Threaded inserts in polycarbide or polyurethane enclosures.
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Threaded inserts in polycarbide or polyurethane enclosures.

by asgard on Wed Mar 06, 2013 5:42 pm

I am beginning some design work for enclosures for a wireless power charger project that is expected to see rugged use. I took a very good look at the threaded brass inserts that were used in the Arduino cases. They looked close to the dimension I am likely to spec, but did not find them in Grainger or any other "large" supplier. Where did they come from, and is there a dimensional datasheet for them?

J.R. Stoner
BDG

P.S. I am too good a chemist to let a misspeak get loose like that :) I meant polycarbonate.
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Re: Threaded inserts in polycarbide or polyurethane enclosures.

by Zener on Wed Mar 06, 2013 7:47 pm

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Re: Threaded inserts in polycarbide or polyurethane enclosures.

by john444 on Mon Mar 11, 2013 12:30 am

Hi Mr. Stoner,

You also might look at these: http://www.mcmaster.com/#threaded-inserts/=ltr023
I have found most plastics, including polycarbonate, to be rather soft for the knurled type inserts. I would be inclined to recommend the 'helical-coil' type for rugged service. In addition to having a large, course thread to grip into the plastic, the metal coil provides a reliable surface for the fastener's threads to engage.

Good Luck, John
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Re: Threaded inserts in polycarbide or polyurethane enclosures.

by Zener on Mon Mar 11, 2013 1:33 am

I was assuming the OP was designing custom molded enclosures. But if he/she is retrofitting existing enclosures then that is a big difference.
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Re: Threaded inserts in polycarbide or polyurethane enclosures.

by asgard on Mon Mar 11, 2013 6:27 pm

Zener wrote:I was assuming the OP was designing custom molded enclosures. But if he/she is retrofitting existing enclosures then that is a big difference.


Yes. It is my intention that the enclosure be a custom design. The power receiver is going to fit in a box approximately the size of an inkjet cartridge. What I was thinking is that the board stack (the receiver/shield/coil) be fitted to the inserts with 2mm screws while the top cover be clamshell fitted to the bottom by way of one-time snap fittings designed into the enclosure structure. The bottom shell would also contain a centering jig to slot the receiver against the transmitter coil assembly. The board stack would be around 1" x 1.5", which could then slot into either a Raspberry Pi or Arduino, perhaps by way of an adapter shield. I hope this assembly will achieve a PI rating of 52.2 or 52.3.
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Re: Threaded inserts in polycarbide or polyurethane enclosures.

by john444 on Mon Mar 11, 2013 9:15 pm

My apology Asgard,
I saw:
asgard wrote:wireless power charger project that is expected to see rugged use.
and I thought of the auto charging system I worked on a couple of years ago.
Sorry, my thoughts jumped to that project not realizing you were looking at watts instead of KWs.
I would like to hear more. Can you write about the project and maybe post some photos.
Pi's are very popular here on the forum.

John
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Re: Threaded inserts in polycarbide or polyurethane enclosures.

by asgard on Tue Mar 12, 2013 12:02 pm

Well, I suppose I could run down a general roadmap of this project. There are three interconnected systems. The first is prerequisite for everything. The BLiVIT is a smart lithium ion cell charger/manager that includes full power isolation, a soft on/off switch, and a boost/buck converter to supply either 3.3V or 5V, depending on a jumper selection. The BLiVIT is a 1.2" x 1" board that can have it's power fed from either a wall adapter or USB. The Li+ cell I am using for the prototype is a 950mAH cell that happily is nearly the same dimensions as the BLiVIT. I am also thinking how to adapt the output power, which is available on a 2-terminal screw block or Berg KK header, to supplying an Arduino (Flora?) or RPi. My current thinking is a simple short USB with a pigtail directly to the terminal block. If it is deemed preferable to have more mechanical security than that I could leave it as an exercise for the student to design an Arduino shield that directly mounts the BLiVIT/Battery stack.

The second essential component of the total project is the POQiRX, a receiver/shield/coil unit that directly mounts on the BLiVIT, and provides a wireless power source consistent with the Qi specification of the Wireless Power Consortium. The current thinking is to use a combined coil/shield assembly available from Vishay that is 28mm x 32 mm. The POQiRX is a 1" x 0.8" PCB.

The third essential component is the POQiTX, which is a WPC compliant power transmitter that feeds the POQiRX. Since the WPC's Qi specification requires the transmitter to radiate 5W effective power through the air it is necessarily beefier circuitry than either of the other two components. The POQiTX power comes from either a wall adapter or USB connector. This board is approx. 2" x 1.8". My fervent hope is that this design will be able to achieve EnergyStar certification, since the transmitter is going to be the most power-hungry when in the active transmission modes.
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Re: Threaded inserts in polycarbide or polyurethane enclosures.

by tastewar on Tue Mar 12, 2013 1:02 pm

The names remind me of Ikea product names ;-)
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