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How to switch on/off an LED pen idea Answered

I have this idea on trying to design a pen that lights up using an LED and some button batteries. I just don't know how to design the switch. I'm a pen turner and want to try to keep the electronics down to the size of the inside of a brass tube that has a 6.22mm inside diameter.

what i have decided on so far:

  • light source: 3mm white LED
  • power source: SR521 button cell x 3 (stacked in a pack that i'm designing for 3D-printing)

I would love to use a standard slimline pen cap for a finished look...which normally would be pressed into the brass tube...but i'm not against modifying it to work as the "button". I've attached an image of an example of the pen cap and tube.

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Downunder35m
Downunder35m

1 year ago

For a bottom end switch:
Have a plastic sleeve around the batteries and a thin plastic washer at their bottom - to insulated them from the case and screw cap.
LED is wired to the negative of the battery and the housing.
In the cap you have a hole.
The hole is filled by a metal plug acting as a switch.
Inner end of the plug has a little spring pressing against the PLASTIC WASHER and a metal pin dead center that is just shy of touching the battery.
Press button and you got light.
Please don't forget something to stop to the plug from popping out but I guess you know it needs a collar or similar...

Top end switch:
Bit harder...
You again need a plastic sleeve around the batteries and a full disk at the bottom.
Similar design as above but you have a thin strip of brass or copper running on the outside of your plastic sleeve.
Isolated with some tape or paint except for the area of the switch and where the battery connects on your plastic sleeve bottom.
A ring of soft foam or rubber on the inner ring of the switch acts like the spring from above and provides the required insulation.
The pin is just slightly shorter than the rubber so when you press the rubber compresses and the switch closes the circuit.

1
Jack A Lopez
Jack A Lopez

1 year ago

A switch can be two pieces of metal, arranged so a small movement will cause these pieces of metal to touch, or not touch, each other.

https://en.wikipedia.org/wiki/Electrical_contacts

https://en.wikipedia.org/wiki/Switch

A sliding contact might work well for a small space, in which you do not have a lot of room to work. The old school, 2x D-cell flashlight, often had a switch of this kind. I will attach a diagram I found, showing how that works.

Also, one time, I built a kind of pen with a single LED light source in it, including a switch. Although that switch was a momentary kind of switch, only closed while pressed down. I drew a diagram of it, in Step 8 of this 'ible,

https://www.instructables.com/id/Phosphorescent-No...

By the way, there exist mass produced, plastic, clicky type (retractable) ball point pens, with LED and batteries inside.

Link to image search for, "promotional lighted led pens"
https://duckduckgo.com/?q=promotional+lighted+led+...

Also patents for these kind of pens exist. I have not looked at all of them, but I think USP 5131775 (granted in 1992)

http://www.freepatentsonline.com/5131775.html

is typical.

flashlight-slide-switch-diagram.gif