About two weeks ago, I bought 10pcs of the A3144 (or at least a compatible variant) Hall Effect switch. Today, I’ve had a go at using one.
I hadn’t really looked at the datasheet properly so I was expecting the output to just go high when there’s a magnetic field nearby. So a magnetic field could increment a counter in an Arduino. As it turns out, the output pin is pulled low when activated and floats when not.
The datasheet even tells one what to do when using CMOS logic (which the ATMega328P (the chip the Arduino Uno uses) is).
So, with pull-up resistor (I used a 1.5k ) put between the supply and output pins, I was able to get the Arduino to register when a magnetic field came close to the switch.
I was even able to ditch the Arduino altogether – I wanted to demonstrate the switch using an LED and a way to demonstrate this easily on camera. Simply connecting an LED and series resistor (I re-used the 1.5k) between the output and the supply pins worked. With the magnetic field nearby, the LED lit up; with no field, the LED remained off. The Arduino was used just to tap the 5 volts from the computer.
There are other devices which are useful for switching on/off when a magnet is nearby, such device is a reed switch. This type of switch has moving parts which make or break contact due to a magnet pulling on the contacts and they are usually long, thin and fragile (long compared to the A3144). A great advantage of using a Hall Effect switch is no moving parts – it is a solid-state component. This means there’s nothing to break from constant use and it’s form factor is much much smaller and more convenient. The theory on the Hall effect is much too complicated for me to explain, so I’ll leave it to Wikipedia (link at top of post).
And that’s it for now.
The un-bagging and quick look video can be found on my normal YouTube channel, video:
This is the very affordable (cheap) universal programmer available from many sources on eBay. I first heard of this magic box on Dave Jones’ EEVBlog YouTube video where he shows us the device.
Here, it is pictured with a PLCC32 EEPROM inserted, ready for programming. This EEPROM came from an old graphics card.
It came with a few other bits – a PLCC44 socket adaptor, two yellow thingies (the name escapes me) (the location of the smaller of the two eludes my knowledge and I’ve drawn a smiley face on the bigger) and that other SMD board, which I’ve used to read an EEPROM from a wireless home electricity monitor. Another interesting ‘bit’ is the PLCC extractor tool included.
Something not mentioned in the video is the quality of the USB cable. At first I was surprised it was included but was happy it was since I only have a few of this type, and the’re never where I look when I want one. The first impression of the cable was that it was a bit cheap, but soon realised that that could be due to the slightly rubbery feel of the plugs. This is a decent quality cable and should last the life of the programmer.
That’s all for now.