![]() ![]() Another second order R-C filter was used in the output of A 2, so the voltage V 1 will also present a low ripple when measured. Depending on the input voltage and impedance applied to the DC–DC converter, we can observe a small ripple in its output, so we added a simple second order passive R-C low-pass filter to the output of the INA125, in order to obtain a very stable dc voltage V 2, which will be measured to calculate the EM8900 output current. The INA125 gain expression ( G V = 4 + 60 k / R G) is specified with an error of only ± 0.05 %, so we measured the real values of the gain G V to calculate the power in Equation ( 1). The INA125 has a low off-set voltage (typically ± 50 μV) and since a 1 μA current creates a voltage of 1 mV in the shunt resistor, and the value of the off-set was neglected. The differential amplifier, implemented with a single supply instrumentation amplifier (INA125 from Texas Instruments (Dallas, TX, USA)), was designed to have a gain G V = 34 ( R G = 1000 Ω) and was powered by the same 5 V external power supply. The measured results show that, for ultra-low voltages, the TEG ensemble’s output impedance plays an important role not only in the amount of the energy scavenged, but also in the onset temperature of the energy harvesting. Using a mechanical set-up able to apply precise low temperature gradients between the hot and cold side of the TEGs, experimental data using different configurations of TEGs are obtained. The developed circuit is an electronic controlled load that drains the maximum current from the output of the DC–DC converter while maintaining its output voltage at the maximum allowed value. Here, we present an electronic circuit to measure the maximum power that can be harvested with low-voltage TEGs connected to a DC–DC converter. Therefore, it is essential to determine the output power of the system in different configurations, in order to decide on the optimum TEG connection. ![]() Impedance matching between TEGs and DC–DC converter plays a fundamental role in the energy harvesting efficiency. However, most of these temperature gradients are in the range of very few degrees and, while TEGs are able to harvest them, the resulting output voltages are extremely small (a few hundreds of mV), and DC–DC converters are necessary to boost them to usable levels. Solar radiation and human activity generate ubiquitous temperature gradients that could be harvested by thermoelectric generators (TEGs). ![]()
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