OWADC1 - 1-wire 8-channel ADC board

Introduction

OWADC1 is a small, compact board designed by M.Traxler and S.Voltz (GSI/EE) to provide an 8 channel, max. 16bit ADC to be accessed by 1-wire protocol

Documentation

Layout

• OWADC1.pdf: Schematics of OWADC1

1-wire ADC

Family code	Device and datasheet
20h	DS2450 1-Wire Quad A/D Converter , (DS2450.pdf: Local copy)

RC time

• Apparently the input resistance of the ADC seems to be around 10¹⁰ Ω, therefore the time constant τ is around 1000s, improving noise resilience, but reacting quite slow to rapid changes.
  • NOTE: we deduced those numbers the other way around: having 100nF, we saw a decay time of a 3V input value (~36000 adc counts) to 0 less than 1000, to take more than 10 minutes. Details on purpose.
  • The datasheet says: 1MOhm.
• To decrease τ smaller capacities should be used.

known 1-wire IDs

Board Number/Name/ID	Position	ID	user
I	U1	205607100000001A	HADES magnet
I	U2	---	HADES magnet

Notes and Remarks

1. Make sure to have (at least) 1 pull-up resistor of about 3.3kΩ on the data line of the 1-wire bus to the power VDD.
   • Recommended to have it at the master, e.g. at HadCon's connector JDINOUT2.

Future/Extensions/Wish list

• 10 pin 1-wire connector:
  • pin layout compatible to JDINOUT of HadCon and HadCon2
  • but with a switch/dial (?) to connect internal 1-wire bus to one of the available 6 positions
  • switch for allowing/blocking (default) connection to external V_DD of HadCon(2)
  • alternative:
    • 2 pin connector (screws/clamps) connecting only data and ground line
• RJ-45 connectors
  • 90° bending

Applications

• HADES I/O Box
  • HADES Box Introduction
  • HADES I/O Box (HADES internal)
• HADES direct Magnet-Sensor-Readout