Cheap digital calipers can be bought almost anywhere, they might not be as nice or accurate as Mitutoyo calipers, but if they're a good value, what's not to love? The battery life. These things drain the battery even when you press the off button. This instructable will show how to modify the battery cover so that it acts like a switch, so that the battery can be physically disconnected from the circuit.
- Digital Caliper
- Copper Tape
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Step 1: Add Conductive Tape to Cover
The battery cover slides much like a switch, but is non-conductive. To make it act like a switch, copper tape is placed under the cover so that it touches the top of the battery. It extends from the under-side of the cover around the side and over the top, slightly.
- Place conductive copper tape under the battery cover.
- Wrap the tape over to the top of the cover.
Step 2: Add Conductive Tape to Caliper
The sliding contact on the lid needs to make contact with another piece of conductive tape to complete the circuit. In this step, complete the path by using another piece of conductive tape to route the battery housing's side contact to a position where the battery cover's contact will touch.
- Trim conductive tape into a point.
- Position tape behind battery housing's side contact.
- Bend tape into position with tweezers .
- Trim until contact wraps around battery housing's edge.
Step 3: Insulate and Place Battery
Before placing the battery back into the housing, isolate the battery from the side-contact by placing the conductive tape's non-stick backing in front of the battery housing's side-contacts. This will keep the circuit from being completed unless the battery cover is on.
- Place conductive tape's backing material into battery housing in front of side contacts.
- Place battery into battery housing.
Step 4: Done
In this step, use the caliper.
- In the first picture, there is a small gap between the two copper contacts because the battery cover is slightly off so the caliper is also powered off.
- In the second picture, the cover is slid fully on, so there is no longer a gap between the two copper contacts. The caliper is powered on.