Hello Everyone, I have a question about a basic RF Harvest circuit I am working on: The following is a link to my schematic. https://ibb.co/sJr89rj I live relatively close to a transmission source, and as a result the circuit charges up very quickly. The caps will actually change to 9v in about one hour or so. I want to use this to send pulses of energy into a rechargeable battery. I am not worried about overcharging at this time as the battery has an full charge safeguard. Conceptually I would like to send a series of small changes to the battery overnight and see where I end up at. Normally this battery would take a 5v source for charging. What I would like to do is wait until the caps charge to 8-10v and pulse that energy into the battery. I am stuck on how to 'signal' a charge when the voltage reaches the threshold. I have tried with a Zener diode 1N4738A with has a rb of 8.2v. I ttied putting the Zener with a LED completing the circuit. I assumed once the threshold of 8.2 is reached the LED would flash and the circuit would drop below 8.2v and repeat the process. However, when I do this the output voltage just drops to 2-3 volts and does not incrementally change. When I pull the Zener the incremental charge starts to accumulate again. Any assistance would be greatly appreciated!! Thank you! |
by wmikrut
November 14, 2021 |
Is a simple example. Use D1 as a Schottky diode (low threshold voltage). Use an NMOS, M1, with a Vgs(th) of 8 Volt. You may have to add a small extra resistor to limit the initial current when the battery is totally discharged. Consider, in the simulation, the difference of voltage between the two named nodes to get the voltage in the battery. The source V1 simulates a voltage which increases, then drops, and repeat. |
by vanderghast
November 15, 2021 |
Wow, thank you very much! |
by wmikrut
November 15, 2021 |
No answers yet. Contribute your answer below!
You must log in or create an account (free!) to answer a question.
Anyone can ask a question.
Did you already search (see above) to see if a similar question has already been answered? If you can't find the answer, you may ask a question.
CircuitLab's Q&A site is a FREE questions and answers forum for electronics and electrical engineering students, hobbyists, and professionals.
We encourage you to use our built-in schematic & simulation software to add more detail to your questions and answers.
Acceptable Questions:
Unacceptable Questions:
Please respect that there are both seasoned experts and total newbies here: please be nice, be constructive, and be specific!
CircuitLab is an in-browser schematic capture and circuit simulation software tool to help you rapidly design and analyze analog and digital electronics systems.