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Old 02-02-2014, 08:45 PM   #706
craftycoder OP
Motobrain PDU
 
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I just tested it and it appears to be working fine.
For those following along at home, the final dimensions are 3.5 x 2.25 x 1" not including the tabs for bolting it down.
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Old 02-02-2014, 09:52 PM   #707
Mike.C
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Quote:
Originally Posted by Gany View Post
How bout making a silicone mould instead? You could make one off one of your castings?
Great idea, we do it all the time.

Just be sure to use an addition curing grade not a condensation curing grade (ask the supplier). Most addition types are more chemically resistant and usually hve a higher tear resistance depending on the particular one you use.

The up side is no release issues. The down side is you can't easily have a split mould so any tabs or undercuts have to be able to be "prised" out wiothout tearing the silicone.
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Old 02-03-2014, 06:50 AM   #708
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Originally Posted by Mike.C View Post
Great idea, we do it all the time.

Just be sure to use an addition curing grade not a condensation curing grade (ask the supplier). Most addition types are more chemically resistant and usually hve a higher tear resistance depending on the particular one you use.

The up side is no release issues. The down side is you can't easily have a split mould so any tabs or undercuts have to be able to be "prised" out wiothout tearing the silicone.
One of my friends makes what I consider split moulds all the time in his business of making costume reproductions, later after I get up this afternoon I will try to link some of his processes and hopefully I am thinking of the same type of mould. Good night for now.

sent from my phablet.
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Old 02-03-2014, 12:31 PM   #709
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Encapsulated Thermal Tests

I ran a test of the encapsulated Motobrain to confirm the thermal characteristics in its new potted state. I started the test by turning it up to 50A for 30 minutes. I took a measurement and then turned it up 10A and set a timer for 10 minutes. After 10 minutes I took a measurement, reset the timer, waited, took another measurement and then turned it up 10A. So it ran for 30 minutes @ 50A, 20 minutes @ 60A, 20 minutes @ 70A, 20 minutes at 80A, 20 minutes @ 90A. The next step was to turn it back down to 50A and check it every 10 minutes for 40 minutes to see how long it takes to get back to a similar temp as before. The ambient temp in the lab was 19C when I began and was 26C when I finished the 90A test because the power supply and DC load are really hot creating and dissipating all that current (so I can add 7C to the first 50A reading and say I achieved a baseline reading which I failed to achieve in 40 minutes). I then let it run with no load for 10 minutes and called the test complete. Results are below.
I took a few internal temp sensor readings along the way. The internal temp sensor is on the far side of a second PCB from the power transistors and the potting compound is not a great conductor of heat so I expect a large temperature delta. When I pot on of these in thermally conductive epoxy I expect to see much greater correlation between the two numbers. When no current is flowing, I would expect the external and internal temps to be roughly the same.

One edge of Motobrain is bolted to a table with most of it hanging in still air. See the last post for a photo of its location in space.

50A 30 minutes (internal temp sensor was 25C)


FLIR0048

60A 10 minutes


FLIR0049

60A 10 minutes


FLIR0050

70A 10 minutes


FLIR0051

70A 10 minutes


FLIR0052

80A 10 minutes (internal temp sensor was 41C)


FLIR0053

80A 10 minutes


FLIR0054

90A 10 minutes


FLIR0055

90A 10 minutes (internal temp sensor was 51C)


FLIR0056

50A 10 minutes


FLIR0057

50A 10 minutes (internal temp sensor was 41C)


FLIR0058

50A 10 minutes (internal temp sensor was 39C)


FLIR0059

50A 10 minutes (internal temp sensor was 39C)


FLIR0060

0A 10 minutes (internal temp sensor was 35C)


FLIR0061

Test completed. The results are suspiciously like my previous unencapsulated tests where 80A was in the low 60s and 90A was in the low 70s. This tells us that the epoxy is not significantly worse than nothing. The final 0A measurement shows that the internal temp sensor and external temp sensor are well correlated to each other and that there is a pretty significant thermal gradient inside Motobrain when it is running. When I get the fancy (and expensive) thermally conductive epoxy we should be in good shape!


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Old 02-03-2014, 01:27 PM   #710
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posted without comment


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Old 02-03-2014, 06:49 PM   #711
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Originally Posted by Mike.C View Post
Great idea, we do it all the time.

Just be sure to use an addition curing grade not a condensation curing grade (ask the supplier). Most addition types are more chemically resistant and usually hve a higher tear resistance depending on the particular one you use.

The up side is no release issues. The down side is you can't easily have a split mould so any tabs or undercuts have to be able to be "prised" out wiothout tearing the silicone.
So, here is his process for what I consider split moulds, and a teaser picture so as not to clutter up Crafty's thread, is this what you are talking about?



http://protagonist4hire.blogspot.com...t-part_22.html
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Old 02-07-2014, 09:13 AM   #712
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New Input Terminals

On the current version of Motobrain, I have the inputs terminated with 2x4 headers sticking out of the epoxy. I didn't love this design but I wanted to test some things and I didn't want to delay my testing while I tried to find the "perfect" solution for the inputs. I created a little "disposable" break out board so I could attach wires to the board with standard tools and attach that board to the Motobrain headers. After seeing and feeling this setup, I recognized it just will not be sufficient for our needs. Much too fragile! I've redesigned the board with terminals directly mounted to the PCB which will extend out of the epoxy. I ordered these new boards with an express three day turn around. Likewise, I redesigned the mold and also ordered it to be delivered post haste. I also took this opportunity to add some temperature compensation (in hardware) to the inputs. I found on the current version that the voltage sensed would drift a few volts when we approached the far end of its operating temperature envelope. The new amplifiers I've included will not drift significantly over the temperature range specified for Motobrain (-20C to 80C). Lastly, I decided to include a thermal cutoff circuit to the device. If the device reaches 112C, it will shut off. This is hardware enforced, so there is no getting around this. As such, it should so a good job protecting itself from would-be Motobrain killers.

