My goal is to Have an isolated voltage source to allow me to give a level of safety That amplifier is connected to the patient; the amplifier formerly worked at 3-volt batteries for a symmetrical input voltage.
In this Blog applied an isolate source designed by the company Texas Instruments, with a small alteration That I will describe step by step.
The amplifier of cardiac signals, working at first with double AA 1.5 volt batteries.
These batteries allow me a supply of +3.0 and -3.0 volts.
This wasn't very efficient, the level of electrical protection given to patient is very poor; is true that the voltage is too low to harm the patient but working with batteries all the time is uncomfortable and you need to be checking the voltage levels of the batteries every few periods of use.
|Heart amplifier circuit|
Solution to the Problem
He noted that the isolated power supply TIDA-00349 allows me an electrical protection.
was presented to the output of tension is 5 volts, but if we look at the configuration of the secondary winding on the transformer pulses, can see that is a FLYBACK configuration, which can be altered.
|TIDA-00349 (Original Circuit)|
Because the capacitor C5, seen in the picture above; I can't obtain a symmetrical output voltage directly from the TIDA-00349, so I had to add the modification.
Externally it is added to TIDA-00349, diodes and condensers so that the biased diode allow me to charge the capacitors.
(I would use the isolated source in other applications, so that for me isn't good idea desolder the capacitor C5)
Implementation Video (Spanish)
The following waveforms were taken, after implementing the TIDA-00349 with heart Amplifier
|Cardiac wave form|