Thread: Repaired Harbor Freight digital caliper
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Winston Winston is offline
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Default Repaired Harbor Freight digital caliper
wrote:
On Nov 29, 10:05 am, wrote:

(...)

I like an elastomer carbon button driven by a threaded
knob that makes contact between the '+' side of the
button cell and the caliper cell contact instead:

|---- Caliper
| '+' contact
----
| /----------- Single sided
.---. | |.--------. Flex PCB
| | | || | interposer
| | | || ..
| P | | || ||
| o | /\/.-.|| ||
| w |-\/\/| ||| ||
| e | | ||| ||
| r | | | | || Caliper
| | | | | Button || '-' contact
| K | | | | ||
| n |-\/\/| | | Cell ||
| o | /\/'-' | ||
| b | | | ||
| | | | ||
| | | | ||
'---' | | ''
| | |
| '--------'

(created by AACircuit v1.28.6 beta 04/19/05www.tech-chat.de)

--Winston

The knob could drive a screw, compressing a leaf spring contact onto
the cell. Or, use a slide mechanism, if you prefer. Viola.

I see the interposer flex PCB as a 'T'- shape in plan view.
The horizontal arm goes between the caliper's '+' contact and
wraps around the body of the cell. The vertical arm is bent
90 and can be enlarged to provide adequate contact for the
elastomer switch element.

I'd call for 2 oz. copper with heavy tin plating so that the
part would keep it's 'bend' and not tear under torque.

Alternative embodiments including one in which the power
knob houses an external cell are included by implication.

The cover would be slid in place without the knob and then
the knob would be screwed in; it'd be removable for cleaning.

A ratcheting torque-limiting clutch
inside the knob is left as an exercise....

--Winston
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