Photos of the current board with break out board and renderings of the new board and mold are below.

Out with the Old


IMG_20140204_101652_602[1]

IMG_20140204_101742_427[1]

In with the New


Fullscreen capture 272014 105045 AM


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Old 02-10-2014, 07:49 AM   #713
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Great progress on this entire development CC. You're obviously down to the nitty gritty.
On the configuration of those terminals, it looks risky for short circuit from one to the next. It would be fine for someone as fastidious a yourself, but some of us are all thumbs, and I can just imagine a mis-sized termination ring on another manufactures wiring harness being jammed in there and connecting two circuits accidentally. Any thoughts on the final configuration here? Perhaps plastic dividers between them like some terminal strips have?
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Old 02-10-2014, 08:11 AM   #714
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I assume you are talking about the outputs and not the new inputs I was just showing. The outputs are pretty tightly packed, but the terminals are M6 threaded and ring terminals for them are readily available. I do not consider the install to be finicky in the least. The power input is a little close when you consider that you need a large terminal to handle the large currents. Even still, it isn't an issue for me. Plus you do it once, so do it right and forget about it. I might still lengthen the entire thing a little bit to provide more room for the input, but seriously the outputs are no big deal.





Quote:
Originally Posted by Captain Excellent View Post
Great progress on this entire development CC. You're obviously down to the nitty gritty.
On the configuration of those terminals, it looks risky for short circuit from one to the next. It would be fine for someone as fastidious a yourself, but some of us are all thumbs, and I can just imagine a mis-sized termination ring on another manufactures wiring harness being jammed in there and connecting two circuits accidentally. Any thoughts on the final configuration here? Perhaps plastic dividers between them like some terminal strips have?
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Old 02-10-2014, 08:40 AM   #715
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Yes it is the outputs I was referring to. Those other photos show the clearance from a better angle. I agree with you about the input. Lots if amperage on that one lead, and it's very close to the other terminals.
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Old 02-10-2014, 08:50 AM   #716
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Originally Posted by Captain Excellent View Post
Yes it is the outputs I was referring to. Those other photos show the clearance from a better angle. I agree with you about the input. Lots if amperage on that one lead, and it's very close to the other terminals.
Proximity is all about voltage rather than current and we are talking about 12V which is not very high voltage. I don't think distances are technically an issue. Those smaller screw terminals are shorter so while they are close in the X and Y axis there is also clearance in the Z axis which all adds up to the safety margin. Part of this entire project is making something small enough to fit on a modern motorcycle which have pretty seriously limited under seat space available. I am trying to do the right balancing act here. I may not have it quite right, but I promise I am trying.
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Old 02-10-2014, 08:59 AM   #717
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Don't get me wrong. I can see you've put heart and sole into the Moto Brain, you've done a great job, and all while sharing so much info with the inmates. You've put so much thought into this and so I really look forward to the first release.
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Old 02-10-2014, 09:02 AM   #718
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Originally Posted by Captain Excellent View Post
Don't get me wrong. I can see you've put heart and sole into the Moto Brain, you've done a great job, and all while sharing so much info with the inmates. You've put so much thought into this and so I really look forward to the first release.
No worries. I know you are offering constructive observations and I appreciate it.
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Old 02-14-2014, 02:03 PM   #719
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The new boards just arrived. They were delayed by Atlanta's second blizzard in as many weeks. I spent 4 hours yesterday shoveling snow off my entire street so that FedEx would not have an excuse to not deliver them today. I will work on building one up tomorrow. Assuming testing goes well, I will be building up several more for immediate shipment to some prospective customers. At this point I am late on my test unit shipments. I promised one person a unit in January but my molds were delayed two weeks and then since then I decided that the inputs locations were really not acceptable to me and I did not want to send a version of Motobrain out with those awkward inputs. Now I am feeling the pressure of being behind schedule which I really don't like.

The boards in the photo below are resting on some MDF which will become a custom made manual pick and place machine. The hand building of Motobrain is by far the worst part of the entire process and I hope this little gizmo will make it pleasant enough that I can hand make a couple dozen of these guys before I have them manufactured in bulk.

IMG_0038[1]
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Old 02-17-2014, 05:44 AM   #720
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Thumb

Captain Excellent makes an interesting point. When the Motobrain is installed in a tight location, say under a seat, what happens if a tool, or some other metal item touches any combination of the posts? Would that not generate a spark or two? Is some form of protective cover needed?

Like the rest of the guys, I really appreciate your extra effort, documenting the project and look forward to a retail product.



MM

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