Keychain sized simple circuit

I plan on making an Instructable about making a keychain sized simple circuit. I will be using the circuit board  shown below but I'm having inventors block. It should be able to take the stress of being jumbled up in a pocket. What should I put on it? If I use your idea I will mention and thank you in the Instructable. Thanks in advance.

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If you made a torch you could dip it in clear cast resin as a protective cover then add the switch.

A laser maybe? How about a blacklight LED and some invisible ink
pgd5000 (author)  killerjackalope7 years ago
Thanks I might do that, I was thinking about making a light but I hadn't thought about using resin.
el.lori6 years ago


All light sources in our houses or at work must give an appropriate amount of light depending on the type of activities we perform. While working on a task that requires medium concentration the illuminance in a room should be at least 300 lx. The desks and keyboards while working at a computer should be illuminated with about 500 lx and while performing tasks that require high precision and concentration the luminous flux density should be about 750 lx. For comparison the amount of light that is enough for relaxing and watching tv is about 20 lx. Under this value the human eye is not able to recognize the features of a face.

Examples of suggested illuminance in rooms

Living room

1.main lighting: 100-200 lx.

2.surface of a table for reading and writing: 300-500 lx.

3.dining table: 300-500 lx. stand: 500-750 lx.


1.main lighting: 200-300 lx.

2.under shelf lighting: 500 lx.

Other rooms

1.hallways, stairs: 50-100 lx

2.bathroom and toilet: 300-500 lx

Other exemplary values

1.facial features recognition: 20lx.

2.sunny day: up to 10 000 lx.

Multifunctionality of lighting

While designing lighting in a house or flat it is important to keep in mind, that very often one room is used for many different kind of activities. For example a living room is a good place to relax and watch TV (where a subtle, slightly diffused light is most appropriate) but also for family meetings and meals for which the luminous flux density should be about 300-500 lx. This is why we should not limit the light sources to only one, but to few different lighting points that can work independently from each other.

Many sources of light in one room

Due to the fact that most of the rooms in our homes are used for different activities, it is suggested to use multiple independent lighting circuits. A very good solution, that is more and more popular in interior design, is diffuse lighting. Diffused light may be produced both by a reflection of light from a completely nonspecular surface and by using multiple small point light sources.

Energy efficient and environmentally friendly

While designing the lighting in a house it is good to choose light fixtures that can work with energy saving light sources. This environmentally friendly lighting not only helps to save money, but it is also shows our care about the environment.

Good quality light sources

We should always remember to choose good quality light sources. Very often a theoretically cheaper light source is actually more expensive because of its shorter lifetime and because its performance is much lower than stated by the manufacturer.

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No.406 HongTeng Building,

No.392# Xihong Rd,Gulou.




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jeff-o7 years ago
Once finished you could coat it in a few layers of epoxy.
How about using it for a small buzzer circuit w/ push button? It does require 8 button cell batteries, but it works! All you need is a 2N 2222A, a small capacitor, resistor, and piezo speaker. I can't recite the schematic right off the bat, but if your interested, just let me know! (just give me some time to get the schm. from my friend who built one)
seandogue7 years ago
A case. Ideally, a molded plastic case. Or you could just artistically wrap it with duct tape.