Threaded Mode | Linear Mode

twoweims · 06-27-2019, 02:05 PM

I am working on designing a smart charger that will charge NiMH properly and not alter the internals of the calculator in any way so that the original charger and NiCd battery could still be used.
I have 3D Printed a connector with the same dimensions as the original HP Wall Wart. I am now trying to find a source for the Female contacts in the connector.

I would appreciate any assistance in tracking down a suitable part.

Thanks!

mfleming · (This post was last modified: 06-28-2019 05:42 AM by mfleming.)

Sounds like a very interesting project, hopefully details to follow. There is no direct replacement for the power connector to the calculator that I'm aware of, but there is a vendor on TAS (TAS==The Auction Site==eBay) that offers a USB to Classic calculator cable for recharging batteries. The connector seems to be assembled from three individual receptacles that fit over the calculator pins.

This is one of those projects that involve a patient search though vendor catalogs online looking for suitable substitute parts. Someone has already figured out a solution and the result may be posted somewhere (if you're lucky!). Check TAS first for ideas, buy a part to reverse engineer, etc.

Good luck, post progress!
~Mark

P.S. You might want to start with wire crimp connectors, those where you push wires in either end and crimp the ends down. Each end's opening varies according to the size of the wire inserted. One would likely make a tight friction fit over a calculator power pin. Then there are Molex connector pins, and so on ...

[kby] · 06-28-2019, 06:46 AM

The vendor you referenced is the honorable Mark Hoskins who is on this forum.

Robert VM · 06-29-2019, 10:31 AM

The contacts in the "Molex" connectors used to connect power to hard disk drives (pre-SATA) fit nicely. They are somewhat long though.
Robert

twoweims · (This post was last modified: 06-29-2019 02:39 PM by twoweims.)

Here is progress so far:

This is my first attempt using a LiPo battery and charger. Unfortunately the largest LiPo battery that I have found that will fit in the battery compartment is 1000 mAh. But the setup works very well. The photo also shows my first attempt at recreating the connector. It fits and operates the shorting mechanism properly. I just need to find the sockets so I can finalize the model.

The connector will eventually be built into the charger case so there will be no wires hanging out.

I even found some PLA that almost matches the HP-67 original color. Sample chip is to the right of the calculator.

Still a work in progress but moving in a positive direction.

Thanks for all your suggestions.

-Dan

[kby] · 06-30-2019, 07:06 AM

(06-29-2019 10:31 AM)Robert VM Wrote: The contacts in the "Molex" connectors used to connect power to hard disk drives (pre-SATA) fit nicely. They are somewhat long though.
Robert

EIther we're thinking of different plug sumewhere, or…?

The molex pins in the usual 4-pin power connector for a 3.5" disk drive are are much larger in diameter.-kby

mfleming · 06-30-2019, 02:52 PM

It looks as though you've modeled the connector body quite well. I assume you envision plugging the charger into the 67 and using USB as a charger power source. How do you plan to fit and connect the LiPo?

~Mark

twoweims · 06-30-2019, 04:27 PM

(06-30-2019 07:06 AM)[kby] Wrote:
(06-29-2019 10:31 AM)Robert VM Wrote: The contacts in the "Molex" connectors used to connect power to hard disk drives (pre-SATA) fit nicely. They are somewhat long though.
Robert

EIther we're thinking of different plug sumewhere, or…?

The molex pins in the usual 4-pin power connector for a 3.5" disk drive are are much larger in diameter.-kby

I did manage to find an old hard drive power connector. I removed the Molex female pins from the connector. They fit perfectly in my connector (diameter) but are much too long. I will try to cut them short and just solder wires to what is left.

I also tried some 2mm bullet connectors they are very loose on the connector i will try modifying the model to fit.

twoweims · 06-30-2019, 04:32 PM

(06-30-2019 02:52 PM)mfleming Wrote: It looks as though you've modeled the connector body quite well. I assume you envision plugging the charger into the 67 and using USB as a charger power source. How do you plan to fit and connect the LiPo?

~Mark

Here is what I have come up with so far.
It is only a prototype. I know copper is not the best material but it is all I had on hand.