Instructables

Multi-Color Light Painter (Touch Sensitive)

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Light painting is a photographic technique used to create special effects at slow shutter speeds. A flashlight is usually used to "paint" the images. In this Instructable, I will show you how to build an all in one light painter with touch switches. The touch switches are very simple to build.
 
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Step 1: Materials and tools

Touch Switch
Prototyping board
Enclosure (eg. pen case)
Lead free solder
1 x 9V battery
1 x 9V battery clip
5 x 2N7000 N-channel MOSFET
5 x 10M resistors
Heat shrink tubing
Wires

Multicolor lights
4 x 5mm red LEDs
4 x 5mm yellow LEDs
2 x 5mm green LEDs
2 x 5mm blue LEDs
2 x 5mm white LEDs
2 x 20 ohm resistors
3 x 82 ohm resistors
Quick setting epoxy

Tools
Soldering iron
Hot glue gun
Drill

Step 3: Touch Switch

Picture of Touch Switch
The touch switch here is a momentary switch which uses N-channel MOSFETs. When you touch +9V and gate, the LEDs turn on. The MOSFET requires up to 3 volts to turn on. Compared to mechanical switches, touch sensitive switches respond instantaneously and allow you to use multiple colors at the same time. In this circuit, there are six wires which are the electrodes. The 10M resistors allow the MOSFETs to turn off when you release the switches.

Update: 20 ohm resistors can be used for the red and yellow LEDs. 82 ohm resistors can be used for the green, blue, and white LEDs.

Step 4: Attach LEDs to the case

Picture of Attach LEDs to the case
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Attach LEDs using epoxy. Allow them to set before soldering.

Step 5: Solder the LEDs

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led touch circuit.JPG

Step 6: Electrodes for the Switch

To make the switches, strip the wires and coat it with lead free solder. Solder the wires to the gate of each MOSFET. Hot glue the wires to the case. If the case is conductive, you may use hot glue to insulate it from the wires.

Tip: If you have scarp solder, this is where you can use it.

Step 7: Mount the PCB

kostya2 years ago
Nice and simple project. Thanks for sharing! I think you can build 4 touch switches around one 4001 CMOS chip.The circuitry will probably draw less current and the battery will live longer.
hanlin_y (author)  kostya2 years ago
To get those values, you can add resistors in parallel or series but their values do not need to be precise. That's what I did. Here's a calculator for parallel resistors. http://www.1728.org/resistrs.htm
kostya hanlin_y2 years ago
Thank you. I'll try to use your shematic idea in my micro LED flashlight on a super capacitor. These MOSFETs (2N7000) are dirty cheap here. As touch pads I'm going to use snap buttons. Those nickel-covered ones are easily soldered.
kostya kostya2 years ago
Thanks for the reply.The only problem is that 4001 gates can produce just a few mA, so the LEDs won't be half so bright as in your project. It can be cured by adding NPN transistors but the game is not worth candles, assuming cost and complexity. I was wondering where you managed to get those resistors of 20,40,60 and 80 Ohm. Here in Ukraine they are considered non-standard. The closest standard ones are 18,36,62 and 82 Ohm.
hanlin_y (author)  kostya2 years ago
You mean less current with the LEDs off? From the data sheets, both have similar standby current but the chip may be great for smaller PCB's. Thanks for the suggestion.
kubaa4342 years ago
It looks amazing :)
Love the last step - the colors look great!
ncoleman22 years ago
Good job, this looks really cool! I want to try this sometime...