[Oberon] A universal control for laboratory centrifuges.

John R. Strohm strohm at airmail.net
Sat Nov 18 18:17:38 CET 2017

Something similar is already being done in Amateur Radio.

A particular antenna rotator system has been very popular for many years. 
The rotator controller has long since been discontinued and is no longer 
available.  Service parts are equally unavailable.

Someone had a good idea, and built a new controller, using an Arduino board 
and software to replace the original controller module.

-----Original Message----- 
From: peter at easthope.ca
Sent: Saturday, November 18, 2017 8:32 AM
To: oberon at lists.inf.ethz.ch
Subject: [Oberon] A universal control for laboratory centrifuges.

A vexing problem with contemporary centrifuges is failure of the
control system while housing, motor and mechanical components remain
in almost new condition.  A machine that will cost 8-20 k$ to replace
becomes unusable from failure of a capacitor or integrated circuit
worth pennies to a few dollars.

From: Chris Burrows <chris at cfbsoftware.com>
Date: Sat, 18 Nov 2017 10:52:50 +1030
> We have now added real-time time and date support for RISC5 FPGA
> Project Oberon systems ...

Time and speed are the salient parameters of a centrifuge.  Typically
the user sets duration and speed of a spin.  Some machines have a
refrigeration unit allowing control of temperature.  Some machines
have an accelerometer to detect rotor imbalance.

For example, an instruction manual for an IEC machine specified
replacement of the main p.c.b. in case of failure of power supply to
the motor.  Unfortunately the board is not available.  For another
machine, purchased about a decade ago, no parts are available.
Schematics for the boards are not available, components are surface
mounted and some components have o.e.m. markings which can't be
traced.  Under these conditions, troubleshooting a board manifesting
intermittent failure can be impractical.

So I wonder about feasibility of a universal control for a centrifuge,
built from inexpensive components and software.  Tachometry is
commonly done by counting and timing pulses from an encoder wheel,
similar to the wheel in a mechanical mouse.  Temperature is sensed as
a voltage from a transducer.  Rotor imbalance might also be detected
as  voltage.

This isn't a one-off project.  World-wide, thousands of centrifuges
are built annually.  Seems that a universal control kit might be a
viable commercial product.

Regards,                ... Lyall E.

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