Little help please with solar

Ideas and questions about MintyBoost kits

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disco dan
 
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Little help please with solar

Post by disco dan »

I wanted to make my own iPhone charger so picked up a voltage regulator and set to work... however I encountered a few issues.

My first attempt (See pic):
IMG_1168.JPG
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This one simply discharged my phone. The batteries and solar panels go through the voltage regulator to give a constant 5v with a potential divider giving 2ish volts to the center pins. However the test meter barely registered an Amp reading. Plus I'm not 100% sure I was testing it correctly.

Phone is iPhone 4s and said it was 'charging' but actually started discharging the phone whilst connected.

Next I came across this site, ordered a mintyboost kit and thought I could re-design my circuit to supplement the power of the minty boost.
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This one is not quite finished, only took an hour or so to get to this stage but I don't want spend ages chiselling out the wooden panel to recess the solar panels and router out holes for the battery packs etc - UNLESS I'm sure this actually works.

Basically the two solar panels give out just over 6v and the battery pack about 6v are wired to a 1000mh 5v voltage regulator. This gives me a constant 5v. I was thinking I could wire this in parallel to the minty boost battery pack and this would give me a big enough capacity to fully charge my phone and the solar panels would in theory charge the batteries back up.

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disco dan
 
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Re: Little help please with solar

Post by disco dan »

Circuit diagram for first project:
circuit diagram.png
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Circuit diagram for second project:
circuit diagram1.png
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adafruit_support_bill
 
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Re: Little help please with solar

Post by adafruit_support_bill »

That is one way to do it. Not sure what kind of voltage regulator you are using, but the common 7805 needs about 7v to properly regulate the 5v output. You might also look at the LiPo-based Solar Mintyboost: http://www.adafruit.com/blog/2012/02/13 ... ost-build/

I went down a similar path a few years ago. The problem with trying to charge directly from a solar panel is that the output voltage will collapse when it is overloaded and that confuses the heck out of the phone. The net result is that the phone ends up discharging :( Adding batteries to smooth over the low spots helps to keep the phone charging.

Ladyada has a lot of good information on solar charging here: http://learn.adafruit.com/usb-dc-and-so ... sign-notes

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disco dan
 
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Re: Little help please with solar

Post by disco dan »

Yes it is the 7805CT voltage regulator.

Lipo does look like the way to go - eliminating the charging issues and providing a high capacity/discharge battery. However the cost is quite high*.


*I have just ordered a MintyBoost from this site then read about Lipo batteries and chargers... I don't want to have to pay postage from US to New Zealand TWICE! It would be great to get the charger and a Lipo battery - would make a very compact and efficient system.

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adafruit_support_bill
 
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Re: Little help please with solar

Post by adafruit_support_bill »

Orders do get processed rather quickly so we can't modify them once they are placed. However, we do have an distributor in NZ. That should save you shipping costs on future purchases: http://nicegear.co.nz/adafruit/

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disco dan
 
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Re: Little help please with solar

Post by disco dan »

Thank you for that link ! Most helpful! I have just ordered the lipo battery and charger too.

I plan to just use my own 6v Solar panels and find a suitable box to put it all in.

I love learning about this stuff! Wish I had gone down this road earlier in life !

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disco dan
 
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Re: Little help please with solar

Post by disco dan »

Wow my Adafruit Lipo charger and battery arrived today! One day from South Island of New Zealand to Auckland! Amazing!

Wish I ordered the mintyboost from same place.... currently UPS says it is in Jamaica! Looks like I will have to wait until Monday to finish my project - I'm sooo impatient!

Waiting for paint to dry on my enclosure. Made a small plywood box with recessed top that will take solar panels. Inside will be MintyBoost, Lipo Charger and 2000mah Lipo battery and two AA batteries.

Going to add LED's on traces to some small holes in the box for charging status etc.

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adafruit_support_bill
 
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Re: Little help please with solar

Post by adafruit_support_bill »

Sounds like a nice build. Be sure to post a photo when you get it all together. :)

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disco dan
 
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Re: Little help please with solar

Post by disco dan »

This is a mock up of the enclosure. I would like a 'charging' LED but cannot see any indicator lights on the MintyBoost. The LiPo charger has all the LED but it would be good if I could have a LED come on when I plug in my phone to the USB port. Do you think that is possible?
enclosure.JPG
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disco dan
 
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Re: Little help please with solar

Post by disco dan »

The USB/5V jack ports are not to scale with the rest of the drawing - I'm not very good with Google Sketchup! They should be a lot bigger.

The enclosure is about 6 inches square cube.

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adafruit_support_bill
 
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Re: Little help please with solar

Post by adafruit_support_bill »

it would be good if I could have a LED come on when I plug in my phone to the USB port.
Other than some sort of mechanical solution that closes a switch when the plug is inserted, the only thing I could think of would be a current sensor to detect charge current going to the Minty Boost.

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disco dan
 
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Re: Little help please with solar

Post by disco dan »

I was toying with the idea of modifying the USB socket so that the 'casing' was in two halves - when a usb plug is inserted it acts as a switch connecting the two halves. Not sure if they need to be grounded etc or even if the USB plug has any sort of current. Just thought of it, may do a little test.

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adafruit_support_bill
 
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Re: Little help please with solar

Post by adafruit_support_bill »

The metal shell on the USB socket is not connected to the MintyBoost circuit in any way. However, the shells on the cable plugs are typically connected to the shield and may be grounded on the device at the other end.

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disco dan
 
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Re: Little help please with solar

Post by disco dan »

This is a photo of just the charger and battery installed in the enclosure.

Still waiting for the MintyBoost to arrive (been a week now) and plan to pop it in there too.

I like the 'sleek' and minimalist look so far!
IMG_1182 (Medium).JPG
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adafruit_support_bill
 
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Re: Little help please with solar

Post by adafruit_support_bill »

Looks good! That is going together nicely. :)

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