I am using MAX17710 energy harvesting evaluation kit for wireless sensor networking. My sensor node consumes a peak current of ~90mA during transmission. The 3.3V regulated output of MAX17710 is unable to supply this peak current. Can anyone suggest an energy harvester which can supply a peak current of 100mA?
Dear Praveen,
In order to size the harvester you have to dtermine your load demand or the load profile. It just the power consumption along the time. For how long the supply must 100mA and with which frequency it will be repeated.
Then i would propose that you use the most reliable energy harvester the solar cells.
Since your power management circuit works from a power source whose voltage may be 1V to 2V then you need to connect 4 solar cells in series. Assuming 1A solar cells , then the produced power will be 2 watt. If these solar cells are working with the solar radiation. The module will produce about 10 watthour assuming five woring hours per day at the maximum power point.. Then if the load is 100 mA, at 3.3V , then the operating time of the load will be = 10/ 0.33= about 30 hours. which means that the harvested energy will be sufficient to derive such load and the other lighter loads which you did mention in your question.
So, one of the best solutions is to use a solar module consisting from 4 cells with one ampere. Such cells are available in the market.
wish you succes
Dear Dr. Zekry,
Thanking you for your valuable suggestions.
Yes, if I am using 4 solar cells with one ampere, it would be able to drive the load of 100mA for 30 hrs appx. In my case, MAX17710 energy harvesting evaluation kit comes with inbuilt solar cells and a thin film battery. Also,there is option for connecting additional sources like solar cells/ TEG/ Peizo electric crystal etc. Even though the energy harvesting sources are able to supply enough energy for driving the load, power management circuit (i.e. MAX17710) is unable to supply 90mA peak current.
In my application, power management circuit should be able to drive the load from different energy harvesting sources available and also able to charge the battery. MAX17710 was a good option which satisfies these conditions and its datasheet mentions that it is able to drive a continuous load of 75mA. Unfortunately it is not working for my sensor node whose average current consumption is 0.5mA peak current is 90mA (for a time period of 1ms).
Dear Praveen,
You can feed it from the unregulated power supply output since it has a capacitor of 10 uF. It stores much higher energy than the regulated one. The other solution is to increase the output capacitor of the regulated power supply such that it can supply the required current for the intended duration. You need 90mA x ims= .09x1ms=.09mAs the voltage drop= .09mAs/ iuF= 90V, which means that it will be longest depleted. You have to increase the capacitor to more than 200 uF.
PLEASE TRY AND TELL ME THE RESULTS.
Dear Dr. Zekry,
Thanking you for your advice.
I have already tried by feeding MAX17710 from an unregulated power supply. But neither PCKP (Battery output) nor REG output is able to drive 90mA peak current even with the external source. Output voltage drops to 2.1V which is the threshold for output shutdown (a feature of MAX17710 to save the battery life)
I have also tried connecting capacitors at Regulated output. During the initial power on reset, load consumes 90mA peak current in frequent intervals. I have started with 470 uF capacitor. Capacitor discharges during the peak and unable to charge before the next peak, thus reducing the voltage beyond the threshold and thereby causing the shutdown of regulated output. I increased to capacitance till 2200uF and the result was same.
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