Belt

item-attachment

attachments for additional features including weapon features

Parts List

3d printed parts
Various Resisters (2 per Pickup)
Soldering Tabs for connections

How they Work

The Pickups are basically a voltage regulator circuit made of 2 resistors. The resistors form an upside down V where the bottom two connections are the power and ground and the top (where the resistors meet) is the reduced voltage output.

The output voltages below 1.0 volts are traps which can cause harm to the player who tries to use them or somehow incacitates the player.

The output voltages between 1.0 and 2.0 volts are beneficial to the players health in that they will shield or give them faster healing abilities.

The output voltages above 2.0 volts are offensive buffs which increase a weapons ability to do damage or give it faster recharge times.

Voltage Divider Resistors

See this document for our analysis of resistor dividers: https://github.com/moonbeaminteractive/item-attachment/blob/master/references/voltageDividerCalculations.xlsx

   VCC
      |
  < R1 >
      |
     +--------< R3 >------ to Analog pin on MCU
      |
  < R2 >
      |
   GND

ASCII based voltage divider circuit diagram

Since these resistor dividers are connected to VCC, they will always be draining power from VCC. We add an additional resistor, R3, to control the lowest impedance values. We want to make them as small as possible. We can go as small as 100MOhm of total impedance. If we expect to sample different analog values rapidly, then we should keep the total impedance less than 10K. However, for our resistor dividers, we expect the analog voltage value to be constant, so designing a very high impedance circuit design is the best solution. R3 could be 10K, but 100K uses even less current. Even 1MOhm or 10MOhm resistor values for R3 would work too, but resistors over 1MOhm start to become more expensive, while 10K and 100K are commonly available.

Table of resistor values

We used this tool: http://www.electronics2000.co.uk/calc/potential-divider-calculator.php

To compute resistor values using E12 resistor to have a total resistance of around 100K ohms. Assuming only a 5% accuracy in resistors (we use 1% accurate resistors) as worst case scenario, we are able to easily differentiate 25 distint values. We begin by using the first set