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Frustrated - what components can I use with Pi + Piface?

e14 Contributor

I have just bought a Pi (model B) and Piface with the aim of teaching kids to interact with the real-world using Scratch.

Though I know programming, I'm an electronics newbie. The Element14 site (and any other site I've found) gives no indication as to what components can sensibly be used either as sensors (e.g. sound, temperature, switches) or actuators (motors etc).

I just end up with a totally bewildering list of components - most aimed at industrial applications.

Ideally I'd like a page that provides a simple list of either components to buy or specifications (voltage, inputs/outputs) I can search on.

But in the meantime any advice people can offer here would be appreciated.

Even better some projects that show how they can all be connected.

I like this RoadTest http://www.element14.com/community/roadTestReviews/1457 but all it says is "I've attached infrared proximity sensors." with no indication as to their specification or how to source them.

This http://www.element14.com/community/roadTestReviews/1479 is also good (especially since it uses Scratch) but without detail of the motor or microswitches.

This http://www.element14.com/community/roadTestReviews/1471 is the only one I've seen that specifies the PIR sensors used. But when I search the Element14 site for LHI778 I get nothing. And when I Google, it seems I have to order direct from China.

 

Alternatively is there an educational resource that would make me less of a newbie, so I can work out for myself what I can safely buy and connect?

Thanks,

Pete

  • Hi Pete,

     

    Most components are just that, components that need to be assembled together into a circuit to form a function. A sensor can be an individual component, but rarely will it interface to a digital circuit such as a RPI without being assembled into a circuit.

    Some sensors are more like 'modules' and already contain an assembly of components inside, and they provide a nice 3.3V digital output, all ready for a processor.

    Industrial modules tend to be expensive, and are possibly not what you're looking for, but it is no surprise that this is what you're finding on the Farnell site, because many people just purchase individual components (for any application) or modules for industrial apps. There are some lower cost modules from places like ebay, and they can suit an experimenter.

    Switches can be directly connected to a piface digital, because a switch supplies a digital (on/off) signal when connected to a voltage.

    Sound is analog, and cannot be interfaced easily, unless you just want an on/off indication of sound/no sound. It would require a circuit consisting of a microphone, and an amplifier which could be constructed with a transistor and some resistors and capacitors for example.

     

    If you want some components that are easy-ish to construct into a circuit compatible with your RPI, then search for sensors in a DIP package (easy to solder) and a digital output. A good starting point is here, but it will need some manual effort to identify the ones with a digital output, by looking at the datasheet.

     

    There are some "well known" sensors, depending on what interests you. One trick to find them is to search for (say) "I2C temperature ic" or "spi temperature ic" with google, because I2C and SPI are digital interfaces. These ics will require a (usually) very small circuit - usually explained in the datasheet; it could be as little as a single capacitor. If you don't wish to assemble the circuit, they you could check ebay for pre-soldered modules for the sensor type you require.

     

    For output devices, LEDs can be controlled as long as you place a resistor in series. Motors can be controlled as long as they are low voltage and low current.

    For example projects, the online, free magpi magazine will help; it will have LED and motor circuits, as well as circuits using sensors.

     

    For easy circuits, a textbook would be most useful - often some websites have less than useful circuits, with errors. I don't know of a textbook, but hopefully others can recommend some.