Make: DIYSUPERHUMAN
Make a blood pressure tester
that’s tough, smart, and mobile.
BY ALEX RUSSELL, GARRICK ORCHARD, AND CAROL REILEY
High blood pressure, also called hypertension, is deadly: it can
lead to heart failure, stroke, and kidney failure. One-third of
Americans have it, and in the developing world it’s the leading
killer of pregnant women due to lack of screening.
$50 and test your blood pressure anytime.
that measures the air pressure inside the
cuff. When the cuff is inflated sufficiently it
completely occludes the artery. As the cuff
is deflated blood starts to flow through the
artery, and pressure on the arterial walls rises
and falls with every heartbeat.
This causes oscillations of the cuff’s
pressure that are detected by the sensor,
and can be used to calculate both the systolic
(maximum) and diastolic (minimum) blood
pressures. This is known as the oscillometric
blood pressure method (for details, see
makezine.com/go/obpm). Our algorithm to
calculate both pressures is implemented in
C for programming onto a PIC microchip.
For energy efficiency in areas of the world
without reliable electricity, our device uses
NiCad batteries that are recharged using a
hand crank generator. Fully charged, they
power the device for about 50 hours. We also
removed the delicate mechanical pressure
meter from the device to reduce the size and
Existing blood pressure tests are painless
but the equipment is flawed: it’s delicate and
impractical in many settings, and it contains
mercury, which is toxic when released into the
environment. It’s also prone to human error,
because it depends on a doctor listening to
the patient’s pulse through a stethoscope.
So we came up with a DIY blood pressure monitor that’s better. It’s portable and
battery-powered, making it great for areas
with unreliable electricity. It’s solid-state, so
it’s tough and reliable and doesn’t contain
mercury. And it detects high blood pressure
automatically, drastically reducing error.
Here’s how you can build one for less than
Garry McLeod
OUR DIY BPM
Our Self-powered, Environmental, Affordable
Blood Pressure Monitor (SEA-BPM, or sea-
bump) is easy to use. An inflatable arm
cuff contains an electronic pressure sensor
70 Make: makezine.com/29
