Hi Folks,
I am building a small monitoring project for a solar array. For it I need to power the netduino and a couple of devices such as ACS714, a xbee etc. Nothing huge.
My issue comes in that I would like this all housed in the PV junction box which has the positive and negative from the panels in it (which I am measuring) - the kicker, these are anywhere from 200-500V (max) DC.
Looking at a simple voltage divider does not make sense due to the swing on the input.
Any tips? I also think that the current draw would be too high for it to run off batteries.
Cheers,
Crispin
leach power
Started by Crispin, Jul 03 2011 08:57 PM
4 replies to this topic
#1
Posted 03 July 2011 - 08:57 PM
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Take a seat, I'll be right with you.
#2
Posted 04 July 2011 - 12:21 PM
Hi Crispin,
I'm confused by
Myself I'd be tempted to look at a small cheap usb charger and modify it.
As you point out resistor dividers have issues not least being VERY wasteful when it comes to power. eg a 25w 10k resistor would be required to give 5v at 50mA. (a lot of power lost!)
I'd rip apart a switch mode 5v psu, and look at the chip set. They work by rectifying the mains, then using a high frequency oscillator to get the power through a step down transformer, to get the power conversion.
I'm sure I telling you some thing you already know: DC KILLS! That's my HSE and get out clause!
Yours Simon M.
I'm confused by
Do you mean non rechargeable?current draw would be too high for it to run off batteries
Myself I'd be tempted to look at a small cheap usb charger and modify it.
As you point out resistor dividers have issues not least being VERY wasteful when it comes to power. eg a 25w 10k resistor would be required to give 5v at 50mA. (a lot of power lost!)
I'd rip apart a switch mode 5v psu, and look at the chip set. They work by rectifying the mains, then using a high frequency oscillator to get the power through a step down transformer, to get the power conversion.
I'm sure I telling you some thing you already know: DC KILLS! That's my HSE and get out clause!
Yours Simon M.
#3
Posted 04 July 2011 - 12:33 PM
Ya, but the input source is 200..500VDC...Crispin should have to install a step-down DC-DC converter able to accept up to 600V in input. I'd prefer to swim in a pool fill of sharks!I'd rip apart a switch mode 5v psu, and look at the chip set. They work by rectifying the mains, then using a high frequency oscillator to get the power through a step down transformer, to get the power conversion.
Cheers
Biggest fault of Netduino? It runs by electricity.
#4
Posted 05 July 2011 - 12:53 PM
Even if I ran it off rechargeables I would have to keep replacing them - anything more frequent than 6 months would be a PIA. After a lot of digging I've decided to change things and rather run a CAT5 to it and run power through there as well as return data.
More of a PIA than I would have liked and not as cool but hey...
I did find some (single package) DC-DC convertors which would accept upto 600VDC (think 100V was min) and give you back 12 or 5 at 10A or 25A depending. The size and sheer overkill of them made me leave them alone.
't-was a cool idea while it lasted...
--
Take a seat, I'll be right with you.
Take a seat, I'll be right with you.
#5
Posted 26 July 2011 - 10:01 PM
Why can't you tap off a small group of panels? Use the right taps, and tap off any where from 4 to 12 volts then use a boost/buck regulator and some lifepo or nicad batteries. No fancy charging circuits.
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