Help needed with solar powered LEGO project

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Help needed with solar powered LEGO project

Postby dreiter » Sun Feb 03, 2013 12:08 am

I'm an elementary teacher and I'd like to have my students build an amusement park constructed out of Lego which uses a 3V motor to drive the rides. We'll probably have 24 rides going. I am presently using solar cell yard lights which output a peak of 7V to power each ride and this works fine. What I'd prefer to do though, is use a larger solar array - I found a neat one at Princess Auto, which comes with four 18Watt panels, it's designed to be a charger for an RV or boat. I want to use it to directly power the rides, and not store the energy in batteries. So, I don't want to use the inverter or any of the real features of the mini solar farm, just wire it up to these motors and I'm hoping I can do this safely and simply. The peak amperage is 8A. I have no technical specifications on the motors, though they operate with a small 6 cell AA pack, so I'm assuming a typical circuit with these motors will draw a maximum of about 7A ( 6x1200mA).

It doesn't matter to me whether the rides spin at full speed, they're all geared anyways - I just want them all working. Before I spend the money on the panels, I'd love to hear any feedback on my idea.
Thanks!
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Re: Help needed with solar powered LEGO project

Postby Tracker » Mon Feb 04, 2013 10:16 am

what about starting at basics... ;)

What about ebay "Cells", and build them into the structures

http://www.ebay.com.au/itm/10-pcs-3-65W-POLY-Cell-6x6-for-DIY-solar-panel-polycrystalline-cell-solar-cell-/330866858449?pt=AU_Solar&hash=item4d093399d1&_uhb=1#ht_2451wt_950

Cheap as chups... and disposable.. :idea:
..
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Re: Help needed with solar powered LEGO project

Postby Smurf1976 » Mon Feb 04, 2013 6:17 pm

I'd be very surprised if it draws anywhere near 7A from the AA batteries.

More likely, the 6 AA cells are connected in series to produce 9 volts (or 7.2 V if they are rechargeable type) and this runs with a fairly small current well below 1 amp.

It's not impossible to get 7 Amps out of an AA but (1) not for very long (few minutes) and (2) the battery will get very hot if you try this.
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Re: Help needed with solar powered LEGO project

Postby dreiter » Mon Feb 04, 2013 9:19 pm

Thanks, Tracker, those cells look interesting. I'll keep them in mind.

Smurf, you're right. As it turns out the motors are 9V and I think the battery pack is partially series and partially parallel to get the 9V. I thought 7 A was high , too.

I purchased the solar cell panel yesterday and got 19V from it and hooked it up to three Lego models and the whole circuit was drawing 20 mA, which seems very low to me, barely enough to do anything, does it makes sense that the current was so low? It was working perfectly and I'm happy the current is low, but wondering why?

Darryl
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