PACEMAKER BATTERIES

Introduction -pacemaker  Small electrical device that runs on batteries.  Watches electrical signal of our heart and provide the electrical signal if our heart does not do so.  When heart produces its own electrical signal then pacemaker continue to monitor

Mercury cells  Negative electrode - zinc  Positive electrode -mercury liberated from mercuric oxide  Electrolyte -sodium hydroxide.  Outer case –stainless steel.

 zn + + NaOH > NaZnO + H + (+ive ions with mercuric oxide gives +ive ions of mercury and water)  2H + + Hgo > Hg + + H 2 O (mercury ions combine with incoming electron & neutralized)  Hg + +e > Hg

Lithium cells  Anode --- lithium  Cathode---iodine  Life span more than 5 years  Discharge time will be low.  It will give low signal when they go beyond a particular level.  Efficiency is high.

Advantages  Higher cell voltage.  Higher capacity.  Greater life span.  Smaller size.  Operation over a wide range of temperature

Working of lithium cells  Li > Li + + e -  I 2 + 2e > 2I -  2Li + I > 2LiI

Rechargeable batteries  They are not wisely used because they are not reliable.  Galvanic action in these cell evolves gas.  If the cell is sealed these gases must be consumed in balancing reaction.  So it is designed that the rate of evolution of oxygen gas from negative electrode equal to the rate of recombination of with cadmium.

Nuclear cells  Nuclear fuel can deliver enough power to operate pacemakers.  pu-238 produces radiation and hits the container and thus produces the heat.  Thermopile is inserted which converts thermal energy to electrical energy.  Thermopile is stack of thermocouple.

High voltage nuclear cells  Uses radioactive material.  Radioactive material have too much of energy and releases the extra energy (electrons).  It hits the outer surface and makes it negative  The two surfaces are perfectly insulated.

Low voltage nuclear cells  Uses radioactive material.  Here semiconductor is placed between the emitter and collector.  Hence moving of electrons will be slow.  Nuclear cells having long life time.  But the patients are not willing to accept due to danger through radioactive radiation leakage.

External power sources using Telemetry  Here multivibrators are used which generates desired pulses at the rate of 70 beats / minute.  Pulses are used to turn R.F oscillator of frequency 2 MHZ.  Modulated R.F waves are amplified and transmitted through the transmitter coil.  This type is also not liked by the cardiac patients.