Play Dough Circuits: A Session at Women In Computing Day — By Rob Szewczyk
This post is the fourth in our series of posts on events held at Women in Computing Day at Next Century this year. You can read our previous posts on Problem Solving with Tower of Hanoi, Programming, and Beyond The Technology on this blog as well.
Each year at Women in Computing Day we run a session on computer hardware or electronics. This year Rob Szewczyk ran a fantastic session on circuits made out of play-doh. Yes, you read that right. Play-doh! Is there anything greater than play dough? We had a great cooking day at my house and made kinetic dough. Then, with the play-doh the girls were able to do some hands on learning with to talk about how electricity is conducted and how form plays into how electricity is distributed. Plus, we got to play with play-doh at every step of the event, which makes it all worth it.
To put this post together Rob answered some questions about his event and how he pulled it all together. I’ve included each question with his response and some links to materials. If you have any questions, feel free to email WIC@NextCentury.com.
Can you provide a general description of your session?
In this session the students combined special play-doh with multi colored LEDs to create fun, battery powered works of art. By utilizing insulating and conductive dough, that can be made from household ingredients and powered by normal AA batteries, they learned basic principles of circuits, including how to wire components in parallel and in series, and properties of light emitting diodes.
What online websites did you use to learn how to do this activity?
The website I used has since been updated. It includes recipes for making both types of dough and project ideas.
What materials are needed to do this?
You need ingredients for both conductive dough and insulating dough. You also need basic electrical components, I used: AA batteries, 4x battery holders, 22 gauge stranded wire and multi colored 5mm LEDs. Tools that are necessary for preparation include wire cutter/strippers, mixing bowels, sauce pans and sturdy kitchen utensils (for stirring the dough). You will also probably want some ziplock bags or containers for storage.
One item that cannot be forgotten, big muscles. All that stirring builds up some mighty arm muscles! It is also good to consider using pots that do not have any coating as you really don’t want it to come off while you are making the dough.
What are the steps you did to make the play dough circuits?
To build a simple circuit that can power an LED, first connect each terminal of the battery pack to a blob of conductive play-doh. Make sure the two blobs are not touching. Then insert each terminal of the LED into one of the blobs. The longer LED terminal should go in the blob that is connected to the red (positive) battery pack wire. To make a solid shape that can power the LED, insert some insulating dough between the two blobs, making sure again that the conducting blobs do not touch.
How did you make the play dough?
The play-doh consists of ingredients that can be found in a grocery store. The two recipes are similar, but differ in key ways — namely the insulating dough uses sugar, whereas the conductive dough uses salt. You can prepare small batches of the dough in less than an hour with access to basic kitchen tools like pots, sturdy stirring utensils and a range. For detailed instructions refer to the links in #3.
One item to think about is the cost of the materials. It is much easier if you are going to scale to buy all the materials in bulk. Cream of Tatar is cheap in bulk but expensive in small doses at the grocery store. For instance, you can buy two pounds of it here but it costs $7.00 to buy two ounces at the grocery story.
What did you hope the girls would learn in this activity?
The objective of this activity was to allow the girls free range to create something fun while learning about circuits. It didn’t matter if they spent their time iterating on their circuit to determine how to make their display shine the brightest, or on creating intricate sculptures of nesting birds softly illuminated by colored light. We wanted to give them an open activity for them to explore the properties of electricity and to express their individual interests.
How could the activity be made easier or harder based on age level and background experience?
The activity itself doesn’t require much modification for all but the oldest girls participating. For the most part, the activity seemed to self adjust with older students picking up the basics sooner and thus having more time to get creative with their circuits. In order to keep the activity going the younger kids sometimes need a little help getting things hooked up for the first time, but once they see it they have little further difficulty.
How does your activity relate to computing?
Learning that the presence or absence of current in a circuit can alternate the state of a component like an LED a precursor to understanding that information can be encoded via circuits.
What are things people can do to troubleshoot the situation?
There were a few issues that occasionally cropped up:
- Problems with LEDs. Since LEDs have polarity, they only work when wired up such that the longer terminal is towards the positive side of the circuit. Also, occasionally LEDs would come in direct contact with the battery terminals, which can damage them such that they no longer work.
- Since play-doh is very malleable, it’s relatively easy to accidentally cause pieces of conductive dough from different sides of the circuit to touch, thus causing a short. The younger students in particular needed help making sure they used enough insulating dough to prevent this.
- Towards the end of the day, bits of conducting dough get mixed into the insulating dough. It helps, if between sessions, you take a minute to try and remove and discard parts of the dough that look “blended”.
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