The Pocket-Sized Power Supply Tests Electronics Anywhere

If you're the type to hit up thrift stores or garage sales then you know that most used electronics don't have power supplies or batteries handy. Make Magazine shows you off how to build a simple pocket sized power so you can generate power anywhere you are.

You don't need much in the way of materials to get this to work, just a few capacitors, resistors, a perf board, and a 9V battery connector. When you're done, you'll have a tiny little power supply that you can fit in your pocket that you can use to test all the weird electronics you find on your shopping adventures.

Pocket-Size Power Supply | Make Magazine

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Build Fake Batteries to Run Electronics On AC Power

If you have any gadgets that only use batteries, and don't accept AC power, you can convert them to run on the grid by building a fake battery pack and hooking it up to a power adapter.

Jason Poel Smith wanted to run his electronic baby swing off a wall outlet, but it lacked a standard barrel jack. This hack isn't for the faint of heart, so if you aren't comfortable with electronics, it might be better to sit this one out. Basically you'll need to convert an off-the-shelf power adapter to wire directly into the fake battery pack, which will involve soldering on resistors to match your target voltage. Once your power supply is ready, you can cut your fake batteries out of dowel rods, then add some screws to each end to act as the contacts. Finally, wire up the screws to your power supply, and pop the battery pack into your desired gadget. For complete instructions (you'll need them), check out the source link.

Convert Battery Powered Electronics to Run on AC | Instructables via Hackaday

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Convert Battery Powered Electronics to Use an AC Adapter

We're in a day in age where battery powered electronics are just an annoyance to most of us. Charging, or even plug-in power is so much easier to use. Instructables user DIYHacksAndHowTos shows off how to convert those battery powered electronics to run on AC.

Although the process sounds pretty complicated, it's not as difficult as you might think. It uses a voltage regulator circuit, , a switch, and a dummy battery system to take up space. The dummy battery also makes the whole thing removable in case you want to revert back to the batteries. As with any project where you're working with electricity, you'll want to be careful, but the process here is pretty straight-forward. Head over to Instructables for the full guide.

Convert Battery Powered Electronics to Run on AC | Instructables via Hack a Day

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Paper Electronics: Conductive Paints, Inks, and More

     This Instructable is all about the amazing technology of paper electronics and conductive materials. Instead of using stubborn wires and your rusty soldering skills to painstakingly connect components, why not use paint and glue? This tutorial will share various recipes to create your very own conductive paint, tape, glue, and ink. Using a maximum of 3 easy to find ingredients, these simple materials are easy to make. All of the conductive materials explained in this Instructable are based around the conductive paint (step 1). Using increments of different chemicals, the consistency of the paint can be changed from thick to thin (glue to ink). At the end of the Instructable a simple project will be shown using conductive materials (step 5). There is also a step that is dedicated interfacing conductive materials with kits and teaching classes and workshops.
Even though commercially available conductive materials work great, they are a wee pricey and often need to be ordered online. Another disadvantage of commercial products is that they are usually only available in conductive paint form.
To start off, I would like to share some of the science behind the main ingredient used in the conductive materials; graphite. Graphite is a mineral and a form of pure carbon. Graphite is very conductive and is sometimes used in arc-lamp electrodes. Because of its conductivity, graphite is the primary candidate for making conductive materials. Its other bonuses include being easy to obtain, mixing well with paint, and coming in a very fine powdered form. 

     Here are the supplies needed to make the conductive materials in this Instructable:

- powdered graphite lubricant- from from Ace Hardware or other hardware store
- black poster paint- from local craft store or from Amazon
- paint thinner- from local hardware store or from Amazon   
- popsicle/mixing sticks- from local craft store or Walmart 
- mixing cups- I used styrofoam cups from grocery store
- measuring spoon- baking spoons will work 

     To complete the ink and stamping steps and the project, you will need these additional supplies:
- light emitting diode (led) available at local Radioshack
- 3-volt coin cell battery- available at grocery store
- sponge- some type of sponge, I got mine out of an old printer ink cartridge
- airtight vial- any type of airtight container will work
- airtight plastic container- possibly tupperware or old food container  
- paper

     Now that the materials have been gathered, it is time to begin making conductive materials!

Warnings: Some of the projects and instructions in this Instructable use paint thinner. This chemical produces nasty fumes that probably aren't very healthy for you. Perform all projects using paint thinner in a well-ventilated room. I am not responsible for any accidents that may occur while using this Instructable. 

Please don't forget to vote for this Instructable in the Pocket Sized Electronics Contest and all of the other contests.

This Instructable is submitted for Powell Cubs for the Instructables Sponsorship Program.

