Topic: VP2 ISS questions about solar and UV

[dalecoy]

Smart converters?

Remember when this design was done, and what integrated technology was available.

And the question is the circuitry for charging the supercap - not the circuitry for powering the logic and transmitter.

[kobuki]

Smart converters?

"smart" I wrote.

And the question is the circuitry for charging the supercap - not the circuitry for powering the logic and transmitter.

Do you think they're not the same? Why?

[dalecoy]

And the question is the circuitry for charging the supercap - not the circuitry for powering the logic and transmitter.

Do you think they're not the same? Why?

Yes.  One controls the current going into the supercap to charge it.  The other controls whether there is current coming out of the supercap to power the logic and transmitter.

For instance: when the solar panel is producing voltage that is high enough to charge the supercap, it is charging the supercap.  But the supercap is not powering the logic and transmitter - the solar panel is powering the logic and transmitter.

When it's dark, you want the supercap powering the logic and transmitter - but you don't want the supercap electrically connected to the solar panel.

That all was generally done with "isolation diodes".  Of course, today's technology could provide two smart converters - one for charging the supercap, and the other for selecting the best available power source and powering the logic and transmitter.

Of course, adding a battery (and perhaps a mains adapter) to the situation increases the complexity.

I'm probably not explaining that very well - so perhaps someone else can chime in.

[kobuki]

Certainly there are many possibilities. How I'd imagine it is when there's enough current for charging the supercap and powering the electronics you can do that using a single DC converter. If the battery is indeed charging the cap (as I experienced) without sunlight then the control logic becomes simpler. You just need to take care of the backwards flow to the battery. The mistery is still on, eg. what about the wall adapter. Alright, it's just theorising. Also, the cap isn't supposed to be charged by the battery yet it still seems to be happening. It would be great indeed that someone with definite knowledge chimed in.

[dalecoy]

If the battery is indeed charging the cap (as I experienced) without sunlight then the control logic becomes simpler.

That's simply not correct.  You perhaps have 3 things that could charge the supercap - and then 4 things that could power the logic and transmitter.  Your logic has to pick the correct sets.  And avoid incorrect ones (example: never connect the battery to the solar panel), and avoid over-voltage conditions.

However, that discussion is well beyond the questions here.

[kobuki]

However, that discussion is well beyond the questions here.

No problem. However, I'll get a 2-3V panel and use that. Simplest.

[SLOweather]

Or... get a 2 D cell pack and wire it in via the battery terminals or DC jack, and put 2 alkaline Ds in it.

An Energizer CR123A 1500 mah cell will run one of my temp/hum stations about 6 months. If Wikipedia is correct and an alkaline D cell has about 12,000 mah in it, that's 8x the CR123A, so the 2 D pack should run it for 4 years.

I'm gonna have to try that...

[kobuki]

Or... get a 2 D cell pack and wire it in via the battery terminals or DC jack, and put 2 alkaline Ds in it.

Yeah, I thought of that too. But it's not as elegant as a solar panel

EDIT: oh, and I think the anemometer + solar + UV that runs off this sim consumes more power. I'd guesstimate 3-4 months, but multiply that with (12k/1.5k) and it's still about 2+ years... Tempting...

[rdsman]

Well, perhaps I'm incorrect about the battery charging the supercap.  I'm quite willing to hear an authoritative correction (or an experiment in a system like yours, that has no solar panel, removes the battery after some charging time, and then demonstrates that the system continues to operate for several hours)

I connected a completely dead Vue ISS to a benchtop power supply set at 3.3 vdc.  I let it run for a few hours and then disconnected the power supply at 13:25.  The last transmission from the ISS was at 14:05.

I repeated this only this time, the power supply was connected at 14:24 and disconnected at 14:25.  The last transmission from the ISS was at 15:04.

My guess:  Its charging a filter capacitor (Not the Supercap)! 

Ray

[dalecoy]

I connected a completely dead Vue ISS to a benchtop power supply set at 3.3 vdc.  I let it run for a few hours and then disconnected the power supply at 13:25.  The last transmission from the ISS was at 14:05.

I repeated this only this time, the power supply was connected at 14:24 and disconnected at 14:25.  The last transmission from the ISS was at 15:04.

My guess:  Its charging a filter capacitor (Not the Supercap)! 

Ray

Thanks for the test, Ray.  I agree with your conclusion.

[kobuki]

Or... get a 2 D cell pack and wire it in via the battery terminals or DC jack, and put 2 alkaline Ds in it.

OK, so I finally did just this. Let's see how long it lasts...

[dalecoy]

Or... get a 2 D cell pack and wire it in via the battery terminals or DC jack, and put 2 alkaline Ds in it.

OK, so I finally did just this. Let's see how long it lasts...

"did this"?   Where did you attach the wires?

[kobuki]

Battery terminals.

[kobuki]

Sorry for resurrecting this old thread, but I just replaced the 2x D-type batteries in the SAT. It still has the anemometer and solar+UV sensors connected. It lasted about 1.5 years, still had juice in it but below -2-3°C the transmitter started to drop out sometimes so I replaced the batteries. Old ones were "Varta Long Life", new ones are "Varta High Energy" (this is what the store had) - I guess the former ought to last longer for this type of load. If the new one goes for another year, I'm satisfied. I'll probably replace them before winter every year from now on.

[azchrisf]

And to answer the first question in my opening post, the UVI values are correctly transmitted as 0.0 now, in darkness. It seems the ISS needs to sense something above zero UVI before it decides to have a UV sensor.

Not sure if this will help or even applies, but there is a supposed to be a correction somewhere that if it senses less than 0.5 UV, it will cut off the value to straight 0. So it needs at least 0.5 UV to start reporting.

[kobuki]

Thanks, the original issue was that it reported no values, as if the UV sensor wasn't connected at all. Then it started reporting 0.0, then daylight values.