is and star washer is great, I'll do that myself.

Of course, as a conductor aluminum isn't as good as copper, so the ground won't be perfect.

Thanks for the tip!

?

Bill

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


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codecage
(@codecage)
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Posts: 624
2019-07-13 7:24 pm  

I like the idea of the aircraft connectors on the Actobotics frame of DB1, but wouldn't these Molex plugs be better on the Distribution Hub end of the cables instead of the larger aircraft connectors?  The plug connectors on the ends of the cables would mate with these Molex headers on the circuit board.  They would take up much less real estate and would alleviate the need to mount the board much higher off of the acrylic sheet next to the other mounted boards.

Then the same plugs and headers can be used on the nodes as well.

SteveG


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codecage
(@codecage)
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Posts: 624
2019-07-14 2:06 pm  

I now have more questions after watching Episode 14 than I had before watching it.  I'm sure they will all get answered in time, but with the redesign on the motor controller and the addition of the I2C Buss Distribution Hub and Nodes, I seem to have lost the picture of how all of these components are wired together.

While some wiring diagrams were shown in Episode 14, I was still left a little puzzled as to what to wire next and what to connect where!

SteveG


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stven
(@stven)
Trusted Member
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Posts: 64
2019-07-14 6:33 pm  

@codecage

Using Molex on the distribution board sounds like a good idea to me. I'm also in favor of using 4-pin aviation connectors for the I2C bus and perhaps a separate two-wire cable for Emergency stop & GPIO, or use a six-conductor cable with two connectors.... I've got a ways to go before I really need to worry about that. So far I have built the base, mounted motors and wheels and wired all the power strips. I've cut the acrylic sheets for shelves, now I need to start working on the NAV layer electronics so I can do the motor test 🙂

 

Steve


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codecage
(@codecage)
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Posts: 624
2019-07-14 9:40 pm  

@stven

Maybe just have the 6-pin molex connectors on both the distribution hub and on the nodes.  Then have the 6-pin mating molex connectors on each end of the cables.

SteveG


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JBeazy
(@jbeazy)
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2020-03-02 9:06 pm  

@codecage

Does anyone have a suggested part number and source for crimping tool that works with these Molex connectors?


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codecage
(@codecage)
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2020-03-02 9:29 pm  

@jbeazy

@dronebot-workshop might have a suggestion for us as I think he has used these pins and connectors.

SteveG


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Spyder
(@spyder)
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2020-03-03 1:44 am  
Posted by: @jbeazy

Does anyone have a suggested part number and source for crimping tool that works with these Molex connectors?

Hammer and chisel ?

I work with those stupid things all day long at my real job, and I despise them immensely.

They are the bane of my existence

In fact, it's just a plain old multi-size wire crimper that you need. You just strip the wire, stick the wire into the pin, crimp it down, and insert it into the molex housing. There's a little metal tab that pops out of the pin that locks it into place inside the molex housing. Simple enough to be sure, it's just that it never works that way for me. Not at work anyway. Those machines where I work get too much abuse, and things get shaken loose all the time.

Personally, I usually end up crimping the wire, then dropping a bit of solder on it, which everybody tells me is the wrong way to do it, to which I tell them that, yes, you're right, and then I go ahead and do it anyway. It saves me headaches down the road

If it were up to me, I'd just use JR45 connectors for everything that didn't require high voltage or amperage. And even then I could just double up the pins to compensate if the power requirements were low enough. The RJ45 is simple enough that I could do those in my sleep, and as long as you test them after you make them, it's typically a reliable connection


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JBeazy
(@jbeazy)
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2020-03-03 2:16 am  

@codecage

I decided to get some JST-XH type board-to-wire and crimp-on connectors since they are less expensive than the Molex. Also have a 4-die crimping tool coming and will see how it works.  Of course the $490+ "pro-tool" would work best but I can't justify that cost. I just saw there were some discussions on crimping tools in "Specialty Tools" discussion so I will try and give my feedback on how well the tool worked.


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Robo Pi
(@robo-pi)
Robotics Engineer Moderator
Joined: 12 months ago
Posts: 1757
2020-03-03 9:47 am  
Posted by: @jbeazy

@codecage

Does anyone have a suggested part number and source for crimping tool that works with these Molex connectors?

I bought these for under $20 at AliExpress.  They seem to work.  The pins are so small to work with.  What I do is use a long square pin that fits in the end of the JST pin.  That way I can just hold onto that pin instead of trying to hold onto the tiny JST pin.  I'm getting by with these, but because of the small size of the pins it take a bit of care to do them.  I'm getting better at it over time.  It takes a bit of patience.  But I have found that if I just relax and take my time I can create some pretty dependable crimps.   I also crimp it in two steps.  The first time to crimp the actual bare wire, and then I use a different place on the crimping tool to crimp the insulated part of the wire.  So it's a two-step crimping process.  And often times I need to make the final crimp twice to get it nice and square.  It requires a bit of practice and skill.  The JST pins are just tiny.  That's the real problem.  But this tool does a fair job.  Better than trying to crimp freehand with needle-nose pliers which I tried and quickly abandoned.

AliExpress JST Crimping Tool

DroneBot Workshop Robotics Engineer
James


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Robo Pi
(@robo-pi)
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Joined: 12 months ago
Posts: 1757
2020-03-03 9:51 am  
Posted by: @spyder

Personally, I usually end up crimping the wire, then dropping a bit of solder on it, which everybody tells me is the wrong way to do it, to which I tell them that, yes, you're right, and then I go ahead and do it anyway. It saves me headaches down the road

I tried soldering them too, but because the pins are so tiny they tend to heat up and suck the solder down into the hole where the connector pin goes.  I soldered them on and was happy with the results until I tried to plug them into the mating connector and realized that the solder had filled up the receptor holes.  So they wouldn't plug in.  That's when I broke down and ordered the crimping tool. ? 

The crimping tool works.  It was worth the $20 investment.  Especially if you're going to be using a lot of JST connectors.

DroneBot Workshop Robotics Engineer
James


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