Basic components

Resistors

Use thick film 1% resistors in 0603 package. Except where tolerances or power requirements make this impractible. Use Vishay D/CRCW E3 or Multicomp MC 0603. Vishay Use E24 resistor values: E24 (100, 110, 120, 130, 150, 160, 180, 200, 220, 240, 270, 300, 330, 360, 390, 430, 470, 510, 560, 620, 680, 750, 820, 910) Buy them at Farnell.

Capacitors Use 50 V X7R Ceramic Capacitors on small packages. 0603 and 0805 are preffered. 100nf, X7R, 50 V in 0603 is available. Larger can become problematic Buy them at Farnell.

Use a 9V battery as main power block.
USB 5v cable on the Arduino should also be able to power the device.
Also a 9V adapter is available that connects to the Arduino.

9V and 5V input filtering Use an LCL input filter. Farnell: 9528172
Murata: NFE31PT222Z1E9L

shape: EMIFILNFE31

Shiftregisters will be based around 74HC595 shift registers with serial out.

The datasheet of the 74HC595 from NXP.

The tutorial about shift registers from Arduino.cc The code reference about shift registers from Arduino.cc The arduino examples don't use the SPI pins to clock out the signals.

An example using the correct pins for the SPI.h library.

Use a SO-16 package. At RS-online they have them with code number: 436-7638 but a tube of 50 costs 29.95 EUR.

Farnell: 1201269

The image on the right shows the basic layout for the current sources.

The circtuit uses the dual NPN transistor:NXP BC847BS as the core component.

The following calculations are used: \[ R1 = \frac{U_{in} - U_{V1,B}}{I_b} \]
\[= \frac{(U_{in} - 2 * U_{BE}) * H_{FE}}{I_E} \] \[ = \frac{(4.5-2\cdot0.65)\cdot 400}{4\cdot10^{-3}}\] \[ = 270 k\Omega \] \[ \Rightarrow 120 k\Omega \]

source: RS-online: 484-5059

datasheet of the BC847BS

The Emitter resistors for the current sources.

The input of the Hall sensor shall consist of an inverter with Schmitt-trigger. With 10K pull-up resistor. The low-pass input filter shall consist of a 10K resistor with 10 nF capacitor.

The sensor itself shall consist of a unipolar Hall sensor. The magnet will only be able to deliver 50 gauss max to the sensor.

The Allegro A1120-EUA-T consists of a unipolar hall sensor in a TO-92 package.
$B_{OP}$ = 35 G
$B_{RP}$ = 25 G

The part can be ordered from Farnell with number 1791402 and costs around 1.27 EUR (for 1+ units)

The output is active/pull-down when the south pole magnetic field exceeds $B_{OP}$. The supply voltage can range from 3.0V up to 26 V. So the 5V input voltage shall power the sensor. This will put an additional load on the voltage regulator of the Arduino, but shall reduce external current loops through the system. (i.e. pulled up inputs shall be powered by the voltage that the pull-up sensor connects to. )

The current consumption is worst-case is 4 mA max. The input will be pulled-up to 5V.

Design maakt gebruik van 5V voedingspanning.
Procurement: Probeer alles via Digikey te pakken te krijgen

74HC595 NXP: 8-bit serial-in, serial or parallel-out shift register with output latches; 3-state

Lightpipes voor 8 truecolor LEDs Bivar inc, PLP2-xxx, waarbij xxx in duizendste inches. Moet alleen nog een manier vind om dit in te bouwen/lijmen. Dit zijn lightpipes met diameter 3 mm. en moeten via de voorkant geplaatst worden. Meest logische lijkt mij om vast te plakken met lijm.

Soldering tips for my WECP-20 Weller soldering station which uses a LR 21 soldering pencil. Order at Farnell or Digikey.