Small solar panel + ultracapacitor + zener why

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MatteP
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Joined: Tue Nov 22, 2016 8:07 am

Small solar panel + ultracapacitor + zener why

Post by MatteP » Sat Nov 26, 2016 7:18 am

I am buliding a very small and low power "intermittent" sensor, powered by a tiny solar panel and an ultracapacitor. It works with a voltage from 1.9V to 3.3V, but the transmitted radio range greatly depends on it.
:hamster:
When I used an LDO voltage regulator I had to "target" a lower-than-necessary voltage for it to work properly. But having a constant voltage is not required in my case: I would better benefit from a higher power when the sun is shining a lot.

What are the tradeoff if I ditch the LDO regulator and I simply cap the maximum tension with a Zener diode as shown below?

I do not want the zener to draw energy while the circuit is idle, due to its leakage current. So I moved it "before" the usual schottky diode.

Also, I use a slightly higher zener value to compensate for the schottly voltage drop, so as to charge the cap to the maximum voltage that the circuit withstands.

Still, I have the weird feeling there is a drawback. Am I just too cautious?

Also, the tiny solar panel will probably not reach its dangerous 4V level when loaded. Actually, I could even wake the MCU up to keep a load when the tension is "too" high, but this is a riskier business I guess.
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mike09
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Re: Small solar panel + ultracapacitor + zener why

Post by mike09 » Tue Jul 04, 2017 6:08 am

MatteP wrote:
Sat Nov 26, 2016 7:18 am
I am buliding a very small and low power "intermittent" sensor, powered by a tiny solar panel Cleaning company and an ultracapacitor. It works with a voltage from 1.9V to 3.3V, but the transmitted radio range greatly depends on it. :hamster: When I used an LDO voltage regulator I had to "target" a lower-than-necessary voltage for it to work properly. But having a constant voltage is not required in my case: I would better benefit from a higher power when the sun is shining a lot.
What are the tradeoff if I ditch the LDO regulator and I simply cap the maximum tension with a Zener diode as shown below?
I do not want the zener to draw energy while the circuit is idle, due to its leakage current. So I moved it "before" the usual schottky diode.
Also, I use a slightly higher zener value to compensate for the schottly voltage drop, so as to charge the cap to the maximum voltage that the circuit withstands.
Still, I have the weird feeling there is a drawback. Am I just too cautious?

Also, the tiny solar panel will probably not reach its dangerous 4V level when loaded. Actually, I could even wake the MCU up to keep a load when the tension is "too" high, but this is a riskier business I guess.
Image

Hello,
Thanks for the post.
I want to buy some Led lights but I don't know which type of Led lights are good for home??
Thanks In Advance.

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