Continue to Site

Welcome to our site!

Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

  • Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

Step-up from a solar panel

Status
Not open for further replies.

elMickotanko

New Member
I was asked to build a step-up regulator for a friend. He has a 1-watt solar panel charging 5 rechargeable AAAs.

We need a circuit to step the 6V from this battery to 12V. Ive looked at some posts here and applications notes, I think ill use the LT1372 chip from linear.

Is this worth doing?
I mean what is the highest capacity AAAs (it has to be AAAs) available and how long will they run say, 0.5amps at 12V (remembering the loss in the boost circuit)? Also i take it this circuit wouldnt work connected straight to the solar panel?

What determines how much current is drawn from the battery?
(hope thats not a stupid question! is it to do with what load is connected to the circuit?)

Does anyone recomend a different IC for this?

Thanks,
Mick.
 
Mick - I don't have time at the moment to dig out much info but -

A. The current consumption is dependent on the load. It's not a stupid question. You might need to estimate it or measure it - either way it's important if you want to understand battery life.

B. There are quite a few sites on batteries. I know there's at least one link on the ARRL website. What you'd need to know is the mah or milliamphours capacity of the batteries. Amp-hours would apply to larger batteries. Amps times hours gives amp hours though I don't think I'd expect you'd get 100% of the amp hours or milliamp hours out of a battery.

C. There is a limit to the current that a battery can supply so be sure that the version of AAA cell will supply the current.

You might do an approximate input-output check just to see how things come out. You would calculate the milliamp hours of your load (milliamps times hours) and compare that to your batteries - and then compare that to the capability of your charger. Assume full output on the charger the first time around even though we know it won't deliver that on a cloudy day or all hours of the day. If the balance doesn't check this way something needs to change so that the overall input power to the system is equal or greater than the output - including whatever inefficiencies there are in the regulator, batteries or other parts of the system.
 
You might try using a voltage doubler. It may take more time to charge your circuit, but it should get the job done.
 
The Energizer AAA Ni-MH rechargable battery cell has the highest capacity that I've seen. It has 34% the capacity of their 2500mA/hr AA cell.
 

Attachments

  • aaa_rechargable_battery.png
    aaa_rechargable_battery.png
    26 KB · Views: 893
Hi,

Thanks for the help.

The lm2577 looks good.
Im a bit confused by application notes. The diagram given is for a 5v input. How do I modify it for 6v input? or will this be ok?

Also, where can I get inductors (UK)? Im not very clued up on them, but I want this one described in the data sheet :

AIE: ferrite, pot-core inductors; Benefits of this type are
low electro-magnetic interference (EMI), small physical
size, and very low power dissipation (core loss).

Going by the formulas in the app notes I need a 100uH that can handle 2 amps

Thanks, Mick
 
elMickotanko said:
The lm2577 looks good.
How do I modify it for 6v input?
Shhhh. It won't know you are feeding it 6V unless you tell it. :lol:
 
audioguru said:
Shhhh. It won't know you are feeding it 6V unless you tell it. :lol:

Hehe thanks, i thought it might be ok as it was but wasnt sure.

Still looking for inductors though. Does any one know a good source on the web or in the UK.
The sites i found are asking how much (in thousands) i will purchase each month. I just want a couple for non-commercial use.

This is the kind i want:

AIE: ferrite, pot-core inductors; Benefits of this type are
low electro-magnetic interference (EMI), small physical
size, and very low power dissipation (core loss).

100-150uH
 
elMickotanko said:
AIE: ferrite, pot-core inductors; Benefits of this type are
low electro-magnetic interference (EMI), small physical
size, and very low power dissipation (core loss).
100-150uH

Digikey and Mouser are great suppliers.
Look up Mouser part # 542-2114-H
http://www.jwmiller.com/pdf2/2100.pdf

Also the Bournes series (look up Mouser# 652-SDR1806-471K ) is a good series but smaller. I can't get their datasheet page to come up right now though. I'd start by looking at the JW Miller toroids.
 
elMickotanko said:
Also, where can I get inductors (UK)? Im not very clued up on them, but I want this one described in the data sheet :

Try Maplin. I had a quick look and **broken link removed** should be close to what you need.

Mike.
 
Status
Not open for further replies.

Latest threads

New Articles From Microcontroller Tips

Back
Top