TeleHealth Hardware

  This page is part of the OLPC Health Project. Hardware | Software | Content | Health Jam

OLPC TeleHealth Hardware

User:DyD has been working on designing (and learning everything needed to design) a TeleHealth Module for several months

EKG

Simple 3 lead EKG for arrhythmia and trauma diagnosis. Also facilitates pedagogical exercises into

Hardware

Currently in design phases Four parts:

• Connection
  • Electrodes connecting device to person
• Amplification
  • Multiplies the voltage of the heart's electrical signal into something computer-usable
• Opto-Isolation
  • Protection circuits
• USB ADC
  • Inputs data to the XO

Main Chipset

The AD8541/2/4 series op-amps fulfill the target specs perfectly.

Target Specs

• Low frequency: -3 db @ 0.1 Hz
• High frequency: -3 db @ 45 Hz
• Patient leakage current: <10 µA with acquisition module connected (meets AAMI standard SCL 1278)
• Chassis leakage current: <100 µA (meets AAMI standard SCL 1278)
• Common mode rejection: 130 dB minimum with balanced leads. With 5Kohm imbalance 100dB

• A/D conversion: 10-12 bits
• Impedance: 100 Mohm, defibrillator-protected (optional for the XO)
• Signal Dynamic range: 10 mV
• Electrode offset tolerance: + - 320 mV dc (this is due to the fact the electrodes get polarized)

Circuit Schematics

EKG Temptative scematics this is approximated to technical steps noted above.

Problems

• Current problems include tuning op-amps and prototyping.
• Determine efficient alternatives to the classical electrodes.

Pulse Oximeter

An invaluable piece of medical equipment relaying information about pulse and oxygen saturation by analyzing the output of two filtered photodiodes in two different frequencies.

Hardware

Currently nonfunctional: design consists of two MAX4006 OpAmps(Designed for telecom photo-diodes) connected to an IR and a red filtered photodiode outputting a measurable voltage. A finger would be positioned between the photodiodes and a red and IR LED. The pulse oximeter operates on the theory that oxygenated an oxygenated hemoglobin have different absorption and reflection frequencies. The same principle can be applied to any other small organic molecule with identifiable spectra, with proper calibration.

Main Chipset

MAX4006 Op-Amp

Problems

Once again, op-amp tuning.

Stethoscope

A simple microphone and audio amplifier to pick up heart, lung and bowel sounds.

Hardware

• Button Mic
• Audio amplifier
• Shielded twisted-pair cable
• Mic plug

ADC

• MCU Specs
  • Speed: 25+ MIPS
  • 5 or more channels of ADC
  • 10 or 12 bits of ADC
  • 5V, 100ma or less
  • USB
  • Price, less than 6usd
• User:Mchua and User:Nlee have offered assistance
• BIG STRUGGLING POINT
• X.Looking at the C8051F321 until an alternative is found.X
• Now looking at the PIC18F2455/2550/4455/4550, a commonly used MCU supporting multiple channels of 10b ADC and USB

Power Supply

Due to the nature of medical instrumentation as necessitating high-precision power supply, some combination of a regulator chip, fuse, and smoothing capacitor are needed.

Main Chipset

LP2982

Hardware

• LP2982 5, 4.5, or 3v regulator
• Over-voltage protector
  • Fuse
• USB Connector
• Shielding

What Can I Do?

• Provide talent, time, or treasure:
  • If you have experience designing medical instrumentation, and are willing to mentor or assist high school age students...
  • If you have extra time and are able to send emails, track down sample components, or raise awareness...
  • If you don't know what to do with your old soldering iron, oscilloscope, or components collection...
• Program! We're in need of PIC and python programmers.