Week 9 Input devices

This page documents the group assignment for week 09 of Högni, Jóhannes and Ólöf.

Group assignment:

• Probe an input device(s)'s analog levels and digital signals
• Document your work to the group work page and reflect on your individual page what you learned

Overview and approach

We did the group assignments in two different locations.

Ólöf worked at Fab Lab Austurland and documented about it.

Högni and Jóhannes worked at Fab Lab Ísafjörður and documented about it.

Fab Lab Ísafjörður

Analog input device

Högni tested the Hall effect sensor with the oscilloscope and in the video below you can see the oscilloscope responding to the magnetic field being applied to the Hall effect sensor.

Jóhannes tested the Hall effect sensor A1324 with his own breakout board. It has a sensitivity of 5 mV/G. Even though the minimum supply voltage is stated to be 4,5 V it works with 3,3 V as well.

You can see the voltage response, when moving a strong magnet close to the sensor and remove it again on the screenshot below.

The increase is around 1 V, which would calculate to a magnetic flux density of 200 G or 20 mT. According to this table the typical household magnet has a magnetic flux density of 5 mT, so the one I used is four times stronger.

Digital input device

Jóhannes tested the GY-521 breakout board with I2C.

There are two pins to probe - the clock (SCL) and data (SDA) pin.

First the clock pin was probed. It shows a high frequency regular signal with a low level of around 1 V and high level of around 4 V at a frequency of 100 kHz. According to this page the clock frequency is usually 400 MHz, but for certain conditions it can be slower.

Then I probed both lines using CH1 for data and CH2 for clock.

And here is what it looks like.

The clock channel shows again a regular pattern, but of course the data channel shows a more intermitted signal while sending the data. The voltage levels are similar on both channels.

Fab Lab Austurland

Analog input device

A breakoutboard with a Hall effect sensor

Looking into analog levels and digital signals

Ólöf made a breakout board with a Hall effect sensor. Then she used the Oscilloscope to probe the breakout board to check out the analog levels and digital signals.

Video of magnetic effects

Video of the Oscilloscope showing changes in analog and digital signals

Here you can see the effects of magnets on the Hall effect sensor. The Oscilloscope is set to showing both analog and digital signals.

Looking into analog levels and digital signals

In machine week I went to Ísafjörður and Þórarinn Bjartur Breiðfjörð explained more about using the Oscilloscope. He told me that the probe should usually be set to 10x. Then by pushing the Ch1 (Channel 1) button you can adjust settings on that channel, f.ex. set it to 10x. The same goes for Channel 2. Here you can see that he has connected both probes to the Oscilloscope and is adjusting the channels. Thumbs down for adjustment that isn't good with wawes that bend upwards or downwards, and thumbs up for good adjustment with rectangular wawes.