Brass Liquid Solenoid and Solar

Breakout boards, sensors, other Adafruit kits, etc.

Moderators: adafruit_support_bill, adafruit

Please be positive and constructive with your questions and comments.
Locked
User avatar
Bellatrix
 
Posts: 19
Joined: Fri Nov 08, 2013 1:16 am

Brass Liquid Solenoid and Solar

Post by Bellatrix »

I'm trying to setup an automatic garden watering system with the Brass Liquid Solenoid, Product ID 996, Arduino Uno r3, and xbee unit to connect to pc wirelessly to change variables of the watering schedule.
The problem I'm running into is how to adequately power the solenoid via solar power and lithium ion batteries. Since the solar charger on the storefront for li-ions only charges the batteries at 1a max, my concern is that i wouldn't be able to recharge the batteries quick enough. Other part I can't seem to figure out is what configuration I should use for batteries or up-converters for proper voltage.

As of right now I'm thinking two or three of the 6600mah Li-ion batteries with the solenoid running for 2 hours a day.

User avatar
adafruit_support_mike
 
Posts: 67454
Joined: Thu Feb 11, 2010 2:51 pm

Re: Brass Liquid Solenoid and Solar

Post by adafruit_support_mike »

Hmm.. given the figures in the current consumption table, your best choice will probably be to put two LiPos in series for roughly 7v of supply and about 1.86A of current. A garden watering system probably won't suffer from a reduction in valve speed, so adding another battery would just waste power.

In terms of power, your solar array will impose more limits than just a 1A maximum current.

The LiPo charging cycle is complex, so chargers are generally made for a specific number of cells, or at least a specific charging voltage. If your charger is designed for a single cell, you're looking at an output limit of about 4v @ 1A, or 4W. The solenoid draws about 1.86A at 7v, or about 13W. You'll need a bit more than 3 hours of charging time per hour of use, assuming the panel works at peak efficiency the whole time.

It's possible to charge LiPos in parallel, though you don't want to discharge them that way. We have a tutorial on charging cells in parallel then reconnecting them to deliver power in series here: http://learn.adafruit.com/multi-cell-lipo-charging

Thing is, charging cells in parallel means each cell gets half the current, so charging will take twice as long.

What are the specs for your panel and charger?

User avatar
Bellatrix
 
Posts: 19
Joined: Fri Nov 08, 2013 1:16 am

Re: Brass Liquid Solenoid and Solar

Post by Bellatrix »

Lipo's in series for running actually sounds like a good idea. I haven't gotten a solar array or charger yet, but i was thinking of getting the LTC4155 charger for providing 3.5A peak to single cell. It also has a system load output on the chip which i figured would be benificial if i did a step up converter.

For fast charging LiPos via seperate chargers or via a high powered charger, would there be an easy way for the arduino to autoswitch the batteries between parallel and series?

User avatar
adafruit_support_bill
 
Posts: 88097
Joined: Sat Feb 07, 2009 10:11 am

Re: Brass Liquid Solenoid and Solar

Post by adafruit_support_bill »

For fast charging LiPos via seperate chargers or via a high powered charger, would there be an easy way for the arduino to autoswitch the batteries between parallel and series?
If you have 2 independent solar panels to power the chargers, there is no need to switch. The switching requirement in the above-mentioned tutorial is due to the common ground between the chargers. If there is no common ground, you can just connect them in series.

User avatar
Bellatrix
 
Posts: 19
Joined: Fri Nov 08, 2013 1:16 am

Re: Brass Liquid Solenoid and Solar

Post by Bellatrix »

Thank you both for the help. When I get the cash, I'm definitely going to get started on this project

Locked
Please be positive and constructive with your questions and comments.

Return to “Other Products from Adafruit”