     The first part of this tutorial features conductive paint. The paint will be the base of all of the other materials that are explained in this Instructable. The paint makes an ideal base because of its consistency. To make glue you add slightly more graphite powder, and to make ink a few drops of paint thinner is added... but onto that in later steps.
Conductive paint sticks well to most materials, especially paper and cardboard. Anything that the poster paint will bond to, the conductive paint will as well. I have found that this mixture of conductive paint flexes well on paper. However, sharp creases and folds will lead to a crack, usually causing a shaky connection. The conductive paint will turn out to have the same flexibility as the paint that is mixed in. 
As a general rule of thumb, use this paint in low-medium areas of stress to ensure a reliable connection. For higher stress applications resort to one of the conductive inks mentioned later in the Instructable.
The two materials used in conductive paint are powdered graphite and the poster paint. After much experimentation, I found that a mixture of 2 parts powdered graphite to 1 part black paint worked exceptionally well. 
Instructions: Using the measuring spoon, measure out two spoonfuls of powdered graphite and pour it into a mixing cup. Add 1 spoonful of the poster paint. Mix well, making sure all of the graphite is added. 

Application: Slather heavily onto the material (i.e- paper, cardboard) in the desired pattern using a paintbrush. Make sure that all lines are coated evenly. Allow a few hours to dry before using. Store remaining paint in an airtight container.
When dry, the conductive paint has a very low amount of resistance. After several tests, I calculated the resistance to be around  
115 ohms per centimeter. Even though 1 centimeter of standard 22 gauge hookup wire has a resistance of about 2 ohms, the 113 ohms difference will barely make a difference in the circuit. If the circuit schematic calls for a small resistor  (<115 ohms), it would be alright to omit it. I found that when you connect a new 9-volt battery to a painted line (of conductive paint) and attach a digital multimeter on the other side, the voltage detected is 9.27-9.28 volts out of 9.29-9.30 volts. In sum, there is a very minimal amount of voltage lost when using conductive paint. 

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Convert Battery Powered Electronics to Run on AC

It is very rare to find a power supply that will perfectly match an electrical appliance unless they are sold together as a pair. So we are going to have to modify our power adapter to match the circuit that we want to power. The easiest way to do this is to use a variable voltage regulator such as a LM317. The typical configuration for this kind of circuit is shown in the picture above. This regulator uses two resistors to set the output according to the formula: Vout=1.25*(1+R2/R1).

For most applications this circuit can be simplified a little bit. The capacitors are only needed if your load circuit is sensitive to small power fluctuations. So in many cases, these can be eliminated. The variable resistor R2 is useful if you want to be able to power multiple different devices. But if you are going to use the power supply exclusively on one device you can replace it with a fixed value resistor. Wire the circuit as shown with Vin connected to the power supply and Vout connected to the circuit that you want to power. The regulator will bring down the output of the power supply down to the value that you set.

Depending on the power rating of your circuit, you may need to add a heat sink. 

Example:
My son's swing normally runs on four C size batteries. So I found an old power supply with a 9V 1000mA output. I figured that would be enough to replace the battery pack. Then I soldered together the LM317 regulator circuit with a 220 ohm resistor for R1 and a 820 ohm resistor for R2. These resistor values give an output voltage of 5.9V. (It would have been ideal to use a 240 ohm for R1 and a 910 ohm for R2 but I didn't have those values on hand) This output is still well within the operating range for a four cell battery pack. Anything between 1.25V and 1.5V per battery will usually work. Since the electronics on the swing just consists of a motor and a speed controller, I decided that the filtering capacitors weren't unnecessary and I left them off. See the following steps for the best methods for connecting everything together. 

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Paper Electronics: Make Interactive, Musical Artwork with Conductive Ink

Before you go crazy with your conductive ink, there are a few constraints to your artwork.

1. There must be four separate sections of conductive ink. One acts as a distance sensor and will eventually control the pitch of the audio. This part of the artwork should ideally be as large as possible as the larger it is, the more sensitivity the sensor will have. The other three sections  will act as buttons that will allow us to control the frequency of the audio and don't need to be as large. It is important that none of these sections touch each other.

2. The four sections should have traces (a painted/printed line no thinner than 1mm) taking them to the edge of the paper terminating in a 5mm x 5mm square of ink. These squares of ink should be side by side with a 5mm gap in-between. This is clearly shown in the image of my print on the bottom right hand corner. This print was A5 in size.

When it comes to creating your artwork it doesn't really matter how you do it, but the two easiest ways are to either paint by hand or to screen print. Screen printing means that not only do you get a high quality print, but you can print as many as you like easily.

Painting is easy, just remember to follow the constraints above.

Screen printing with Bare Conductive is a little trickier as it tends to dry quickly in the screen. To get around this I found it best to dilute Bare Conductive with roughly 1 part water 10 parts Bare Conductive. This makes the whole process a hell of a lot less stressful. When it comes to selecting a good screen for the ink, I recommend using a textiles screen with a mesh of around 90t.

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