Building telephones with children

Introduction

Friends of mine organize events for children where they play games, discuss together and have fun. I offered to build simple telephones with a couple of kids between 10 and 15 years because I thought some might really enjoy it and I myself liked the idea of bringing kids into contact with electronics a lot, also. A telephone was chosen because I think it has a bit of a wow-effect when you can hear your friend through the device you’ve built. Furthermore, it could be built relatively cheap and has about the right complexity to fill a couple of hours.

Design

First, a little circuit around one transistor was tested on the breadboard and tweaked until it delivered satisfying results.

Then, it was drawn in inkscape so it could be printed out and glued on a wooden board. Into each grey circle, a tack is pressed so the individual components can be soldered to it.

The mechanical parts of the phone are all made from wood. This takes some time, but the raw materials are very cheap. I prepared 10 “telephone-kits” for the event.

The original plan was to use handsets from old phones out of the trash or so. Unfortunately, such old phones were surprisingly hard to find. So I needed to make some handsets from wood, using a little electret microphone and a small speaker. Because the signal from the electret microphone is quite small, a little transistor preamplifier is added directly in the handset. That said, its actually a two-transistor design, but only one is visible on the “circuit board”.

In preparation, two phones were built to finally test the functionality and also have two reference pieces for the kids. The two devices are connected together with a 20m cable that can be unplugged for easier “installation”. Furthermore, it has a (black) button and a little buzzer to “ring” up your opposite, so to say.

The event

At the event on a Sunday, I was quite excited how it would work out and if we would be able to complete the phones in time. Four kids took part in this phone building endeavour, and each one could take his or her working phone home! I was glad, however, that all the other adults also helped along and that there were only four children, otherwise probably time would have been too short. I think it was funny and interesting to the children, and also I enjoyed a lot, it was definitely worth all the preparation.

Some of the devices the kids built:

Drop me an Email